Space physics
Encyclopedia
Space physics, also known as space plasma physics, is the study of plasmas
as they occur naturally in the universe
. As such, it encompasses a far-ranging number of topics, including the sun
, solar wind
, planetary magnetospheres and ionosphere
s, auroras
, cosmic rays, and synchrotron radiation
. Space physics is a fundamental part of the study of space weather
and has important implications not only to understanding the universe, but also to practical everyday life, including the operation of communications
and weather satellite
s. Space physics is unique from other fields of astrophysics
which study similar phenomenon, in that space physics utilizes in-situ measurements from high altitude rockets and spacecraft.
, but did not understand how it worked. During the 16th century, in De Magnete
, William Gilbert gave the first description of the Earth's magnetic field, showing that the Earth itself is a great magnet, which explained why a compass needle points north. Deviations of the compass needle magnetic declination
were recorded on navigation charts, and a detailed study of the declination near London by watchmaker and Fellow of the Royal Society, George Graham
resulted in the discovery of irregular magnetic fluctuations that we now call magnetic storms, so named by Alexander Von Humboldt
. Gauss and William Weber
made very careful measurements of Earth's magnetic field which showed systematic variations and random fluctuations. This suggested that the Earth was not an isolated body, but was influenced by external forces. A relationship between individual aurora and accompanying geomagnetic disturbances was noticed by Anders Celsius
and Olof Peter Hiorter in 1747. In 1860, Elias Loomis
(1811–1889) showed that the highest incidence of aurora is seen inside an oval of 20 - 25 degrees around the magnetic pole. In 1881, Hermann Fritz published a map of the "isochasms" or lines of constant magnetic field.
In the late 1870s, Henri Becquerel
offered the first physical explanation for the statistical correlations that had been recorded: sunspots must be a source of fast protons. They are guided to the poles by the Earth's magnetic field. In the early twentieth century, these ideas led Kristian Birkeland
to build a terella, or laboratory device which simulates the Earth's magnetic field in a vacuum chamber, and which uses a cathode ray tube to simulate the energetic particles which compose the solar wind. A theory began to be formulated about the interaction between the Earth's magnetic field and the solar wind.
Space physics did not begin in earnest, however, until the first in situ measurements in the early 1950s, when a team led by Van Allen
launched the first rockets to a height around 110 km. In 1958, a Geiger counter on board the first US satellite, Explorer 1 detected the Earth's radiation belts, later named the Van Allen belts. The boundary between the Earth's magnetic field and interplanetary space was studied by Explorer 10
. Future space craft would travel outside Earth orbit and study the composition and structure of the solar wind in much greater detail. These include WIND (spacecraft), (1994), Advanced Composition Explorer
(ACE), Ulysses, the Interstellar Boundary Explorer
(IBEX) in 2008, and Solar Probe+. Other spacecraft would study the sun, such as STEREO
and Solar and Heliospheric Observatory
(SOHO).
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...
as they occur naturally in the universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...
. As such, it encompasses a far-ranging number of topics, including the sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
, planetary magnetospheres and 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...
s, auroras
Aurora (astronomy)
An aurora is a natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere...
, cosmic rays, and synchrotron radiation
Synchrotron radiation
The electromagnetic radiation emitted when charged particles are accelerated radially is called synchrotron radiation. It is produced in synchrotrons using bending magnets, undulators and/or wigglers...
. Space physics is a fundamental part of the study of space weather
Space weather
Space weather is the concept of changing environmental conditions in near-Earth space or thespace from the Sun's atmosphere to the Earth's atmosphere. It is distinct from the concept ofweather within the Earth's planetary atmosphere...
and has important implications not only to understanding the universe, but also to practical everyday life, including the operation of communications
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...
and weather satellite
Weather satellite
The weather satellite is a type of satellite that is primarily used to monitor the weather and climate of the Earth. Satellites can be either polar orbiting, seeing the same swath of the Earth every 12 hours, or geostationary, hovering over the same spot on Earth by orbiting over the equator while...
s. Space physics is unique from other fields of astrophysics
Astrophysics
Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...
which study similar phenomenon, in that space physics utilizes in-situ measurements from high altitude rockets and spacecraft.
History
Space physics can be traced back to the ancient Chinese, who discovered and recorded sun spots. The Chinese also discovered the principle of the compassCompass
A compass is a navigational instrument that shows directions in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions – north, south, east, and west. Intermediate directions are also defined...
, but did not understand how it worked. During the 16th century, in De Magnete
De Magnete
De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure is a scientific work published in 1600 by the English physician and scientist William Gilbert and his partner Aaron Dowling...
, William Gilbert gave the first description of the Earth's magnetic field, showing that the Earth itself is a great magnet, which explained why a compass needle points north. Deviations of the compass needle magnetic declination
Magnetic declination
Magnetic declination is the angle between magnetic north and true north. The declination is positive when the magnetic north is east of true north. The term magnetic variation is a synonym, and is more often used in navigation...
were recorded on navigation charts, and a detailed study of the declination near London by watchmaker and Fellow of the Royal Society, George Graham
George Graham (clockmaker)
George Graham was an English clockmaker, inventor, and geophysicist, and a Fellow of the Royal Society.He was born to George Graham in Kirklinton, Cumberland. A Friend like his mentor Thomas Tompion, Graham left Cumberland in 1688 for London to work with Tompion...
resulted in the discovery of irregular magnetic fluctuations that we now call magnetic storms, so named by Alexander Von Humboldt
Alexander von Humboldt
Friedrich Wilhelm Heinrich Alexander Freiherr von Humboldt was a German naturalist and explorer, and the younger brother of the Prussian minister, philosopher and linguist Wilhelm von Humboldt...
. Gauss and William Weber
Wilhelm Eduard Weber
Wilhelm Eduard Weber was a German physicist and, together with Carl Friedrich Gauss, inventor of the first electromagnetic telegraph.-Early years:...
made very careful measurements of Earth's magnetic field which showed systematic variations and random fluctuations. This suggested that the Earth was not an isolated body, but was influenced by external forces. A relationship between individual aurora and accompanying geomagnetic disturbances was noticed by Anders Celsius
Anders Celsius
Anders Celsius was a Swedish astronomer. He was professor of astronomy at Uppsala University from 1730 to 1744, but traveled from 1732 to 1735 visiting notable observatories in Germany, Italy and France. He founded the Uppsala Astronomical Observatory in 1741, and in 1742 he proposed the Celsius...
and Olof Peter Hiorter in 1747. In 1860, Elias Loomis
Elias Loomis
- Life and work :Loomis was born in Willington, Connecticut in 1811. He graduated at Yale College in 1830, was a tutor there for three years , and then spent the next year in scientific investigation in Paris. On his return, Loomis was appointed professor of mathematics in the Western Reserve...
(1811–1889) showed that the highest incidence of aurora is seen inside an oval of 20 - 25 degrees around the magnetic pole. In 1881, Hermann Fritz published a map of the "isochasms" or lines of constant magnetic field.
In the late 1870s, Henri Becquerel
Henri Becquerel
Antoine Henri Becquerel was a French physicist, Nobel laureate, and the discoverer of radioactivity along with Marie Curie and Pierre Curie, for which all three won the 1903 Nobel Prize in Physics.-Early life:...
offered the first physical explanation for the statistical correlations that had been recorded: sunspots must be a source of fast protons. They are guided to the poles by the Earth's magnetic field. In the early twentieth century, these ideas led Kristian Birkeland
Kristian Birkeland
Kristian Olaf Birkeland was a Norwegian scientist. He is best remembered as the person who first elucidated the nature of the Aurora borealis. In order to fund his research on the aurorae, he invented the electromagnetic cannon and the Birkeland-Eyde process of fixing nitrogen from the air...
to build a terella, or laboratory device which simulates the Earth's magnetic field in a vacuum chamber, and which uses a cathode ray tube to simulate the energetic particles which compose the solar wind. A theory began to be formulated about the interaction between the Earth's magnetic field and the solar wind.
Space physics did not begin in earnest, however, until the first in situ measurements in the early 1950s, when a team led by Van Allen
Van Allen
Van Allen may refer to:* Van Allen Building, a four story building in Clinton, Iowa* Van Allen radiation belt, a torus of energetic charged particles around EarthPeople named Van Allen:* James Van Allen , American space scientist...
launched the first rockets to a height around 110 km. In 1958, a Geiger counter on board the first US satellite, Explorer 1 detected the Earth's radiation belts, later named the Van Allen belts. The boundary between the Earth's magnetic field and interplanetary space was studied by Explorer 10
Explorer 10
Explorer 10 was an American Earth-orbital satellite that investigated Earth's magnetic fields and nearby plasma...
. Future space craft would travel outside Earth orbit and study the composition and structure of the solar wind in much greater detail. These include WIND (spacecraft), (1994), Advanced Composition Explorer
Advanced Composition Explorer
Advanced Composition Explorer is a NASA space exploration mission being conducted as part of the Explorer program to study matter in situ, comprising energetic particles from the solar wind, the interplanetary medium, and other sources. Real-time data from ACE is used by the Space Weather...
(ACE), Ulysses, the Interstellar Boundary Explorer
Interstellar Boundary Explorer
Interstellar Boundary Explorer is a NASA satellite that will make the first map of the boundary between the Solar System and interstellar space. The mission is part of NASA's Small Explorer program. The IBEX satellite was launched with a Pegasus-XL rocket on October 19, 2008, at 17:47:23 UTC...
(IBEX) in 2008, and Solar Probe+. Other spacecraft would study the sun, such as STEREO
STEREO
STEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...
and Solar and Heliospheric Observatory
Solar and Heliospheric Observatory
The Solar and Heliospheric Observatory is a spacecraft built by a European industrial consortium led by Matra Marconi Space that was launched on a Lockheed Martin Atlas IIAS launch vehicle on December 2, 1995 to study the Sun, and has discovered over 2100 comets. It began normal operations in May...
(SOHO).