Lower hybrid oscillation
Encyclopedia
A lower hybrid oscillation is a longitudinal
oscillation of ions and electrons in a magnetized plasma
. The direction of propagation must be very nearly perpendicular to the stationary magnetic field, within about √(me/mi) radian
s. Otherwise the electrons can move along the field lines fast enough to shield
the oscillations in potential, in which case an electrostatic ion cyclotron wave
results. The frequency of oscillation is
,
where Ωi is the ion cyclotron frequency, Ωe is the electron cyclotron frequency and ωpi is the ion plasma frequency. This is the lower hybrid frequency, so called because it is a "hybrid", or mixture, of two frequencies. There are also an upper hybrid frequency and upper hybrid oscillation
. The lower hybrid oscillation is unusual in that the ion and electron masses play an equally important role. This mode is relatively unimportant in practice because the necessary precise orientation relative to the magnetic field is seldom achieved. Exceptions are the use of lower hybrid waves to heat fusion
plasmas and the lower hybrid drift instability, which was thought to be an important determinant of transport in the Field-Reversed Configuration
(but was not found experimentally).
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...
oscillation of ions and electrons in a magnetized plasma
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...
. The direction of propagation must be very nearly perpendicular to the stationary magnetic field, within about √(me/mi) radian
Radian
Radian is the ratio between the length of an arc and its radius. The radian is the standard unit of angular measure, used in many areas of mathematics. The unit was formerly a SI supplementary unit, but this category was abolished in 1995 and the radian is now considered a SI derived unit...
s. Otherwise the electrons can move along the field lines fast enough to shield
Electric field screening
Screening is the damping of electric fields caused by the presence of mobile charge carriers. It is an important part of the behavior of charge-carrying fluids, such as ionized gases and conduction electrons in semiconductors and metals....
the oscillations in potential, in which case an electrostatic ion cyclotron wave
Electrostatic ion cyclotron wave
An electrostatic ion cyclotron wave is a longitudinal oscillation of the ions in a magnetized plasma, propagating nearly perpendicular to the magnetic field...
results. The frequency of oscillation is
,where Ωi is the ion cyclotron frequency, Ωe is the electron cyclotron frequency and ωpi is the ion plasma frequency. This is the lower hybrid frequency, so called because it is a "hybrid", or mixture, of two frequencies. There are also an upper hybrid frequency and upper hybrid oscillation
Upper hybrid oscillation
An upper hybrid oscillation is a mode of oscillation of a magnetized plasma. It consists of a longitudinal motion of the electrons perpendicular to the magnetic field with the dispersion relation...
. The lower hybrid oscillation is unusual in that the ion and electron masses play an equally important role. This mode is relatively unimportant in practice because the necessary precise orientation relative to the magnetic field is seldom achieved. Exceptions are the use of lower hybrid waves to heat fusion
Fusion power
Fusion power is the power generated by nuclear fusion processes. In fusion reactions two light atomic nuclei fuse together to form a heavier nucleus . In doing so they release a comparatively large amount of energy arising from the binding energy due to the strong nuclear force which is manifested...
plasmas and the lower hybrid drift instability, which was thought to be an important determinant of transport in the Field-Reversed Configuration
Field-Reversed Configuration
A Field-Reversed Configuration is a device developed for magnetic fusion energy research that confines a plasma on closed magnetic field lines without a central penetration....
(but was not found experimentally).
See also
- Electrostatic ion cyclotron waveElectrostatic ion cyclotron waveAn electrostatic ion cyclotron wave is a longitudinal oscillation of the ions in a magnetized plasma, propagating nearly perpendicular to the magnetic field...
- Waves in plasmasWaves in plasmasWaves in plasmas are an interconnected set of particles and fields which propagates in a periodically repeating fashion. A plasma is a quasineutral, electrically conductive fluid. In the simplest case, it is composed of electrons and a single species of positive ions, but it may also contain...
- Ion acoustic waveIon acoustic waveAn ion acoustic wave is one type of longitudinal oscillation of the ions and electrons in a plasma, much like acoustic waves traveling in neutral gas. However, because the waves propagate through positively charged ions, ion acoustic waves can interact with their electromagnetic fields, as well as...
- Upper hybrid oscillationUpper hybrid oscillationAn upper hybrid oscillation is a mode of oscillation of a magnetized plasma. It consists of a longitudinal motion of the electrons perpendicular to the magnetic field with the dispersion relation...