• Received : 2015.10.01
  • Accepted : 2016.01.03
  • Published : 2016.02.29


Magnetic decreases are often observed in various regions of interplanetary space. Many studies are devoted to reveal the physical nature and generation mechanism of the magnetic decreases, but still we do not fully understand magnetic decreases. In this study, we investigate the structure of a magnetic decrease observed in a corotating interaction region using multi-spacecraft measurements. We use three spacecraft, ACE, Cluster, and Wind, which were widely separated in the x- and y-directions in the geocentric solar ecliptic (GSE) coordinates. The boundaries of the magnetic decrease are the same at the three locations and can be identified as tangential discontinuities. A notable feature is that the magnetic decrease has very large dimension, ≳ RE, along the boundary, which is much larger than the size, ~ 6 RE, along the normal direction. This suggests that the magnetic decrease has a shape of a long, thin rod or a wide slab.


Solar wind plasma;Interplanetary magnetic fields;Discontinuities;Corotating streams


  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
  2. Baumgärtel, K. 1999, Soliton Approach to Magnetic Holes, J. Geophys. Res., 104, 28295
  3. Burlaga, L. F., & Lemaire, J. F. 1978, Interplanetary Magnetic Holes: Theory, J. Geophys. Res., 83, 5157
  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
  5. Lepping, R. P., Acuña, M. H., Burlaga, L. F., et al. 1995, The WIND Magnetic Field Investigation, Space Sci. Rev., 71, 207
  6. McComas, D. J., Bame, S. J., Barker, P., et al. 1998, Solar Wind Electron Proton AlphaMonitor (SWEPAM) for the Advanced Composition Explorer, Space Sci. Rev., 86, 563
  7. 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
  8. Smith, C. W., Acuña, M. H., Burlaga, L. F., et al. 1998, The ACE Magnetic Field Experiment, Space Sci. Rev., 86, 613
  9. Sonnerup, B. U. Ö., & Cahill, Jr. L. J. 1967, Magnetopause Structure and Attitude from Explorer 12 Observations, J. of Geophys. Res., 72, 171
  10. Tsubouchi, K. 2009, Alfvén Wave Evolution within Corotating Interaction Regions Associated with the Formation of Magnetic Holes/Decreases, J. Geophys. Res., 114, A02101
  11. Tsurutani, B. T., & Ho, C. M. 1999, A Review of Discontinuities and Alfvén Waves in Interplanetary Space: Ulysses Results, Rev. Geophys., 37, 517
  12. 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
  13. 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
  14. Tsurutani, B. T., Lakhina, G. S., Pickett, J. S., et al. 2005a, Nonlinear Alfvén waves, Discontinuities, Proton Perpendicular Acceleration, and Magnetic Holes/Decreases in Interplanetary Space and the Magnetosphere: Intermediate Shocks?, Nonlin. Proc. Geophys., 12, 321
  15. Tsurutani, B. T., Guarnieri, F. L., Lakhina, G. S., & Hada, T. 2005b, Rapid Evolution of Magnetic Decreases (MDs) and Discontinuities in the Solar Wind: ACE and CLUSTER, Geophys. Res. Lett., 32, L10103
  16. Tsurutani, B. T., Guarneiri, F. L., Echer, E., Lakhina, G. S., & Verkhoglyadova, O. P. 2009, Magnetic Decrease (MD) Formation from <1 AU to ∼5 AU: Corotating Interaction Region Reverse Shocks, J. Geophys. Res., 114, A08105
  17. Tsurutani, B. T., Lakhina, G. S., Verkhoglyadova, O. P., Echer, E., & Guarnieri, F. L. 2010, Magnetic Decreases (MDs) and Mirror Modes: Two Different Plasma β Changing Mechanisms, Nonlin. Proc. Geophys., 17, 467
  18. Turner, J. M., Burlaga, L. F., Ness, N. F., & Lemaire, J. F. 1977, Magnetic Holes in the Solar Wind, J. Geophys. Res., 82, 1921
  19. 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, 23,371
  20. 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


Grant : 지구 뱃머리 충격파의 상류에서 플라즈마 교란의 비선형 발달에 대한 연구