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We saw some very low levels of sunspot activity in July, dropping to a level not seen since 2010 based on SPA Solar Section observations. Due to the slow gradual unwinding of the Sun’s global magnetic field, sunspots either do not appear, or when they do, they are fairly inactive and many are small. Solar flares are few and far between for much the same reasons. Despite the low activity we had a fine sunspot group cross the disk mid-month and there was more to see in H-alpha for those with H-alpha scopes.
Here are the highlights for July 2016 together with a selection of images from members of the SPA Solar Section.
If you were looking for sunspots in early July, you would have been disappointed as there were none to be seen in the first 6 days. The Sun’s blank disk, which is a common sight the closer we are to Sunspot Minimum, was only broken on the 6th by two very small sunspots AR (Active Region)2559 (sunspot type Bxo) and and AR2560 (type Axx) appearing on the solar disk. Of the two, AR2559 had disappeared the next day leaving AR2560 all on its own.
AR2561 (type Cro) appeared near the W limb from the 8th to the 11th. It was over at the E limb that sunspot activity was building and in particular AR2564 (a Dai type sunspot lying just north of the solar equator) which at first looked promising and it was thought it might produce M-class flares, but this did not happen.
The 12th saw another sunspot, AR2565, appear near the E limb. This was quite a big Hsx type sunspot, but it was known to be magnetically “stable” and therefore pretty inactive. However, as ever, it pays to be alert and it was this sunspot together with the following sunspots of AR2567 that developed suddenly on the 16th. They both neared the Central Meridian (CM) on the 18th and once over it they seemed to keep going in activity showing much detail even as they neared the W limb. AR2565 (now Cko) and AR2567 (now Dki) were flare active from the 20th onwards. It was not until the 23rd as they were about to depart over the W limb that two M-class solar flares erupted within hours of each other. Sadly, both flares occurred in the hours of darkness here in the UK so we could not see them with H-alpha equipment but it was exciting to know these flares had appeared especially as they had been the first for some time.
With AR2565 and AR2567 going over the W limb on the 26th the Sun was again without sunspots until the 29th when small Bxo type sunspot AR2570 was the only one visible near the E limb.
If you want to know more about the sunspot classification, see the guidance on our website.
SPA Sunspot Mean Daily Frequency (MDF): 1.59 (was 2.12)
SPA Relative Sunspot Number: 25.55 (was 35.97)
PROMINENCES, PLAGE, FILAMENTS AND FLARES
In the first few days of July there did not seem to be much in the way of prominences, apart from a low hedgerow prominence on the NE limb (the edge of the Sun’s disk) on the 2nd and a slightly higher hedgerow type on the SE limb on the 5th. There were more filaments on the solar disk however.
It seems it was not until the 12th the final saw more in the way of prominences. By this time, we also had the sunspots: AR2562, AR2563, AR2564 and AR2566 on the disk and the associated bright areas of plage and a few short filaments as well. By the 13th and 14th the prominences had mostly disappeared but there was still a quite a lot of plage and filament activity near AR2562 and AR2565. By the 18th we saw quite a lot of plage activity around sunspots AR2565 and AR2567 plus a scattering of short dark filaments across the solar disk but only a few small prominences around the Sun’s limb. We saw a similar scene on the 19th but there seemed more plage and filament activity and AR2569 had appeared by then.
As we went into the last week or so of July we saw more prominences especially on the 22nd along the SE limb (AR2565 and AR2567 were nearing the SW limb too but there was no connection between the two), on the 25th (along SE and SW limbs) and the 26th. Also in that period was the appearance of a long dark winding filament that crossed the solar disk from about the 25th to 31st and seemed to fade over time. Its longest extent was reached on the 30th when it was nearly half a solar diameter long.
Alan Heath observed 2 solar flares (one on the 8th and one on the 17th):
8th 0825UT: Flare.
17th 0845UT: Flare with AR (2565/2567?). 0950UT: Flare still there. 1020UT: Flare still there, but weaker. 1220UT: Flare weak. 1250UT: Flare gone.
SPA Prominence Mean Daily Frequency (MDF): 4.48 (was 4.71)
Welcome and well done to Bob Steele who observed every day in July. Brian Gordon-States, Alan Heath and Jonathan Shanklin all observed 29 days, Michael Fullerton was not far behind on 24 days.
Detailed count records of Active Regions and Relative Sunspot Numbers came from: Brian Gordon-States, Michael Fullerton, Alan Heath, Mick Jenkins, Ian Lee, Lee Macdonald, Jonathan Shanklin, Bob Steele and Julia Wilkinson.
Images and drawings were supplied by: Mark Beveridge, Carl Bowron, Paul Brierley, Mick Jenkins, Ian Lee, Cliff Meredith, Peter Paice, Julia Wilkinson and Brian Woosnam.