Convective and diffusive ULF wave driven radiation belt electron transport

被引:15
作者
Degeling, A. W. [1 ]
Rankin, R. [1 ]
Elkington, S. R. [2 ]
机构
[1] Univ Alberta, Dept Phys, Edmonton, AB T6G 2G7, Canada
[2] Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA
基金
美国国家科学基金会; 加拿大自然科学与工程研究理事会;
关键词
KELVIN-HELMHOLTZ INSTABILITY; FIELD LINE RESONANCES; RELATIVISTIC ELECTRONS; ALFVEN WAVES; ACCELERATION; DIPOLE;
D O I
10.1029/2011JA016896
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The process of magnetospheric radiation belt electron transport driven by ULF waves is studied using a 2-D ideal MHD model for ULF waves in the equatorial plane including day/night asymmetry and a magnetopause boundary, and a test kinetic model for equatorially mirroring electrons. We find that ULF wave disturbances originating along the magnetopause flanks in the afternoon sector can act to periodically inject phase space density from these regions into the magnetosphere. Closely spaced drift-resonant surfaces for electrons with a given magnetic moment in the presence of the ULF waves create a layer of stochastic dynamics for L-shells above 6.5-7 in the cases examined, extending to the magnetopause. The phase decorrelation time scale for the stochastic region is estimated by the relaxation time for the diffusion coefficient to reach a steady value. This is found to be of the order of 10-15 wave periods, which is commensurate with the typical duration of observed ULF wave packets in the magnetosphere. For L-shells earthward of the stochastic layer, transport is limited to isolated drift-resonant islands in the case of narrowband ULF waves. We examine the effect of increasing the bandwidth of the ULF wave driver by summing together wave components produced by a set of independent runs of the ULF wave model. The wave source spectrum is given a flat-top amplitude of variable width (adjusted for constant power) and random phase. We find that increasing bandwidth can significantly enhance convective transport earthward of the stochastic layer and extend the stochastic layer to lower L-shells.
引用
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页数:11
相关论文
共 25 条
[1]   Large-m waves generated by small-m field line resonances via the nonlinear Kelvin-Helmholtz instability [J].
Allan, W ;
Wright, AN .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 1997, 102 (A9) :19927-19933
[2]   ULF WAVES - THEIR RELATIONSHIP TO THE STRUCTURE OF THE EARTHS MAGNETOSPHERE [J].
ALLAN, W ;
POULTER, EM .
REPORTS ON PROGRESS IN PHYSICS, 1992, 55 (05) :533-598
[3]   DIPOLE FIELD MODEL FOR AXISYMMETRIC ALFVEN WAVES WITH FINITE IONOSPHERE CONDUCTIVITIES [J].
ALLAN, W ;
KNOX, FB .
PLANETARY AND SPACE SCIENCE, 1979, 27 (01) :79-85
[4]  
Braess D., 2001, FINITE ELEMENTS
[5]   The energization of relativistic electrons in the outer Van Allen radiation belt [J].
Chen, Yue ;
Reeves, Geoffrey D. ;
Friedel, Reiner H. W. .
NATURE PHYSICS, 2007, 3 (09) :614-617
[6]   The effect of ULF compressional modes and field line resonances on relativistic electron dynamics [J].
Degeling, A. W. ;
Rankin, R. ;
Kabin, K. ;
Marchand, R. ;
Mann, I. R. .
PLANETARY AND SPACE SCIENCE, 2007, 55 (06) :731-742
[7]   Modeling ULF waves in a compressed dipole magnetic field [J].
Degeling, A. W. ;
Rankin, R. ;
Kabin, K. ;
Rae, I. J. ;
Fenrich, F. R. .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2010, 115
[8]   Resonant drift echoes in electron phase space density produced by dayside Pc5 waves following a geomagnetic storm [J].
Degeling, A. W. ;
Rankin, R. .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2008, 113 (A10)
[9]   Drift resonant generation of peaked relativistic electron distributions by Pc 5 ULF waves [J].
Degeling, A. W. ;
Ozeke, L. G. ;
Rankin, R. ;
Mann, I. R. ;
Kabin, K. .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2008, 113 (A2)
[10]   Acceleration of relativistic electrons via drift-resonant interaction with toroidal-mode Pc5 ULF oscillations [J].
Elkington, SR ;
Hudson, MK ;
Chan, AA .
GEOPHYSICAL RESEARCH LETTERS, 1999, 26 (21) :3273-3276