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Abstract Previous studies have shown that solar flares can significantly affect Earth's ionosphere and induce ion upflow with a magnitude of ∼110 m/s in the topside ionosphere (∼570 km) at Millstone Hill (42.61°N, 71.48°W). We use simulations from the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM) and observations from Incoherent Scatter Radar (ISR) at Millstone Hill to reveal the mechanism of ionospheric ion upflow near the X9.3 flare peak (07:16 LT) on 6 September 2017. The ISR observed ionospheric upflow was captured by the TIEGCM in both magnitude and morphology. The term analysis of the F‐region ion continuity equation during the solar flare shows that the ambipolar diffusion enhancement is the main driver for the upflow in the topside ionosphere, while ion drifts caused by electric fields and neutral winds play a secondary role. Further decomposition of the ambipolar diffusive velocity illustrates that flare‐induced changes in the vertical plasma density gradient is responsible for ion upflow. The changes in the vertical plasma density gradient are mainly due to solar extreme ultraviolet (EUV, 15.5–79.8 nm) induced electron density and temperature enhancements at the F2‐region ionosphere with a minor and indirectly contribution from X‐ray (0–15.5 nm) and ultraviolet (UV, 79.8–102.7 nm).
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This content will become publicly available on August 1, 2026
Modeling MSTIDs Produced by Gravity Waves With Parameters Obtained From All‐Sky Imager Observations and Comparisons to Incoherent Scatter Radar Observations
Abstract Hypotheses concerning processes related to medium‐scale traveling ionospheric disturbances (MSTIDs) are investigated with the application of models and the analysis of observational data. Wave‐packet parameters for MSTIDs from 2011 through 2022 are obtained from OI 6300 Å observations from the Boston University all‐sky imager (ASI) at the Millstone Hill Observatory during periods for which concurrent Millstone Hill (MH) incoherent scatter radar (ISR) observations are available. A combination of a numerical multi‐layer (NML) model for gravity waves (GW) in the thermosphere with the Field‐Line Interhemispheric Plasma (FLIP) model for ionospheric processes and upper‐atmospheric emissions is applied to generate perturbation electron‐density values, which are compared with ISR‐observed perturbation electron‐density values. A detailed comparison is made between model‐generated and ISR‐observed electron density for two cases, and the comparisons show notably good agreement. Twelve other MSTID cases are also described, giving a total of 14 cases. The results confirm that some nighttime MSTIDs at midlatitudes directly correspond to local GWs. They also suggest that some MSTIDs occurring over MH primarily consist of plasma fluctuations without corresponding local neutral fluctuations and that such MSTIDs are more common during winter months. The phase relationship between electron density and neutral vertical velocity variations is examined for two cases. Additionally, the hypothesis that standard thermospheric dynamic molecular viscosity values should be reduced is evaluated, and it is found that this is not supported by the results.
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- Award ID(s):
- 2130749
- PAR ID:
- 10629711
- Editor(s):
- St_Maurice, Jean_Pierre
- Publisher / Repository:
- Journal of Geophysical Research: Space Physics
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 130
- Issue:
- 8
- ISSN:
- 2169-9380
- Subject(s) / Keyword(s):
- medium-scale traveling ionospheric disturbances atmospheric gravity waves upper thermosphere ionospheric F region numerical multilayer method
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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