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Solar Highlights for May 15

Solar Rotation Nos: 2163 to 2164

There was another small rise in sunspot activity overall bringing us back to a level last seen in October 2014 and in mid-2012.

Here are the highlights for May 2015 together with a small selection of images from the many that were sent to me.


There was a quiet start to this month with some members recording a blank solar disk on the 1st. There was one very small spot visible this being Active Region (AR) 2334. This had gone by following day leaving AR2335 not far from the Eastern (E) limb.

AR2335 did develop over the next few days bringing with it the increasing chance of flares. There was an X-class flare on the 5th but it was from AR2339 on the E limb that created it. Even so AR2335 and the following AR2337 showed plenty of sunspot activity which seemed to reach a peak around the 6th and then faded as they headed westwards.

AR2339 was now further away from the E limb and was active. Alan Heath reported a double light-bridge across the umbra of the leading spot on the morning of the 8th. This sunspot group continued to develop at a steady pace as it began to near the Central Meridian (CM) around the 11th. Carl Bowron photographed the setting Sun on the 11th and the 12th while in the USA and these image taken through a telephoto lens show AR2339. It might have been visible to the protected naked eye (just) but no one has reported it as such. Other sunspots visible at that time were a small round single spot, AR2341, and at least two small spots with faculae, AR2344, near the E limb.

It was around the 14th that we saw the highest number of sunspots for the month. AR2339 began to fade in activity from the 15th onwards especially as it approached the W limb. By the 17th much of the sunspot activity was seen approaching the W limb.

By the 20th there were only small sunspots visible, AR2348, a single oval spot and by now on the CM being the most obvious. As this and the other small spots headed westwards the solar disk became largely blank until the 28th when a single sunspot with bright faculae was seen near the E limb. This was AR2356. It was joined by a group of small spots and pores, AR2357, as May drew to a quiet close. 

SPA Sunspot Mean Daily Frequency (MDF): 3.99  

SPA Relative Sunspot Number: 58.73


There was plenty to see in Hydrogen-alpha this month.

AR2335 showed plage activity around it on the 1st and a long line of very dark filaments were seen right across most of the solar disk on the 2nd having developed from the previous day and persisting right through to the 4th. Meanwhile AR2335, AR2336 and AR2338 all showed plage activity around them. Richard Bailey imaged the solar flare while observing AR2339 in H-alpha light on the 5th. The 7th and 8th and 9th saw lots of activity with plages around all the sunspot groups plus some filaments and several prominences around the solar limb.

A large hedgerow prominence appeared on the NE limb on the 12th with some small dark filaments and plages on the disk mainly associated with the sunspots seen at that time (AR2339, AR2345, AR2342, AR2344 and AR2346). By the 13th the hedgerow prominence was still very much visible and the activity on the disk seemed to have intensified a little.

The 14th saw three large prominences round the limb (on the NW, NE and E limb) together with plage and filaments on the disk around or near the sunspots. The prominences persisted the following day but had diminished by the 16th.

There were a number of small spike-like prominences along the E and W limb on the 19th plus a fair bit of plage and filament activity that was not connected with the two sunspots AR2342 and AR2348. As we entered the last week of May there were several very long, sometimes broad dark filaments to be seen (see the image of the Sun in H-alpha on the 27th for example). Another beautiful hedgerow prominence appeared on the SW limb on the 30th.    

SPA Prominence Mean Daily Frequency (MDF): 5.38  

Well done to Brian Gordon-States who observed on 30 days in May. Jonathan Shanklin made 29 observations and Alan Heath a highly respectable 28 days.  Finally, welcome back to John Chapman-Smith, a former Director of the SPA Solar Section, who has been able to return to solar observing during the Summer months.

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

Images and drawings were supplied by: Richard Bailey, Mark Beveridge, Carl Bowron, Paul Brierley, John Chapman-Smith, Michael Fullerton, Mick Jenkins, Ian Lee, Cliff Meredith, Julia Wilkinson and Brian Woosnam.

Geoff Elston

SPA Solar Section Director

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