Kinetic theory of geomagnetic pulsations: I. Internal excitations by energetic particles

Technical Report · Tue May 01 00:00:00 EDT 1990

DOI:https://doi.org/10.2172/7163461· OSTI ID:7163461

Chen, Liu ^[1]; Hasegawa, Akira ^[2]

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1. Princeton Univ., NJ (USA). Plasma Physics Lab. Princeton Univ., NJ (USA). Dept. of Astrophysical Sciences
2. AT and T Bell Labs., Murray Hill, NJ (USA)

Motivated by recent satellite observations, we have carried out a comprehensive theoretical analysis on the generation of hydromagnetic Alfven waves in a realistic magnetospheric plasma environment consisting of a core and an energetic components. Our theoretical formulation employs the gyrokinetic equations and, thus, retains nonuniform plasma equilibria, anisotropy, finite Larmor radii, magnetic trapping as well as wave-particle interactions. A set of coupled equations for transverse and compressional magnetic perturbations is derived and analyzed for its stabilities assuming interchange stable equilibrium distribution functions. Our findings are compressional and tranverse shear Alfven oscillations are generally coupled in realistic plasmas. In the decoupled limit, for the compressional wave branch, one recovers the drift-mirror instability due to the Landau resonances and {tau} {equivalent to} 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. 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. For both branches, the most unstable modes have antisymmetric structures and propagate in the diamagnetic drift direction of the energetic ions. Finite coupling can be shown to further enhance the drift Alfven ballooning instabilities. Thus, we 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 also found to be consistent with satellite observations.

• Research Organization: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 7163461
• Report Number(s): PPPL-2691; ON: DE90010280; TRN: 90-015642
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
EARTH MAGNETOSPHERE
PULSATIONS
GEOMAGNETIC FIELD
KINETIC EQUATIONS
ALFVEN WAVES
BALLOONING INSTABILITY
CHARGED PARTICLES
DISPERSION RELATIONS
DISTRIBUTION FUNCTIONS
SHEAR
EARTH ATMOSPHERE
EQUATIONS
FUNCTIONS
HYDROMAGNETIC WAVES
INSTABILITY
MAGNETIC FIELDS
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
640201* - Atmospheric Physics- Auroral
Ionospheric
&amp; Magetospheric Phenomena