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Traveling Ionospheric Disturbances in the Vicinity of Storm‐Enhanced Density at Midlatitudes

ABSTRACT: Abstract This study provides first storm time observations of the westward‐propagating medium‐scale traveling ionospheric disturbances (MSTIDs), particularly, associated with characteristic subauroral storm time features, storm‐enhanced density (SED), subauroral polarization stream (SAPS), and enhanced thermospheric westward winds over the continental US. In the four recent (2017–2019) geomagnetic storm cases examined in this study (i.e., 2018‐08‐25/26, 2017‐09‐07/08, 2017‐05‐27/28, and 2016‐02‐02/03 with minimum SYM‐H index −206, −146, −142, and −58 nT, respectively), MSTIDs were observed from dusk‐to‐midnight local times predominately during the intervals of interplanetary magnetic field (IMF) Bz stably southward. Multiple wavefronts of the TIDs were elongated NW‐SE, 2°–3° longitude apart, and southwestward propagated at a range of zonal phase speeds between 100 and 300 m/s. These TIDs initiated in the northeastern US and intensified or developed in the central US with either the coincident SED structure (especially the SED basis region) or concurrent small electron density patches adjacent to the SED. Observations also indicate coincident intense storm time electric fields associated with the magnetosphere–ionosphere–thermosphere coupling electrodynamics at subauroral latitudes (such as SAPS) as well as enhanced thermospheric westward winds. We speculate that these electric fields trigger plasma instability (with large growth rates) and MSTIDs. These electrified MSTIDs propagated westward along with the background westward ion flow which resulted from the disturbance westward wind dynamo and/or SAPS. Key Points Storm time medium‐scale traveling ionospheric disturbances occur regularly near the base of storm‐enhanced density in the continental US Disturbance wavefronts developed primarily during storm main phase at evening–midnight local times, elongated NW‐SE, and traveled southwestward Disturbance onset coincided with intense electric fields and zonal propagation was synchronized with enhanced westward thermospheric winds

SUBMITTER: Zhang S

PROVIDER: S-EPMC9539488 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature

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Project description:The Bering Sea meteor explosion that occurred on 18 December 2018 provides a good opportunity to study the ionospheric disturbances caused by meteor explosions. Total electron content (TEC) is the core parameter of ionospheric analysis. TEC and its changes can be accurately estimated based on the Global Positioning System (GPS). TID is detected in time and frequency domain based on power spectrum and Butterworth filtering method. By analyzing the waveform, period, wavelength, propagation speed and space-time distribution of TID, the location of the TID source is determined, and the process of TID formation and propagation is understood. The TID caused by meteor explosions has significant anisotropy characteristic. Two types of TID were found. For the first type, the average horizontal propagation velocity is 250.22 ± 5.98 m/s, the wavelength is ~135-240 km, the average period is about 12 min, and the propagation distance is less than 1400 km. About 8 min after the meteor explosion, the first type of TID source formed and propagated radially at the velocity of 250.22 ± 5.98 m/s. For the second type, the propagation velocity is ~434.02 m/s. According to the waveform, period, wavelength and propagation velocity of the TID, it is diagnosed to be the midscale traveling ionospheric disturbances (MSTID). Based on the characteristics of TID, we infer that the TID is excited by the gravity waves generated by the meteor explosion, which is in accordance with the propagation law of gravity waves in the ionosphere. And it is estimated that the average velocity of the up-going gravity waves is about 464.58 m/s. A simple model was established to explain the formation and the propagation of this TID, and to verify the characteristics of the TID propagation caused by nuclear explosion, earthquake, tsunami, and Chelyabinsk meteorite blast. It is estimated that the position of the TID source is consistent with the meteor explosion point, which further indicates that the TID is caused by the meteor explosion and propagates radially.

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Traveling Ionospheric Disturbances in the Vicinity of Storm‐Enhanced Density at Midlatitudes

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