Complex Sub‐Auroral Flow Channel Structure Formed by Double‐Peak Sub‐Auroral Ion Drifts (DSAID) and Abnormal Sub‐Auroral Ion Drifts (ASAID). Issue 1 (29th December 2020)

• Record Type: Journal Article
• Authors: Horvath, Ildiko; Lovell, Brian C.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 1(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-12-29
• Subjects: ASAID -- cross‐tail currents -- dipolarization -- DSAID -- Harang Reversal -- R1‐R2 FACs; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA028475
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: By utilizing multi‐instrument and multi‐satellite/spacecraft observations, we report the repeated development of a temporary and complex sub‐auroral flow channel (FC) structure during the intensive storms investigated. Appearing as combined double‐peak sub‐auroral ion drifts (DSAID) and abnormal SAID (ASAID), it is called DSAID‐ASAID FC structure. Revealing its development, various other FCs and features appeared in the auroral and polar regions simultaneously. These include the auroral Harang Region (HR) that is the Substorm Current Wedge's ionospheric signature and the Eastward FC (E‐FC) indicating the arrival of the Westward Travelling Surge. Results show that in the HR and E‐FC, the locally enhanced duskside upward Region 1 Field Aligned Currents (↑R1 FACs) connected in the magnetosphere with the meridional partial ring current characterized by a double plasma density/pressure peak structure, of which signature was seen in the 225 keV proton density data, leading to the development of two sets of ↓R2 FACs and DSAID. Meanwhile, large auroral undulations appeared and were driven, via magnetosphere‐ionosphere coupling, by Kelvin‐Helmholtz instability mechanisms that also drove plasma sheet rippling leading to ASAID development. Plasma sheet rippling occurred during magnetotail reconnection, as demonstrated with its ionospheric polar cap signature, known as FC‐3, in a stretched tail region according to the b2i boundary located at ∼60° magnetic latitude. Then, the earthward flows' braking/slowing down provided the energy for driving the R1‐R2 FACs. From the observational evidence presented we conclude that the DSAID‐ASAID features investigated developed due to the maintenance of DSAID during plasma sheet rippling triggering ASAID development. Key Points: The complexDouble‐Peak Sub‐Auroral Ion Drifts (DSAID) and Abnormal Sub‐Auroral Ion Drifts (ASAID) flow channel (FC) structure investigated appeared as a DSAID centered over an ASAID The DSAID‐ASAID events presented occurred during intensive storms when conditions were favorable for both DSAID and ASAID development The DSAID‐ASAID FC structure appeared as a conjugate and transient feature that declined to DSAID