Substorm‐Related Near‐Earth Reconnection Surge: Combining Telescopic and Microscopic Views

Abstract

A strong ~11‐min‐long surge of the lobe reconnection was observed during a substorm on the tailward side of the near‐Earth neutral line. In the southern lobe near the reconnection separatrix the MMS spacecraft observed short‐duration earthward electron beams providing the local Hall current, tailward propagating Alfven wave (AW) bursts with Poynting flux up to 10−4 W/m2, and large‐amplitude E field spikes (e‐holes) and low hybrid waves. The reconnection surge was accompanied by substorm current wedge formation and fast poleward expansion of auroral bulge‐related westward electrojet in the conjugate ionosphere. During its meridional crossing above the expanding bulge the Metop‐2 spacecraft observed an intense energetic precipitation spike near the expected X line foot point and confirmed the dipolarized character of magnetic field lines inside of the bulge. Globally the observed average reconnection rate (<Ey > ~3.3 mV/m) was sufficient to produce the magnetic flux increase in the bulge, associated with observed fast poleward expansion (about 6° latitude in 5 min).

Jupiter's Double‐Arc Aurora as a Signature of Magnetic Reconnection: Simultaneous Observations From HST and Juno

“…The terrestrial equatorial oval is associated with magnetospheric current disruption, while the poleward auroral oval is associated with the open‐closed magnetic field line boundary, where magnetic reconnection takes place. Coordinated remote observations of auroras and in situ measurements in the magnetosphere show direct connections between auroral intensification and magnetic reconnection (Borg et al., 2007; Fuselier et al., 2007; Matar et al., 2020; Øieroset et al., 1997; Phan et al., 2003; Sergeev et al., 2019; Varsani et al., 2017). Although terrestrial substorms are traditionally caused by magnetospheric current disruption (Lui, 1996), reconnection may directly drive pseudo‐breakup substorms (Pu et al., 2010).…”