Identifying the magnetotail lobes with Cluster magnetometer data

J. C. Coxon*, C. M. Jackman, M. P. Freeman, C. Forsyth, I. J. Rae

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

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 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.

Original languageEnglish
Pages (from-to)1436-1446
Number of pages11
JournalJournal of Geophysical Research A: Space Physics
Volume121
Issue number2
Early online date19 Feb 2016
DOIs
Publication statusPublished - Feb 2016
Externally publishedYes

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