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Title: An investigation of the field-aligned currents associated with a large-scale ULF wave using data from CUTLASS and FAST
Authors: Scoffield, H. C.
Yeoman, Timothy Kenneth
Wright, D. M.
Milan, Stephen Eric
Wright, A. N.
Strangeway, R. J.
First Published: 28-Feb-2005
Publisher: Copernicus Publications on behalf of the European Geosciences Union
Citation: Annales Geophysicae, 2005, 23 (2), pp. 487-498 (12)
Abstract: On 14 December 1999, a large-scale ULF wave event was observed by the Hankasalmi radar of the SuperDARN chain. Simultaneously, the FAST satellite passed through the Hankasalmi field-of-view, measuring the magnetic field oscillations of the wave at around 2000km altitude, along with the precipitating ion and electron populations associated with these fields. A simple field line resonance model of the wave has been created and scaled using the wave's spatial and temporal characteristics inferred from SuperDARN and IMAGE magnetometer data. Here the model calculated field-aligned current is compared with field-aligned currents derived from the FAST energetic particle spectra and magnetic field measurements. This comparison reveals the small-scale structuring and energies of the current carriers in a large-scale Alfvén wave, a topic, which at present, is of considerable theoretical interest. When FAST traverses a region of the wave involving low upward field-aligned current densities, the current appears to be carried by unstructured downgoing electrons of energies less than 30eV. A downward current region appears to be carried partially by upgoing electrons below the FAST energy detection threshold, but also consists of a mixture of hotter downgoing magnetospheric electrons and upgoing ionospheric electrons of energies <30eV, with the hotter upgoing electrons presumably representing those upgoing electrons which have been accelerated by the wave field above the low energy detection threshold of FAST. A stronger interval of upward current shows that small-scale structuring of scale ~50km has been imposed on the current carriers, which are downgoing magnetospheric electrons of energy 0-500eV.
DOI Link: 10.5194/angeo-23-487-2005
ISSN: 0992-7689
eISSN: 1432-0576
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © Author(s) 2005. This work is distributed under the Creative Commons Attribution 3.0 License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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