As of 8:00pm EST tonight, we have entered the watch period for the G1 Geomagnetic storm watch posted by the Space Weather Prediction Center. The watch runs from midnight April 2nd to midnight April 3rd UTC and means that there is a chance that Global Kp values will increase to minor storm level of Kp=5 during the watch period.
This watch is prompted by three recent CMEs originating from flares at Solar Region 2017 over the weekend. All three CMEs have a chance of producing a glancing geomagnetic blow to Earth.
The biggest of the three flares reached X-Class levels with a measured X-Ray flux of X1.01 on Saturday. This flare produced a Type-II radio sweep with an estimated speed of 4,508 km/s, and a Tenflare of 360 sfu. That is a strong radio sweep and a big Tenflare. The location of the flare was in the northwest portion of the solar disk – specifically at N10W20. You can see the location in the image of the flare below. Due to this location and the orientation of the flare, most of the associated CME will travel to the North of Earth. However, it is a large CME and we expect to see a glancing blow.
The other two flares contributing to today’s G1 watch happened 17 and 24 hours earlier. Both were M2 class flares and produced slower moving CMEs. Both of these flares are also directed to the North of Earth. They will arrive at roughly the same time as the faster moving CMEs from the X-Class flare.
The combination of three flares arriving at roughly the same time makes predicting the specific timing of the CME arrival even more difficult than normal. Our favorite CME prediction model, the WSA-Enlil Solar Wind Prediction Model, shows the bulk of the two CMEs arriving between about 1:00am and 10:00am UTC April 2.
Our best guess is that Kp values will stay fairly subdued for this event. We will probably see Kp reaching 4 with a couple short periods at or above 5. Of course, we’d love to see it go higher and get a chance to see some Northern Lights in some of the mid-latitudes. As it stands, areas like Iceland, Greenland, most of Canada, Alaska and eastern Russia will have the best chance for Northern Lights from this storm.