Magnetic local time, substorm, and particle precipitation-related variations in the behaviour of SuperDARN Doppler spectral widths

Parkinson, M.L.; Chisham, G. ORCID: https://orcid.org/0000-0003-1151-5934; Pinnock, M.; Dyson, P.L.; Devlin, J.C.. 2004 Magnetic local time, substorm, and particle precipitation-related variations in the behaviour of SuperDARN Doppler spectral widths. Annales Geophysicae, 22 (12). 4103-4122. https://doi.org/10.5194/angeo-22-4103-2004

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Abstract/Summary

Super Dual Auroral Radar Network (DARN) radars often detect a distinct transition in line-of-sight Doppler velocity spread, or spectral width, from <50 m s(-1) at lower latitude to >200 m s(-1) at higher latitude. They also detect a similar boundary, namely the range at which ionospheric scatter with large spectral width suddenly commences (i.e. without preceding scatter with low spectral width). The location and behaviour of the spectral width boundary (SWB) (and scatter boundary) and the open-closed magnetic field line boundary (OCB) are thought to be closely related. The location of the nightside OCB can be inferred from the poleward edge of the auroral oval determined using energy spectra of precipitating particles measured on board Defence Meteorology Satellite Program (DMSP) satellites. Observations made with the Halley SuperDARN radar (75.5degrees S, 26.6degrees W, geographic; -62.0degrees Lambda) and the Tasman International Geospace Environment Radar (TIGER) (43.4degrees S, 147.2degrees E; -54.5degrees Lambda) are used to compare the location of the SWB with the DMSP-inferred OCB during 08:00 to 22:00 UT on 1 April 2000. This study interval was chosen because it includes several moderate substorms, whilst the Halley radar provided almost continuous high-time resolution measurements of the dayside SWB location and shape, and TIGER provided the same in the nightside ionosphere. The behaviour of the day- and nightside SWB can be understood in terms of the expanding/contracting polar cap model of high-latitude convection change, and the behaviour of the nightside SWB can also be organised according to substorm phase. Previous comparisons with DMSP OCBs have proven that the radar SWB is often a reasonable proxy for the OCB from dusk to just past midnight (Chisham et al., 2004). However, the present case study actually suggests that the nightside SWB is often a better proxy for the poleward edge of Pedersen conductance enhanced by hot particle precipitation in the auroral zone. Simple modeling implies that the large spectral widths must be caused by similar to10-km scale velocity fluctuations.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.5194/angeo-22-4103-2004
Programmes:	BAS Programmes > Antarctic Science in the Global Context (2000-2005) > Magnetic Reconnection, Substorms and their Consequences
ISSN:	0992-7689
Additional Information. Not used in RCUK Gateway to Research.:	Open access journal
Additional Keywords:	ionosphere, auroral ionosphere, ionosphere-magnetosphere interactions, magnetospheric physics, storms and substorms
NORA Subject Terms:	Physics Atmospheric Sciences Space Sciences
Date made live:	23 Jan 2012 13:33 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/12325

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