Kinetic simulations of magnetic reconnection in presence of a background O⁺population

Abstract

[1] Particle-in-Cell simulations of magnetic reconnection with an H + current sheet and a mixed background plasma of H + and O + ions are completed using physical mass ratios. Four main results are shown. First, the O + presence slightly decreases the reconnection rate and the magnetic reconnection evolution depends mainly on the lighter H + ion species in the presented simulations. Second, the Hall magnetic field is characterized by a two-scale structure in presence of O + ions: it reaches sharp peak values in a small area in proximity of the neutral line, and then decreases slowly over a large region. Third, the two background species initially separate in the outflow region because H + and O + ions are accelerated by different mechanisms occurring on different timescales and with different strengths. Fourth, the effect of a guide field on the O + dynamics is studied: the O + presence does not change the reconnected flux and all the characteristic features of guide field magnetic reconnection are still present. Moreover, the guide field introduces an O + circulation pattern between separatrices that enhances high O + density areas and depletes low O + density regions in proximity of the reconnection fronts. The importance and the validity of these results are finally discussed.

Current Sheets in the Earth Magnetotail: Plasma and Magnetic Field Structure with Cluster Project Observations

“…The increase of O + results in the increase of the CS thickness in agreement with modeling (Zelenyi et al 2006). This effect confirms kinetic nature of CS and can play the important role in CS stability (Shay and Swisdak 2004;Markidis et al 2011;Karimabadi et al 2011;Liu et al 2014).…”

Magnetic reconnection and modification of the Hall physics due to cold ions at the magnetopause

“…In separatrix regions, separating the inflow and outflow plasmas and extending away from the X line, the situation is similar. This is somewhat similar to the larger scale introduced by heavy ions [Shay and Swisdak, 2004;Markidis et al, 2011]. At high magnetopause latitudes, where cold ions are not so common, observations by the four Cluster satellites show that this electric field is balanced mainly by the Hall term (j × B)/(en), i.e., by E × B drifting electrons [André et al, 2004;Retinò et al, 2006;Khotyaintsev et al, 2006].…”

Čerenkov Emission of Quasiparallel Whistlers by Fast Electron Phase-Space Holes during Magnetic Reconnection

“…The bipolar fields associated with the Čerenkov-emitting holes near the separatrix have been verified both by observation [18] and by PIC simulations [18,[20][21][22]. Our simulations of magnetotail reconnection show that electrons are trapped by the potential created by an inhomogeneous two-stream electron instability, as will be discussed in a future publication.…”

“…The implicit 2D particle-in-cell reconnection simulations used here are based on a code which has been published and vetted extensively [20][21][22]25]. The parameters employed in these simulations are appropriate to Earth's magnetotail and identical to those employed in our published simulations [26] and confirmed by others [27].…”