Peculiarities of magnetic barrier formation for southward and northward directions of the IMF

Тип публикации: статья из журнала

Год издания: 2015

Идентификатор DOI: 10.1002/2015JA021250

Аннотация: The magnetic barrier is a region which is formed in the course of the solar wind flow around the Earth's magnetosphere and is characterized by depleted plasma and an enhanced magnitude of the magnetic field. There is a general point of view that the magnetic barrier can persist only for the northward interplanetary magnetic field (IMF), whereas it is practically absent if the IMF is southward directed. We studied the presence of the magnetic barrier for low-shear (predominantly northward IMF) and high-shear (predominantly southward IMF) magnetopause conditions and analyzed 74 events of low-latitude dayside magnetopause crossings by the Time History of Events and Macroscale Interactions during Substorms satellites. We used the superposed epoch analysis to study variations of magnetic field and plasma parameters near the magnetopause. Results of Phan et al. (1994) that the magnetic barrier is well pronounced for low-shear magnetopauses and practically absent for high-shear events have been confirmed by our analysis. However, 5 from 49 high-shear events show clear signatures of a magnetic barrier. Hence, we conclude that the magnetic barrier is formed in the same manner for all direction of IMF but for high-shear events it is destroyed by reconnection much faster than it accumulates. Ratio of the events with and without magnetic barrier signatures (5/44) is approximately equal to the ratio of characteristic times of disruption due to reconnection (1-2 min) and the formation of a magnetic barrier (10 min). The reduction of the magnetic field due to reconnection can be used to estimate reconnection rate which turns out to be rather high of the order of 0.3 in 19 from 31 cases.

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Издание

Журнал: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS

Выпуск журнала: Vol. 120, Is. 11

Номера страниц: 9471-9483

ISSN журнала: 21699380

Место издания: WASHINGTON

Издатель: AMER GEOPHYSICAL UNION

Авторы

  • Slivka K.Yu. (St Petersburg State Univ, Earth Phys Dept, St Petersburg 199034, Russia)
  • Semenov V.S. (St Petersburg State Univ, Earth Phys Dept, St Petersburg 199034, Russia)
  • Erkaev N.V. (Inst Computat Modelling SB RAS, Krasnoyarsk, Russia; Siberian Fed Univ, Dept Appl Mech, Polytech Inst, Krasnoyarsk, Russia)
  • Dmitrieva N.P. (St Petersburg State Univ, Earth Phys Dept, St Petersburg 199034, Russia)
  • Kubyshkin I.V. (St Petersburg State Univ, Earth Phys Dept, St Petersburg 199034, Russia)
  • Lammer H. (Austrian Acad Sci, Space Res Inst, A-8010 Graz, Austria)

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