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Estimating the Location of the Open-closed Magnetic Field Line Boundary from Auroral Images : Volume 28, Issue 9 (10/09/2010)

By Longden, N.

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Book Id: WPLBN0003974714
Format Type: PDF Article :
File Size: Pages 20
Reproduction Date: 2015

Title: Estimating the Location of the Open-closed Magnetic Field Line Boundary from Auroral Images : Volume 28, Issue 9 (10/09/2010)  
Author: Longden, N.
Volume: Vol. 28, Issue 9
Language: English
Subject: Science, Annales, Geophysicae
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Publication Date:
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications


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Longden, N., Sotirelis, T., Abel, G. A., Chisham, G., & Freeman, M. P. (2010). Estimating the Location of the Open-closed Magnetic Field Line Boundary from Auroral Images : Volume 28, Issue 9 (10/09/2010). Retrieved from

Description: British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK. 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.

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

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