Solar Highlights for May 2018

Solar Rotation Numbers: 2203 – 2204

Another very quiet month with many days when the Sun appeared without any sunspots. Most, if not all, were made up of small sunspots or pores. There was a very slight rise in the average number of sunspots (the Mean Daily Frequency). There is a certain amount of speculation that possibly Sunspot Cycle 24 has decreased faster than we expected and has arrived early. The only way we will know is by watching sunspot activity and keeping a sharp look-out for the appearance of high-latitude sunspots of the new Cycle 25.

Here is a summary together with a selection of images made by our observers in May 2018.


The Sun was spotless from the 1st until the 3rd.

AR2708 then appeared near the eastern solar limb on the 4th at latitude -10°. This small pairing of spots was seen decaying by the 5th and the 6th and had disappeared by the 11th.

2018 May 6 @1207UT AR2708 white light whole disc. Image by Mick Jenkins.

AR2709 appeared near the eastern limb around the 8th at latitude +05°. This too was made up of small sunspots and on the 9th extensive faculae were seen trailing behind it, towards the limb. The sunspots lasted up until the 14th but the remains of the sunspots could still be seen in Hydrogen-alpha light.

2018 May 8 @1304UT white light whole disc. Image by Carl Bowron.

The Sun was then spotless from the 15th until the 21st.

AR2710 suddenly appeared around the 21st at latitude +16°, of type Cro but still small. It was still visible at the 25th but had disappeared by the 26th.

AR2711 came into view on the 24th at latitude +06° and remained visible up until the end of the month.

2018 May 23 @1329UT whole disc and close up of AR2710 & 2711. Images by Mick Jenkins.

AR2712 turned-out to be a bit of a “stop-start” sunspot group. It appeared on the 25th at latitude +13° and for a very short while (about a day) it was active with minor solar flares. On the 28th it resembled the small constellation of Ursa Minor!

2018 May 28 @1301UT white light whole disc. Image by Carl Bowron.

SPA Sunspot Mean Daily Frequency (MDF): 0.68 (was 0.42).
SPA Relative Sunspot Number: 10.02. (was 5.99).

Solar Prominences, Plage, Filaments and Flares

A very slight upturn in the Prominence MDF in May. Generally, it seems that solar activity seen in Hydrogen-alpha is nearly always more than we generally see in “white light” and May was no exception to the general rule!

A quite small bright spot was seen near the Sun’s north eastern limb on the 4th (1609UT) by Cliff Meredith (possible flare?).

We had some lovely prominences in early May. The 4th was especially good.

2018 May 4 @0709-0719UT Prominence images by Carl Bowron.

As was the 7th.

2018 May 7 @0851-0859UT Prominence images by Carl Bowron.

The 14th and 20th were especially good too, with an eruptive prominence seen by Carl Bowron on the northern limb on the 20th.

2018 May 20 @0910UT Ha prominence images by Carl Bowron.
2018 May 24 @0630UT whole disc Ha drawing by Ian Lee.
2018 May 31 @1330UT whole disc Ha drawing by Ian Lee.

Several small filaments were seen especially around AR2712.

No solar flares were reported.

SPA Prominence Mean Daily Frequency (MDF): 2.39 (was 1.71).

Both Jonathan Shanklin and Alan Heath observed 29 days this month with Michael Fullerton and Brian Gordon-States on 28 and 27 days respectively.

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

Images and drawings were supplied by: Mark Beveridge, Carl Bowron, Paul Brierley, Dave Eagle, Mick Jenkins, Ian Lee and Cliff Meredith.

Geoff Elston