Magnetic turbulence and particle dynamics in the Earth’s magnetotail

Abstract

Abstract. The influence of magnetic turbulence in the nearEarth magnetotail on ion motion is investigated by numerical simulation. The magnetotail current sheet is modelled as a magnetic field reversal with a normal magnetic field component B n , plus a three-dimensional spectrum of magnetic fluctuations δB which represents the observed magnetic turbulence. The dawn-dusk electric field E y is also considered. A test particle simulation is performed using different values of B n and of the fluctuation level δB/B 0 . We show that when the magnetic fluctuations are taken into account, the particle dynamics is deeply affected, giving rise to an increase in the cross tail transport, ion heating, and current sheet thickness. For strong enough turbulence, the current splits in two layers, in agreement with recent Cluster observations.

Double peak structure and diamagnetic wings of the magnetotail current sheet

“…In comparison to our previous works, we note that in the present runs the ion temperature at injection is assumed to be 2 keV, while in Greco et al (2002); Zimbardo et al (2003) it was 0.3 keV. This implies that the current sheet thickness is increased (we have ρ 0 λ/5 rather than ρ 0 λ/12) and that the separation of the current density peaks is larger with respect to those reported by Greco et al (2002).…”

“…The magnetic field model used in the simulation is described in full detail in Veltri et al (1998);Greco et al (2002); Zimbardo et al (2003). For completeness, we recall here some of the main features: The considered magnetic field configuration consists of an unperturbed, sign reversing component, directed along the Earth-Sun axis, B 0x (z)=B 0x (z)e x ; an unperturbed, constant, normal component B n =B n e z ; and of three-dimensional stationary magnetic fluctuations δB(r) having a power law spectrum.…”

“…In this paper we extend the work of Greco et al (2002); Zimbardo et al (2003), by tailoring the simulation parameters to the Cluster observations during the magnetotail crossings which exhibited a bifurcated current sheet. We consider moderate turbulence levels, and we pay attention to the anisotropy of the injected ion distribution function, that is to the ratio =v th /v D between the thermal velocity v th and the drift velocity of ions along the average magnetic field v D .…”

“…They found that for fluctuation levels δB/B 0 >0.2 the current sheet has a double layer structure, with a current density minimum in the center of the neutral sheet. Recently, Greco et al (2002); Zimbardo et al (2003) considered the near-Earth magnetotail, where B n >0, and found that even in this case the magnetic fluctuations induce a double layer structure in the current sheet.…”

Effect of geomagnetic activity, solar wind and parameters of interplanetary magnetic field on regularities in intermittency of Pi2 geomagnetic pulsations

“…Например, турбулентная плазма солнечного ветра, флуктуации ММП и маг-нитосферная активность (магнитные бури и суббури) обладают свойствами перемежаемости Рязанцева, Застенкер, 2008;Zotov et al, 2008;Yordanova et al, 2009]. Кроме того, в широком спектре магнитогид-родинамических волн были выделены импульсные или всплесковые режимы геомагнитных пульсаций, относящиеся к классу перемежающихся процессов [Клайн и др., 2007;Куражковская, Клайн, 2009].…”