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Solar wind‐driven variations of electron plasma sheet densities and temperatures beyond geostationary orbit during storm times
Author(s) -
Dubyagin S.,
Ganushki. Yu.,
Sillanpää I.,
Runov A.
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja022947
Subject(s) - solar wind , plasma sheet , physics , geomagnetic storm , electron density , substorm , atmospheric sciences , interplanetary magnetic field , magnetopause , local time , earth's magnetic field , geophysics , computational physics , plasma , magnetosphere , magnetic field , statistics , mathematics , quantum mechanics
The empirical models of the plasma sheet electron temperature and density on the nightside at distances between 6 and 11 R E are constructed based on Time History of Events and Macroscale Interactions During Substorms (THEMIS) particle measurements. The data set comprises ∼400 h of observations in the plasma sheet during geomagnetic storm periods. The equatorial distribution of the electron density reveals a strong earthward gradient and a moderate variation with magnetic local time symmetric with respect to the midnight meridian. The electron density dependence on the external driving is parameterized by the solar wind proton density averaged over 4 h and the southward component of interplanetary magnetic field (IMF B S ) averaged over 6 h. The interval of the IMF integration is much longer than a typical substorm growth phase, and it rather corresponds to the geomagnetic storm main phase duration. The solar wind proton density is the main controlling parameter, but the IMF B S becomes of almost the same importance in the near‐Earth region. The root‐mean‐square deviation between the observed and predicted plasma sheet density values is 0.23 cm −3 , and the correlation coefficient is 0.82. The equatorial distribution of the electron temperature has a maximum in the postmidnight to morning MLT sector, and it is highly asymmetric with respect to the local midnight. The electron temperature model is parameterized by solar wind velocity (averaged over 4 h), IMF B S (averaged over 45 min), and IMF B N (northward component of IMF, averaged over 2 h). The solar wind velocity is a major controlling parameter, and IMF B S and B N are comparable in importance. In contrast to the density model, the electron temperature shows higher correlation with the IMF B S averaged over ∼45 min (substorm growth phase time scale). The effect of B N manifests mostly in the outer part of the modeled region ( r > 8 R E ). The influence of the IMF B S is maximal in the midnight to postmidnight MLT sector. The correlation coefficient between the observed and predicted plasma sheet electron temperature values is 0.76, and the root‐mean‐square deviation is 2.6 keV. Both models reveal better performance in the dawn MLT sector.