Estimating the location of the open-closed magnetic field line boundary from auroral images

Longden, Nicola; Chisham, Gareth ORCID: https://orcid.org/0000-0003-1151-5934; Freeman, Mervyn P. ORCID: https://orcid.org/0000-0002-8653-8279; Abel, Gary A.; Sotirelis, Tom. 2010 Estimating the location of the open-closed magnetic field line boundary from auroral images. Annales Geophysicae, 28 (9). 1659-1678. https://doi.org/10.5194/angeo-28-1659-2010

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Abstract/Summary

The open-closed magnetic field line boundary (OCB) delimits the region of open magnetic flux forming the polar cap in the Earth’s ionosphere. We present a reliable, automated method for determining the location of the poleward auroral luminosity boundary (PALB) from far ultraviolet (FUV) images of the aurora, which we use as a proxy for the OCB. This technique models latitudinal profiles of auroral luminosity as both a single and double Gaussian function with a quadratic background to produce estimates of the PALB without prior knowledge of the level of auroral activity or of the presence of bifurcation in the auroral oval. We have applied this technique to FUV images recorded by the IMAGE satellite from May 2000 until August 2002 to produce a database of over a million PALB location estimates, which is freely available to download. From this database, we assess and illustrate the accuracy and reliability of this technique during varying geomagnetic conditions. We find that up to 35% of our PALB estimates are made from double Gaussian fits to latitudinal intensity profiles, in preference to single Gaussian fits, in nightside magnetic local time (MLT) sectors. The accuracy of our PALBs as a proxy for the location of the OCB is evaluated by comparison with particle precipitation boundary (PPB) proxies from the DMSP satellites. We demonstrate the value of this technique in estimating the total rate of magnetic reconnection from the time variation of the polar cap area calculated from our OCB estimates.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.5194/angeo-28-1659-2010
Programmes:	BAS Programmes > Polar Science for Planet Earth (2009 - ) > Environmental Change and Evolution
ISSN:	0992-7689
NORA Subject Terms:	Physics Atmospheric Sciences Space Sciences
Date made live:	25 Nov 2010 12:19 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/11064

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