Solar Highlights for September

Solar Rotation Numbers: 2207 – 2208

Very little to see in terms of sunspots. The Sun was spotless for most of September.

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


The Sun was spotless from the 1st to the 8th.

2018 September 5 @1651UT white light whole disc. Image taken by Cliff Meredith.

AR2721 appeared on the 9th just west of the Central Meridian (the ‘CM’ divides the Sun’s disc into two neat halves, one east, the other west). It was a small Bxo type sunspot of about half dozen spots and was north of the solar equator (this divides the solar disc into northern and southern hemispheres) at latitude +9°. By the 19th it was decaying and by the 11th it had disappeared.

2018 September 9 @0848UT white light whole disc. Image taken by Carl Bowron.

The Sun was spotless on the 11th.

AR2722 was seen on the 12th and 13th just east of the CM. This was another Bxo type sunspot with 4 sunspots but was on the Sun’s solar hemisphere at latitude -7°.

The Sun was spotless again from the 14th until the 30th.

AR2723 came into view at the centre of the solar disc on the last day of September just south of the solar equator, at latitude -8°. It was a type Bxo sunspot group with 3 sunspots.

SPA Sunspot Mean Daily Frequency (MDF): 0.08 (was 0.43).
SPA Relative Sunspot Number: 1.15 (was 6.95).

Solar Prominences, Plage, Filaments and Flares

With not much in the way of sunspots, few dark filaments or bright areas of plage were seen this month, but they did make an appearance here and there. There were more in the way of prominences (although some were quite small / low-lying) visible especially in the first half of September.

The 5th saw several attractive prominences around the solar limb (the edge of the solar disc) plus a “filaprom” and several dark filaments near the north east limb and along much of the west limb.

2018 September 5 @0855UT whole disc Ha drawing by Ian Lee.

A cluster of 3 spike-like prominence was seen on the SW limb on the 8th with one of the spikes noticeably reaching-up above the solar limb.

Two sizable prominences were seen on the SE limb on the 9th and a cluster of prominences were visible on the north west limb on the 12th.

2018 September 13 @1147 Ha proms on NW limb. Image taken by Mick Jenkins

Another cluster of three spike-like prominences appeared along the eastern limb on the 21st, but they were not as high as those seen on the 8th.

Small but numerous prominences were seen on the 25th mostly along the north limb, and to a slightly lesser extent, along the east and south limb.

2018 September 29 @1407UT whole disc Ha. Image taken by Carl Bowron.

No solar flares were reported.

SPA Prominence Mean Daily Frequency (MDF): 3.21 (was 1.99).

Well done to Brian Gordon-States who observed 28 days in September and to Jonathan Shanklin on 27 days. Well done to Alan Heath and to Michael Fullerton who observed 25 and 21 days respectively.

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

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

Alan Heath wrote recently that the solar observation he made on the 1st September was his 13,000th solar observation. An amazing total!

Geoff Elston