The dependence of magnetospheric plasma mass loading on geomagnetic activity using Cluster

Sandhu, Jasmine, Yeoman, T. K., Rae, I. J., Fear, R. C. and Dandouras, I. (2017) The dependence of magnetospheric plasma mass loading on geomagnetic activity using Cluster. Journal of Geophysical Research: Space Physics, 122 (9). pp. 9371-9395. ISSN 2169-9380

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Official URL: https://doi.org/10.1002/2017JA024171

Abstract

Understanding changes in the magnetospheric mass density during disturbed geomagnetic conditions provides valuable insight into the dynamics and structure of the environment. The mass density plays a significant role in a variety of magnetospheric processes, such as wave propagation, magnetic reconnection rates, and radiation belt dynamics. In this study, the spatial variations of total plasma mass density are explored through the analysis of Cluster observations. Data from the WHISPER (Waves of High frequency and Sounder for Probing of Electron density by Relaxation) and CODIF (ion Composition and Distribution Function analyzer) instruments, on board the four Cluster spacecraft for a time interval spanning 2001–2012, are used to determine empirical models describing the distribution of the total plasma mass density along closed geomagnetic field lines. The region considered covers field lines within 5.9≤L < 9.5, corresponding to the outer plasmasphere, plasmatrough, and near‐Earth plasma sheet. This study extends previous work to examine and quantify spatial variations in the electron density, average ion mass, and total plasma mass density with Dst index. The results indicate that during periods of enhanced ring current strength, electron density is observed to decrease and average ion mass is observed to increase, compared with quiet geomagnetic conditions. The combination of these variations shows that although heavy ion concentration is enhanced, the decrease in plasma number density results in a general decrease in total plasma mass density during disturbed geomagnetic conditions. The observed decrease in mass density is in contrast to prevailing understanding and, due to the dependence of the Alfvén speed on mass density, has important implications for a range of plasma processes during storm time conditions (e.g., propagation of wave modes).

Item Type: Article
Additional Information: Research funded by Science and Technology Facilities Council (ST/K502121ST/N0007722/1) | Natural Environment Research Council (ST/H002480/1NE/L007495/1ST/N0007722/1) | Centre National d’Etudes Spatiales | STFC Ernest Rutherford Fellowship (ST/K004298/2)
Uncontrolled Keywords: WHISPER, CODIF, geomagnetic storms, Cluster, ion composition, mass density
Subjects: F300 Physics
F600 Geology
F800 Physical and Terrestrial Geographical and Environmental Sciences
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Rachel Branson
Date Deposited: 14 Apr 2021 09:21
Last Modified: 14 Apr 2021 09:30
URI: http://nrl.northumbria.ac.uk/id/eprint/45917

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