Identifying the magnetotail lobes with Cluster magnetometer data

Coxon, John, Jackman, C. M., Freeman, M. P., Forsyth, C. and Rae, Jonathan (2016) Identifying the magnetotail lobes with Cluster magnetometer data. Journal of Geophysical Research: Space Physics, 121 (2). pp. 1436-1446. ISSN 2169-9380

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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 σ 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.

Item Type: Article
Additional Information: Funding Information: This work is supported by Natural Environment Research Council (NERC) joint grants NE/L007177/1 (J.C.C. and C.M.J.), NE/L006456/1 (M.P.F.), and NE/L007495/1 (C.F. and I.J.R.).
Uncontrolled Keywords: magnetic field, magnetotail, magnetotail lobes
Subjects: F300 Physics
F500 Astronomy
F800 Physical and Terrestrial Geographical and Environmental Sciences
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Rachel Branson
Date Deposited: 22 Feb 2022 12:01
Last Modified: 22 Feb 2022 12:15

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