St. Patrick’s Day—Storm of the Decade

By Nathan Case

Image credit: Sebastian Saarloos

Image credit: Sebastian Saarloos

Ongoing, right now, is a large geomagnetic storm. The storm has had a constant G2-G4 rating, Kp levels are in the6-8 range and the solar wind power has been in the 3000GW + range for over 24 hours.

All of this means, it’s a great time for aurora hunting!

This level of activity is pretty rare and makes this a once in a year, or perhaps even a once in a decade, event. What’s been great is that these extreme levels have been sustained for a considerable period of time. In fact, if they continue to hold, we expect to see awesome aurora sightings from the UK and perhaps even further south (clear skies permitting).

These conditions have meant good auroral viewing already. In fact, so far today, we have had 11 positive aurora sightings reported on Aurorasaurus and our citizen scientists have verified 54 Twitter sightings. We have found some of the furthest south sightings on Twitter thus far– Nice work @theumno (Colorado), @five15design (New Zealand), and @dangottschalk (Iowa)!

What’s driven this storm?

Well, there was a fairly large coronal mass ejection (CME) that blasted off from the Sunday on March 15 that has now arrived at the earth. The CME was strong enough to really compress the Earth’s magnetic field and increase the processes behind the aurora. Specifically, the magnetic field in the CME has been pointed strongly southward (i.e. opposite to our terrestrial field) and the speed of the CME has been pretty high (around 650 km/s). Our plot of solar wind power shows that the combined effect on Earth’s magnetosphere has been large—off our scale for good viewing. Unfortunately, the peak of this storm hit during daytime over most of the US and Europe.




The conditions are still great for aurora viewing and the prediction is that they will remain so (at least for the next few hours). At the time of this blog post we still have quite a few hours till darkness in the US, so we need these conditions to remain favorable for wide-spread auroral visibility (i.e. down in to the mid-US). However, even if conditions do start to ease up, it is likely that the strength of the disturbance will mean that aurora will still be spectacular at high latitudes.

At the moment we cannot tell for sure as we have only a one-hour warning of conditions from space. Oh and those pesky clouds need to keep away too! So remember to sign up for Aurorasaurus so you can get an alert for your location, and be ready to go aurora hunting! If you’re lucky enough to see the aurora, please let us know and report your observation. Too far south? You can also help us by verifying tweets from others who might have seen the aurora. All of this data helps scientists build better models of strong storms. Our knowledge of these events is very coarse because they are so rare – so help out at with the strongest storm of this solar cycle, the first with social media!


Nathan is a space weather scientist based at NASA’s Goddard Space Flight Center. As a core member of the Aurorasaurus team, he is primarily responsible for merging traditional forms of space weather data with citizen science observations to improve the nowcasting ability of the auroral oval models – though you may also see the occasional blog post or Facebook update from him too!

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