Intense Energy Conversion Events at the Magnetopause Boundary Layer

Abstract

This paper investigates intense energy conversion events (IECEs) at the dayside magnetopause boundary layer (MBL) using high-resolution data from the Magnetospheric Multiscale (MMS) spacecraft. Most events were detected by MMS in a duration less than 0.5 s, corresponding to a thickness below one ion inertia length. About three-quarters of the events occurred in local reconnecting current sheets. Interestingly, there are more electron-only reconnections than standard reconnections. Most of the reconnection IECEs are within the exhaust of the primary reconnection and the Kelvin-Helmholtz vortices, suggesting that secondary reconnections are important building blocks for the overall energy conversion at the magnetopause. The nonreconnection events are also primarily within the reconnection exhaust and the Kelvin-Helmholtz vortices, highlighting the importance of reconnection and Kelvin-Helmholtz instability in regulating the energy conversion at the MBL.Plain Language Summary Solar wind-magnetosphere coupling is one of the long-standing questions in magnetosphere physics. Part of the input energy from the solar wind is converted and dissipated at the magnetopause boundary layer. Identifying where does energy conversion occurs is valuable for understanding the solar wind-magnetosphere coupling. Here we picked up hundreds of intense energy conversion events using high precision data from Magnetospheric Multiscale at the magnetopause boundary layer to study their locations and fundamental properties. It is found that most events are associated with magnetic reconnection and are more likely located in the reconnection exhaust and Kelvin-Helmholtz vortices. An interesting finding is that most of these intense energy conversion events are associated with reconnection in which only electrons participate, that is, without ion coupling.MAN ET AL.

Electron Heating in Magnetosheath Turbulence: Dominant Role of the Parallel Electric Field Within Coherent Structures

“…Moreover, we transfer the magnetic field, electron bulk flow, and electric current to the local LMN coordinates (Figures 4f-4h) to see whether this event was associated with a local reconnection. We employ the same procedure as Man et al (2022) to identify local reconnection, such as the electron outflowing jets and the out-of-plane current supporting the magnetic field reversal. We see a clear electron bulk flow reversal corresponding well to the current sheet crossing, implying that MMS encountered an active reconnection in this coherent structure.…”

“…We employ the same procedure as Man et al. (2022) to identify local reconnection, such as the electron outflowing jets and the out‐of‐plane current supporting the magnetic field reversal. We see a clear electron bulk flow reversal corresponding well to the current sheet crossing, implying that MMS encountered an active reconnection in this coherent structure.…”

Small-scale Field-aligned Currents in the Magnetopause Boundary Layer

“…To explore in which background conditions SFACs are more likely to form, we statistically analyzed the background environment of each SFAC. Based on the characteristics of the environmental conditions, as described in previous studies (e.g., Man et al 2022), we categorized the SFACs into wellknown magnetopause structures: (a) magnetic reconnection region: a reversal of the magnetic field in the L-direction, coupled with a magnitude difference in electron velocity within the L-direction that exceeds 3 times the standard deviation during the continuous duration of FACs; (b) FTE: the bipolar variations in the normal component of the magnetic field and an enhancement in the core field; (c) KHV: the magnetic field exhibits quasiperiodic variations, with the total pressure reaching the maximum (minimum) at the edge (center); (d) exhaust region: the ion outflow speed V iL is greater than 100 km s −1 . Any remaining events were classified as "others," as some SFACs satisfy various feature criteria, for instance, SFACs present in FTE are identified in the exhaust region.…”

“…Furthermore, solar wind can also be injected into the magnetosphere through the flux transfer events (FTE) and Kelvin-Helmholtz vortex (KHV) (e.g., Lee & Fu 1985;Hasegawa et al 2004Hasegawa et al , 2006Liu et al 2008;Hasegawa et al 2009;Taylor et al 2012;Merkin et al 2013;Pu et al 2013;Li et al 2016;Jiang et al 2019;Guo et al 2021). Using high-resolution data from the Magnetospheric Multiscale (MMS) mission, Man et al (2021Man et al ( , 2022 conducted a statistical investigation of intense current structures and intense energy conversion events within the magnetopause boundary layer (MBL). Their findings indicate that intense current structures are widely distributed throughout the MBL and play a crucial role in the dissipation of energy within the boundary layer, as well as the coupling between the solar wind and the magnetosphere.…”

Enhanced Energy Conversion by Turbulence in Collisionless Magnetic Reconnection

“…To identify the CS, the peak value of PVI index should exceed the threshold value 〈PVI〉 + σ PVI , where σ PVI is the standard deviation of the PVI index in the whole interval (Greco et al 2008). The boundary of each CS is defined as the rms of the PVI index (Califano et al 2020;Man et al 2022). ) is the inflow plasma β, where P B is the magnetic pressure; n e is the plasma density; T i and T e are the ion and electron temperature, respectively; and K B is the Boltzmann constant.…”