Explosive Magnetotail Activity

Abstract

Modes and manifestations of the explosive activity in the Earth’s magnetotail, as well as its onset mechanisms and key pre-onset conditions are reviewed. Two mechanisms for the generation of the pre-onset current sheet are discussed, namely magnetic flux addition to the tail lobes, or other high-latitude perturbations, and magnetic flux evacuation from the near-Earth tail associated with dayside reconnection. Reconnection onset may require stretching and thinning of the sheet down to electron scales. It may also start in thicker sheets in regions with a tailward gradient of the equatorial magnetic field ; in this case it begins as an ideal-MHD instability followed by the generation of bursty bulk flows and dipolarization fronts. Indeed, remote sensing and global MHD modeling show the formation of tail regions with increased , prone to magnetic reconnection, ballooning/interchange and flapping instabilities. While interchange instability may also develop in such thicker sheets, it may grow more slowly compared to tearing and cause secondary reconnection locally in the dawn-dusk direction. Post-onset transients include bursty flows and dipolarization fronts, micro-instabilities of lower-hybrid-drift and whistler waves, as well as damped global flux tube oscillations in the near-Earth region. They convert the stretched tail magnetic field energy into bulk plasma acceleration and collisionless heating, excitation of a broad spectrum of plasma waves, and collisional dissipation in the ionosphere. Collisionless heating involves ion reflection from fronts, Fermi, betatron as well as other, non-adiabatic, mechanisms. Ionospheric manifestations of some of these magnetotail phenomena are discussed. Explosive plasma phenomena observed in the laboratory, the solar corona and solar wind are also discussed.

Signatures of Nonideal Plasma Evolution During Substorms Obtained by Mining Multimission Magnetometer Data

“…Moreover, PIC simulations confirmed that the onset of fast dipolarization, including the spontaneous generation of fast earthward flows with the speed ∼ v A , may proceed very rapidly, consistent with observations, as long as the CS thickness is comparable to ρ 0 i . Furthermore, it was shown that the spontaneous dipolarization process leads, on the one hand, to the formation of dipolarization fronts, one of the most ubiquitous transient processes in the tail (e.g., Sitnov et al, , and refs. therein), and on the other hand, it naturally causes the formation of new X‐lines due to the flux starvation mechanism (Pritchett, ).…”

Ion‐Beam‐Driven Intense Electrostatic Solitary Waves in Reconnection Jet

“…During reconnection processes, the initially separated plasmas become magnetically connected, and the connected plasmas get ejected from reconnection region, producing high‐speed plasma flows, commonly referred to as reconnection jets or burst bulk flows (Angelopoulos et al, ; Cao et al, , ). Reconnection jets have been suggested to be responsible for energy dissipation, particle heating, and acceleration in space plasmas (e.g., Khotyaintsev et al, ; Fu et al, ; Lapenta et al, ; Lu, Angelopoulos, et al, ; Zhou et al, ; Sitnov et al, ; Chen, Fu, Liu, et al, ; Zhao et al, ).…”

Understanding Spacecraft Trajectories Through Detached Magnetotail Interchange Heads

“…Presently, the exact mechanisms driving the magnetotail reconnection remain unresolved (Sitnov et al, 2019). Various theoretical models suggest that reconnection emerge spontaneously through tearing instability (Sitnov et al, 2013) or could be externally driven through forming a thin current sheet (Hesse & Schindler, 2001), for instance by increasing the lobe pressure or by current sheet bending (Kivelson & Hughes, 1990).…”