Solar Highlights for June 18

Solar Rotation Numbers: 2204 – 2205

Not as many spotless days in June and a burst of sunspot activity around the longest day (in the northern hemisphere). A small rise in the Sunspot MDF.

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


AR2712 was still visible in June but just west of the Central Meridian. This group you may recall appeared on the solar disc in late May and its small sunspots resembled the small constellation of Ursa Minor. It was still quite active and for a while was considered to be minor solar flare active. It was still positioned just north of the Sun’s equator, at latitude +16°, and was type Dro on the 1st. It was not until the 3rd that AR2712 showed signs of rapid decay and over the next couple of days it gradually faded away.

The Sun was then spotless from the 6th to the 12th.

AR2713 appeared over the east limb on the 13th. It was close to the solar equator, latitude +3° and was a small Bxo type sunspot. It developed a little initially but was seen to fade a little from the 15th onwards until it disappeared from view over the west limb on the 25th.

AR2714 appeared on the 18th, just north of the solar equator at latitude +08°, near to AR2713. This too was a small Bxo type sunspot but it developed a little before it went over the west limb on the 23rd.

2018 June 20 @1530UT_AR2713 AR2714 AR2715 white light whole disc. Image by Mick Jenkins.
2018 June 20 @1639UT white light whole disc. Image by Cliff Meredith.

Another sunspot group then appeared over the east limb on the 20th and this was AR2715. It was quite an active group. AR2715 was just north of the equator at latitude +07° and a more substantial type Cro. Further development followed on the 21st, when it peaked as a type Dao sunspot and it had the potential to produce minor solar flares for a while. No more development was seen after the 22nd and AR2715 decayed as it headed west finally disappearing on the 27th.

2018 June 22 @0802UT white light whole disc. Image by Carl Bowron.
2018 June 22 @1059UT AR2713 AR2715 white light whole disc. Image by Mick Jenkins.

The Sun was then spotless from the 28th to the 30th.

SPA Sunspot Mean Daily Frequency (MDF): 0.81 (was 0.68)
SPA Relative Sunspot Number: 13.82 (was 10.02)

Solar Prominences, Plage, Filaments and Flares

There were more prominences in June compared to last month when we saw very few. The appearance of AR2712-15 also saw more in the way of disc features such as filaments and plage. A solar flare was seen in early June. We did see, however, a decline in the Prominence MDF.

A detached and quite complex prominence was seen on the northern limb on the 4th and a filaprom was seen on the east limb on the 6th and 7th. A tall bright prominence was seen on the 13th on the west limb that by the 14th had doubled in height, extending upwards away from the solar limb into a tall slender slightly curved spike. Later in the month, a lengthy dark filament was seen crossing the solar northern hemisphere, someway behind AR2715, from the 24th onwards. It was last seen on the 27th near the Central Meridian and looking somewhat broader and fragmented by then.

2018 June 6 @1510UT whole disc Ha drawing by Ian Lee.
2018 June 7 @1332-1343UT Prominences. Image by Carl Bowron.
2018 June 22 0846UT AR2715 H-alpha. Image by Carl Bowron.

A solar flare was observed on the 3rd at 0800UT (AR2712) persisting until 1100UT by Alan Heath.

SPA Prominence Mean Daily Frequency (MDF): 1.21 (was 2.39)

Brian Gordon-States, Alan Heath and Jonathan Shanklin observed 28 days this month with Michael Fullerton observing at total of 26 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, Bob Steele and Graham Taylor.

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

Geoff Elston