Solar Highlights for August 2018

Solar Rotation Numbers: 2206 – 2207

Mostly quiet with a few small sunspots appearing in August but a new Sunspot Cycle (No. 25) was seen.

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


AR2717 was seen in the first few days of August. It was a small Axx type sunspot, sitting between the Central Meridian (CM) and the solar east limb. The sunspot was positioned just south of the solar equator at the low latitude of -07°. AR2717 had disappeared by the 4th.

2018 August 2 @0941UT white light whole disc image by Carl Bowron.

The Sun was spotless from the 4th to the 15th.

On the 11th there was a partial eclipse of the Sun (this is where the Moon appears to bite-out a curved segment of the Sun’s disc. A safe solar filter is always needed and neither the Chromosphere nor the Corona are visible). The eclipse was just visible from the UK, from the northern tip of Scotland in the early morning but was better seen from northern Europe and Asia.

AR2718 arrived on the 15th ending a spell of 11 days without sunspots. AR2718 was a small quiet sunspot (type Bxo) lying just south of the solar equator at latitude -08°. By the 19th AR2718 was near the disc centre, with little having changed much in the intervening days. AR2718 started to decay and was gone by the 20th.

AR2719 became visible on the 29th as AR2718 disappeared. The new sunspot was another small and quiet sunspot (type Axx) once again on the southern hemisphere, at latitude -06°. In the following days it developed so that by the 24th it was a type Cro sunspot. However, despite its recent growth, it quickly faded and had gone by the 30th.

AR2720 appeared on the 25th near to AR2719 but it was the other side of the solar equator at latitude +08°. It was later that day that would announce that this sunspot showed a “reversed polarity” meaning it was part of the new Sunspot Cycle (No. 25). Despite this, AR2720 was not around for long and it too went into a rapid decline and had faded away by the 30th.

2018 August 25 @0819UT white light whole disc image taken by Carl Bowron.
2018 August 25 @1132UT white light image of AR2720 by Cliff Meredith.

The Sun was spotless again from the 30th to the 31st.

SPA Sunspot Mean Daily Frequency (MDF): 0.43 (was 0.00).
SPA Relative Sunspot Number: 6.95 (was 0.00).

Solar Prominences, Plage, Filaments and Flares

There was more to see in H-alpha but there were fewer prominences visible this month and most of those that did appear were smaller and weaker in nature.

Four prominences were seen along the south east solar limb on the 1st with a small area of bright plage and dark filaments roughly coinciding with AR2717 on the solar disc.

2018 August 5 @1017UT Halpha image taken by Paul Brierley.

A tall arch-like prominence was seen on the west limb on the 11th.

Plage and filament activity were seen around AR2718 on the 15th, but it seemed to fade by the 16th. The 21st saw some area of plage around AR2719 (2718 having disappeared) and some interesting quite tall proms on the north east and north west limbs. As AR2719 neared the CM, a lengthy filament was seen stretching along the northern hemisphere of the Sun.

2018 August 23 @1515UT whole disc Halpha drawing made by Ian Lee.

The developing AR2720 was seen in H-alpha on the 24th not far from the already established AR2719. Both showed great development in Ha light on the 25th.

2018 August 25 @0840UT whole disc Halpha drawing by Ian Lee.
2018 August 25 @0859-0902UT Ha Prominences. Images by Carl Bowron.
2018 August 25 0841UT AR2720 Halpha image by Carl Bowron.

No solar flares were reported.

SPA Prominence Mean Daily Frequency (MDF): 1.99 (was 2.64)

Well done to Brian Gordon-States who observed on 30 days in August and to Jonathan Shanklin on 29 days. Well done to Michael Fullerton and Alan Heath who each observed 27 days.

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: Carl Bowron, Paul Brierley, Mick Jenkins, Ian Lee and Cliff Meredith.

Geoff Elston