G1 Geomagnetic Storm from January 30, 2015 through February 2, 2015

The first geomagnetic storming of February 2015 is now winding down.

This storm was unique in its long duration. It prompted four continuous days of G1 geomagnetic storm watches from NOAA’s Space Weather Prediction Center. This storm was also unique in that there was a long lead on predictions that there might be Aurora. The first hints there might be a storm were on Saturday, January 24th, almost a week in advance of the onset of high solar winds that prompted the watch. We noted this chance in our blog post on “How to read the WSA-Enlil Model.” By Tuesday, it was clear there was a good chance a watch would be issued as we detailed in “Next Chance for Aurora Jan 30, 2015.” The watch was finally issued Wednesday evening, for Friday.

Over the course of the storm, solar winds gradually climbed from 350-375 Km/s to a maximum peak of 783 km/s. The threshold for “very high” wind is 800km/s. The wind was coming from the co-rotating interaction region (CIR) and from the coronal hole high speed stream (CH HSS) coming off the coronal hole in the southern hemisphere of the Sun. This hole has persisted for several weeks now. As it rotates and the northern extensions cross the Earth-Sun line, Earth experiences higher solar wind speeds 3-5 days later. Keep an eye on the CH as these extensions rotate around again in two weeks.

Southern Hemisphere Coronal Hole in AIA 211
Large Coronal Hole in Southern Hemisphere shown with northern extension near the Earth-Sun line

KP readings never reached extreme levels. In fact, there was only one period with G1 storming on Feb 1 and two periods on Feb 2. [As we write this, activity has increased again and there is an outside chance we may see an additional period of G1 storming.] The main reason the storming was not more significant was a lack of proton density – with fewer protons traveling on the wind, there is less energy to displace the Earth’s magnetosphere. The periods of active storming coincided with increased proton activity. Had there been any solar eruptions that released proton solar storms along the Earth-Sun line during this period of high solar wind, we could have easily seen much stronger storming.

chart of K-index showing 9 hrs of G1 storming
Planetary K index reporting by SWPC Febrary 2, 2015

Even with KPs in the 4.67-5.33 range, our Twitter feed lit up with beautiful pictures of the Northern Lights and Aurora Australis. We featured the following tweets in our new Aurora Briefs Section. All of the pictures come from higher latitudes. The moon was bright and waxing gibbous, one day away from full. The peak of the storm happened just as the furthest south portion of the auroral oval was over a giant winter storm covering many viewers with a thick layer of clouds. The extra light, and lack of visibility was frustrating to many aurora viewers. This makes us appreciate the successful pictures even more! Here are were some of our favorites:

We seem to still be in an active pattern. While the current storm is winding down, we’re already looking ahead to the next potential storm. WSA-Enlil is showing increasing solar winds again with an increase in solar proton density on Friday, February 6. We’ll be keeping an eye out for stroming on that date.

Happy Hunting!