Traveling ionospheric disturbances and their relations to storm‐enhanced density features and plasma density irregularities in the local evening and nighttime hours of the Halloween superstorms of 29–31 October 2003

Abstract

This study focuses on the local evening or nighttime hours of the Halloween superstorms. Its database, containing multi‐instrument Defense Meteorological Satellite Program data plus ionosonde and magnetometer data, allowed us to investigate the various plasma density features developed and the impact of traveling ionospheric disturbances (TIDs), drift perturbations, and South Atlantic Magnetic Anomaly (SAMA) effects on them. We identified the midlatitude trough, some topside bubbles, the equatorial ionization anomaly (EIA), and some storm‐enhanced density (SED) features. Results reveal that these features' underlying vertical plasma flows became enhanced (degraded) when they were in the same (opposite) direction as the field‐aligned flows associated with a TID. Demonstrated with some Coupled Thermosphere‐Ionosphere‐Plasmasphere–simulated wind vector maps, high (low) plasma densities were maintained by equatorward (poleward) winds. We observed some descending (∼600 m/s) bubbles with increased temperatures (∼4500°K), due to their fast poleward movement (∼1.4 km/s), structuring some nearby SED features in the SAMA region and some low‐latitude plasma in the Australian sector. During the second superstorm's main phase (30 October 2003), a rising bubble with increased temperatures (∼5000°K), due to the SAMA's energetic electrons, further depleted the EIA trough. This observation contradicts a current interpretation of this depleted EIA trough as bubble. At the time of prereversal enhancement (∼2300 UT on 30 October), some extremely large SED features (∼85 × 104 ions+/cm3) developed (∼±30°N geomagnetic latitude) around the symmetrical EIA over Brazil. This scenario created a symmetrical plasma density profile contradicting some current speculations on the EIA's asymmetry and its southern crest's displacement to higher latitudes over Brazil. Indeed, a SED feature appeared at higher latitudes (∼35°S geographic latitude).

A Statistical Study on the Climatology of the Equatorial Plasma Depletions Occurrence at Topside Ionosphere During Geomagnetic Disturbed Periods

“…A steep upward plasma density gradient forms from the ionospheric E region where the recombination rate is higher, toward the F region where the recombination rate is much lower. The upward E × B drifts (e.g., Burke, Gentile, et al, ; Burke, Huang, et al, ; Stolle et al, ; Su et al, ; Xiong et al, ) are recognized as one of the primary factors for modulating the R‐T instability growth rate, along with seeding mechanisms like gravity waves (e.g., Krall et al, ; McClure et al, ; Taori et al, ) and traveling ionosphere disturbances (e.g., Batista et al, ; Horvath & Lovell, ; Krall et al, ), to facilitate the generation and development of the EPDs. The influence of meridional neutral wind has also been discussed, as it can affect the F region peak height and modify the field line‐integrated conductivities (e.g., Dao et al, ; Huba & Krall, ; Krall et al, ; Maruyama et al, ).…”

Dynamical Complexity Response in Traveling Ionospheric Disturbances Across Eastern Africa Sector During Geomagnetic Storms Using Neural Network Entropy

“…During the equinoctial and summer months, the ionospheric system is induced by the equatorial ionospheric anomaly (EIA); in that, the daytime (nighttime) F region plasma is transported by a vertical upward (downward) $$E\times B$$ drift, created by interaction between the ionospheric electric‐field and the geomagnetic B field over the dip equator, and by field‐aligned diffusion on both sides of the dip equator. These processes have a tendency to create a plasma distribution symmetric to the dip equator and local TEC gradient (Bolaji et al., 2022; Horvath & Lovell, 2010; Maruyama et al., 2005; Spogli et al., 2009).…”