DOI QR코드

DOI QR Code

Magnetic Turbulence Associated with Magnetic Dipolarizations in the Near-Tail of the Earth's Magnetosphere: Test of Anisotropy

  • Lee, Ji-Hee (Department of Astronomy and Space Science, Chungbuk National University) ;
  • Lee, Dae-Young (Department of Astronomy and Space Science, Chungbuk National University) ;
  • Park, Mi-Young (Department of Astronomy and Space Science, Chungbuk National University) ;
  • Kim, Kyung-Chan (Department of Astronomy and Space Science, Chungbuk National University) ;
  • Kim, Hyun-Sook (Depart of Astronomy and Atmospheric Sciences, Kyungpook National University)
  • Received : 2011.04.18
  • Accepted : 2011.05.20
  • Published : 2011.06.15

Abstract

In this paper, the anisotropic nature of the magnetic turbulence associated with magnetic dipolarizations in the Earth's plasma sheet is examined. Specifically, we determine the power spectral indices for the perpendicular and parallel components of the fluctuating magnetic field with respect to the background magnetic field, and compare them in order to identify possible anisotropic features. For this study, we identify a total of 47 dipolarization events in February 2008 using the magnetic field data observed by the THEMIS A, D and E satellites when they are situated near the neutral sheet in the near-Earth tail. For the identified events, we estimate the spectral indices for the frequency range from 1.3 mHz to 42 mHz. The results show that the degree of anisotropy, as defined by the ratio of the spectral index of the perpendicular components to that of the parallel component, can range from ~0.2 to ~2.6, and there are more events associated with the ratio greater than unity (i.e., the perpendicular index being greater than the parallel index) than those which are anisotropic in the opposite sense. This implies that the dipolarization-associated turbulence of the magnetic field is often anisotropic, to some non-negligible degree. We then discuss how this result differs from what the theory of homogeneous, anisotropic, magnetohydrodynamic turbulence would predict.

Keywords

Acknowledgement

Supported by : Chungbuk National University

References

  1. Angelopoulos V, Mukai T, Kokubun S, Evidence for intermittency in Earth's plasma sheet and implications for self-organized criticality, PhPl, 6, 4161-4168 (1999). doi: 10.1063/1.873681
  2. Borovsky JE, Elphic RC, Funsten HO, Thomsen MF, The Earth's plasma sheet as a laboratory for flow turbulence in high-[beta] MHD, JPlPh, 57, 1-34 (1997). doi: 10.1017/S0022377896005259
  3. Borovsky, JE, Funsten HO, MHD turbulence in the Earth's plasma sheet: dynamics, dissipation, and driving, JGR, 108(A7), 1284 (2003). doi: 10.1029/2002JA009625
  4. Park MY, Lee DY, Ohtani S, Kim KC, Statistical characteristics and significance of low-frequency instability associated with magnetic dipolarizations in the near-Earth plasma sheet, JGR, 115, A11203 (2010). doi: 10.1029/2010JA015566
  5. Shiokawa K, Shinohara I, Mukai T, Hayakawa H, Cheng CZ, Magnetic field fluctuations during substorm-associated dipolarizations in the nightside plasma sheet around X = −10 RE, JGR, 110, A05212 (2005). doi: 10.1029/2004JA010378
  6. Voros Z, Baumjohann W, Nakamura R, Runov A, Volwerk M, Zhang TL, Balogh A, Wavelet analysis of magnetic turbulence in the Earth's plasma sheet, PhPl, 11, 1333-1338 (2004). doi: 10.1063/1.1667499
  7. Weygand J, Kivelson MG, Khurana KK, Schwarzl HK, Thompson SM, McPherron RL, Balogh A, Kistler LM, Goldstein ML, Borovsky J, Roberts DA, Plasma sheet turbulence observed by Cluster II, JGR, 110, A01205 (2005). doi: 10.1029/2004JA010581

Cited by

  1. Plasma Flows and Bubble Properties Associated with the Magnetic Dipolarization in Space Close to Geosynchronous Orbit vol.30, pp.2, 2013, https://doi.org/10.5140/JASS.2013.30.2.095