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Abstract During space weather events, a large amount of energy and momentum from the solar wind inputs into the ionosphere‐thermosphere. A critical question is that if the solar wind‐magnetosphere interaction drives only the open field region in the polar caps, how the solar wind energy and momentum are transmitted to the low latitude and equatorial ionosphere. This important issue has been studied over decades and is still poorly understood, impeding space weather forecasting ability. Here we use our newly developed 2.5‐D ionosphere‐thermosphere simulation model that self‐consistently solves the density, velocity, and temperature for electrons, multiple ion and neutral species, and electromagnetic fields to study this challenging problem. The focus of the present study is on the prompt response of the ionosphere to a convection disturbance from the polar magnetosphere. The longer time scale responses caused by the neutral winds from the polar caps will be the topic of future studies. We show that the momentum is transferred from polar to equatorial ionosphere predominately by fast magnetosonic waves, and propagation of perturbations from the source region experiences delay, damping, and substantial reflection, and the ionosphere/thermosphere behaves like a low‐band‐pass filter. The finding from this study sheds new insight onto coupling processes within the magnetosphere‐ionosphere system.
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Improving ionospheric predictability requires accurate simulation of the mesospheric polar vortex
The mesospheric polar vortex (MPV) plays a critical role in coupling the atmosphere-ionosphere system, so its accurate simulation is imperative for robust predictions of the thermosphere and ionosphere. While the stratospheric polar vortex is widely understood and characterized, the mesospheric polar vortex is much less well-known and observed, a short-coming that must be addressed to improve predictability of the ionosphere. The winter MPV facilitates top-down coupling via the communication of high energy particle precipitation effects from the thermosphere down to the stratosphere, though the details of this mechanism are poorly understood. Coupling from the bottom-up involves gravity waves (GWs), planetary waves (PWs), and tidal interactions that are distinctly different and important during weak vs. strong vortex states, and yet remain poorly understood as well. Moreover, generation and modulation of GWs by the large wind shears at the vortex edge contribute to the generation of traveling atmospheric disturbances and traveling ionospheric disturbances. Unfortunately, representation of the MPV is generally not accurate in state-of-the-art general circulation models, even when compared to the limited observational data available. Models substantially underestimate eastward momentum at the top of the MPV, which limits the ability to predict upward effects in the thermosphere. The zonal wind bias responsible for this missing momentum in models has been attributed to deficiencies in the treatment of GWs and to an inaccurate representation of the high-latitude dynamics. In the coming decade, simulations of the MPV must be improved.
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- Award ID(s):
- 1543446
- PAR ID:
- 10392396
- Date Published:
- Journal Name:
- Frontiers in Astronomy and Space Sciences
- Volume:
- 9
- ISSN:
- 2296-987X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fspas.2022.1041426
