STUDY OF UNPREDICTED FIRST GEOMAGNETIC STORM OF 2020, DUE TO INTERACTION OF ICME WITH NEAR-EARTH SPACE ON APRIL 20

The GeoMagnetic Storm (GMS) on April 20, 2020 (with Ap=16 and Kpm=5-) is the first storm for the year. About a year ago on May 11 and 14, 2019, there were two GMSs of G1 and G2 classes, respectively, (with Ap=32 and Kpm=6+ on 2019/05/14) [(1)]. Likewise exactly 2 years ago - on April 20, 2018, it was a GMS of G2 - moderate class with Ap=43 and Kpm=6 [(2)]. Given that we are in a deep solar minimum, such a time delay of GMSs is natural and understandable. In the studied case, it is interesting that none of the world's centres for space weather forecasting was able to predict the occurrence of the considered GMS. Therefore, it is of interest to analyze and understand the general situation, both on the Sun and in the interplanetary environment, which led to the geomagnetic storm on April 20, 2020. We have shown that the coronal mass ejection (CME) on April 15, 2020 was not squarely Earth-directed, and forecasters did not think it was likely to hit our planet. Nevertheless, it apparently did. Solar wind data suggest that the interplanetary CME (ICME) sideswiped Earth with a snowplow-like buildup of plasma shortly after 0130 UT on April 20th. Such an analysis is useful both in this specific case and for future forecasts of space weather as well.