When Plasma Streams Tie up Equatorial Plasma Irregularities with Auroral Ones

Abstract

We present a new pattern of storm‐induced ionospheric irregularities behavior at midlatitudes—poleward‐streaming plasma density depletions. Under disturbed conditions, they appear at North America low latitudes as a part of extended postsunset equatorial plasma bubbles, and further, they are streaming from low latitudes in a northwestward, poleward direction toward the main ionospheric trough and auroral irregularities zone. The poleward‐streaming plasma depletions represent a new phenomenon with the similar northwestward transportation path across the continental United States as storm‐enhanced density (SED) plumes. The channels of poleward‐streaming plasma depletions were stretched from low‐latitude base toward higher latitudes—they are found to occur for geomagnetic storms under specific combination of steady southward interplanetary magnetic field, subauroral polarization streams (SAPS) electric fields, and enhanced westward drifts at midlatitudes, resulting in northwestward plasma transportation equatorward of the SAPS region. The poleward‐streaming plasma depletions form an illusion of traveling ionospheric disturbances (TIDs) moving in a poleward, northwestward direction—this propagation direction is opposite to typical equatorward propagation of storm‐induced large‐scale TIDs generated in the auroral zone and propagated toward the equator. This phenomenon is accompanied by strong ionospheric irregularities that occurred over both edges of plasma depletion channel at midlatitudes. For two comparable geomagnetic storms, these poleward‐streaming plasma depletions persisted for several hours, posing a localized threat for GPS‐based positioning applications. Even moderate‐to‐intense storms (Dst minimum−145 nT) can promote such effects at midlatitudes.

Leveraging Geodetic GPS Receivers for Ionospheric Scintillation Science

“…The results of the presented case study indicate that there are other midlatitude mechanisms producing both amplitude and phase scintillation. The climatology and controlling parameters of these events are mysterious, as it appears that they occur during large storms (Aa et al, 2019; Ledvina et al, 2002; Zakharenkova & Cherniak, 2020). Leveraging 1‐Hz geodetic receivers, such as the one operated by UNAVCO, could be utilized to gain insight into the midlatitude scintillation phenomenon through a comprehensive retrospective analysis.…”

“…The ionosphere exhibited several distinct perturbations at this local time sector, in the form of equatorial plasma bubbles (EPBs), severe auroral activity, and multiple TEC gradients at midlatitudes (over CONUS). Impulsive perturbations have been reported (Aa et al, 2019; Mrak et al, 2020; Zakharenkova & Cherniak, 2020), but small‐scale density irregularity distribution remains unknown, due to the lack of scintillation receivers. Severe space weather impacts on GNSS over the contiguous United States have been presented (Yang et al, 2020); however, associated scintillation or small‐scale irregularities have not been yet reported.…”

“…In the next frame (panel b), the morphology of scintillation at the poleward portion of the CONUS remained unchanged, while a meridional density depletion (seen in the TEC map) over the eastern United States hosted another disturbance with elevated ROTI and both amplitude and phase scintillation. For the evolution of the TEC depletion, we refer readers to recent storm studies (Mrak et al, 2020; Zakharenkova & Cherniak, 2020).…”

Westward Plasma Drifts in the Nighttime Equatorial Ionosphere During Severe Magnetic Storms: A New Type of Penetration Electric Fields Caused by Subauroral Polarization Stream

“…Therefore, the equatorial plasma drifts in the evening sector can become westward during severe magnetic storms. Aa et al (2018) and Zakharenkova and Cherniak (2020) presented observations of large‐scale equatorial plasma bubbles during geomagnetic storms, and the storm time plasma bubbles drift in the westward direction, opposite to the typical eastward drift of plasma bubbles. Because the zonal drift of plasma bubbles is essentially equal to the drift of the F region plasma, the storm‐induced westward drifts reported in our study provide explanation of the storm time westward drifts of plasma bubbles.…”

Ground-Based GNSS and Satellite Observations of Auroral Ionospheric Irregularities during Geomagnetic Disturbances in August 2018

“…We analyzed an occurrence and evolution of the ionospheric irregularities using a specific GPS-based index-ROTI (Rate of TEC Index change)-that was originally proposed by Pi et al [31]. This technique is now widely utilized for detection and specification of the ionospheric irregularities at regional and global scales [32][33][34][35][36]. This index characterizes intensity and sharpness of the GPS/GNSS phase fluctuations caused by ionospheric irregularities and by strong spatial gradients of TEC.…”