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Temporal evolution and electric potential structure of the auroral acceleration region from multispacecraft measurements

Forsyth, C., Fazakerley, A. N., Walsh, A. P., Watt, C. E. J., Garza, K. J., Owen, C. J., Constantinescu, D., Dandouras, I., Fornaçon, K.-H., Lucek, E., Marklund, G. T., Sadeghi, S. S., Khotyaintsev, Y., Masson, A. and Doss, N. (2012) Temporal evolution and electric potential structure of the auroral acceleration region from multispacecraft measurements. Journal of Geophysical Research, 117. A12203. ISSN 0148-0227

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To link to this item DOI: 10.1029/2012JA017655

Abstract/Summary

Bright aurorae can be excited by the acceleration of electrons into the atmosphere in violation of ideal magnetohydrodynamics. Modelling studies predict that the accelerating electric potential consists of electric double layers at the boundaries of an acceleration region but observations suggest that particle acceleration occurs throughout this region. Using multi-spacecraft observations from Cluster we have examined two upward current regions on 14 December 2009. Our observations show that the potential difference below C4 and C3 changed by up to 1.7 kV between their respective crossings, which were separated by 150 s. The field-aligned current density observed by C3 was also larger than that observed by C4. The potential drop above C3 and C4 was approximately the same in both crossings. Using a novel technique of quantitatively comparing the electron spectra measured by Cluster 1 and 3, which were separated in altitude, we determine when these spacecraft made effectively magnetically conjugate observations and use these conjugate observations to determine the instantaneous distribution of the potential drop in the AAR. Our observations show that an average of 15% of the potential drop in the AAR was located between C1 at 6235 km and C3 at 4685 km altitude, with a maximum potential drop between the spacecraft of 500~V and that the majority of the potential drop was below C3. By assuming a spatial invariance along the length of the upward current region, we discuss these observations in terms of temporal changes and the vertical structure of the electrostatic potential drop and in the context of existing models and previous observations single- and multi-spacecraft observations.

Item Type:Article
Refereed:Yes
Divisions:No Reading authors. Back catalogue items
Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:32799
Uncontrolled Keywords:auroral acceleration; electric potentials; multispacecraft
Publisher:American Geophysical Union

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