A statistical study of unstable particle populations in the global ring current and their relation to the generation of high m ULF waves

A statistical study of unstable particle populations in the global ring current and their relation to the generation of high m ULF waves

The first statistical study of the unstable proton populations which contain "free energy" required to drive small-scale poloidal mode ULF waves in the magnetosphere between L-shell locations of 6 and 9 is presented. The data examined are all in the form of Ion Distribution Functions (IDFs...

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Bibliographic Details
Published in:Annales geophysicae (1988) Vol. 22; no. 12; pp. 4229 - 4241
Main Authors: BADDELEY, L. J, YEOMAN, T. K, WRIGHTL, D. M, TRATTNER, K. J, KELLET, B. J
Format: Journal Article
Language:English
Published: Katlenburg-Lindau European Geophysical Society 2004
Subjects:
Earth, ocean, space
Exact sciences and technology
External geophysics
Physics of the high neutral atmosphere
Physics of the ionosphere
Physics of the magnetosphere
Polar satellite
Plasma physics
L shell
poloidal mode
Electrostatic wave
Ion distribution
Statistical study
Space plasma physics (wave-particle interactions)
MHD wave
magnetosphere
Analysis method
Magnetospheric physics (Energetic particles, trapped; MHD waves and instabilities)
free energy
Ring current
Distribution function
MHD instability
trapped particles
protons
Relativistic particle
Particle wave interaction
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Summary:The first statistical study of the unstable proton populations which contain "free energy" required to drive small-scale poloidal mode ULF waves in the magnetosphere between L-shell locations of 6 and 9 is presented. The data examined are all in the form of Ion Distribution Functions (IDFs) covering a particle energy range of 0.025 keV to 328 keV, amassed over 2.5 years from the TIMAS and CAMMICE (MICS) instruments on-board the Polar spacecraft. Any free energy which is available to drive a resonant wave mode manifests itself as a positive gradient region in the IDF. A new analysis technique applied to the data, allows for the first time, the amount of free energy contained in each IDF to be quantified. The results show that IDFs are a common occurrence in the magnetosphere at these L-shells, although they are most common in the dawn/pre-noon sector. Lower energy (10-45 keV) protons are the most commonly observed unstable populations and also contain the largest amounts of free energy (> 10 super(10)J). Positive gradient regions at higher energies (> 100keV) are rarely observed and also contain greatly reduced free energies (< 10 super(9)J).
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ISSN:0992-7689
1432-0576
DOI:10.5194/angeo-22-4229-2004