Effective Resistivity in Collisionless Magnetic Reconnection

Abstract

An effective resistivity relevant to collisionless magnetic reconnection (MR) in plasma is presented. It is based on the argument that pitch angle scattering of electrons in the small electron diffusion region around the X line can lead to an effective, resistivity in collisionless plasma. The effective resistivity so obtained is in the form of a power law of the local plasma and magnetic field parameters. Its validity is confirmed by direct collisionless particle-in-cell (PIC) simulation. The result agrees very well with the resistivity (obtained from available data) of a large number of environments susceptible to MR: from the intergalactic and interstellar to solar and terrestrial to laboratory fusion plasmas. The scaling law can readily be incorporated into existing collisional magnetohydrodynamic simulation codes to investigate collisionless MR, as well as serve as a guide to ab initio theoretical investigations of the collisionless MR process.

Effects of Cross‐Sheet Density and Temperature Inhomogeneities on Magnetotail Reconnection

“…There are other effects related to density and temperature that can also control the reconnection and thus the energy conversion efficiency, for example, the temperature decrease and density increase during current sheet thinning before reconnection (e.g., Artemyev et al, 2016;Xu et al, 2018) and the electron inertia/collisionless resistivity during reconnection (e.g., Hesse et al, 1999;Ma et al, 2018). Background density drastically modifies the reconnection rate (i.e., the magnitude of the reconnection electric field); low background density leads to faster reconnection which has a stronger reconnection electric field to accelerate and heat particles.…”

“…Background density drastically modifies the reconnection rate (i.e., the magnitude of the reconnection electric field); low background density leads to faster reconnection which has a stronger reconnection electric field to accelerate and heat particles. There are other effects related to density and temperature that can also control the reconnection and thus the energy conversion efficiency, for example, the temperature decrease and density increase during current sheet thinning before reconnection (e.g., Artemyev et al, 2016;Xu et al, 2018) and the electron inertia/collisionless resistivity during reconnection (e.g., Hesse et al, 1999;Ma et al, 2018). 2.…”

Instabilities in a current sheet with plasma jet

“…In macroscopic current sheets, this mechanism is either collision-induced resistivity, or some kind of effective resistivity caused by microscopic wave-particle interactions (e.g. Büchner & Elkina 2006;Ma et al 2018). Hence, the triggering problem of reconnection at MHD scales is essentially the stability problem of the resistive current sheet.…”

“…Büchner & Elkina 2006; Ma et al. 2018). Hence, the triggering problem of reconnection at MHD scales is essentially the stability problem of the resistive current sheet.…”

Chaos-induced resistivity in different magnetic configurations

“…The early concept of magnetic reconnection was proposed by Giovanelli in 1946 to explain energy release in solar flares (Giovanelli 1946). Nowadays it has been extensively believed that the magnetic reconnection is one of the most effective processes of magnetic energy releasing in various eruptive phenomena (Ma et al 2018;Lu et al 2018), such as terrestrial aurora (Dungey 1961;McPherron 1979), solar flares (Parker 1957), γ-ray bursts (Lyutikov 2006) and the instability in fusion devices (Furth et al 1963). The magnetic reconnection process reconfigures the magnetic field topology and converts the magnetic energy into the kinetic energy of the plasma particles via the heating or acceleration (Dungey 1953).…”