A possible mechanism of the enhancement and maintenance of the shear magnetic field component in the current sheet of th
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E PLASMA
A Possible Mechanism of the Enhancement and Maintenance of the Shear Magnetic Field Component in the Current Sheet of the Earth’s Magnetotail1 E. E. Grigorenkoa, H. V. Malovaa, b, A. Yu. Malykhinc, and L. M. Zelenyia a
Space Research Institute, Russian Academy of Sciences, Profsoyuznaya ul. 84/32, Moscow, 117997 Russia b Skobeltsyn Research Institute of Nuclear Physics, Moscow State University, Moscow, 119991 Russia c Moscow Institute of Physics and Technology, Institutskii per. 9, Dolgoprudnyi, Moscow oblast, 141700 Russia email: [email protected], [email protected], [email protected], [email protected] Received May 20, 2014
Abstract—The influence of the shear magnetic field component, which is directed along the electric current in the current sheet (CS) of the Earth’s magnetotail and enhanced near the neutral plane of the CS, on the nonadiabatic dynamics of ions interacting with the CS is studied. The results of simulation of the nonadia batic ion motion in the prescribed magnetic configuration similar to that observed in the magnetotail CS by the CLUSTER spacecraft demonstrated that, in the presence of some initial shear magnetic field, the north– south asymmetry in the ion reflection/refraction in the CS is observed. This asymmetry leads to the formation of an additional current system formed by the oppositely directed electric currents flowing in the northern and southern parts of the plasma sheet in the planes tangential to the CS plane and in the direction perpen dicular to the direction of the electric current in the CS. The formation of this current system perhaps is responsible for the enhancement and further maintenance of the shear magnetic field near the neutral plane of the CS. The CS structure and ion dynamics observed in 17 intervals of the CS crossings by the CLUSTER spacecraft is analyzed. In these intervals, the shear magnetic field was increased near the neutral plane of the CS, so that the bellshaped spatial distribution of this field across the CS plane was observed. The results of the present analysis confirm the suggested scenario of the enhancement of the shear magnetic field near the neutral plane of the CS due to the peculiarities of the nonadiabatic ion dynamics. DOI: 10.1134/S1063780X1501002X 1
1. INTRODUCTION
the dusk. The simplest CS geometry suggests that the sheet represents the planar horizontal layer oriented in the (XY)GSM plane and has a finite thickness. The elec tric current in the sheet is directed along the Y and flows from the dawn flank of the magnetotail to the dusk flank (Fig. 1). The CS is embedded into the thicker plasma sheet (PS). In the northern part of the PS, the magnetic field lines are directed along +X (i.e., to the Earth), while in its southern part, the magnetic field lines are directed from the Earth (i.e., along –X). The reverse of sign of the X component of the mag netic field takes place in the neutral plane of the CS. In this simplest magnetic configuration, the maximum of the electric current density is located in th
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