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Abstract Electron density irregularities on the dayside in the low‐latitudeFregion are understood as remnants (or fossils) of nighttime plasma bubbles. We provide observational evidence of the connection of daytime irregularities to nighttime bubbles and the transport of the daytime irregularities by the vertical motion of the background ionosphere. The distributions of irregularities are derived using the measurements of the ion density by the first Republic of China satellite from March 1999 to June 2004. The seasonal and longitudinal distributions of daytime and nighttime irregularities in low latitudes show a close similarity. The high occurrence rate of daytime irregularities at the longitudes where strong irregularities occur frequently at night provides strong evidence of the association of daytime irregularities with nighttime bubbles. Nighttime irregularities are concentrated in the equatorial region, whereas daytime irregularities spread over broader latitudes. The seasonal and longitudinal variation of the latitudinal spread of daytime irregularities is consistent with the morphologies of plasma density and vertical plasma velocity. The zonal wave number 4 pattern, which corresponds to that in plasma density, is identified in the distribution of daytime irregularities. These observations lead to the conclusion that the morphology of daytime irregularities in the low‐latitudeFregion is dominated by the morphology of bubbles at night and the ionospheric fountain process on the dayside.
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Global Modeling of Equatorial Spread F with SAMI3/WACCM‐X
Abstract We report the first results of a global ionosphere/thermosphere simulation study that self‐consistently generates large‐scale equatorial spreadF(ESF) plasma bubbles in the postsunset ionosphere. The coupled model comprises the ionospheric code SAMI3 and the atmosphere/thermosphere code WACCM‐X. Two cases are modeled for different seasons and geophysical conditions: the March case (low solar activity: F10.7 = 70) and the July case (high solar activity: F10.7 = 170). We find that equatorial plasma bubbles formed and penetrated into the topsideFlayer for the March case but not the July case. For the March case, a series of bubbles formed in the Atlantic sector with irregularity spacings in the range 400–1,200 km, rose to over 800 km, and persisted until after midnight. These results are consistent with recent GOLD observations. Calculation of the generalized Rayleigh‐Taylor instability (GRTI) growth rate shows that the e‐folding time was shorter for the March case than the July case.
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- Award ID(s):
- 1931415
- PAR ID:
- 10375343
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 47
- Issue:
- 14
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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