Development of the storm-induced ionospheric irregularities at equatorial and middle latitudes during the 25-26 August 2018 geomagnetic storm

We analyzed the ionospheric response to the 25-26 August 2018 geomagnetic storm and revealed formation of intense ionospheric plasma irregularities over broad latitudinal ranges from equatorial toward middle latitudes in the American and Pacific sectors. Storm-induced penetration electric fields created favorable conditions for strong fountain effect uplifted the equatorial ionosphere, enhancement of the equatorial ionization anomaly (EIA), and postsunset EPBs generation.

We found two patterns of equatorial ionospheric irregularities expansion toward low and middle latitudes: (a) storm-induced EPBs developed over a large latitudinal extent between widely spread EIA crests, (b) narrow channel of the ionospheric irregularities stretched away from the EPB location toward the auroral zone in the northwestward direction. The EPBs latitudinal extent largely exceeded climatological-based expectations for solar minimum conditions; EPBs reached atypically high latitudes (20 degrees-25 degrees magnetic latitude [MLAT]) in the Pacific Ocean sector.