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Solar Highlights for July 15

Solar Rotation Nos: 2165 to 2166

A quiet month for sunspots but there was a small rise in the MDF up to 4.15 (R=57.90) in July compared to 3.36 (R=51.33) in June. The Earth passed through several gusty solar wind streams throughout July bringing aurora to those living at high geographical latitudes.

Here are the highlights for July 2015 together with a small selection of images.


A quiet start to July with sunspots visible near the (E)astern limb in the form of AR2373, AR2375 and AR2376. Of these, AR2376, was thought to be solar flare active. On the 3rd AR2378 had appeared and this too was increasingly flare active. There was a fairly strong geomagnetic storm on the 4th but the cause was not sunspots but due to the Earth passing through a high speed solar wind coming out from the Sun. Aurora was seen at high latitudes but I don’t think we saw anything from the UK.

By the 5th there was a peppering of small spots across the Sun. It was about this time that AR2381 appeared over the E limb. This was a rapidly developing sunspot group spanning almost 100,000 km in length. By the time AR2381 had reached the (C)entral (M)eridian on the 8th it showed a clear leader and follower type structure but no flares had been produced. It was clear that by the 10th AR2381 was decaying as it headed westwards. There was another geomagnetic storm due to a gusty solar wind buffeting the Earth. By the 11th there were several sunspots nearing the W limb with only one new Active Region (AR2384) visible on the E limb.

On the 13th AR2384 was almost at the CM and once again there was another geomagnetic storm bringing aurora to those people living at high geographical latitudes. As the New Horizons probe made it’s closest approach to Pluto on the 14th, AR2381 was by now near the W limb while new AR2386 was near the E limb, and that was all there was to be seen. There was little change over the following few days even as AR2387 came over the E limb on the 17th. AR2387 reached the CM on the 21st and the Sun was very quiet.

On the 25th as AR2381 and AR2387 neared the W limb we saw some pores over on the E limb and these were designated AR2389 and AR2390. AR2390 seemed to develop up slightly by the next day and as it reached the CM on the 27th and beyond up until the 28th thereafter it faded away as we reached the end of the month. AR2391, AR2392, AR2393 and AR2394 were seen over on the E limb but there were all of small size. 

SPA Sunspot Mean Daily Frequency (MDF):  4.15 
SPA Relative Sunspot Number: 57.90


The first few days of July we saw a wealth of features come and go in Hydrogen-alpha. The 1st saw a magnificent hedgerow-type prominence on the E limb as well as extensive plage and filament activity around AR2373, AR2375 and AR2376. By the 3rd there was still a lot of plage and filament activity east of the CM with only a few prominences to be seen around the limb. Outstanding was a curved dark broad filament near the N limb. On the 4th we saw another hedgerow-type prominence on the NE limb (RB) while on the disk the plage and filament activity had spread westwards. It was the same on the 5th, except the prominence had gone by then.

By the 8th and 9th we saw several small prominences around the solar limb plus several plages and filaments associated with sunspots AR2373 and AR2375 by then nearing the W limb and AR2381 and AR2383 now over the CM. AR2384 showed plage and filaments trailing behind it and almost reaching the E limb on the 11th. On the 14th we saw not much in the way of prominences but that was made up for in the number of plages around AR2381, AR2384 and AR2386 and filaments across the solar disk.

There was a long dark filament slightly broken in places seen almost across the disk on the 16th as well as two smaller filaments seen threading away from AR2384. These were seen again the next day.

After the 20th there was more in the way of prominences, mostly small and low-lying in nature. On the 25th a small detached jet-like prominence was seen on the SE limb. As we approached the end of July there was a gradual return to small prominences on the limb and some scattered plage and filament activity on the disk especially on the 31st when sunspots AR2390, AR2391, AR2393 and AR2394 were visible. 

SPA Prominence Mean Daily Frequency (MDF): 5.17 
Well done to Brian Gordon-States who observed the Sun on 30 days in July and to Alan Heath and Jonathan Shanklin who observed on 28 and 27 days respectively.

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

Images and drawings were supplied by: Richard Bailey, Mark Beveridge, Carl Bowron, Paul Brierley, John Chapman-Smith, Michael Fullerton, Mick Jenkins, Ian Lee, Cliff Meredith and Julia Wilkinson.

Geoff Elston

Solar Section Director

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