| Autor: |
Michael, C. M.1,2 (AUTHOR) chizurumokem@gmail.com, Yeoman, T. K.2 (AUTHOR), Wright, D. M.2 (AUTHOR), Chelpanov, M. A.3 (AUTHOR), Mager, P. N.3 (AUTHOR) |
| Předmět: |
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| Zdroj: |
Journal of Geophysical Research. Space Physics. Mar2024, Vol. 129 Issue 3, p1-23. 23p. |
| Abstrakt: |
An ultralow frequency (ULF) wave was simultaneously observed in the ionosphere by the Super Dual Auroral Radar Network (SuperDARN) radar at Hankasalmi, Finland and on the ground by the International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometers with close proximity to the radar. The onset time of the wave event was around 03:00 magnetic local time. Fourier wave analysis of the event suggests a wave period of about 1,340 s with an equatorward latitudinal and eastward longitudinal wave phase propagation, and an effective azimuthal wave number of 17 ± 1, in the intermediate range of those observed in ULF waves. This wave has been interpreted as resulting from drifting electrons of energies of 13 ± 5 keV in a drift resonance condition linked to energetic particle populations during a magnetospheric substorm. The latitudinal phase characteristics of this wave experienced temporal evolution, believed to be caused by additional injected particle populations associated with the same substorm driving the wave, which resulted in an observed loss of HF backscatter. This observation of a unique type of temporal evolution in the phase propagation characteristics of ULF waves enhances current understanding about the structure, dynamics and source of these types of ULF waves. Plain Language Summary: The ultralow frequency (ULF) waves provide information about the Earth's global magnetic field known as magnetosphere. These waves contribute to the circulation of mass, energy and momentum in the near‐earth space environment. However, the sources of these waves as well as the generation and propagation mechanisms behind them are not fully understood. In this paper, we have used Super Dual Auroral Radar Network (SuperDARN) radar and magnetometer observations to characterize a ULF wave event and investigate noticeable changes in the wave phase propagation over space and time during the wave event. The results show that the case‐study ULF wave is localized with very long period. We find that the wave appears to be driven by resonance with energetic electrons injected into the magnetosphere by a process in the magnetosphere known as a substorm. We also find that the wave event is particularly unusual in that its phase propagation characteristics appear to change during the event. The results enhance current understanding of changes in the characteristics of ULF waves over space and time using a multi‐instrument measurements. Key Points: The case‐study ultralow frequency wave, localized but with very long period, and with m number of ≈17 was simultaneously observed in the ionosphere by ground‐based radar and on the Earth's surface by ground‐based magnetometersThe wave phase propagates eastward and appears to be driven by resonance with energetic electrons injected into the magnetosphere during a recent magnetospheric substormThe wave event is particularly unusual in that its latitudinal phase propagation characteristics appear to change during the event [ABSTRACT FROM AUTHOR] |
| Databáze: |
GreenFILE |
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