DOI QR코드

DOI QR Code

KINETIC PROPERTIES OF MAGNETIC DECREASES OBSERVED IN THE SOLAR WIND AT ~1 AU

LEE, ENSANG;PARKS, GEORDE K.

  • Received : 2016.02.26
  • Accepted : 2016.03.24
  • Published : 2016.04.30

Abstract

In this study, we investigate the kinetic properties of magnetic decreases observed in the solar wind at ~1 AU using the Cluster observations. We study two different magnetic decreases: one with a short observation duration of ~2.5 minutes and stable structure and the other with a longer observation duration of ~40 minutes and some fluctuations and substructures. Despite the contrast in durations and magnetic structures, the velocity space distributions of ions are similar in both events. The velocity space distribution becomes more anisotropic along the direction parallel to the magnetic field, which differs from observations obtained at high heliographic latitudes. On the other hand, electrons show different features from the ions. The core component of the electrons shows similar anisotropy to the ions, though the anisotropy is much weaker. However, while ions are heated in the magnetic decreases, the core electrons are slightly cooled, especially in the perpendicular direction. The halo component does not change much in the magnetic decreases from the ambient solar wind. The strahl component is observed only in one of the magnetic decreases. The results imply that the ions and electrons in the magnetic decreases can behave differently, which should be considered for the formation mechanism of the magnetic decreases.

Keywords

solar wind plasma;interplanetary magnetic fields;discontinuities

References

  1. Balogh, A., Carr, C. M., Acuña, M. H., et al. 2001, The Cluster Magnetic Field Investigation: Overview of In-Flight Performance and Initial Results, Ann. Geophys., 19, 1207 https://doi.org/10.5194/angeo-19-1207-2001
  2. Baumgärtel, K. 1999, Soliton Approach to Magnetic Holes, J. Geophys. Res., 104, 28295 https://doi.org/10.1029/1999JA900393
  3. Burlaga, L. F., & Lemaire, J. F. 1978, Interplanetary Magnetic Holes: Theory, J. Geophys. Res., 83, 5157 https://doi.org/10.1029/JA083iA11p05157
  4. Buti, B., Tsurutani, B. T., Neugebauer, M., & Goldstein, B. E. 2001, Generation Mechanism for Magnetic Holes in the Solar Wind, Geophys. Res. Lett., 28, 1355 https://doi.org/10.1029/2000GL012592
  5. Chisham, G., Schwartz, S. J., Burgess, D., Bale, S. D., Dunlop, M. W., & Russell, C. T. 2000, Multisatellite Observations of Large Magnetic Depressions in the Solar Wind, J. Geophys. Res., 105, 2325 https://doi.org/10.1029/1999JA900446
  6. Escoubet, C. P., Fehringer, M., & Goldstein, M. 2001, The Cluster Mission, Ann. Geophys., 19, 1197 https://doi.org/10.5194/angeo-19-1197-2001
  7. Johnstone, A. D., et al. 1997, PEACE: A Plasma Electron and Current Experiment, Space Sci. Rev., 79, 351 https://doi.org/10.1023/A:1004938001388
  8. Lee, E., & Parks, G. K. 2016, Structure of a Magnetic Decrease Observed in a Corotating Interaction Region, JKAS, 49, 19
  9. Neugebauer, M., Goldstein, B. E., Winterhalter, D., et al. 2001, Ion Distributions in Large Magnetic Holes in the Fast Solar Wind, J. Geophys. Res., 106, 5635 https://doi.org/10.1029/2000JA000331
  10. Tsurutani, B. T., Dasgupta, B., Galvan, C., et al. 2002a, Phase-Steepened Alfvén Waves, Proton Perpendicular Energization and Creation of Magnetic Holes and Magnetic Decreases: The Ponderomotive Force, Geophys. Res. Lett., 29, 2233
  11. Rème, H., Aoustin, C., Bosqued, J. M., et al. 2001, First Multispacecraft Ion Measurements in and near the Earth’s Magnetosphere with the Identical Cluster Ion Spectrometry (CIS) Experiment, Ann. Geophys., 19, 1303 https://doi.org/10.5194/angeo-19-1303-2001
  12. Tsubouchi, K. 2009, AlfvénWave Evolution within Corotating Interaction Regions Associated with the Formation of Magnetic Holes/Decreases, J. Geophys. Res., 114, A02101 https://doi.org/10.1029/2008JA013568
  13. Tsurutani, B. T., & Ho, C. M. 1999, A Review of Discontinuities and Alfvén Waves in Interplanetary Space: Ulysses Results, Rev. Geophys., 37, 517 https://doi.org/10.1029/1999RG900010
  14. Tsurutani, B. T., Galvan, C., Arballo, J. K., et al. 2002b, Relationship between Discontinuities, Magnetic Holes, Magnetic Decreases, and Nonlinear Alfvén Waves: Ulysses Observations over the Solar Poles, Geophys. Res. Lett., 29, 1528 https://doi.org/10.1029/2001GL013623
  15. Tsurutani, B. T., Lakhina, G. S., Pickett, J. S., et al. 2005, Nonlinear Alfvén Waves, Discontinuities, Proton Perpendicular Acceleration, and Magnetic Holes/Decreases in Interplanetary Space and the Magnetosphere: Intermediate Shocks?, Nonlin. Proc. Geophys., 12, 321 https://doi.org/10.5194/npg-12-321-2005
  16. Turner, J. M., Burlaga, L. F., Ness, N. F., & Lemaire, J. F. 1977, Magnetic Holes in the Solar Wind, J. Geophys. Res., 82, 1921 https://doi.org/10.1029/JA082i013p01921
  17. Winterhalter, D., Neugebauer, M., Goldstein, B. E., et al. 1994, Ulysses Field and Plasma Observations of Magnetic Holes in the Solar Wind and Their Relation to Mirror-Mode Structures, J. Geophys. Res., 99, 23371 https://doi.org/10.1029/94JA01977
  18. Winterhalter, D., Smith, E. J., Neugebauer, M., Goldstein, B. E., & Tsurutani, B. T. 2000, The Latitudinal Distribution of Solar Wind Magnetic Holes, Geophys. Res. Lett., 27, 1615 https://doi.org/10.1029/1999GL003717

Acknowledgement

Grant : BK21플러스

Supported by : 경희대학교