Preprints
https://doi.org/10.5194/angeo-2021-69
https://doi.org/10.5194/angeo-2021-69

  07 Jan 2022

07 Jan 2022

Review status: this preprint is currently under review for the journal ANGEO.

Ionospheric Plasma Flows Associated with the Formation of the Distorted Nightside End of A Transpolar Arc

Motoharu Nowada1, Adrian Grocott2, and Quan-Qi Shi1 Motoharu Nowada et al.
  • 1Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Institute of Space Sciences, Shandong University, Weihai, Shandong, 264209, People’s Republic of China
  • 2Space and Planetary Physics Group, Department of Physics, Lancaster University, LA1 4YW, Lancaster, UK

Abstract. We investigate ionospheric flow patterns from 28th January 2002 associated with the development of the nightside distorted end of a “J”-shaped Transpolar Arc (nightside distorted TPA). Based on the nightside ionospheric flows near to the TPA, detected by the SuperDARN radars, we discuss how the distortion of the nightside end toward the pre-midnight sector is produced. The “J”-shaped TPA was seen under southward Interplanetary Magnetic Field (IMF) conditions, in the presence of a dominant dawnward IMF-By component. At the onset time of the nightside distorted TPA, particular equatorward plasma flows at the TPA growth point were observed in the post-midnight sector, flowing out of the polar cap and then turning toward the pre-midnight sector of the main auroral oval along the distorted nightside part of the TPA. We suggest that these plasma flows play a key role in causing the nightside distortion of the TPA. SuperDARN also found ionospheric flows typically associated with “Tail Reconnection during IMF Northward Non-substorm Intervals” (TRINNIs) on the nightside main auroral oval before and during the TPA interval, indicating that nightside magnetic reconnection is an integral process to the formation of the nightside distorted TPA. During the TPA growth, SuperDARN also detected anti-sunward flows across the open-closed field line boundary on the dayside that indicate the occurrence of low-latitude dayside reconnection and ongoing Dungey cycle driving. This suggests that nightside distorted TPA can grow even in Dungey-cycle-driven plasma flow patterns.

Motoharu Nowada et al.

Status: open (until 18 Feb 2022)

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Motoharu Nowada et al.

Motoharu Nowada et al.

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Short summary
We report that the ionospheric plasma flow patterns associated with the “J”-shaped Transpolar Arc (a type of nightside distorted TPA), detected by the SuperDARN radar, reveal the formation process of the nightside distortion of a TPA. Equatorward flows at the TPA growth point were observed flowing out of the polar cap and then turning toward the pre-midnight main auroral oval along the TPA nightside distortion. These ionospheric flow patterns would cause the distortion at the TPA nightside end.