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Solar Highlights for March 17

 

Solar Rotation Nos: 2186 to 2187

Very low level of sunspot activity for most of the month, but an unexpected burst right at the end of the month. Lots of high-latitude aurora seen through March, the result of a persistently strong solar wind and coronal hole activity.

Here are the solar highlights of March 2017 together with a selection of images.

Sunspots

1st to 6th March
The beginning of the month saw Active Regions (AR) 2638, AR2640 and AR2641 still visible. All three were north of the solar equator. AR2641 had shown the most development with additional sunspots suddenly appearing within it. For a while it was thought it could produce minor solar flares as well. However, as we have seen in recent times, the anticipated burst of sunspot activity did not come about and while new sunspots had appeared near the AR2641 (labelled separately as AR2642) sunspot activity seemed to be waning again. By the 5th we had a blank solar disc.  Remarkably, AR2641 briefly reappeared on the 6th near the western limb but only for a day and we were left with no sunspots once again. High-latitude (by this I mean places like Alaska, Canada and Scandinavia) aurorae were seen most nights and there was an SPA aurora alert sent out on the 6th as AurorawatchUK had issued an amber alert that the northern lights might be seen from Scotland, northern England and Northern Ireland.

7th to 21st March
There were no sunspots visible at all and the Sun’s disc was blank for about two weeks. Despite the lack of sunspots, high-latitude aurorae were almost commonplace (but not from the UK this time) with displays on the nights of the 8th, 11th, 15th and 21st the last one the result of a large coronal hole pointing Earthwards.

22nd to 31st March
Finally, on the 22nd AR2643 a small Axx type sunspot appeared near the eastern limb of the Sun. This lasted until the 27th when AR2643 disappeared and it was not until the last few days of March that we saw any real increase in sunspots with the appearance of AR2644 on the 27th and AR2645 on the 28th. Both were initially solar flare active for a short while and both showed some development particularly when AR2646 appeared nearby AR2645. Surprisingly, AR2645 was the first sunspot to appear on the southern hemisphere throughout the whole month as all the others were situated north of the solar equator!

More high-latitude aurorae were seen on the nights of the 27th and 28th (not from the UK though) the result of a gigantic coronal hole facing the Earth around the 25th. 

SPA Sunspot Mean Daily Frequency (MDF): 0.90 (was 1.04).
SPA Relative Sunspot Number: 12.97 (was 13.45).

Solar Prominences, Plage, Filaments and Flares

Mostly small prominences were seen throughout most of March with more towards the month-end. More filaments areas of bright plage seen when there were sunspots visible too at the beginning and end of March. No solar flares were seen.

1st to 6th March
Plenty of plage activity seen on the 1st accompanying the sunspots AR2638, AR2640, AR2641 and near the NE limb but only a few small prominences.

7th to 21st March
During this period, very little was seen on the disc but there was the occasional prominence and filament. It was not until the 20th that we noticed an upturn with three filaments on the disc and many small prominences along the NE and SW limbs. There were several fine prominences on the eastern and western limbs on the 21st.

22nd to 31st March
With the appearance of AR2643 we saw, on the 23rd and 24th, bright plage activity around it and several dark filaments elsewhere on the disc and prominences on the northern limb and SW limb too. Two quite complex and extensive prominences were seen along the NE and NW limbs on the 25th. The most activity was seen from the 27th onwards as AR2644 and AR1645 crossed the solar disc with lots of small dark filaments, bright plage activity and prominences on the solar limb right up until the end of the month. 

SPA Prominence Mean Daily Frequency (MDF): 3.60 (was 4.04).

Well done to Brian Gordon-States who observed 29 days. Also to Jonathan Shanklin and Bob Steele who observed 20 and 18 days respectively.

Detailed count records of Active Regions and Relative Sunspot Numbers came from: Brian Gordon-States, Michael Fullerton, Alan Heath, Mick Jenkins, Ian Lee, Jonathan Shanklin, Bob Steele and Julia Wilkinson.

Images and drawings were supplied by: Mark Beveridge, Carl Bowron, Mick Jenkins, Ian Lee, Cliff Meredith and Julia Wilkinson.

Geoff Elston

Director

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