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We present an analysis of 6 h oscillations in the thermosphere ranging from 150 km to 400 km. The analysis applies 134 days of data from an incoherent scatter radar located at Arecibo Observatory (18.3°N, 66.7°W) from 1984 to 2015. To our knowledge, the climatological and seasonal characteristics of the 6 h oscillations in the thermosphere were investigated for the first time over Arecibo. The climatological mean amplitude of the 6 h oscillation in the thermosphere is about 11 m/s, and it increases slowly with altitude above 225 km. The climatological mean amplitude of the 6 h oscillation is comparable with semidiurnal and terdiurnal tides at Arecibo above 250 km. The climatological mean phase exhibits limited vertical variation. The 6 h oscillation is the most prominent in autumn, with amplitudes reaching around 20 m/s compared to approximately 10 m/s in other seasons. The phase structure in all seasons exhibits weak vertical variations. The responses of the thermospheric 6 h oscillation to solar and geomagnetic activities are also analyzed in this study. Our results indicate that at low latitude, solar activities have a small impact on the variation in the thermospheric 6 h oscillation, while it appears that the amplitude of the 6 h oscillation increases with increasing geomagnetic activity. Above 250 km, the amplitude of the 6 h oscillation reaches ~20 m/s during strong geomagnetic activity, which is almost twice of that occurring during weak geomagnetic activity.
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Seasonal and Geomagnetic Activity Dependence of Auroral E ‐Region Neutral Winds at Poker Flat
In this paper, we investigated the seasonal and geomagnetic dependence of the auroral ‐region neutral winds and the tidal components between 90 and 125 km using nearly continuously sampled measurements from the Poker Flat Incoherent Scatter Radar (PFISR) from 2010 to 2019. The average winds show consistent semidiurnal oscillations between 100 and 115 km and diurnal oscillations above 115 km in all seasons with some seasonal and geomagnetic activity dependencies. In general, the semidiurnal oscillation in zonal and meridional directions is strongest in summer and weakest in winter. The diurnal oscillation is strongest in winter and weakest in spring. More details on the seasonal and geomagnetic activity dependencies are revealed in the tidal decomposition results. Tidal decomposition results show eastward mean wind below 115 km in summer, fall, and winter and westward mean wind above 115 km in all seasons. The meridional mean is northward below 115 km and southward above in all seasons. The diurnal amplitudes are small below 110 km and increase with altitude above 110 km in all seasons with larger enhancements in the meridional direction. The semidiurnal amplitudes increase with altitude below 110 km and reach a maximum at around 110 km, then decrease or keep stable (depending on the geomagnetic activity) above 110 km in both directions and all seasons. The diurnal phases shift to earlier times with the increase of geomagnetic activity but show different variations with altitudes in zonal and meridional directions. The semidiurnal phases show a downward progressing trend in both directions and in all seasons.
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- Award ID(s):
- 2028032
- PAR ID:
- 10648714
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 130
- Issue:
- 2
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2024JA033074
