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Solar Rotation Nos: 2179 to 2180
A slight upturn in activity this month.
While there is not a lot happening in terms of sunspot activity, the Sun is continually bathing the Earth in the solar wind, a constant but sometimes gusty stream of charged particles coming out from the Sun in all directions. The Earth, as it orbits the Sun, passes through these streams of particles where they are funnelled down towards the north and south poles and into the upper atmosphere. The interaction between the solar wind and the Earth’s magnetic field results meant that at high geographical latitudes at least many people have seen numerous displays of aurora despite solar activity being low. Sadly, in the UK we are often too far south to see the aurora but it is always worth being alert as you never know what you might get.
Here are the highlights for August 2016 together with a selection of images from members of the SPA Solar Section.
We had a single small sunspot visible throughout the first five days of early August. This was Active Region (AR)2570, a type Axx sunspot, lying just north of the solar equator. Another small northern hemisphere spot appeared on the 5th AR2571 (type Dro) and on the 6th AR2572 (type Dao) also appeared near the west (W) limb. By the 7th AR2570 had long since disappeared but AR2571 was by now developing as it crossed the Central Meridian (CM) and we had more sunspot activity rapidly appearing near the east (E) limb.
The new activity by the E limb was AR2573, AR2574, AR2575 and AR2576. Of these, AR2574 and AR2576 were the largest (types Cao and Hsx). Even so, none of these sunspots were particularly active but they were interesting to watch as they crossed the face of the Sun over the following few days. All except AR2576 were on the northern hemisphere. They were over the CM by the 15th and had reached the W limb around the 20th and had faded a little by then.
On the 21st the Sun was very nearly blank, except for AR2578, a small type Cro sunspot on the northern hemisphere. By the following day we also had AR2579, a rapidly developing spot that suddenly appeared on the solar disk and the decayed away after that. By the 26th we also had AR2580 and AR2581. AR2581 developed rapidly initially but then started to decay. It was AR2582 and AR2583, that appeared suddenly near the W limb on the 27th that were minor solar flare active on the 29th. It was on the last day of August that something was about to appear over the E limb but what exactly we could not yet tell.
If you want to know more about the sunspot classification, see the guidance on our website (items 4 and 5).
SPA Sunspot Mean Daily Frequency (MDF): 2.70 (was 1.59)
SPA Relative Sunspot Number: 36.31 (was 25.55)
PROMINENCES, PLAGE, FILAMENTS AND FLARES
Despite the lack of sunspots, the beginning of August saw more disk filaments than prominences. The 1st saw a long broad filament lying near the CM on the northern hemisphere but there was a low hedgerow type prominence on the SE limb. The 2nd saw similar activity. By the 4th filaments had died away but there was a tall mound prominence on the W limb. On the 6th a fairly substantial prominence was seen on the N limb.
By the 8th we not only had a substantial hedgerow on the SE limb but several tall spike prominences along the N and NW limbs. There were several filaments across the southern hemisphere and bright plage activity around AR2571, AR2572, AR2573 and AR2574.
On the 15th there were a number of fine prominences on view lying along the SE and NW limbs, meanwhile, on the disk AR2573, AR2574, AR2576 and AR2577 all had plage activity clustered around them and some short dark filaments just to the north. From the 15th to the 18th the NW limb was a complex jumble of intricate prominences, filaments and plage activity all connected with the sunspots approaching the limb at that time.
In the last week, prominence activity died away until the 29th when there was a large intricate hedgerow type prominence along much of the SE limb. There were several short dark filaments and plage activity associated with the sunspots AR2580, AR2581, AR2582 and AR2583. A long dark filament was seen on the 31st near the SE limb
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): 6.37 (was 4.48)
Welcome and well done to Brian Gordon-States who observed every day in August. Alan Heath and Bob Steele were not far behind on 26 and 24 days respectively.
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, Bob Steele, Julia Wilkinson and the Director.
Images and drawings were supplied by: Carl Bowron, Paul Brierley, Mick Jenkins, Ian Lee, Cliff Meredith, Julia Wilkinson and Brian Woosnam.