manuscript submitted to replace this text with name of AGU journal 1
Dawn-Dusk Confinement of Magnetic Reconnection Site in the Near-Earth 1
Magnetotail and its Implication for Dipolarization and Substorm Current
System
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 mid-latitude
magnetic variations. The site is confined to the localized dawn–dusk
extent of the 1-h 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.