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Identifying the magnetotail lobes with Cluster magnetometer data

Identifying the magnetotail lobes with Cluster magnetometer data
Identifying the magnetotail lobes with Cluster magnetometer data
We describe a novel method for identifying times when a spacecraft is in Earth’s magnetotail lobes solely using magnetometer data. We propose that lobe intervals can be well identified as times when the magnetic field is strong and relatively invariant, defined using thresholds in the magnitude of BX and the standard deviation ???? of the magnetic field magnitude. Using data from the Cluster spacecraft at downtail distances greater than 8 RE during 2001–2009, we find that thresholds of 30 nT and 3.5 nT, respectively, optimize agreement with a previous, independently derived lobe identification method that used both magnetic and plasma data over the same interval. Specifically, our method has a moderately high accuracy (66%) and a low probability of false detection (11%) in comparison to the other method. Furthermore, our method identifies the lobe on many other occasions when the previous method was unable to make any identification and yields longer continuous intervals in the lobe than the previous method, with intervals at the 90th percentile being triple the length. Our method also allows for analyses of the lobes outside the time span of the previous method.
0148-0227
1436-1446
Coxon, John
566baea5-6a30-4855-bde3-a09c115efde4
Jackman, Caitriona
9bc3456c-b254-48f1-ade0-912c5b8b4529
Freeman, Mervyn P.
dc974e00-a73d-4d41-a2a8-3c5aebd7a5b5
Forsyth, Colin
176bc4c5-4e98-4419-ad12-631e231b338b
Rae, I. Jonathan
25677763-0501-4b69-859e-fab930260c69
Coxon, John
566baea5-6a30-4855-bde3-a09c115efde4
Jackman, Caitriona
9bc3456c-b254-48f1-ade0-912c5b8b4529
Freeman, Mervyn P.
dc974e00-a73d-4d41-a2a8-3c5aebd7a5b5
Forsyth, Colin
176bc4c5-4e98-4419-ad12-631e231b338b
Rae, I. Jonathan
25677763-0501-4b69-859e-fab930260c69

Coxon, John, Jackman, Caitriona and Freeman, Mervyn P. et al. (2016) Identifying the magnetotail lobes with Cluster magnetometer data Journal of Geophysical Research, 121, (2), pp. 1436-1446.

Record type: Article

Abstract

We describe a novel method for identifying times when a spacecraft is in Earth’s magnetotail lobes solely using magnetometer data. We propose that lobe intervals can be well identified as times when the magnetic field is strong and relatively invariant, defined using thresholds in the magnitude of BX and the standard deviation ???? of the magnetic field magnitude. Using data from the Cluster spacecraft at downtail distances greater than 8 RE during 2001–2009, we find that thresholds of 30 nT and 3.5 nT, respectively, optimize agreement with a previous, independently derived lobe identification method that used both magnetic and plasma data over the same interval. Specifically, our method has a moderately high accuracy (66%) and a low probability of false detection (11%) in comparison to the other method. Furthermore, our method identifies the lobe on many other occasions when the previous method was unable to make any identification and yields longer continuous intervals in the lobe than the previous method, with intervals at the 90th percentile being triple the length. Our method also allows for analyses of the lobes outside the time span of the previous method.

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Accepted/In Press date: 21 January 2016
e-pub ahead of print date: 28 January 2016
Published date: 19 February 2016
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 391201
URI: http://eprints.soton.ac.uk/id/eprint/391201
ISSN: 0148-0227
PURE UUID: 1195215e-4d49-4495-a9df-0f97fe0cc789
ORCID for John Coxon: ORCID iD orcid.org/0000-0002-0166-6854

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Date deposited: 06 Apr 2016 15:12
Last modified: 04 Nov 2017 22:54

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Contributors

Author: John Coxon ORCID iD
Author: Caitriona Jackman
Author: Mervyn P. Freeman
Author: Colin Forsyth
Author: I. Jonathan Rae

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