Storm Time Electrified MSTIDs Observed Over Mid‐Latitude North America

Abstract

Traveling Ionospheric Disturbances (TIDs; Munro, 1948) are wave-like structures which propagate through the ionosphere. TIDs are most commonly expected to be driven by Atmospheric Gravity Waves (AGWs) originating in the neutral atmosphere (Hines, 1960) and can be sensed with instruments used for monitoring ionospheric dynamics such as Global Navigational Satellite Service (GNSS) Total Electron Content (TEC;Saito et al., 1998) and coherent scatter radars (Fukao et al., 1991;Samson et al., 1990). TIDs are further classified as either Large-Scale (LSTIDs) or MSTIDs based on their spatio-temporal scales (Georges, 1968). MSTIDs typically have a time period of 15-60 min, phase velocities of 100-300 m/s, and wavelengths between 200 and 800 km. On the other hand, LSTIDs have phase speeds between 400 and 10,00 m/s, periods above 30 min, and wavelengths above 1,000 km (Hocke & Schlegel, 1996;Hunsucker, 1982). The differences between MSTIDs and LSTIDs are not just limited to their spatio-temporal scales, previous studies have shown that the underlying generation mechanisms and the physics of their propagation also differ (Hocke & Schlegel, 1996). MSTIDs are often linked to AGWs, which are a neutral atmospheric phenomenon generally carrying more energy than the TIDs themselves (Hunsucker, 1982). Such AGW-driven MSTIDs are more commonly reported at high latitudes, and on the dayside, and in the winter (Bristow et al., 1994;Frissell et al., 2014). The AGWs are in turn expected to be driven by factors such tropospheric weather (Chou et al., 2017), Joule heating (Chimonas & Hines, 1970), and ground-based disturbances including tsunamis and earthquakes (Liu et al., 2011). Determining the sources of AGWs/MSTIDs can be challenging since they travel thousands of kilometers from the source and dissipate along the propagation paths (e.g.,

Large‐Scale Traveling Ionospheric Disturbances Over the European Sector During the Geomagnetic Storm on March 23–24, 2023: Energy Deposition in the Source Regions and the Propagation Characteristics

“…At high latitudes, electric fields may play an active role in the triggering as well as horizontal propagation of TIDs. Such electric field oscillations were previously indicated during MSTID occurrence (Kelley et al, 2023). Therefore, we examined the presence of significant ion velocity oscillation in the EISCAT measurements.…”

“…EISCAT IS radar measurements of electron density have been used to study the propagation characteristics of LSTIDs (Cai et al., 2011; Ma et al., 1998) as well as Medium‐Scale TIDs (MSTIDs), which are often forced by upward‐propagating gravity waves (Günzkofer et al., 2023; Hocke & Schlegel, 1996; Kirchengast et al., 1996; Vlasov et al., 2011). Other forcing mechanisms include interhemispheric electrodynamic coupling along magnetic field lines (Otsuka et al., 2004; Shiokawa et al., 2005; Tsunoda & Cosgrove, 2001) and storm time electric fields which can force TIDs electrodynamically, for example, via the Perkins instability (Kelley et al., 2023; Tsugawa et al., 2007; Zhang et al., 2019, 2022). IS radar can also measure the oscillation period and the vertical wavelength associated with generated gravity waves with high accuracy.…”

Simultaneous Occurrence of Traveling Ionospheric Disturbances, Farley Buneman and Gradient Drift Instabilities Observed by the Zhongshan SuperDARN HF Radar

“…Those values could be caused by the relative velocity between the E ‐region NREs and the F ‐region MSTIDs switching the electric field polarities between the crests and the troughs (Kelley et al., 2023). Either positive or negative polarization electric field is mapped down to the E ‐region to affect the NREs (Hiyadutuje et al., 2022).…”

Significant Midlatitude Bubble‐Like Ionospheric Super‐Depletion Structure (BLISS) and Dynamic Variation of Storm‐Enhanced Density Plume During the 23 April 2023 Geomagnetic Storm

“…Examples of BLISS in GNSS TEC (Figure 8) also reveal similar structures, where the depletion channel is sandwiched between high‐density regions. Some studies have indicated that the presence of such sandwiched density gradient structures at midlatitude ionosphere is likely associated with SAPS and polarization electric fields (I. J. Kelley et al., 2023; S.‐R. Zhang et al., 2022).…”

“…These observations are consistent with our first explanation that high‐altitude/latitude EPB/ESF structures can indeed intrude into the midlatitude region under strong PPEF condition. On the other hand, some studies using Super Dual Auroral Radar Network (SuperDARN) and GNSS TEC measurements have observed polarities switching of plasma velocities between midlatitude MSTID‐like electron density crests and troughs under background SAPS electric fields, indicating the presence of polarization electric fields and associated electrodynamic/Perkins instability processes (I. J. Kelley et al., 2023; S.‐R. Zhang et al., 2022).…”