First Detection of Midlatitude Plasma Bubble by SuperDARN During a Geomagnetic Storm on May 27 and 28, 2017

Abstract

We used the global navigation satellite system‐total electron content (TEC) and Super Dual Auroral Radar Network (SuperDARN) radar to elucidate the characteristics of the plasma bubble extending to midlatitudes over North America during a geomagnetic storm on 27 and 28 May 2017. To identify plasma bubbles, we analyzed the rate of the TEC index (ROTI), which is a good indicator of the occurrence of plasma bubbles. The enhanced ROTI region expanded up to 50°N (geomagnetic latitude), and the upper limit of this region coincided with the equatorward wall of the midlatitude trough. Two‐dimensional ROTI maps show that the enhanced midlatitude ROTI region moved westward at a bulk speed of approximately 310 m/s. The Fort Hays East SuperDARN radar also detected the radar echo, showing the existence of plasma density irregularities at ∼10‐m scales within the midlatitude plasma bubble. The radar echo had a westward velocity of ∼300 m/s, which is almost consistent with the westward motion of the enhanced midlatitude ROTI region. We deduced that the westward propagation of the plasma bubble could be caused by a poleward sub‐auroral polarization stream electric field. The observed radar echo overlapping with the enhanced ROTI region had a narrower spectral width (<50 m/s) than that of the auroral activity. This feature resembled that of the type 1 echo, although the Doppler velocity was smaller than the ion acoustic speed at the F‐region height. This is the first case in which plasma density irregularities within plasma bubbles were captured by the SuperDARN radar.

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

“…Similarly, Foster and Rich (1998) measured a distinct EPB‐like ionospheric depletion using the Millstone Hill incoherent scatter radar around 35–37° MLAT. Moreover, recent studies employing coordinated ground‐based observations and satellite in‐situ measurements have revealed that these bubble‐like plasma depletions can form poleward‐streaming structures that extend considerably across the midlatitude region, reaching unexpectedly subauroral latitudes of 40–50° MLAT, such as over the European longitude sector (Cherniak & Zakharenkova, 2016; Katamzi‐Joseph et al., 2017), Asian‐Pacific longitude sector (Aa et al., 2018; Huang et al., 2007; Li et al., 2018), and American longitude sector (e.g., Aa et al., 2019; Chang et al., 2022; Cherniak & Zakharenkova, 2022; Martinis et al., 2015; Sori et al., 2023; Zakharenkova & Cherniak, 2020).…”