Kinetic theory of geomagnetic pulsations 1. Internal excitations by energetic particles

Journal Article · Fri Feb 01 00:00:00 EST 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/90JA02346· OSTI ID:5222976

Chen, Liu ^[1]; Hasegawa, Akira ^[2]

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1. Princeton Univ., NJ (USA)
2. AT and T Bell Labs., Murray Hill, NJ (USA)

Motivated by recent satellite observations. the authors have carried out a comprehensive theoretical analysis on the generation of hydromagnetic Alfven waves in a realistic magnetospheric plasma environment consisting of a core ({approximately}100 eV) component and an energetic ({approximately}10 keV) component. The theoretical formulation employs the gyrokinetic equations and, thus, retains anisotropy, finite Larmor radii, magnetic trapping, and wave-particle interactions in addition to nonuniform plasma equilibria. A set of coupled equations for transverse and compressional magnetic perturbations is derived and analyzed for its stabilities assuming equilibrium distribution functions which are interchange stable. The findings are as follows: (1) compressional and transverse shear Alfven oscillations are generally coupled in realistic plasmas; (2) in the decoupled limit, for the compressional wave branch, one recovers the drift mirror instability due to the Landau resonances and {tau}{triple bond} 1 + 4{pi}({partial derivative}P{sub {perpendicular}}/B{partial derivative}B) < 0; here, P{sub {perpendicular}}=P{sub {perpendicular}}({psi},B) is the perpendicular pressure and {psi} is the magnetic flux function; (3) for the decoupled transverse shear Alfven branch, one obtains the drift Alfven ballooning instability due to the Landau resonances and free energy of the pressure gradient for {tau} > 0; (4) for both branches, the most unstable modes have antisymmetric structures and propagate in the diamagnetic drift direction of the energetic ions; and (5) finite coupling can be shown to further enhance the drift Alfven ballooning instabilities. Thus they conclude that for {tau}{ge}0, the coupled drift Alfven ballooning mirror instability constitutes an important internal generating mechanism of geomagnetic pulsations. The various predicted features of this instability are consistent with satellite observations.

• DOE Contract Number: AC02-76CH03073
• OSTI ID: 5222976
• Journal Information: Journal of Geophysical Research; (United States), Vol. 96:A2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
EARTH MAGNETOSPHERE
ALFVEN WAVES
ANISOTROPY
BALLOONING INSTABILITY
DISTRIBUTION FUNCTIONS
DRIFT INSTABILITY
ION DRIFT
KINETIC EQUATIONS
MATHEMATICAL MODELS
MHD EQUILIBRIUM
PRESSURE GRADIENTS
EARTH ATMOSPHERE
EQUATIONS
EQUILIBRIUM
FUNCTIONS
HYDROMAGNETIC WAVES
INSTABILITY
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PLASMA MICROINSTABILITIES
640201* - Atmospheric Physics- Auroral
Ionospheric
&amp; Magetospheric Phenomena