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Timescales for the penetration of IMF B y into the Earth's magnetotail
Author(s) -
Browett S. D.,
Fear R. C.,
Grocott A.,
Milan S. E.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023198
Subject(s) - solar wind , interplanetary magnetic field , physics , plasma sheet , astrophysics , magnetosphere , magnetic field , geophysics , quantum mechanics
Previous studies have shown that there is a correlation between the B y component of the interplanetary magnetic field (IMF) and the B y component observed in the magnetotail lobe and in the plasma sheet. However, studies of the effect of IMF B y on several magnetospheric processes have indicated that the B y component in the tail should depend more strongly on the recent history of the IMF B y rather than on the simultaneous measurements of the IMF. Estimates of this timescale vary from ∼25 min to ∼4 h. We present a statistical study of how promptly the IMF B y component is transferred into the neutral sheet, based on Cluster observations of the neutral sheet from 2001 to 2008, and solar wind data from the OMNI database. Five thousand nine hundred eighty‐two neutral sheet crossings during this interval were identified, and starting with the correlation between instantaneous measurements of the IMF and the magnetotail (recently reported by Cao et al. (2014)), we vary the time delay applied to the solar wind data. Our results suggest a bimodal distribution with peaks at ∼1.5 and ∼3 h. The relative strength of each peak appears to be well controlled by the sign of the IMF B z component with peaks being observed at 1 h of lag time for southward IMF and up to 5 h for northward IMF conditions, and the magnitude of the solar wind velocity with peaks at 2 h of lag time for fast solar wind and 4 h for slow solar wind conditions.