Observation of ionospheric Alfven resonance at a middle latitude station
This paper intends to report on the statistical results on the spectral resonance structures of the ionospheric Alfven resonances (IAR) in the ULF frequency range 0.1-5.0 Hz on the basis of the analysis of long-term data obtained from July 2000 to December 2002 (2.5 years) at the Karimshino station...
| Main Authors: | , , , |
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| Format: | Report |
| Language: | English |
| Published: |
University of Electro-Communications
2004
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| Subjects: | |
| Online Access: | https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=6381 http://id.nii.ac.jp/1291/00006381/ https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=6381&item_no=1&attribute_id=18&file_no=1 |
| Summary: | This paper intends to report on the statistical results on the spectral resonance structures of the ionospheric Alfven resonances (IAR) in the ULF frequency range 0.1-5.0 Hz on the basis of the analysis of long-term data obtained from July 2000 to December 2002 (2.5 years) at the Karimshino station (Kamchatka, Russia) (L=2.1) by the conventional 3-component search-coil magnetometer. We analyze both the dynamic spectra of three components and polarization spectra in order to distinguish IAR from other possible noises. The average frequency difference _F between the adjacent maxima, intensity and occurrence rate of the IAR spectra have been estimated from the averaged spectra. Early papers at middle latitudes have been based on a small data base. Based on our first long-term observation at middle latitude, new findings, especially related to the seasonal variation, have emerged from this analysis. (1) There is an evident seasonal variation in the occurrence rate with a maximum in the September-January period and an almost complete absence of IAR structures in the spring-early summer time. (2) Occurrence maximum in the diurnal variation is found at 21-23 LT in the autumn and winter. Almost all the IAR structures are observed at local nighttime. (3) The averaged _F is found to be about 0.2-0.5 Hz in the autumn period but it seems to increase up to 0.5-0.7 Hz in winter. (4) The IAR occurrence rate is inversely correlated with the Kp index of global magnetic activity. (5) The intensity of D component exceeds essentially that of H component of the IAR structures in a majority of cases. Diurnal variations of resonance frequencies in the H and D components are not always identical. Finally the mechanisms to explain the observed characteristics of the IAR have been discussed. |
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