Abstract
On 14 December 1999, a large-scale ULF wave event was observed by the Hankasalmi radar of the Super-DARN 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 Alfven 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 30 eV. 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 < 30 eV, 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 0-500 eV.
Original language | English |
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Number of pages | 487 |
Volume | 23 |
Publication status | Published - 2005 |
Keywords
- ionosphere
- particle acceleration
- magnetospheric physics
- magnetosphere-ionosphere interactions
- MHD waves and instabilities
- HF RADAR BACKSCATTER
- LINE RESONANCES
- ALFVEN WAVES
- PHASE MOTION
- PULSATIONS
- ELECTRON
- MAGNETOSPHERE
- ACCELERATION
- EXCITATION
- PLASMA