The Detached Auroras Induced by the Solar Wind Pressure Enhancement in Both Hemispheres From Imaging and In Situ Particle Observations. Issue 4 (21st April 2018)

• Record Type: Journal Article
• Authors: Zhou, Su; Luan, Xiaoli; Søraas, Finn; Østgaard, Nikolai; Raita, Tero
• Is Part Of: Journal of geophysical research. Volume 123:Issue 4(2018)
• Page Start: 3170
• Page End: 3182
• Publication Date: 2018-04-21
• Subjects: detached aurora -- solar wind pressure enhancement -- loss cone -- EMIC waves; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2017JA024562
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: This paper presents simultaneous detached proton auroras that appeared in both hemispheres at 11:06 UT, 08 March 2012, just 2 min after a sudden solar wind pressure enhancement (~11:04 UT) hit the Earth. They were observed under northward interplanetary magnetic field Bz condition and during the recovery phase of a moderate geomagnetic storm. In the Northern Hemisphere, Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observed that the detached arc occurred within 60°–65° magnetic latitude and covered a few magnetic local time (MLT) hours ranging from 0530 to 0830 MLT with a possible extension toward noon. At the same time (11:06 UT), Polar Orbiting Environment Satellites 19 detected a detached proton aurora around 1300 MLT in the Southern Hemisphere, centering ~62° magnetic latitude, which was at the same latitudes as the northern detached arc. This southern aurora was most probably a part of a dayside detached arc that was conjugate to the northern one. In situ particle observations indicated that the detached auroras were dominated by protons/ions with energies ranging from around 20 keV to several hundreds of keV, without obvious electron precipitations. These detached arcs persisted for less than 6 min, consistent with the impact from pressure enhancement and the observed electromagnetic ion cyclotron (EMIC) waves. It is suggested that the increasing solar wind pressure pushed the hot ions in the ring current closer to Earth where the steep gradient of cold plasma favored EMIC wave growth. By losing energy to EMIC waves the energetic protons (>20 keV) were scattered into the loss cone and produced the observed detached proton auroras. Key Points: The dayside detached auroras caused by the solar wind pressure enhancement were observed in both hemispheres The detached auroras were dominated by hot ions/protons, with energies ranging from 20 keV to more than 240 keV The particles in the detached auroras were scattered into the loss cone by EMIC waves and mapped to the vicinity of plasmapause