27 March Red alert

Woah, what a night!

AW UK activity plot for 27-28 March 2017. Red alert issued at 20:45 BST with heightened activity throughout the period.

For the first time since October last year, AuroraWatch UK issued a red alert (at 20:45 BST). This was then followed up by a couple of hours of amber alert and surrounded by periods of minor geomagnetic activity (yellow alert).

Alert explanation

The red alert was generated by the magnetic disturbance measured at our Crooktree magnetometer (CRK2) located near Aberdeen. This is our primary, science-grade, magnetometer and is the furthest north of our main magnetometer network. The disturbance was also seen in our other magnetometers but they didn’t quite reach the red alert threshold, instead sitting just under it at amber.

AW UK CRK2 magnetogram for 27-28 March 2017. Red alert issued at 20:45 BST.

As described in detail on our website, we measure the magnetic disturbance caused by electric currents in the atmosphere, which gives us some idea of how strong the aurora might be. The magnetic field is measured in three directions: north-south, east-west, and up-down.

The red alert last night was driven mostly by the 200nT or so disturbance in the east-west direction; meaning that the aurora probably wouldn’t have been directly north of us at that time.

What is behind this activity?

This batch of activity is being driven by a high-speed stream of solar wind, coming from a coronal hole on the Sun. It’s actually the same coronal hole that gave us some activity earlier on in March, as coronal holes can last for a little while and the Sun has a rotation period of about 24 Earth days.

Real-time solar wind data from the DSCOVR satellite. Data provided by NOAA SWPC.

The real-time solar wind and interplanetary magnetic field data, as measured by the DSCOVR satellite, are shown in the plots above. The vertical red dashed line shows when the red alert was issued. We can see that since around the start of the 27th March (vertical blue dashed line), the solar wind was really quite elevated. The Bz component of the interplanetary magnetic field (shown in the top panel in red) was southward (negative) for much of the time, and the solar wind speed (shown in the fourth panel in purple) was high (and still climbing!) – both of which allow energy to be transferred into the aurora-generating system.

The good news is that activity is expected to continue for a day or two – so we may be in with another chance of seeing the aurora tonight. Keep an eye on our alerts for the latest details.

Clouds were an issue for some

Unfortunately, but typically, the weather was a hinderance to aurora hunting for many last night. Blanket cloud cover and fog were an unwelcome sight across much of the east coast.

As we all know, clear skies are needed to see an aurora. If it’s cloudy and you think you’ve seen the aurora, it’s probably just light pollution reflecting off the cloud layer.

Though some were lucky enough to get clear skies or a break in the cloud!

Ok, let’s check out those photos!

Aurora 27/03/17
Photo by Simon Ward. Flickr. All rights reserved.

From a little further afield

4 thoughts on “27 March Red alert

  1. Should “solar wind speed (shown in the third panel in orange)” be “solar wind speed (shown in the fourth panel in purple)”?

  2. Pingback: Hello aurora! – Wild about Scotland

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