On May 5, SEISS observed Earth's radiation belt (consisting of electrons and protons surrounding the Earth) responding to a geomagnetic storm - these spikes are visible in the data plot below. The source of this storm was first detected by NOAA’s DSCOVR (Deep Space Climate Observatory) satellite on May 5.
DSCOVR observed a high-speed stream of solar wind plasma that had escaped from a coronal hole, a cooler and less dense area of the sun. The high-speed plasma plowed through the slow solar wind ahead of it and 'kicked' the Earth’s magnetosphere, a “bubble” that protects us from solar wind. This 'kick' started a global disturbance in the magnetic field known as a geomagnetic storm.
NOAA’s Space Weather Prediction Center issued two alerts on May 6 in response to the storm--first, a G2 (moderate) geomagnetic storm warning and then a second alert midday in response to the change in Earth’s radiation belt that was picked up by SEISS. Geomagnetic storms from the sun can impact communications and navigation systems, power grids, and may cause radiation damage to spacecraft.
The GOES-17 SEISS sensors have been collecting data continuously since April 24, 2018. SEISS is better able to detect changes in the radiation belt caused by solar storms than the previous generation of NOAA geostationary satellites. After GOES-17 is commissioned, SEISS will be used by SWPC to issue the radiation belt alerts.