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Subsidence of Ionospheric Flows Triggered by Magnetotail Magnetic Reconnection During Transpolar Arc Brightening

Research output: Contribution to journalJournal article

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  • Motoharu Nowada
  • R.C. Fear
  • Adrian Grocott
  • Quad-Qi Shi
  • Jun Yang
  • Liu-Gang Zong
  • Yong Wei
  • Sui-Yan Fu
  • Zu-Yin Pu
  • Bagrat Mailyan
  • Hui Zhang
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<mark>Journal publication date</mark>05/2018
<mark>Journal</mark>Journal of Geophysical Research: Space Physics
Issue number5
Volume123
Number of pages23
Pages (from-to)3398-3420
Publication statusPublished
Early online date19/04/18
Original languageEnglish

Abstract

A transpolar arc (TPA), which extended from postmidnight to prenoon, was seen on 16 September 2001 in the Northern Hemisphere under northward interplanetary magnetic field (IMF)‐Bz and weakly dawnward IMF‐By conditions. Super Dual Auroral Radar Network detected significant westward plasma flows just equatorward of the poleward edge of the midnight sector auroral oval. These plasma flows were confined to closed field lines and are identified as the ionospheric plasma flow signature of tail reconnection during IMF northward nonsubstorm intervals (TRINNIs). These TRINNI flows persisted for 53 min from prior to the TPA appearance to the cessation of TPA growth. They are usually observed before (and during) intervals when TPAs are present, but in this case, subsided after the TPA was completely connected to the dayside. Additional slower flows across the open/closed polar cap boundary were seen at the TPA onset time in the same magnetic local time sector as the nightside end of the TPA. These ionospheric flows suggest that magnetotail reconnection significantly contributed to the TPA formation, as proposed by Milan et al. (2005, https://doi.org/10.1029/2004JA010835). We propose a possible scenario for an absence of the TRINNI flows during the TPA brightening by considering the relation between the extent of the magnetotail reconnection line mapped onto nightside auroral oval and the TPA width; TRINNI flows would subside when the extent of X‐line is comparable to the TPA width. Therefore, our results suggest that the fate (absence or presence) of TRINNI flows on closed field lines during the TPA formation would be closely related with magnetotail reconnection extent.