Recovery phase of magnetospheric substorms and its association with morning‐sector aurora

Opgenoorth, H. J.; Persson, Moa; Pulkkinen, Tuija; Pellinen, R.

doi:10.1029/93ja01502

Cited by 60 publications

(60 citation statements)

References 43 publications

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“…Despite the lack of optical observations due to the unsuitable season of the interval presented, the asymmetrical distribution of omega band structure presented here is entirely consistent with optical observations in previous studies (e.g. Snyder and Akasofu, 1974;Opgenoorth et al, 1994). These are characterised by a roughly X shaped distortion of the bright poleward boundary of the auroral oval, slightly darker in the central region than at the edge and ofteǹ`l eaning'' slightly in the longitudinal direction.…”

Section: Omega Band Formationsupporting

confidence: 90%

Multi-instrument observations of the electric and magnetic field structure of omega bands

et al. 2000

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Abstract. High time resolution data from the CUT-LASS Finland radar during the interval 01:30±03:30 UT on 11 May, 1998, are employed to characterise the ionospheric electric ®eld due to a series of omega bands extending~5°in latitude at a resolution of 45 km in the meridional direction and 50 km in the azimuthal direction. E-region observations from the STARE Norway VHF radar operating at a resolution of 15 km over a comparable region are also incorporated. These data are combined with ground magnetometer observations from several stations. This allows the study of the ionospheric equivalent current signatures and height integrated ionospheric conductances associated with omega bands as they propagate through the ®eld-of-view of the CUTLASS and STARE radars. The high-time resolution and multi-point nature of the observations leads to a re®nement of the previous models of omega band structure. The omega bands observed during this interval have scale sizes~500 km and an eastward propagation velocity~0.75 km s A1 . They occur in the morning sector (~05 MLT), simultaneously with the onset/intensi®ca-tion of a substorm to the west during the recovery phase of a previous substorm in the Scandinavian sector. A possible mechanism for omega band formation and their relationship to the substorm phase is discussed.

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Section: Omega Band Formationsupporting

confidence: 90%

Multi-instrument observations of the electric and magnetic field structure of omega bands

et al. 2000

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“…Based on the contention of Kamide and Vickrey (1983) that the westward electrojet is conductivity dominated in the midnight and morning sector, and the observations by Brekke et al (1974) and Opgenoorth et al (1994) that the ratio H / P increases to >2:1 during active times in those sectors, we effectively increased H / P in the morning hours while keeping the evening sector conductivity ratio almost unchanged.…”

Section: Motivation For the Choice Of The Model Current Systemmentioning

confidence: 95%

Creation of the substorm current wedge through the perturbation of the directly driven current system: a new model for substorm expansion

Rostoker

Friedrich

2005

Ann. Geophys.

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Abstract. The past four decades have seen a considerable amount of research on the study of magnetospheric substorms, and over most of these years the expansive phase of the substorm has been associated with the development of a three dimensional current system that has been termed the substorm current wedge. This current system has been thought to be a consequence of the short-circuiting of crosstail current through the ionosphere, and is viewed as a distinctive current system operating independently from the directly driven current with which it co-exists. The purpose of this paper is to show that the substorm current wedge should be viewed as an equivalent current system rather than a real current system. It will be shown that the magnetic perturbation pattern associated with the current wedge can be modeled as purely a perturbation of the directly driven current system in the midnight sector.

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“…13, except that instead of activity, the data are binned with respect to season: winter (top), equinox (middle) and summer (bottom). events, during which particle precipitation is higher in the morning sector (Opgenoorth et al, 1994). Towards summer, α becomes higher, especially on the sunlit side of the polar cap.…”

Section: Statistical Estimate For α As a Function Of J φmentioning

confidence: 97%

A model for estimating the relation between the Hall to Pedersen conductance ratio and ground magnetic data derived from CHAMP satellite statistics

et al. 2007

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Abstract. The goal of this study is to find a way to statistically estimate the Hall to Pedersen conductance ratio α from ground magnetic data. We use vector magnetic data from the CHAMP satellite to derive this relation. α is attained from magnetic satellite data using the 1-D Spherical Elementary Current Systems (SECS). The ionospheric equivalent current density can either be computed from ground or satellite magnetic data. Under the required 1-D assumption, these two approaches are shown to be equal, which leads to the advantage that the statistics are not restricted to areas covered by ground data. Unlike other methods, using magnetic satellite measurements to determine α ensures reliable data over long time sequences. The statistical study, comprising over 6000 passes between 55 • and 76.5 • northern geomagnetic latitude during 2001 and 2002, is carried out employing data from the CHAMP satellite. The data are binned according to activity and season. In agreement with earlier studies, values between 1 and 3 are typically found for α. Good compatibility is found, when α attained from CHAMP data is compared with EISCAT radar measurements. The results make it possible to estimate α from the east-west equivalent current density J φ [A/km]: α=2.07/(36.54/|J φ |+1) for J φ <0 (westward) and α=1.73/(14.79/|J φ |+1) for J φ >0 (eastward). Using the same data, statistics of ionospheric and field-aligned current densities as a function of geomagnetic latitude and MLT are included. These are binned with respect to activity, season and IMF B Z and B Y . For the first time, all three current density components are simultaneously studied this way on a comparable spatial scale. With increasing activity, the enhancement and the equatorward expansion of the electrojets and the R1 and R2 currents is observed, and in the nightside, possible indications of a Cowling channel appear. During southward IMF B Z , the electrojets and the R1 and R2 currents are stronger and clearer than during northward B Z . IMF B Y affects the orientation of the pattern.

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Recovery phase of magnetospheric substorms and its association with morning‐sector aurora

Cited by 60 publications

References 43 publications

Multi-instrument observations of the electric and magnetic field structure of omega bands

Multi-instrument observations of the electric and magnetic field structure of omega bands

Creation of the substorm current wedge through the perturbation of the directly driven current system: a new model for substorm expansion

A model for estimating the relation between the Hall to Pedersen conductance ratio and ground magnetic data derived from CHAMP satellite statistics

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