Dynamical properties of self‐consistent magnetotail configurations

Abstract

Abstract. This study of the magnetotail employs a large-scale kinetic ion model specifically developed to consider the region's approach to equilibrium and its dynamics under the influence of an imposed electric field. Results from the self-consistent, two-dimensional model indicate that the magnetotail achieves equilibrium by maintaining a delicate balance between the influx of plasma from a mantle source and the accelerated loss of these particles resulting from nonadiabatic particle dynamics. The quasi-steady oscillations that result from instantaneous imbalances between sources and losses occur independent of solar wind variations. This variability occurs even for steady solar wind conditions and is caused by the rapid nonadiabatic energization of ions incident on the current sheet and their loss through the flanks of the magnetotail faster than they can be replenished. To determine the influence of external parameters on the dynamical state of the magnetotail, we performed a parameter search in which we varied the magnitude of the convection electric field and the influx of plasma mantle ions. This parameter search showed that the magnetotail configuration can adjust itself to compensate for the various combinations of solar wind parameters. As a rule, this self-adjustment occurs in the form of quasi-steady magnetotail states, where only the average characteristics of the configuration are steady but pronounced cyclic variations occur in the magnetotail topology. For cases in which the magnetotail is underpopulated, the current sheet is depleted via the flanks. In overpopulation cases a flaring of magnetotail field lines caused by the additional current in the neural sheet limits access of additional mantle particles to the region. The magnetotail system is flexible enough to self-consistently regulate its own population. However, the resulting configuration becomes dynamic and only a quasi-steady state is achieved.

Transient ion beamlet injections into spatially separated PSBL flux tubes observed by Cluster‐CIS

“…Temporal fluctuations of the location of the X line of the order of 3.5–5 min were simulated, resulting from the escape of accelerated current sheet ions via the magnetotail flanks. This time scale is comparable to the recurrence rate of the beamlets reported here, and it is thus possible that this mechanism is associated with the recurrent ion beamlet injections into the PSBL, although Peroomian et al [2000] did not show an ion escape into the PSBL.…”

“…Instead, here we show evidence that the ion beamlet injections were transient and recurrent. Later, Peroomian et al [2000] extended the simulation to include time variations. Temporal fluctuations of the location of the X line of the order of 3.5–5 min were simulated, resulting from the escape of accelerated current sheet ions via the magnetotail flanks.…”

Non-adiabatic Ion Acceleration in the Earth Magnetotail and Its Various Manifestations in the Plasma Sheet Boundary Layer

“…The earlier LSK simulations by were carried out without feedback between the particles and magnetic field. Peroomian et al (2000) and Peroomian and Zelenyi (2001) incorporated self-consistently the current carried by nonadiabatic ions into the 2D Birn-Zwingmann equilibrium magnetic field model (Birn et al 1975;Zwingmann 1983) and found that the tail evolved into a quasi-periodic state characterized by the motion of the X-line in the magnetotail. These studies did not investigate the formation of beamlets due to statistical limitations, but found multiple VDIS-like injections as a result of the quasi-periodic nature of their system.…”

A three‐dimensional kinetic‐fluid numerical code to study the equilibrium structure of the magnetotail: The role of electrons in the formation of the bifurcated current sheet

“…Other sources exist, as the low latitude boundary layer and the ionosphere. However, they are a significant source of ions for the plasma sheet mostly during northward or disturbed interplanetary magnetic field [ Ashour‐Abdalla et al , 1994; Peroomian et al , 2000]. The relatively cold ion distribution in the mantle magnetic field can be described as a shifted Maxwellian [ Ashour‐Abdalla et al , 1994; Malova et al , 2000b; Sitnov et al , 2000]: …”