Ground and satellite observations of low‐latitude red auroras at the initial phase of magnetic storms

Abstract

[1] We report ground and satellite observations of unique low-latitude red auroras that appear at the initial phase of geomagnetic storms. For two events on 21 October 2001, and 6 April 2000, the low-latitude red auroras appeared at~45 MLAT (L $ 2) $ 1.5 h after the storm sudden commencement in the postmidnight sector in Japan. Comprehensive satellite data were available for the former event. The energetic neutral atom images obtained by the Imager for Magnetopause-to-Aurora Global Exploration satellite show rapid enhancement of ring current hydrogen and oxygen fluxes at radial distances of $ 2-8 R E after the storm sudden commencement and associated with several storm-time substorms. The hydrogen ring-current enhancement occurred particularly in the postmidnight sector where the red aurora was observed. The timing of oxygen flux enhancement associated with a storm-time substorm coincided with the red aurora appearance. This rapid and significant enhancement of energetic neutral atom flux was also confirmed by energetic ion data obtained by the NOAA/POES-16 satellite. Extreme ultraviolet plasmaspheric images obtained by Magnetopause-to-Aurora Global Exploration indicate that the plasmapause was located at L = 2.3-2.5 in the postmidnight sector during the event, indicating that a spatial overlap occurs between the plasmasphere and the enhanced ring current ions at L $ 2. Based on these observations, we suggest that large energization of high-energy ring-current ions in the postmidnight inner magnetosphere caused the spatial overlap of these ring-current ions with the low-energy plasmaspheric plasmas at L $ 2, producing the low-latitude red auroras at the very beginning of the storms.Citation: Shiokawa, K., Y. Miyoshi, P. C. Brandt, D. S. Evans, H. U. Frey, J. Goldstein, and K. Yumoto (2013), Ground and satellite observations of low-latitude red auroras at the initial phase of magnetic storms,

Statistical Analysis of SAR Arc Detachment From the Main Oval Based on 11‐Year, All‐Sky Imaging Observation at Athabasca, Canada

“…It has been shown that SAR arcs occur during the recovery phase of geomagnetic storms (e.g., Kozyra et al, 1987;Mendillo et al, 2016;Rees & Roble, 1975). Shiokawa et al (2013) reported red aurora that seemed to be SAR arc at low latitudes in Japan when the ring current developed at the beginning of a magnetic storm. Baumgardner et al (2007) reported a rare SAR arc with a very bright intensity reaching 13,000 Rayleigh.…”

A stable auroral red (SAR) arc with multiple emission features

“…It was reviewed recently within the context of red aurora at midlatitudes by Shiokawa et al . []. Our goal is to use the event of 2 October 2013 to illuminate further, and as quantitatively as possible, the multiple modes of inner‐magnetosphere coupling to the subauroral ionosphere, some of which are still poorly understood.…”

IpsDst of Dst Storms Applied to Ionosphere‐Thermosphere Storms and Low‐Latitude Aurora

“…The statistical correlations of ionospheric storms with IpsDst and other parameters will be obtained using the ionospheric peak electron density (NmF2) (Shiokawa et al, 2005) will be used for investigating the intensity of the low-latitude auroras with IpsDst and other parameters. Though the auroral observations were made at midlatitudes, we use the phrase "low-latitude aurora" implying that they occur at much lower latitudes than normal auroras and to be consistent with earlier studies (e.g., Shiokawa et al, 2005Shiokawa et al, , 2013.…”