Magnetometers detected a sudden geomagnetic impulse around 23:30 UTC on September 16 (or around 01:30 CET on September 17). This happened at the moment when the solar wind from the coronal explosion reached the Earth. The coronal explosion is related to the intense eruption X4.5 which happened on Saturday at 19:05 UTC (21:05 CET). A strong geomagnetic storm (G4) was observed.
SOURCE: Astronomical Observatory in Belgrade, Research Unit for Solar Activity Monitoring, Climate Change and Light Pollution
In the photo: An image of the Sun, showing the eruption on the left, taken by the Solar Dynamics Observatory.
The K index, used as a measure of the strength of geomagnetic storms. The red bar marks the eruption X4.5.
