Dawn‐Dusk Confinement of Magnetic Reconnection Site in the Near‐Earth Magnetotail and Its Implication for Dipolarization and Substorm Current System. Issue 11 (22nd November 2021)

• Record Type: Journal Article
• Authors: Nagai, Tsugunobu; Shinohara, Iku
• Is Part Of: Journal of geophysical research. Volume 126:Issue 11(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-11-22
• Subjects: magnetic reconnection -- substorm -- magnetotail -- substorm current system -- X‐line -- magnetic field; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2021JA029691
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: The dawn‐dusk confinement of magnetic reconnection site in the near‐Earth magnetotail is established on the basis of Geotail observations. Geotail has made more than 50 encounters with magnetic reconnection in association with the onset of substorms in the near‐Earth magnetotail at radial distances of 20–30 RE in the period of 1994–2019. Ground magnetic field observations are examined for these events, and geosynchronous spacecraft observations are investigated for a limited number of cases. The magnetic reconnection site is located in the upward (from the ionosphere to the tail) field‐aligned current part of large‐scale substorm current system derived from ground midlatitude magnetic variations. The site is confined to the localized dawn‐dusk extent of the 1‐hr local time, just west of the center of the large‐scale substorm current system. The short dawn‐dusk length of the X‐line implies that magnetic reconnection inherently proceeds as the two‐dimensional dynamics in the magnetotail meridional plane. Rapid dipolarization with upward field‐aligned currents occurs at geosynchronous altitude near the meridian of the magnetic reconnection site. This study demonstrates that rapid dipolarization in the inner magnetosphere is produced with earthward outflows from magnetic reconnection and that intense upward field‐aligned currents are a direct consequence of magnetic reconnection. Key Points: The dawn‐dusk extent of magnetic reconnection site occupies only the 1‐hr magnetic local time sector in the near‐Earth magnetotail Upward field‐aligned currents form in magnetic reconnection site The center of global substorm current system is located just east of the magnetic reconnection site meridian