Investigating the development of double‐peak subauroral ion drift (DSAID)

Abstract

This study focuses on the newly described ionospheric feature, called double‐peak subauroral ion drift (DSAID), which is a subclass of the well‐known single‐peak SAID. Double‐layer Region 2 (R2) field aligned currents (FACs) could be the main driver of DSAID. Our aim is to gain new insights into the development of DSAID during its two‐stage progression. Observational results are provided by five scenarios, each demonstrating a certain progression sequence of DSAID. Results show that SAID/DSAID occurred during flux transfer events and was accompanied by flow channels (FCs) associated with dayside magnetopause (FC‐2) and nightside magnetotail (FC‐3) reconnections, with westward electrojet (eastward FC), and with auroral streamers (FC‐4). In the premidnight magnetic local time (MLT) sector of stage 2, DSAID development was due to the short‐circuiting of the reconnection‐injected plasma jets during substorms or pseudobreakups. Thus, the related ring current pressure buildup enhanced the downward R2 FACs leading to double/multiple circuits forming double‐layer R2 FACs. During the midnight MLT hours of stage 2, DSAID development was closely related to the westward traveling surge (WTS)/substorm current wedge (SCW). WTS/SCW‐related strong upward R1 FACs closed with meriodional currents producing eastward and downward (i.e., downward R2 FAC‐style) return currents enhancing the downward R2 FACs and thus leading to double/multiple circuits forming double‐layer R2 FACs. Auroral streamers/FC‐4 represent a substorm substructure and their occurrence with DSAID after stage 2 demonstrates that this substructure occasionally includes DSAID. Our results demonstrate also that the short‐circuited system underlying SAID/DSAID acted sometimes as a current generator and sometimes as a voltage generator.

The Magnetospheric Driving Source of Double‐Peak Subauroral Ion Drifts: Double Ring Current Pressure Peaks

“…The magnetospheric driving source of double-peak subauroral ion drifts: Double ring current pressure peaks. Geophysical Research Letters,46,[7079][7080][7081][7082][7083][7084][7085][7086][7087] of the two velocity peaks could be either comparable to each other or significantly different (He et al, 2016;Horvath & Lovell, 2017;Wei et al, 2019). Both of the two flow peaks are typically accompanied with two upward flow peaks and two ion temperature peaks.…”

“…Recently, a newly recognized phenomenon called double-peak subauroral ion drifts (DSAIDs) is categorized as a subset of SAPS (He et al, 2016). Observational results showed that DSAIDs appear as sunward drift with two velocity peaks in the subauroral midlatitude trough region in limited MLT sectors, and the magnitude of the two velocity peaks could be either comparable to each other or significantly different (He et al, 2016;Horvath & Lovell, 2017;Wei et al, 2019). Both of the two flow peaks are typically accompanied with two upward flow peaks and two ion temperature peaks.…”

Thermospheric wind response to a sudden ionospheric variation in the trough: event at a pseudo-breakup during geomagnetically quiet conditions

“…Before reports of the SAPS from radar measurements, the poleward electric field was found in satellite measurements (Smiddy et al 1977;Maynard 1978;Spiro et al 1979;Rich et al 1980). Later improvement of the sensor sensitivity enabled measurements of the fine structure in the latitudinal pattern of the electric field (Erickson et al 2016;Horvath and Lovell 2017). Horvath and Lovell (2017) found doublepeak subauroral ion drift (DSAID) in measurements performed with the Defense Meteorological Satellite Program (DMSP) when it flew across the ionospheric trough at an approximately 840-km altitude.…”

Longitudinal Evolution of the Velocity of Subauroral Polarization Streams (SAPS) in Different Phases of Magnetic Storms: SuperDARN Observations

“…Several magnetic factors are also found to be related to SAPS such as Kp, Dst, IMF, cross polar cap potential, conductance, electrojet, and zonal wind as shown in many reports (e.g., Aa et al., 2020; Foster & Vo, 2002; Huang & Foster, 2007; Kunduri et al., 2017; Wang et al., 2008, 2011; Zheng et al., 2008). Besides, SAPS are divided into several types because of the morphological features, such as double subauroral ion drifts (DSAID) and abnormal subauroral ion drifts/abnormal subauroral polarization drifts that are different in their formation mechanisms (Ebihara et al., 2008; He et al., 2014, 2016; Horvath & Lovell, 2017, 2018; Liléo et al., 2010; Voiculescu & Roth, 2008).…”

“…. Besides, SAPS are divided into several types because of the morphological features, such as double subauroral ion drifts (DSAID) and abnormal subauroral ion drifts/abnormal subauroral polarization drifts that are different in their formation mechanisms (Ebihara et al, 2008;He et al, 2014He et al, , 2016Horvath & Lovell, 2017Liléo et al, 2010;Voiculescu & Roth, 2008).…”