Spatial Characteristics on the Occurrence of the Nighttime Midlatitude Medium‐Scale Traveling Ionospheric Disturbance at Topside Ionosphere Revealed by the Swarm Satellite

Abstract

Using 6 years collecting of electron density (Ne) data from the Swarm A satellite, this study portrays comprehensive maps of the occurrence of medium‐scale traveling ionospheric disturbance (MSTID) at middle latitudes, which is characterized by the in situ absolute Ne fluctuations above a certain threshold. Two interesting spatial preferences on the occurrence of MSTID as well as their dependence on local time and solar cycle are captured, that is, (1) regional preference near Weddell Sea Anomaly (WSA) to its west during December solstice, MSTID in this region appears even at very low latitudes (at least to 10°N in magnetic latitude) and (2) preference at middle latitudes with a wide zonal extension, which is similar to the recently disclosed nighttime midlatitude plasma band‐like enhancement (NMPBE) of the background plasma density (Zhong et al., 2019, https://doi.org/10.1029/2018JA026059). The first preference of MSTID occurring near WSA region can be understood as the effects of horizontal neutral wind contribution to the Perkins instability, with the principal requirement of sporadic E occurrence via ionospheric E‐F region coupling. The fundamental mechanism of the second preference of MSTID occurring includes the interhemispheric coupling that the MSTID can also develop in the winter hemisphere where the local growth rate of Perkins instability is low. Besides, the presence of NMPBE during low solar activity years sets up a favorable environment for the appearance of MSTID with considerable fluctuation amplitude.

Disturbance Neutral Winds Effects on the Ionospheric Strip‐Like Bulge at Lower‐Middle Latitudes

“…Note that the observed conjugate patch spans in the same latitude bins as that of the so-called midlatitude band structure (Zhong et al, 2019), which preferably appears during the night as hemispheric symmetric plasma density enhancements between ±30° and ±50° magnetic latitudes, observed by Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) electron density (Ne) data. The same feature had also been noticed by COSMIC TEC, DMSP ion density, CHAllenging Minisatellite Payload (CHAMP) Ne, and Swarm Ne data (Li et al, 2018;Rajesh et al, 2016;Wan et al, 2020;Xiong, Lühr, et al, 2019). The middle-latitude band structure, also known as the midlatitude enhancement is assumed to be associated with the downward flux of plasmaspheric particles (H + /He + ) due to the ambipolar diffusion (Zhong et al, 2019), though the detailed ion composition of the middle-latitude band structure had not been analyzed.…”

Persistent Occurrence of Strip‐Like Plasma Density Bulges at Conjugate Lower‐Mid Latitudes During the September 8–9, 2017 Geomagnetic Storm

“…Such novelty raises the question that whether this is a known ionospheric structure? The bulges are not likely the medium‐scale traveling ionospheric disturbances (e.g., Otsuka et al., 2004; Wan et al., 2020), since they do not appear in an oscillating form. The magnetic signatures and the ion composition of the bulges are different from the ionospheric blobs, which show clear magnetic signatures (Park, Stolle, et al., 2008) and the dominance of O + (Park, Min, et al., 2003).…”

“…Such novelty raises the question that whether this is a known ionospheric structure? The bulges are not likely the medium-scale traveling ionospheric disturbances (e.g., Otsuka et al, 2004;Wan et al, 2020) 2 and reorganized as orbit number 1-4). The SED plume is marked by the black arrows, the SED base which is attached to the SED plume is marked by a wine red arrow in the top-middle panel.…”

Investigation on Horizontal and Vertical Traveling Ionospheric Disturbances Propagation in Global‐Scale Using GNSS and Multi‐LEO Satellites

“…Kil and Paxton (2017), Wan et al. (2020) studied the nighttime MSTIDs revealed by the in situ data onboard Swarm satellites. Nevertheless, the orbit altitudes of Swarm satellites are limited at about 450∼500 km.…”

“…The TID-induced electron density enhancements or depletions at different altitudes could be smeared out, as the TIDs in GNSS TEC data represent perturbations in the altitude-integrated electron content (Zhang et al, 2018). Kil and Paxton (2017), Wan et al (2020) studied the nighttime MSTIDs revealed by the in situ data onboard Swarm satellites. Nevertheless, the orbit altitudes of Swarm satellites are limited at about 450∼500 km.…”