Ionospheric Disturbances and Irregularities During the 25–26 August 2018 Geomagnetic Storm

Abstract

We use ground‐based (GNSS, SuperDARN, and ionosondes) and space‐borne (Swarm, CSES, and DMSP) instruments to study ionospheric disturbances due to the 25–26 August 2018 geomagnetic storm. The strongest large‐scale storm‐time enhancements were detected over the Asian and Pacific regions during the main and early recovery phases of the storm. In the American sector, there occurred the most complex effects caused by the action of multiple drivers. At the beginning of the storm, a large positive disturbance occurred over North America at low and high latitudes, driven by the storm‐time reinforcement of the equatorial ionization anomaly (at low latitudes) and by particle precipitation (at high latitudes). During local nighttime hours, we observed numerous medium‐scale positive and negative ionospheric disturbances at middle and high latitudes that were attributed to a storm‐enhanced density (SED)‐plume, mid‐latitude ionospheric trough, and particle precipitation in the auroral zone. In South America, total electron content (TEC) maps clearly showed the presence of the equatorial plasma bubbles, that, however, were not seen in data of Rate‐of‐TEC‐change index (ROTI). Global ROTI maps revealed intensive small‐scale irregularities at high latitudes in both hemispheres within the auroral region. In general, the ROTI disturbance “imaged” quite well the auroral oval boundaries. The most intensive ionospheric fluctuations were observed at low and mid‐latitudes over the Pacific Ocean. The storm also affected the positioning accuracy by GPS receivers: during the main phase of the storm, the precise point positioning error exceeded 0.5 m, which is more than five times greater as compared to quiet days.

Low-Latitude Ionospheric Responses and Coupling to the February 2014 Multiphase Geomagnetic Storm from GNSS, Magnetometers, and Space Weather Data

“…The post-sunset PPEF of the eastward (daytime) and westward (nighttime) drifts combine to drag plasma from the dip equator by E × B convection, sustaining the plasma pile at the EIA crests. The polarity of the PPEF was eastward and westward during day-and nighttime, respectively ( [40], and references therein), while, during day-side and post-sunset, it has eastward polarity intensified through plasma induction at the EIA crest. The EEJ data show that the storm-time PPEFs are an important contribution of the observed ionospheric responses to this multiphase geomagnetic storm.…”

“…The EIA crests can reach up to ±20 degrees of the magnetic latitude during geomagnetic storms [40], and the PPEF of westward polarity during the night side has Earth directed to a downward drift, which results in plasma depletion at the low-latitude regions. Ref.…”

“…Ref. [40] studied the same storm and found medium-scale positive and negative ionospheric disturbances at middle and high latitudes that were attributed to a storm-enhanced density (SED)-plume, mid-latitude ionospheric trough, particle precipitation in the auroral zone, and equatorial plasma bubbles in South America.…”

Variation of Total Electron Content in the Quiet and Disturbed Period and Their Correlation with Solar Wind Parameters

“…However, during quiet periods, measurements on the ground show no significant disturbances [10,11]. In addition, the geomagnetic storm caused significant ionospheric irregularities in the auroral region [12]. As a result, significant changes in ionospheric parameters such as composition, temperature, and circulation can be observed.…”

“…Due to the significant energy introduced by the solar wind into the polar ionosphere (over a period of several hours to a day), there can be an increase or decrease in electron density during geomagnetic storms compared to quiet conditions, which is known as the positive storm effect and negative storm effect, respectively [14]. The storm also had an impact on GPS receiver positioning accuracy: during the storm's main phase, the precise point positioning error exceeded 0.5 m, which is more than five times greater than on quiet day [12]. The vertical total electron content (VTEC) is one of the key quantities used to describe ionosphere variations and can be used by users to correct ionospheric disturbances for GNSS (Global Navigation Satellite System) positioning [15].…”