Profiles of electron temperature and <I>B</I><sub>z</sub> along Earth's magnetotail

Abstract

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 XB ∈ [−30 RE, −20 RE], XC ∈ [−20 RE, −15 RE], and XD ~ −10 RE. We obtain profiles of the average electron temperature ⟨Te⟩ and the average magnetic field ⟨Bz⟩ along the tail. Electron temperature and ⟨Bz⟩ increase towards the Earth with almost the same rates (i.e., ratio ⟨Te⟩/⟨Bz⟩ ≈ 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 Te and Bz distributions on geomagnetic activity. The ratio ⟨Te ⟩/⟨Bz⟩ depends on geomagnetic activity only slightly. Additionally we demonstrate that anisotropy of the electron temperature ⟨T∥/T⊥⟩ ≈ 1.1 is almost constant along the tail for X ∈ [−30 RE, −10 RE].

Current sheet flapping in the near-Earth magnetotail: peculiarities of propagation and parallel currents

“…The main our findings can be summarised as follows: -Despite the relatively strong gradients ∂B z /∂x in the background CS in the near-Earth tail (Kan and Baumjohann, 1990;Artemyev et al, 2013;Rong et al, 2014), this gradient is significantly reduced in flapping CSs (∼ 0.2 nT/R E ). Moreover, a weak-gradient dB z /dx found in the flapping near-Earth magnetotail questions models of double-gradient and ballooning/interchange instabilities as main candidates for excitation of flapping waves Pritchett and Coroniti, 2010).…”

“…In the near-Earth magnetotail we expect to observe relatively strong gradients of B z along the x axis (Kan and Baumjohann, 1990;Wang et al, 2009;Artemyev et al, 2013). The gradients ∂B z /∂x, ∂B z /∂y and ∂B z /∂r l , where r l = (r · l), of magnetic field in the current sheet centre is calculated for each crossing by means of the curlometer technique (Runov et al, 2005a) and presented in Fig.…”

Average thermodynamic and spectral properties of plasma in and around dipolarizing flux bundles

“…Statistical studies revealed that ion temperature in the central plasma sheet (where nT, the GSM coordinate system was used) does not depend on magnetic activity, characterized by the auroral index ( A E ) [ Baumjohann et al , ]. A radial profile of the average electron temperature and 〈 T e 〉 to 〈 B z 〉 ratio, where B z (GSM) is the northward magnetic field component, were studied using Time History of Events and Macroscale Interactions during Substorms (THEMIS) data [ Artemyev et al , ]. It was found that 〈 T e 〉 and 〈 B z 〉 increase earthward with approximately same rate, and the 〈 T e 〉/〈 B z 〉 is approximately constant along the tail, regardless of the geomagnetic activity.…”

Formation of a quasi-one-dimensional current sheet in the laboratory experiment and in the Earth’s magnetotail

“…It seems reasonable to compare this region with the near Earth region of the magnetotail, , where the transition between the strong dipole field and the field with stretched lines, typical of CS structures, takes place. The fivefold decrease in the magnetic field in the magnetotail is observed over the interval from to (see statistical results in [22,25,85]). Therefore, the laboratory experiment simu lates almost the entire near Earth region of the mag netotail, because, at , the CS configuration is already unstable and the magnetic field is turbulent.…”

“…Therefore, the simultaneous investigation of the longitudinal and transverse CS structures is an extremely complicated task for spacecraft experiments. The modern multisat ellite missions allow one to obtain detailed informa tion on either the transverse (see [18][19][20][21]) or longitu dinal [22] CS structure. Only in the specific case of a particular spacecraft location and special relation between the longitudinal and transverse scales, it becomes possible to simultaneously study the distribu tion of currents and magnetic fields along and across the sheet [23].…”