Electromagnetic ELF wave intensification associated with fast earthward flows in mid-tail plasma sheet
-
Published:2012-03-05
Issue:3
Volume:30
Page:467-488
-
ISSN:1432-0576
-
Container-title:Annales Geophysicae
-
language:en
-
Short-container-title:Ann. Geophys.
Author:
Liang J.,Ni B.,Cully C. M.,Donovan E. F.,Thorne R. M.,Angelopoulos V.
Abstract
Abstract. In this study we perform a statistical survey of the extremely-low-frequency wave activities associated with fast earthward flows in the mid-tail central plasma sheet (CPS) based upon THEMIS measurements. We reveal clear trends of increasing wave intensity with flow enhancement over a broad frequency range, from below fLH (lower-hybrid resonant frequency) to above fce (electron gyrofrequency). We mainly investigate two electromagnetic wave modes, the lower-hybrid waves at frequencies below fLH, and the whistler-mode waves in the frequency range fLH < f < fce. The waves at f < fLH dramatically intensify during fast flow intervals, and tend to contain strong electromagnetic components in the high-plasma-beta CPS region, consistent with the theoretical expectation of the lower-hybrid drift instability in the center region of the tail current sheet. ULF waves with very large perpendicular wavenumber might be Doppler-shifted by the flows and also partly contribute to the observed waves in the lower-hybrid frequency range. The fast flow activity substantially increases the occurrence rate and peak magnitude of the electromagnetic waves in the frequency range fLH < f < fce, though they still tend to be short-lived and sporadic in occurrence. We also find that the electron pitch-angle distribution in the mid-tail CPS undergoes a variation from negative anisotropy (perpendicular temperature smaller than parallel temperature) during weak flow intervals, to more or less positive anisotropy (perpendicular temperature larger than parallel temperature) during fast flow intervals. The flow-related electromagnetic whistler-mode wave tends to occur in conjunction with positive electron anisotropy.
Publisher
Copernicus GmbH
Subject
Space and Planetary Science,Earth and Planetary Sciences (miscellaneous),Atmospheric Science,Geology,Astronomy and Astrophysics
Reference62 articles.
1. Andersson, L., Ergun, R. E., Tao, J., Roux, A., Le Contel O., Angelopoulos, Bonnell, J., McFadden, J. P., Larson, D. E., Eriksson, S., Johansson, T., Cully, C. M., Newman, D. L., Goldman, M. V., Glassmeier, K.-H. , and Baumjohann, W.: New features of electron phase space holes observed by the THEMIS mission, Phys. Rev. Lett., 102, 225004, https://doi.org/10.1103/PhysRevLett.102.225004, 2009. 2. Angelopoulos, V.: The THEMIS Mission, Space Sci. Rev., 141, 5–34, https://doi.org/10.1007/s11214-008-9336-1, 2008. 3. Angelopoulos, V., Baumjohann, W., Kennel, C. F., Coroniti, F. V., Kivelson, M. G., Pellat, R., Walker, R. J., Lühr, H., and Paschmann, G.: Bursty bulk flows in the inner central plasma sheet, J. Geophys. Res., 97, 4027–4039, 1992. 4. Angelopoulos, V., Kennel, C. F., Coroniti, F. V., Pellat, R., Kivelson, M. G., Walker, R. J., Russell, C. T., Baumjohann, W., Feldman, W. C., and Gosling, J. T.: Statistical characteristics of bursty bulk flow events, J. Geophys. Res., 99, 21257–21280, 1994. 5. Angelopoulos, V., Mozer, F. S., Lin, R. P., Mukai, T., Tsuruda, K., Lepping, R., and Baumjohann, W.: Comment on "Geotail survey of ion flow in the plasma sheet: Observations between 10 and 50 RE" by W. R. Paterson et al., J. Geophys. Res., 104, 17521, 1999.
Cited by
12 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献
|
|