Schumann resonance
Encyclopedia
The Schumann resonances (SR) are a set of spectrum peaks in the extremely low frequency
(ELF) portion of the Earth's electromagnetic field
spectrum. Schumann resonances are global electromagnetic resonance
s, excited by lightning
discharges in the cavity formed by the Earth's surface and the ionosphere
.
who predicted it mathematically in 1952. Schumann resonances occur because the space between the surface of the Earth and the conductive ionosphere acts as a closed waveguide
. The limited dimensions of the Earth cause this waveguide to act as a resonant cavity for electromagnetic waves in the ELF
band. The cavity is naturally excited by electric currents in lightning. Schumann resonances are the principal background in the electromagnetic spectrum beginning at 3 Hz and extend to 60 Hz, and appear as distinct peaks at extremely low frequencies (ELF) around 7.83 (fundamental), 14.3, 20.8, 27.3 and 33.8 Hz.
In the normal mode descriptions of Schumann resonances, the fundamental mode
is a standing wave
in the Earth–ionosphere cavity with a wavelength
equal to the circumference of the Earth. This lowest-frequency (and highest-intensity) mode of the Schumann resonance occurs at a frequency
of approximately 7.83 Hz, but this frequency can vary slightly from a variety of factors, such as solar-induced perturbations to the ionosphere, which comprises the upper wall of the closed cavity. The higher resonance modes are spaced at approximately 6.5 Hz intervals, a characteristic attributed to the atmosphere's spherical geometry. The peaks exhibit a spectral width of approximately 20% on account of the damping of the respective modes in the dissipative cavity. The eighth overtone
lies at approximately 59.9 Hz.
Observations of Schumann resonances have been used to track global lightning activity. Owing to the connection between lightning activity and the Earth's climate it has been suggested that they may also be used to monitor global temperature variations and variations of water vapor in the upper troposphere. It has been speculated that extraterrestrial lightning (on other planets) may also be detected and studied by means of their Schumann resonance signatures. Schumann resonances have been used to study the lower ionosphere on Earth and it has been suggested as one way to explore the lower ionosphere on celestial bodies. Effects on Schumann resonances have been reported following geomagnetic and ionospheric disturbances. More recently, discrete Schumann resonance excitations have been linked to transient luminous events – sprites, elves, jets, and other upper-atmospheric lightning
. A new field of interest using Schumann resonances is related to short-term earthquake prediction
.
at his Colorado Springs laboratory in 1899. This observation led to certain peculiar conclusions about the electrical properties of the earth, and which made the basis for his idea for wireless energy transmission.
Tesla researched ways to transmit power and energy wirelessly over long distances (via transverse wave
s, to a lesser extent, and, more readily, longitudinal wave
s). He transmitted extremely low frequencies through the ground as well as between the Earth's surface and the Kennelly-Heaviside layer. He received patents on wireless transceivers that developed standing waves by this method. Making mathematical calculations based on his experiments, Tesla discovered that the resonant frequency of the Earth was approximately 8 hertz (Hz). In the 1950s, researchers confirmed that the resonant frequency of the Earth's ionospheric cavity was in this range (later named the Schumann resonance).
The first suggestion that an ionosphere existed, capable of trapping electromagnetic waves, was made by Heaviside and Kennelly in 1902. It took another twenty years before Edward Appleton and Barnett in 1925, were able to prove experimentally the existence of the ionosphere.
Although some of the most important mathematical tools for dealing with spherical waveguide
s were developed by G. N. Watson
in 1918, it was Winfried Otto Schumann
who first studied the theoretical aspects of the global resonances of the earth–ionosphere waveguide
system, known today as the Schumann resonances. In 1952–1954 Schumann, together with H. L. König, attempted to measure the resonant frequencies. However, it was not until measurements made by Balser and Wagner in 1960–1963 that adequate analysis techniques were available to extract the resonance information from the background noise. Since then there has been an increasing interest in Schumann resonances in a wide variety of fields.
behaves like a resonator
at ELF frequencies and amplifies the spectral signals from lightning at the resonance frequencies.
In an ideal cavity, the resonant frequency of the
-th mode 
is determined by the Earth radius
and the speed of light
.
The real Earth–ionosphere waveguide
is not a perfect electromagnetic resonant cavity. Losses due to finite ionosphere electrical conductivity lower the propagation speed of electromagnetic signals in the cavity, resulting in a resonance frequency that is lower than would be expected in an ideal case, and the observed peaks are wide. In addition, there are a number of horizontal asymmetries – day-night difference in the height of the ionosphere, latitudinal changes in the Earth magnetic field, sudden ionospheric disturbances, polar cap absorption, etc. that produce other effects in the Schumann resonance power spectra.
, and a vertical electric dipole antenna for measuring the vertical component of the electric field
. A typical passband of the instruments is 3–100 Hz. The Schumann resonance electric field amplitude (~300 microvolts per meter) is much smaller than the static fair-weather electric field
(~150 V/m) in the atmosphere
. Similarly, the amplitude of the Schumann resonance magnetic field (~1 picotesla) is many orders of magnitude smaller than the Earth magnetic field (~30–50 microteslas). Specialized receivers and antennas are needed to detect and record Schumann resonances. The electric component is commonly measured with a ball antenna, suggested by Ogawa et al., in 1966, connected to a high-impedance amplifier
. The magnetic induction coil
s typically consist of tens- to hundreds-of-thousands of turns of wire wound around a core of very high magnetic permeability.
. Producing ~50 lightning events per second
, these thunderstorms create the background Schumann resonance signal.
Determining the spatial lightning distribution from Schumann resonance records is a complex problem: in order to estimate the lightning intensity from Schumann resonance records it is necessary to account for both the distance to lightning sources as well as the wave propagation between the source and the observer. The common approach is to make a preliminary assumption on the spatial lightning distribution, based on the known properties of lightning climatology
. An alternative approach is placing the receiver at the North or South Pole, which remain approximately equidistant
from the main thunderstorm centers during the day. One method not requiring preliminary assumptions on the lightning distribution is based on the decomposition of the average background Schumann resonance spectra, utilizing ratios between the average electric and magnetic spectra and between their linear combination. This technique assumes the cavity is spherically symmetric and therefore does not include known cavity asymmetries that are believed to affect the resonance and propagation properties of electromagnetic waves in the system.
A characteristic Schumann resonance diurnal record reflects the properties of both global lightning activity and the state of the Earth–ionosphere cavity between the source region and the observer. The vertical electric field
is independent of the direction of the source relative to the observer, and is therefore a measure of global lightning. The diurnal behavior of the vertical electric field shows three distinct maxima, associated with the three “hot spots” of planetary lightning activity: 9 UT (Universal Time
) peak, linked to the increased thunderstorm
activity from south-east Asia; 14 UT peak associated with the peak in African lightning activity; and the 20 UT peak resulting for the increase in lightning activity in South America. The time and amplitude
of the peaks vary throughout the year, reflecting the seasonal changes in lightning activity.
In general, the African peak is the strongest, reflecting the major contribution of the African “chimney” to the global lightning activity. The ranking of the two other peaks – Asian and American – is the subject of a vigorous dispute among Schumann resonance scientists. Schumann resonance observations made from Europe show a greater contribution from Asia than from South America. This contradicts optical satellite and climatological lightning data that show the South American thunderstorm center stronger than the Asian center., although observations made from North America indicate the dominant contribution comes from South America. The reason for such disparity remains unclear, but may have something to do with the 60 Hz cycling of electricity used in North America (60 Hz being a mode of Schumann Resonance). Williams and Sátori suggest that in order to obtain “correct” Asia-America chimney ranking, it is necessary to remove the influence of the day/night variations in the ionospheric conductivity (day-night asymmetry influence) from the Schumann resonance records. On the other hand, such “corrected” records presented in the work by Sátori et al. show that even after the removal of the day-night asymmetry influence from Schumann resonance records, the Asian contribution remains greater than American. Similar results were obtained by Pechony et al. who calculated Schumann resonance fields from satellite lightning data. It was assumed that the distribution of lightning in the satellite maps was a good proxy for Schumann excitations sources, even though satellite observations predominantly measure in-cloud lightning rather than the cloud-to-ground lightning that are the primary exciters of the resonances. Both simulations – those neglecting the day-night asymmetry, and those taking this asymmetry into account, showed same Asia-America chimney ranking. As for today, the reason for the “invert” ranking of Asia and America chimneys in Schumann resonance records remains unclear and the subject requires further, targeted research.
In the early literature the observed diurnal variations of Schumann resonance power were explained by the variations in the source-receiver (lightning-observer) geometry. It was concluded that no particular systematic variations of the ionosphere (which serves as the upper waveguide
boundary) are needed to explain these variations. Subsequent theoretical studies supported the early estimations of the small influence of the ionosphere day-night asymmetry (difference between day-side and night-side ionosphere conductivity) on the observed variations in Schumann resonance field intensities.
The interest in the influence of the day-night asymmetry in the ionosphere conductivity on Schumann resonances gained new strength in the 1990s, after publication of a work by Sentman and Fraser. Sentman and Fraser developed a technique to separate the global and the local contributions to the observed field power variations using records obtained simultaneously at two stations that were widely separated in longitude. They interpreted the diurnal variations observed at each station in terms of a combination of a diurnally varying global excitation modulated by the local ionosphere height. Their work, which combined both observations and energy conservation arguments, convinced many scientists of the importance of the ionospheric day-night asymmetry and inspired numerous experimental studies. However, recently it was shown that results obtained by Sentman and Fraser can be approximately simulated with a uniform model (without taking into account ionosphere day-night variation) and therefore cannot be uniquely interpreted solely in terms of ionosphere height variation.
Schumann resonance amplitude
records show significant diurnal and seasonal variations which in general coincide in time with the times of the day-night transition (the terminator
). This time-matching seems to support the suggestion of a significant influence of the day-night ionosphere asymmetry on Schumann resonance amplitudes. There are records showing almost clock-like accuracy of the diurnal amplitude changes. On the other hand there are numerous days when Schumann Resonance amplitudes do not increase at sunrise
or do not decrease at sunset
. There are studies showing that the general behavior of Schumann resonance amplitude
records can be recreated from diurnal and seasonal thunderstorm
migration, without invoking ionospheric variations. Two recent independent theoretical studies have shown that the variations in Schumann resonance power related to the day-night transition are much smaller than those associated with the peaks of the global lightning activity, and therefore the global lightning activity plays a more important role in the variation of the Schumann resonance power.
It is generally acknowledged that source-observer effects are the dominant source of the observed diurnal variations, but there remains considerable controversy about the degree to which day-night signatures are present in the data. Part of this controversy stems from the fact that the Schumann resonance parameters extractable from observations provide only a limited amount of information about the coupled lightning source-ionospheric system geometry. The problem of inverting observations to simultaneously infer both the lightning source function and ionospheric structure is therefore extremely underdetermined, leading to the possibility of nonunique interpretations.
of the background signal level by a factor of 10 or more, and appear with intervals of ~10 s, which allows to consider them as isolated events and determine the source lightning location. The source location is determined with either multi-station or single-station techniques, and requires assuming a model for the Earth–ionosphere cavity. The multi-station techniques are more accurate, but require more complicated and expensive facilities.
system, and are accompanied by Q-burst in the Schumann resonances band. Recent observations reveal that occurrences of sprites and Q bursts are highly correlated and Schumann resonances data can possibly be used to estimate the global occurrence rate of sprites.
of the lightning-to-temperature relation provides a natural amplifier
of the temperature changes and makes Schumann resonance a sensitive “thermometer”. Moreover, the ice particles that are believed to participate in the electrification processes which result in a lightning discharge have an important role in the radiative feedback effects that influence the atmosphere temperature. Schumann resonances may therefore help us to understand these feedback
effects. A strong link between global lightning and global temperature has not been experimentally confirmed as of 2008.
is a key element of the Earth’s climate, which has direct effects as a greenhouse gas
, as well as indirect effect through interaction with clouds, aerosols and tropospheric chemistry. Upper tropospheric water vapor (UTWV) has a much greater impact on the greenhouse effect
than water vapor
in the lower atmosphere
, but whether this impact is a positive, or a negative feedback
is still uncertain. The main challenge in addressing this question is the difficulty in monitoring UTWV globally over long timescales. Continental deep-convective thunderstorms produce most of the lightning discharges on Earth. In addition, they transport large amount of water vapor
into the upper troposphere
, dominating the variations of global UTWV. Price [2000] suggested that changes in the UTWV can be derived from records of Schumann Resonances.
there are five candidates for Schumann resonance detection besides the Earth: Venus
, Mars
, Jupiter
, Saturn
and its moon Titan
.
Modeling Schumann resonances on the planets and moons of the Solar System
is complicated by the lack of knowledge of the waveguide
parameters. No in situ capability exists today to validate the results, but in the case of Mars there have been terrestrial observations of radio emission spectra that have been associated with Schumann resonances. The reported radio emissions are not of the primary electromagnetic Schumann modes, but rather of secondary modulations of the nonthermal microwave emissions from the planet at approximately the expected Schumann frequencies, and have not be independently confirmed to be associated with lightning activity at Mars. There is the possibility that future lander missions could carry in situ instrumentation to perform the necessary measurements. Theoretical studies are primarily directed to parameterizing the problem for future planetary explorers.
The strongest evidence for lightning on Venus comes from the impulsive electromagnetic waves detected by Venera
11 and 12 landers. Theoretical calculations of the Schumann resonances at Venus were reported by Nickolaenko and Rabinowicz [1982] and Pechony and Price [2004]. Both studies yielded very close results, indicating that Schumann resonances should be easily detectable on that planet
given a lightning source of excitation and a suitably located sensor.
On Mars
detection of lightning activity has been reported by Ruf et al. [2009]. The evidence is indirect and in the form of modulations of the nonthermal microwave spectrum at approximately the expected Schumann resonance frequencies. It has not been independently confirmed that these are associated with electrical discharges on Mars. In the event confirmation is made by direct, in situ observations, it would verify the suggestion of the possibility of charge separation and lightning strokes in the Martian dust storms made by Eden and Vonnegut [1973] and Renno et al. [2003]. Martian global resonances were modeled by Sukhorukov [1991], Pechony and Price [2004] and Molina-Cuberos et al. [2006]. The results of the three studies are somewhat different, but it seems that at least the first two Schumann resonance modes should be detectable. Evidence of the first three Schumann resonance modes is present in the spectra of radio emission from the lightning detected in Martian dust storms.
It was long ago suggested that lightning discharges may occur on Titan, but recent data from Cassini–Huygens seems to indicate that there is no lightning activity on this largest satellite
of Saturn
. Due to the recent interest in Titan, associated with the Cassini–Huygens mission, its ionosphere is perhaps the most thoroughly modeled today. Schumann resonances on Titan have received more attention than on any other celestial body
, in works by Besser et al. [2002], Morente et al. [2003], Molina-Cuberos et al. [2004], Nickolaenko et al. [2003] and Pechony and Price [2004]. It appears that only the first Schumann resonance mode might be detectable on Titan
.
Jupiter
is the only planet where lightning activity has been optically detected. Existence of lightning activity on that planet was predicted by Bar-Nun [1975] and it is now supported by data from Galileo, Voyagers
1 and 2, Pioneers
10 and 11 and Cassini. Saturn
is also expected to have intensive lightning activity, but the three visiting spacecrafts – Pioneer 11
in 1979, Voyager 1
in 1980 and Voyager 2
in 1981, failed to provide any convincing evidence from optical observations. The strong storm monitored on Saturn
by the Cassini spacecraft produced no visible lightning flashes, although electromagnetic sensors aboard the spacecraft detected signatures that are characteristic of lightning. Little is known about the electrical parameters of Jupiter
and Saturn
interior. Even the question of what should serve as the lower waveguide
boundary is a non-trivial one in case of the gaseous planets. There seem to be no works dedicated to Schumann resonances on Saturn
. To date there has been only one attempt to model Schumann resonances on Jupiter
. Here, the electrical conductivity profile within the gaseous atmosphere of Jupiter was calculated using methods similar to those used to model stellar interiors, and it was pointed out that the same methods could be easily extended to the other gas giants Saturn, Uranus and Neptune. Given the intense lightning activity at Jupiter, the Schumann resonances should be easily detectable with a sensor suitably positioned within the planetary-ionospheric cavity.
where it initially began, to the fields of bioenergetics
and acupuncture
. Critics claim that the studies that support these applications are inconclusive and that further studies are needed.
A small study in Japan found that blood pressure was lowered by the Schumann resonance, with the effects on human health needing to be investigated further.
Websites
Extremely low frequency
Extremely low frequency is a term used to describe radiation frequencies from 3 to 300 Hz. In atmosphere science, an alternative definition is usually given, from 3 Hz to 3 kHz...
(ELF) portion of the Earth's electromagnetic field
Electromagnetic field
An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...
spectrum. Schumann resonances are global electromagnetic resonance
Resonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
s, excited by lightning
Lightning
Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
discharges in the cavity formed by the Earth's surface and the ionosphere
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
.
Description
This global electromagnetic resonance phenomenon is named after physicist Winfried Otto SchumannWinfried Otto Schumann
Winfried Otto Schumann was a German physicist who predicted the Schumann resonances, a series of low-frequency resonances caused by lightning discharges in the atmosphere.-Biography:...
who predicted it mathematically in 1952. Schumann resonances occur because the space between the surface of the Earth and the conductive ionosphere acts as a closed waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
. The limited dimensions of the Earth cause this waveguide to act as a resonant cavity for electromagnetic waves in the ELF
Extremely low frequency
Extremely low frequency is a term used to describe radiation frequencies from 3 to 300 Hz. In atmosphere science, an alternative definition is usually given, from 3 Hz to 3 kHz...
band. The cavity is naturally excited by electric currents in lightning. Schumann resonances are the principal background in the electromagnetic spectrum beginning at 3 Hz and extend to 60 Hz, and appear as distinct peaks at extremely low frequencies (ELF) around 7.83 (fundamental), 14.3, 20.8, 27.3 and 33.8 Hz.
In the normal mode descriptions of Schumann resonances, the fundamental mode
Fundamental frequency
The fundamental frequency, often referred to simply as the fundamental and abbreviated f0, is defined as the lowest frequency of a periodic waveform. In terms of a superposition of sinusoids The fundamental frequency, often referred to simply as the fundamental and abbreviated f0, is defined as the...
is a standing wave
Standing wave
In physics, a standing wave – also known as a stationary wave – is a wave that remains in a constant position.This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling...
in the Earth–ionosphere cavity with a wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
equal to the circumference of the Earth. This lowest-frequency (and highest-intensity) mode of the Schumann resonance occurs at a frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
of approximately 7.83 Hz, but this frequency can vary slightly from a variety of factors, such as solar-induced perturbations to the ionosphere, which comprises the upper wall of the closed cavity. The higher resonance modes are spaced at approximately 6.5 Hz intervals, a characteristic attributed to the atmosphere's spherical geometry. The peaks exhibit a spectral width of approximately 20% on account of the damping of the respective modes in the dissipative cavity. The eighth overtone
Overtone
An overtone is any frequency higher than the fundamental frequency of a sound. The fundamental and the overtones together are called partials. Harmonics are partials whose frequencies are whole number multiples of the fundamental These overlapping terms are variously used when discussing the...
lies at approximately 59.9 Hz.
Observations of Schumann resonances have been used to track global lightning activity. Owing to the connection between lightning activity and the Earth's climate it has been suggested that they may also be used to monitor global temperature variations and variations of water vapor in the upper troposphere. It has been speculated that extraterrestrial lightning (on other planets) may also be detected and studied by means of their Schumann resonance signatures. Schumann resonances have been used to study the lower ionosphere on Earth and it has been suggested as one way to explore the lower ionosphere on celestial bodies. Effects on Schumann resonances have been reported following geomagnetic and ionospheric disturbances. More recently, discrete Schumann resonance excitations have been linked to transient luminous events – sprites, elves, jets, and other upper-atmospheric lightning
Upper-atmospheric lightning
Upper-atmospheric lightning or upper-atmospheric discharge are terms sometimes used by researchers to refer to a family of short-lived electrical-breakdown phenomena that occur well above the altitudes of normal lightning and storm clouds. Upper-atmospheric lightning is believed to be electrically...
. A new field of interest using Schumann resonances is related to short-term earthquake prediction
Earthquake prediction
An earthquake prediction is a prediction that an earthquake of a specific magnitude will occur in a particular place at a particular time . Despite considerable research efforts by seismologists, scientifically reproducible predictions cannot yet be made to a specific day or month...
.
History
The first documented observations of global electromagnetic resonance were made by Nikola TeslaNikola Tesla
Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...
at his Colorado Springs laboratory in 1899. This observation led to certain peculiar conclusions about the electrical properties of the earth, and which made the basis for his idea for wireless energy transmission.
Tesla researched ways to transmit power and energy wirelessly over long distances (via transverse wave
Transverse wave
A transverse wave is a moving wave that consists of oscillations occurring perpendicular to the direction of energy transfer...
s, to a lesser extent, and, more readily, longitudinal wave
Longitudinal wave
Longitudinal waves, as known as "l-waves", are waves that have the same direction of vibration as their direction of travel, which means that the movement of the medium is in the same direction as or the opposite direction to the motion of the wave. Mechanical longitudinal waves have been also...
s). He transmitted extremely low frequencies through the ground as well as between the Earth's surface and the Kennelly-Heaviside layer. He received patents on wireless transceivers that developed standing waves by this method. Making mathematical calculations based on his experiments, Tesla discovered that the resonant frequency of the Earth was approximately 8 hertz (Hz). In the 1950s, researchers confirmed that the resonant frequency of the Earth's ionospheric cavity was in this range (later named the Schumann resonance).
The first suggestion that an ionosphere existed, capable of trapping electromagnetic waves, was made by Heaviside and Kennelly in 1902. It took another twenty years before Edward Appleton and Barnett in 1925, were able to prove experimentally the existence of the ionosphere.
Although some of the most important mathematical tools for dealing with spherical waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
s were developed by G. N. Watson
G. N. Watson
Neville Watson was an English mathematician, a noted master in the application of complex analysis to the theory of special functions. His collaboration on the 1915 second edition of E. T. Whittaker's A Course of Modern Analysis produced the classic “Whittaker & Watson” text...
in 1918, it was Winfried Otto Schumann
Winfried Otto Schumann
Winfried Otto Schumann was a German physicist who predicted the Schumann resonances, a series of low-frequency resonances caused by lightning discharges in the atmosphere.-Biography:...
who first studied the theoretical aspects of the global resonances of the earth–ionosphere waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
system, known today as the Schumann resonances. In 1952–1954 Schumann, together with H. L. König, attempted to measure the resonant frequencies. However, it was not until measurements made by Balser and Wagner in 1960–1963 that adequate analysis techniques were available to extract the resonance information from the background noise. Since then there has been an increasing interest in Schumann resonances in a wide variety of fields.
Basic theory
Lightning discharges are considered to be the primary natural source of Schumann resonance excitation; lightning channels behave like huge antennas that radiate electromagnetic energy at frequencies below about 100 kHz. These signals are very weak at large distances from the lightning source, but the Earth–ionosphere waveguideWaveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
behaves like a resonator
Resonator
A resonator is a device or system that exhibits resonance or resonant behavior, that is, it naturally oscillates at some frequencies, called its resonant frequencies, with greater amplitude than at others. The oscillations in a resonator can be either electromagnetic or mechanical...
at ELF frequencies and amplifies the spectral signals from lightning at the resonance frequencies.
In an ideal cavity, the resonant frequency of the
-th mode is determined by the Earth radiusEarth radius
Because the Earth is not perfectly spherical, no single value serves as its natural radius. Distances from points on the surface to the center range from 6,353 km to 6,384 km...
and the speed of lightSpeed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
.The real Earth–ionosphere waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
is not a perfect electromagnetic resonant cavity. Losses due to finite ionosphere electrical conductivity lower the propagation speed of electromagnetic signals in the cavity, resulting in a resonance frequency that is lower than would be expected in an ideal case, and the observed peaks are wide. In addition, there are a number of horizontal asymmetries – day-night difference in the height of the ionosphere, latitudinal changes in the Earth magnetic field, sudden ionospheric disturbances, polar cap absorption, etc. that produce other effects in the Schumann resonance power spectra.
Measurements
Today Schumann resonances are recorded at many separate research stations around the world. The sensors used to measure Schumann resonances typically consist of two horizontal magnetic induction coils for measuring the north-south and east-west components of the magnetic fieldMagnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
, and a vertical electric dipole antenna for measuring the vertical component of the electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
. A typical passband of the instruments is 3–100 Hz. The Schumann resonance electric field amplitude (~300 microvolts per meter) is much smaller than the static fair-weather electric field
Fair weather condition
Fair weather condition concerns the electric field and the electric current in the air as well as the conductivity of the atmosphere. It is the electrostatic longitudinal modes and electromagnetic transverse mode or state of different meteorological conditions, concerning measurements of...
(~150 V/m) in the atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
. Similarly, the amplitude of the Schumann resonance magnetic field (~1 picotesla) is many orders of magnitude smaller than the Earth magnetic field (~30–50 microteslas). Specialized receivers and antennas are needed to detect and record Schumann resonances. The electric component is commonly measured with a ball antenna, suggested by Ogawa et al., in 1966, connected to a high-impedance amplifier
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
. The magnetic induction coil
Induction coil
An induction coil or "spark coil" is a type of disruptive discharge coil. It is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current supply...
s typically consist of tens- to hundreds-of-thousands of turns of wire wound around a core of very high magnetic permeability.
Dependence on global lightning activity
From the very beginning of Schumann resonance studies, it was known that they could be used to monitor global lightning activity. At any given time there are about 2000 thunderstorms around the globeGlobe
A globe is a three-dimensional scale model of Earth or other spheroid celestial body such as a planet, star, or moon...
. Producing ~50 lightning events per second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
, these thunderstorms create the background Schumann resonance signal.
Determining the spatial lightning distribution from Schumann resonance records is a complex problem: in order to estimate the lightning intensity from Schumann resonance records it is necessary to account for both the distance to lightning sources as well as the wave propagation between the source and the observer. The common approach is to make a preliminary assumption on the spatial lightning distribution, based on the known properties of lightning climatology
Climatology
Climatology is the study of climate, scientifically defined as weather conditions averaged over a period of time, and is a branch of the atmospheric sciences...
. An alternative approach is placing the receiver at the North or South Pole, which remain approximately equidistant
Equidistant
A point is said to be equidistant from a set of objects if the distances between that point and each object in the set are equal.In two-dimensional Euclidian geometry the locus of points equidistant from two given points is their perpendicular bisector...
from the main thunderstorm centers during the day. One method not requiring preliminary assumptions on the lightning distribution is based on the decomposition of the average background Schumann resonance spectra, utilizing ratios between the average electric and magnetic spectra and between their linear combination. This technique assumes the cavity is spherically symmetric and therefore does not include known cavity asymmetries that are believed to affect the resonance and propagation properties of electromagnetic waves in the system.
Diurnal variations
The best documented and the most debated features of the Schumann resonance phenomenon are the diurnal variations of the background Schumann resonance power spectrum.A characteristic Schumann resonance diurnal record reflects the properties of both global lightning activity and the state of the Earth–ionosphere cavity between the source region and the observer. The vertical electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
is independent of the direction of the source relative to the observer, and is therefore a measure of global lightning. The diurnal behavior of the vertical electric field shows three distinct maxima, associated with the three “hot spots” of planetary lightning activity: 9 UT (Universal Time
Universal Time
Universal Time is a time scale based on the rotation of the Earth. It is a modern continuation of Greenwich Mean Time , i.e., the mean solar time on the Prime Meridian at Greenwich, and GMT is sometimes used loosely as a synonym for UTC...
) peak, linked to the increased thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
activity from south-east Asia; 14 UT peak associated with the peak in African lightning activity; and the 20 UT peak resulting for the increase in lightning activity in South America. The time and amplitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
of the peaks vary throughout the year, reflecting the seasonal changes in lightning activity.
”Chimney” ranking
In general, the African peak is the strongest, reflecting the major contribution of the African “chimney” to the global lightning activity. The ranking of the two other peaks – Asian and American – is the subject of a vigorous dispute among Schumann resonance scientists. Schumann resonance observations made from Europe show a greater contribution from Asia than from South America. This contradicts optical satellite and climatological lightning data that show the South American thunderstorm center stronger than the Asian center., although observations made from North America indicate the dominant contribution comes from South America. The reason for such disparity remains unclear, but may have something to do with the 60 Hz cycling of electricity used in North America (60 Hz being a mode of Schumann Resonance). Williams and Sátori suggest that in order to obtain “correct” Asia-America chimney ranking, it is necessary to remove the influence of the day/night variations in the ionospheric conductivity (day-night asymmetry influence) from the Schumann resonance records. On the other hand, such “corrected” records presented in the work by Sátori et al. show that even after the removal of the day-night asymmetry influence from Schumann resonance records, the Asian contribution remains greater than American. Similar results were obtained by Pechony et al. who calculated Schumann resonance fields from satellite lightning data. It was assumed that the distribution of lightning in the satellite maps was a good proxy for Schumann excitations sources, even though satellite observations predominantly measure in-cloud lightning rather than the cloud-to-ground lightning that are the primary exciters of the resonances. Both simulations – those neglecting the day-night asymmetry, and those taking this asymmetry into account, showed same Asia-America chimney ranking. As for today, the reason for the “invert” ranking of Asia and America chimneys in Schumann resonance records remains unclear and the subject requires further, targeted research.
Influence of the day-night asymmetry
In the early literature the observed diurnal variations of Schumann resonance power were explained by the variations in the source-receiver (lightning-observer) geometry. It was concluded that no particular systematic variations of the ionosphere (which serves as the upper waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
boundary) are needed to explain these variations. Subsequent theoretical studies supported the early estimations of the small influence of the ionosphere day-night asymmetry (difference between day-side and night-side ionosphere conductivity) on the observed variations in Schumann resonance field intensities.
The interest in the influence of the day-night asymmetry in the ionosphere conductivity on Schumann resonances gained new strength in the 1990s, after publication of a work by Sentman and Fraser. Sentman and Fraser developed a technique to separate the global and the local contributions to the observed field power variations using records obtained simultaneously at two stations that were widely separated in longitude. They interpreted the diurnal variations observed at each station in terms of a combination of a diurnally varying global excitation modulated by the local ionosphere height. Their work, which combined both observations and energy conservation arguments, convinced many scientists of the importance of the ionospheric day-night asymmetry and inspired numerous experimental studies. However, recently it was shown that results obtained by Sentman and Fraser can be approximately simulated with a uniform model (without taking into account ionosphere day-night variation) and therefore cannot be uniquely interpreted solely in terms of ionosphere height variation.
Schumann resonance amplitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
records show significant diurnal and seasonal variations which in general coincide in time with the times of the day-night transition (the terminator
Terminator (solar)
A terminator, twilight zone or "grey line" is a moving line that separates the illuminated day side and the dark night side of a planetary body...
). This time-matching seems to support the suggestion of a significant influence of the day-night ionosphere asymmetry on Schumann resonance amplitudes. There are records showing almost clock-like accuracy of the diurnal amplitude changes. On the other hand there are numerous days when Schumann Resonance amplitudes do not increase at sunrise
Sunrise
Sunrise is the instant at which the upper edge of the Sun appears above the horizon in the east. Sunrise should not be confused with dawn, which is the point at which the sky begins to lighten, some time before the sun itself appears, ending twilight...
or do not decrease at sunset
Sunset
Sunset or sundown is the daily disappearance of the Sun below the horizon in the west as a result of Earth's rotation.The time of sunset is defined in astronomy as the moment the trailing edge of the Sun's disk disappears below the horizon in the west...
. There are studies showing that the general behavior of Schumann resonance amplitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
records can be recreated from diurnal and seasonal thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
migration, without invoking ionospheric variations. Two recent independent theoretical studies have shown that the variations in Schumann resonance power related to the day-night transition are much smaller than those associated with the peaks of the global lightning activity, and therefore the global lightning activity plays a more important role in the variation of the Schumann resonance power.
It is generally acknowledged that source-observer effects are the dominant source of the observed diurnal variations, but there remains considerable controversy about the degree to which day-night signatures are present in the data. Part of this controversy stems from the fact that the Schumann resonance parameters extractable from observations provide only a limited amount of information about the coupled lightning source-ionospheric system geometry. The problem of inverting observations to simultaneously infer both the lightning source function and ionospheric structure is therefore extremely underdetermined, leading to the possibility of nonunique interpretations.
The “inverse problem”
One of the interesting problems in Schumann resonances studies is determining the lightning source characteristics (the “inverse problem”). Temporally resolving each individual flash is impossible because the mean rate of excitation by lightning, ~50 lightning events per second globally, mixes up the individual contributions together. However, occasionally there occur extremely large lightning flashes which produce distinctive signatures that stand out from the background signals. Called "Q-bursts", they are produced by intense lightning strikes that transfer large amounts of charge from clouds to the ground, and often carry high peak current. Q-bursts can exceed the amplitudeAmplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
of the background signal level by a factor of 10 or more, and appear with intervals of ~10 s, which allows to consider them as isolated events and determine the source lightning location. The source location is determined with either multi-station or single-station techniques, and requires assuming a model for the Earth–ionosphere cavity. The multi-station techniques are more accurate, but require more complicated and expensive facilities.
Transient luminous events research
It is now believed that many of the Schumann resonances transients (Q bursts) are related to the transient luminous events (TLEs). In 1995 Boccippio et al. showed that sprites, the most common TLE, are produced by positive cloud-to-ground lightning occurring in the stratiform region of a thunderstormThunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
system, and are accompanied by Q-burst in the Schumann resonances band. Recent observations reveal that occurrences of sprites and Q bursts are highly correlated and Schumann resonances data can possibly be used to estimate the global occurrence rate of sprites.
Global temperature
Williams [1992] suggested that global temperature may be monitored with the Schumann resonances. The link between Schumann resonance and temperature is lightning flash rate, which increases nonlinearly with temperature. The nonlinearityNonlinearity
In mathematics, a nonlinear system is one that does not satisfy the superposition principle, or one whose output is not directly proportional to its input; a linear system fulfills these conditions. In other words, a nonlinear system is any problem where the variable to be solved for cannot be...
of the lightning-to-temperature relation provides a natural amplifier
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
of the temperature changes and makes Schumann resonance a sensitive “thermometer”. Moreover, the ice particles that are believed to participate in the electrification processes which result in a lightning discharge have an important role in the radiative feedback effects that influence the atmosphere temperature. Schumann resonances may therefore help us to understand these feedback
Feedback
Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...
effects. A strong link between global lightning and global temperature has not been experimentally confirmed as of 2008.
Upper tropospheric water vapor
Tropospheric water vaporWater vapor
Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...
is a key element of the Earth’s climate, which has direct effects as a greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...
, as well as indirect effect through interaction with clouds, aerosols and tropospheric chemistry. Upper tropospheric water vapor (UTWV) has a much greater impact on the greenhouse effect
Greenhouse effect
The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere...
than water vapor
Water vapor
Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...
in the lower atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
, but whether this impact is a positive, or a negative feedback
Feedback
Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...
is still uncertain. The main challenge in addressing this question is the difficulty in monitoring UTWV globally over long timescales. Continental deep-convective thunderstorms produce most of the lightning discharges on Earth. In addition, they transport large amount of water vapor
Water vapor
Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...
into the upper troposphere
Troposphere
The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....
, dominating the variations of global UTWV. Price [2000] suggested that changes in the UTWV can be derived from records of Schumann Resonances.
Schumann resonances on other planets
The existence of Schumann-like resonances is conditioned primarily by two factors: (1) a closed, planetary-sized spherical cavity, consisting of conducting lower and upper boundaries separated by an insulating medium. For the earth the conducting lower boundary is its surface, and the upper boundary is the ionosphere. Other planets may have similar electrical conductivity geometry, so it is speculated that they should possess similar resonant behavior. (2) source of electrical excitation of electromagnetic waves in the ELF range. Within the Solar SystemSolar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
there are five candidates for Schumann resonance detection besides the Earth: Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
, Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
, Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
, Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
and its moon Titan
Titan (moon)
Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....
.
Modeling Schumann resonances on the planets and moons of the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
is complicated by the lack of knowledge of the waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
parameters. No in situ capability exists today to validate the results, but in the case of Mars there have been terrestrial observations of radio emission spectra that have been associated with Schumann resonances. The reported radio emissions are not of the primary electromagnetic Schumann modes, but rather of secondary modulations of the nonthermal microwave emissions from the planet at approximately the expected Schumann frequencies, and have not be independently confirmed to be associated with lightning activity at Mars. There is the possibility that future lander missions could carry in situ instrumentation to perform the necessary measurements. Theoretical studies are primarily directed to parameterizing the problem for future planetary explorers.
The strongest evidence for lightning on Venus comes from the impulsive electromagnetic waves detected by Venera
Venera
The Venera series probes were developed by the Soviet Union between 1961 and 1984 to gather data from Venus, Venera being the Russian name for Venus...
11 and 12 landers. Theoretical calculations of the Schumann resonances at Venus were reported by Nickolaenko and Rabinowicz [1982] and Pechony and Price [2004]. Both studies yielded very close results, indicating that Schumann resonances should be easily detectable on that planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
given a lightning source of excitation and a suitably located sensor.
On Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
detection of lightning activity has been reported by Ruf et al. [2009]. The evidence is indirect and in the form of modulations of the nonthermal microwave spectrum at approximately the expected Schumann resonance frequencies. It has not been independently confirmed that these are associated with electrical discharges on Mars. In the event confirmation is made by direct, in situ observations, it would verify the suggestion of the possibility of charge separation and lightning strokes in the Martian dust storms made by Eden and Vonnegut [1973] and Renno et al. [2003]. Martian global resonances were modeled by Sukhorukov [1991], Pechony and Price [2004] and Molina-Cuberos et al. [2006]. The results of the three studies are somewhat different, but it seems that at least the first two Schumann resonance modes should be detectable. Evidence of the first three Schumann resonance modes is present in the spectra of radio emission from the lightning detected in Martian dust storms.
It was long ago suggested that lightning discharges may occur on Titan, but recent data from Cassini–Huygens seems to indicate that there is no lightning activity on this largest satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
of Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
. Due to the recent interest in Titan, associated with the Cassini–Huygens mission, its ionosphere is perhaps the most thoroughly modeled today. Schumann resonances on Titan have received more attention than on any other celestial body
Astronomical object
Astronomical objects or celestial objects are naturally occurring physical entities, associations or structures that current science has demonstrated to exist in the observable universe. The term astronomical object is sometimes used interchangeably with astronomical body...
, in works by Besser et al. [2002], Morente et al. [2003], Molina-Cuberos et al. [2004], Nickolaenko et al. [2003] and Pechony and Price [2004]. It appears that only the first Schumann resonance mode might be detectable on Titan
Titan (moon)
Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....
.
Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
is the only planet where lightning activity has been optically detected. Existence of lightning activity on that planet was predicted by Bar-Nun [1975] and it is now supported by data from Galileo, Voyagers
Voyager program
The Voyager program is a U.S program that launched two unmanned space missions, scientific probes Voyager 1 and Voyager 2. They were launched in 1977 to take advantage of a favorable planetary alignment of the late 1970s...
1 and 2, Pioneers
Pioneer program
The Pioneer program is a series of United States unmanned space missions that was designed for planetary exploration. There were a number of such missions in the program, but the most notable were Pioneer 10 and Pioneer 11, which explored the outer planets and left the solar system...
10 and 11 and Cassini. Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
is also expected to have intensive lightning activity, but the three visiting spacecrafts – Pioneer 11
Pioneer 11
Pioneer 11 is a 259-kilogram robotic space probe launched by NASA on April 6, 1973 to study the asteroid belt, the environment around Jupiter and Saturn, solar wind, cosmic rays, and eventually the far reaches of the solar system and heliosphere...
in 1979, Voyager 1
Voyager 1
The Voyager 1 spacecraft is a 722-kilogram space probe launched by NASA in 1977, to study the outer Solar System and eventually interstellar space. Operating for as of today , the spacecraft receives routine commands and transmits data back to the Deep Space Network. At a distance of as of...
in 1980 and Voyager 2
Voyager 2
The Voyager 2 spacecraft is a 722-kilogram space probe launched by NASA on August 20, 1977 to study the outer Solar System and eventually interstellar space...
in 1981, failed to provide any convincing evidence from optical observations. The strong storm monitored on Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
by the Cassini spacecraft produced no visible lightning flashes, although electromagnetic sensors aboard the spacecraft detected signatures that are characteristic of lightning. Little is known about the electrical parameters of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
and Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
interior. Even the question of what should serve as the lower waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
boundary is a non-trivial one in case of the gaseous planets. There seem to be no works dedicated to Schumann resonances on Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
. To date there has been only one attempt to model Schumann resonances on Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
. Here, the electrical conductivity profile within the gaseous atmosphere of Jupiter was calculated using methods similar to those used to model stellar interiors, and it was pointed out that the same methods could be easily extended to the other gas giants Saturn, Uranus and Neptune. Given the intense lightning activity at Jupiter, the Schumann resonances should be easily detectable with a sensor suitably positioned within the planetary-ionospheric cavity.
Speculation about Schumann resonance effects in non-geophysics domains
Interest in Schumann resonances extends beyond the domain of geophysicsGeophysics
Geophysics is the physics of the Earth and its environment in space; also the study of the Earth using quantitative physical methods. The term geophysics sometimes refers only to the geological applications: Earth's shape; its gravitational and magnetic fields; its internal structure and...
where it initially began, to the fields of bioenergetics
Bioenergetics
Bioenergetics is the subject of a field of biochemistry that concerns energy flow through living systems. This is an active area of biological research that includes the study of thousands of different cellular processes such as cellular respiration and the many other metabolic processes that can...
and acupuncture
Acupuncture
Acupuncture is a type of alternative medicine that treats patients by insertion and manipulation of solid, generally thin needles in the body....
. Critics claim that the studies that support these applications are inconclusive and that further studies are needed.
A small study in Japan found that blood pressure was lowered by the Schumann resonance, with the effects on human health needing to be investigated further.
See also
- Earth's magnetic fieldEarth's magnetic fieldEarth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...
- Plasma (physics)Plasma (physics)In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
- radiant energyRadiant energyRadiant energy is the energy of electromagnetic waves. The quantity of radiant energy may be calculated by integrating radiant flux with respect to time and, like all forms of energy, its SI unit is the joule. The term is used particularly when radiation is emitted by a source into the...
- Telluric currentTelluric currentA telluric current , or Earth current, is an electric current which moves underground or through the sea. Telluric currents result from both natural causes and human activity, and the discrete currents interact in a complex pattern...
- The HumThe HumThe Hum is a generic name for a series of phenomena involving a persistent and invasive low-frequency humming noise not audible to all people. Hums have been reported in various geographical locations. In some cases a source has been located. A Hum on the Big Island of Hawaii, typically related...
External articles and references
General references- Articles on the NASA ADS Database: http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&db_key=PHY&db_key=PRE&qform=AST&sim_query=YES&ned_query=YES&aut_logic=OR&obj_logic=OR&author=&object=&start_mon=&start_year=&end_mon=&end_year=&ttl_logic=OR&title=%22Schumann+Resonances%22&txt_logic=OR&text=&nr_to_return=100&start_nr=1&jou_pick=ALL&ref_stems=&data_and=ALL&group_and=ALL&start_entry_day=&start_entry_mon=&start_entry_year=&end_entry_day=&end_entry_mon=&end_entry_year=&min_score=&sort=SCORE&data_type=SHORT&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1Full list] | http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&db_key=PHY&db_key=PRE&qform=AST&sim_query=YES&ned_query=YES&aut_logic=OR&obj_logic=OR&author=&object=&start_mon=&start_year=&end_mon=&end_year=&ttl_logic=OR&title=%22Schumann+Resonances%22&txt_logic=OR&text=&nr_to_return=100&start_nr=1&jou_pick=ALL&ref_stems=&data_and=YES&gif_link=YES&group_and=ALL&start_entry_day=&start_entry_mon=&start_entry_year=&end_entry_day=&end_entry_mon=&end_entry_year=&min_score=&sort=SCORE&data_type=SHORT&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1Full text]
Websites
- Schumann resonance reference from University of OuluUniversity of OuluThe University of Oulu is one of the largest universities in Finland, located in the city of Oulu. It was founded on July 8, 1958. The university has around 16,000 students and 3,000 staff...
- bad link 10 Oct 2011 - Schumann Resonance Measurements as a Sensitive Diagnostic for Global Change (fixed)
- Magnetic activity and Schumann resonance
- http://www.iaspacegrant.org/sites/default/files/pdf_files/Kruger-SEED.pdf Well illustrated study from the University of Iowa] explaining the construction of a ULF receiver for studying Schumann resonances. Link updated 3 Nov. 2011