Smith, Andy, Rae, Jonathan, Forsyth, C., Watt, Clare and Murphy, Kyle (2023) Statistical Characterization of the Dynamic Near-Earth Plasma Sheet Relative to Ultra-Low Frequency (ULF) Wave Growth at Substorm Onset. Journal of Geophysical Research: Space Physics, 128 (1). e2022JA030491. ISSN 2169-9380
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JGR Space Physics - 2023 - Smith - Statistical Characterization of the Dynamic Near‐Earth Plasma Sheet Relative to.pdf - Published Version Available under License Creative Commons Attribution 4.0. Download (2MB) | Preview |
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[7]MagnetotailConditions_noBBL.pdf - Accepted Version Available under License Creative Commons Attribution 4.0. Download (1MB) | Preview |
Abstract
Magnetospheric substorms are a complex phenomenon. During the initial stages of a substorm a variety of important processes occur in near-Earth space within a span of several minutes. The relative timing and links between these processes are critical to understanding how, where and when substorms may occur. One of the first observed signatures at substorm onset is the exponential increase in ULF (Ultra-Low Frequency) wave power in the near-Earth magnetotail (e.g., −7.5 ≤ XGSM ≤ −12.5 RE). We use the Time History of Events and Macroscale Interactions during Substorms spacecraft to examine the conditions in the magnetotail plasma sheet before, during and after local ULF wave growth. Prior to the ULF wave growth, the magnetotail stretches with convectional flows dominating. We then find strong earthward and azimuthal flows that peak at a similar time to the peak ULF wave power. These flows are found to be faster in the mid-tail (−10 ≤ XGSM ≤ −12.5 RE) than the near-tail (−7.5 ≤ XGSM ≤ −10 RE). Examining the local plasma energy density (magnetic, thermal and kinetic), we find no statistical decrease that could explain the exponentially growing ULF waves, in fact the local energy density is found to increase. This suggests that there may be an injection of energy from elsewhere in the magnetotail. Following the peak ULF wave power the tail is seen to dipolarize, and the local energy density is enhanced.
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| Additional Information: | Funding information: The authors acknowledge the NASA contract NAS5-02099 and V. Angelopoulos for use of data from the THEMIS Mission. Specifically, C. W. Carlson and J. P. McFadden for use of Electrostatic Analyzer data; D. Larson and the late R. P. Lin for use of Solid State Telescope data; and K. H. Glassmeier, U. Auster and W. Baumjohann for the use of FGM data provided under the lead of the Technical University of Braunschweig and with financial support through the German Ministry for Economy and Technology and the German Center for Aviation and Space (DLR) under contract 50 OC 0302. AWS and CF were supported by STFC Consolidated Grant ST/S000240/1, and NERC grants NE/P017150/1 and NE/V002724/1. AWS was also supported by NERC Independent Research Fellowship NE/W009129/1, while CF was also supported by the NERC Independent Research Fellowship NE/N014480/1. IJR was supported by STFC Consolidated Grant ST/V006320/1. KRM is partially supported by NERC grant NE/V002554/2. |
| Subjects: | F300 Physics F500 Astronomy |
| Department: | Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering |
| Depositing User: | John Coen |
| Date Deposited: | 13 Jan 2023 11:31 |
| Last Modified: | 23 Jan 2023 08:45 |
| URI: | https://nrl.northumbria.ac.uk/id/eprint/51157 |
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