Characteristics of storm time electric fields in the inner magnetosphere derived from Cluster data

• Published in: Journal of Geophysical Research Vol. 115; no. A11; pp. A11215 - n/a
• Main Authors: Matsui, H., Puhl-Quinn, P. A., Bonnell, J. W., Farrugia, C. J., Jordanova, V. K., Khotyaintsev, Yu. V., Lindqvist, P.-A., Georgescu, E., Torbert, R. B.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01-11-2010; American Geophysical Union
• Subjects: Atmospheric sciences; Earth sciences; Earth, ocean, space; electric field; Electric fields; Exact sciences and technology; Fysik; Geocosmophysics and plasma physics; Geokosmofysik och plasmafysik; geomagnetic storm; inner magnetosphere; Magnetism; NATURAL SCIENCES; NATURVETENSKAP; Physics; Storms; models; time scales; latitude; Actinium; recovery; electrons; Superposed epoch analysis; electrical field; magnetosphere; Ion drift; Ring current; Spatial coherence; Magnetospheric tail; Plasma layer; particles; storms
• ISSN: 0148-0227; 2169-9380; 2156-2202; 2156-2202; 2169-9402
• DOI: 10.1029/2010JA015450

Storm‐time electric fields in the inner magnetosphere measured by Cluster are reported in this study. First, we show two events around the time when Dst index is at a minimum. The electric field possibly related to subauroral ion drifts and/or undershielding is measured inside the inner edge of the electron plasma sheet in the eveningside. For the second event observed in the nightside, the electric field is partly related to dipolarization and is considered as inductive. An electric field without coincident magnetic signatures is also observed. Spatial coherence of the electric field is not large when we check multispacecraft data. It is inferred that the electric field in the magnetotail penetrates inside the region 1 current, while it is not clear about the electric field within the region 2 current from our data. Then superposed epoch analyses using 71 storms are performed. Electric fields at R = 3.5–6RE and less than 25 degrees of magnetic latitudes are enhanced around the minimum Dst at all magnetic local times. Electric fields during the recovery phase decay on a time scale shorter than that of Dst index, which could be interpreted in terms of the relation between electric field and ring current during that storm phase. AC electric fields are generally larger than DC electric fields, indicating that the former component might play some role in accelerating ring current particles. These results will be useful to update our empirical electric field model.