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Solar Rotation Nos: 2190 to 2191
Mostly quiet, with a few small sunspots and some days when the Sun was spotless.
Here are the solar highlights of May 2017 together with a selection of images.
1st to 9th May
Active Region (AR) 2651, AR2653 and AR2654 were visible on the first day of the month but by next day only AR2653, a southern hemisphere Hrx type sunspot, remained. By the 3rd another sunspot pair, AR2654, had appeared and this was joined on the 5th by AR2655. All these were stable and quiet in nature. By the 9th AR2653 had gone and the following day AR2654 disappeared too leaving no sunspots.
10th to 16th May
The Sun was blank. There was a large coronal hole on the 14th but there was not much in the way of aurora after that date.
17th to 31st May
By the 17th there were two new sunspots, AR2656 and AR2657, both on the northern hemisphere. Only AR2656 remained the next day and another spot AR2658 appeared on the southern hemisphere on the 19th. These were joined on the 22nd by a Dao type sunspot, AR2659 and on the 23rd by AR2660, at type Cro sunspot this time on the southern hemisphere. All four were visible near the centre of the solar disk. This situation did not last long as all but AR2659 had disappeared by the 25th! AR2659 developed slightly so that it had grown by the 27th into at type Dai on that day. As it neared the west limb of the Sun, it was hard to see on the 30th (many, including myself, saw no sunspots). By the 31st we had another blank solar disc.
SPA Sunspot Mean Daily Frequency (MDF): 1.00 (was 1.66).
SPA Relative Sunspot Number: 13.02 (was 24.01).
Solar Prominences, Plage, Filaments and Flares
Mostly small prominences throughout the month, with a few exceptions, and some long dark filaments on some days.
1st to 15th May
Carl Bowron took some lovely images in hydrogen-alpha light (H-a) at the beginning of the month. Ian Lee observed and drew a high arched prominence on the north east solar limb on the 8th, with the remnants still being visible the following day. Little was seen in H-alpha light on the 10th and 11th as the Sun was so quiet. Three long dark filaments were seen on the 14th.
16th to 31st May
With the Central Meridian crossing of sunspots AR2656, AR2658 and AR2659 on the 22nd a complex clustering of filaments was seen nearby. These had somewhat died away the following day but there was a loop prominence on the north west limb (not related to the sunspots). More prominences were seen on the 23rd on the north east, west, and south west solar limbs. A beautiful hedgerow prominence was imaged by Carl Bowron on the 23rd. Numerous small prominences were seen along the east limb on the 25th. Two detached prominences were seen on the 26th, one by the east limb and the other by the north limb. Also on that day, a complex looking filament was seen close to the east limb. By the 28th, as AR2659 neared the west limb, some small filaments and prominences were visible but these had gone by the end of the month.
SPA Prominence Mean Daily Frequency (MDF): 3.31 (was 4.95).
Well done to Brian Gordon-States, who observed 29 days in May, and to Jonathan Shanklin and Alan Heath who observed 26 and 25 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 and Bob Steele and the Director.
Images and drawings were supplied by: Mark Beveridge, Carl Bowron, Mick Jenkins, Ian Lee, Cliff Meredith.