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Substorm-Related Near-Earth Reconnection Surge: Combining Telescopic and Microscopic Views
St Petersburg State Univ, Earths Phys Dept, St Petersburg, Russia.
St Petersburg State Univ, Earths Phys Dept, St Petersburg, Russia.
Austrian Acad Sci, Space Res Inst, Graz, Austria.
Austrian Acad Sci, Space Res Inst, Graz, Austria.
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2019 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 12, p. 6239-6247Article in journal (Refereed) Published
Abstract [en]

A strong similar to 11-min-long surge of the lobe reconnection was observed during a substorm on the tailward side of the near-Earth neutral line. In the southern lobe near the reconnection separatrix the MMS spacecraft observed short-duration earthward electron beams providing the local Hall current, tailward propagating Alfven wave (AW) bursts with Poynting flux up to 10(-4) W/m(2), and large-amplitude E field spikes (e-holes) and low hybrid waves. The reconnection surge was accompanied by substorm current wedge formation and fast poleward expansion of auroral bulge-related westward electrojet in the conjugate ionosphere. During its meridional crossing above the expanding bulge the Metop-2 spacecraft observed an intense energetic precipitation spike near the expected X line foot point and confirmed the dipolarized character of magnetic field lines inside of the bulge. Globally the observed average reconnection rate (<Ey > similar to 3.3 mV/m) was sufficient to produce the magnetic flux increase in the bulge, associated with observed fast poleward expansion (about 6 degrees latitude in 5 min). Plain Language Summary Although magnetic reconnection in the magnetotail has been proposed to be the core process for the strong global magnetospheric reconfiguration and for huge particle acceleration during magnetospheric substorms, this association is mostly based on indirect evidence, because reconnection intermittently activates in different parts of the tail current sheet, and it is difficult to monitor its location and intensity variations based on direct spacecraft observations. On 28 July 2017 the MMS spacecraft succeeded in staying in the magnetotail near the active reconnection separatrix for a relatively long time during the surge of reconnection. At the same time the electric currents were enhanced and moved poleward in the magnetically conjugate part of the ionosphere, indicating configurational changes in the magnetotail. At the same minute the Metop-2 spacecraft in low-Earth orbit passed above this region and detected precipitating electrons of different energies as well as their distribution in the loss cone, which yielded conclusions about the strength of the equatorial magnetic field in the reconnected flux tubes. This unprecedented combination of conjugate observations allows us to confirm directly the important global consequences of an intense near-Earth reconnection event, which have been suggested in the near-Earth neutral line substorm scenario but could not be previously observed together in the same event.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION , 2019. Vol. 46, no 12, p. 6239-6247
Keywords [en]
substorms, magnetic reconnection, magnetotail, plasma sheet, poleward expansion, precipitation
National Category
Astronomy, Astrophysics and Cosmology Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:uu:diva-392878DOI: 10.1029/2019GL083057ISI: 000477616300010OAI: oai:DiVA.org:uu-392878DiVA, id: diva2:1354706
Available from: 2019-09-26 Created: 2019-09-26 Last updated: 2019-09-26Bibliographically approved

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Khotyaintsev, Yuri V.

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Swedish Institute of Space Physics, Uppsala Division
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