Profiles of electron temperature and B_z along Earth's magnetotail

Abstract

We study the electron temperature distribution and the structure of the current sheet along the magnetotail using simultaneous observations from THEMIS spacecraft. We perform a statistical study of 40 crossings of the current sheet when the three spacecraft THB, THC, and THD were distributed along the tail in the vicinity of midnight with coordinates X_B \in [-30 R_E, -20 R_E], X_C \in [-20 R_E, -15 R_E], and X_D ~ -10 R_E. We obtain profiles of the average electron temperature \mlab T_e\mrab and the average magnetic field \mlab B_z\mrab along the tail. Electron temperature and \mlab B_z\mrab increase towards the Earth with almost the same rates (i.e., ratio \mlab T_e\mrab/\mlab B_z\mrab ≈ 2 keV/7 nT is approximately constant along the tail). We also use statistics of 102 crossings of the current sheet from THB and THC to estimate dependence of T_e and B_z distributions on geomagnetic activity. The ratio \mlab T_e \mrab/\mlab B_z\mrab depends on geomagnetic activity only slightly. Additionally we demonstrate that anisotropy of the electron temperature \mlab T_∥/T_⊥\mrab ≈ 1.1 is almost constant along the tail for X \in [-30 R_E, -10 R_E].