Relative contributions of large-scale and wedgelet currents in the substorm current wedge

• Published in: Earth, planets, and space Vol. 72; no. 1; p. 106
• Main Authors: Nishimura, Y., Lyons, L. R., Gabrielse, C., Weygand, J. M., Donovan, E. F., Angelopoulos, V.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 20.07.2020; Springer; Springer Nature B.V; SpringerOpen
• Subjects: 3. Space science; Auroral substorms; Auroras; Bursty bulk flow (BBF); Earth and Environmental Science; Earth Sciences; Field-aligned current (FAC); Geology; Geomagnetism; Geophysics/Geodesy; Ionosphere; Magnetometers; Magnetosphere; Magnetotails; Observations; Plasma sheet; Substorm current wedge (SCW); Wedges; Westward traveling surge (WTS); United States; Substorm current wedge (SCW); Field-aligned current (FAC); Plasma sheet; Westward traveling surge (WTS); Bursty bulk flow (BBF)
• ISSN: 1880-5981; 1343-8832; 1880-5981
• DOI: 10.1186/s40623-020-01234-x

We examined how much large-scale and localized upward and downward currents contribute to the substorm current wedge (SCW), and how they evolve over time, using the THEMIS all-sky imagers (ASIs) and ground magnetometers. One type of events is dominated by a single large-scale wedge, with upward currents over the surge and broad downward currents poleward-eastward of the surge. The other type of events is a composite of large-scale wedge and wedgelets associated with streamers, with each wedgelet having comparable intensity to the large-scale wedge currents. Among 17 auroral substorms with wide ASI coverage, the composite current type is more frequent than the single large-scale wedge type. The dawn–dusk size of each wedgelet is ~ 600 km in the ionosphere (~ 3.2 R E in the magnetotail, comparable to the flow channel size). We suggest that substorms have more than one type of SCW, and the composite current type is more frequent.