New expression for collisionless magnetic reconnection rate

Abstract

For 2D, symmetric, anti-parallel, collisionless magnetic reconnection, new expressions for the reconnection rate in the electron diffusion region are introduced. It is shown that these expressions can be derived in just a few simple steps from a physically intuitive starting point; the derivations are given in their entirety, and the validity of each step is confirmed. The predictions of these expressions are compared to the results of several long-duration, open-boundary particle-in-cell reconnection simulations to demonstrate excellent agreement. V C 2015 AIP Publishing LLC.

Inner and outer electron diffusion region of antiparallel collisionless reconnection: Density dependence

“…According to common scaling analyses based on conservation laws, 14,15 the width scales well with d e and the EDR width-to-length ratio is identical to the electron reconnection rate e e up to a coefficient. 52 A recent scaling analysis 59 and L e $ 3n 1=4 b d e , respectively, giving the inner EDR aspect ratio L e =l e $ n 1=8 b , which is clearly at odds with our Fig. 6(b).…”

“…Typically, electron velocity there is $1=3 of its peak exhaust value. 14,52 • Green lines mark points where jV ðeÞ x j peaks in the outflow direction (approximately corresponds to the overshoot of jE z þ ½V ðeÞ Â B z j). We define the distance between those points as 2D e .…”

“…For each run, we select an interval matching the following criteria: (1) D e growth saturates implying that L e and D e are also steady, (2) there are no large-scale plasmoids which introduce large asymmetry in reconnection outflows, and (3) reconnection outflows are not affected by periodic BCs. We need to point out that due to limited computational resources we do not consider very long reconnection evolution (hundreds of X À1 ci ), which is perturbed by regular plasmoid formation 52,53 leading to fluctuations in reconnection rate and EDR parameters. The question as to how plasmoid formation impacts reconnection rate and heating globally has long been discussed in literature 19,28,37,53,58 but seems to be open at present.…”

“…3 for each run) at quasisteady stage for the detailed EDR study. Long time simulations with duration exceeding $300X À1 ci in fully open systems 52,53 display periodic formation of magnetic islands near the diffusion region, leading to large variations in EDR scales. Comparing Fig.…”

Electron Inflow Velocities and Reconnection Rates at Earth's Magnetopause and Magnetosheath

“…Pritchard et al (2019) noted the occurrence of converging electron flows in a region of strong out‐of‐plane current and interpreted them as electron inflow velocities to the EDR. Inflow velocities are important because when scaled to the electron Alfvén speed (v Ae ), they provide the reconnection rate (R) (Karimabadi et al, 2013; Klimas, 2015). The use of v Ae instead of v Ai in this context is warranted by the fact that near the EDR the magnetic field is advected by the electrons (Cassak et al, 2005; Tsiklauri, 2008).…”