Bounce-averaged Hamiltonian for charged particles in an axisymmetric but nondipolar model magnetosphere

Journal Article · Sat Apr 01 04:00:00 EST 1995 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/94JA02855· OSTI ID:166205

Schulz, M ^[1]; Chen, M W ^[2]

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1. Lockheed Alto Research Lab., CA (United States)
2. The Aerospace Corporation, El Segundo, CA (United States)

In order to facilitate bounce-averaged guiding center simulations of geomagnetically trapped particles, the authors express the kinetic energy of a particle with magnetic coordinates (L,{Phi}) as an analytic function of the first two adiabatic invariants (M, J) and the L value of the field line. The magnetic field model is axisymmetric, consisting of a dipolar B field plus a uniform southward magnetic field parallel to the dipole moment {mu}{sub E}. This model magnetosphere is surrounded by a circular equatorial neutral line whose radius b is an adjustable parameter. The L value of a field line is (by definition) inversely proportional to the flux enclosed by the corresponding magnetic shell of equatorial radius r{sub O}, and the L value at the neutral line (r{sub 0}=b) is denoted L{sup *}. The azimuthal coordinate {Phi} measures magnetic local time. This representation, which leads (except for a manageable small region of parameter space) to better than 1% accuracy in the specification of B{sub m} as a function of K and L, allows bounce-averaged guiding center simulations to be performed without actually tracing the bounce motions of individual particles. This formulation thus provides a computationally efficient method for tracing the bounce-averaged adiabatic motion (conserving all three invariants) and nonadiabatic transport (violating the third invariant while conserving the first two invariants) of geomagnetically trapped particles in the model magnetosphere. 18 refs., 5 figs., 2 tabs.

• OSTI ID: 166205
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A4 Vol. 100; ISSN 0148-0227; ISSN JGREA2
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
CHARGED PARTICLES
DYNAMICS
EARTH MAGNETOSPHERE
GUIDING-CENTER APPROXIMATION
HAMILTONIAN FUNCTION
TRAPPING