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Solar Highlights for August 17


Solar Rotation Nos: 2193 to 2194

This was a month of two distinct halves, the first part relatively quiet, the send half active with at a sunspot group long enough to be visible to the protected naked eye, and a total solar eclipse.

Here are the solar highlights of August 2017 together with a selection of images.


An increase in sunspot active mainly due to the events in mid to late August.

1st to 14th August
The Sun was almost spotless on the first day of August. Tight to the solar limb was former Active Region (AR) 2665 at a southern latitude of S05°. Of course, we had seen this sunspot before in mid-July. It was now re-designated AR2670 and was type Cso. There was a Coronal Hole on the 3rd which led to some high latitude aurora a couple of days later. AR2670 did not change much in its second passage across the solar disc, being much more stable by now it did not grow or decay, crossing the Central Meridian (CM) on the 8th and went over the west limb of the Sun around the 15th.

15th to 31st August
While AR2670 was leaving over the west solar limb, a new sunspot group had just come over the east limb. This was: AR2671, originally type Hsx and at latitude N11°, it developed to type Eai by the following day, and by the 17th it was type Ehc and flare active. From the 18th and 19th AR2671 reached it greatest extent, of type Fkc, and visible to the protected naked eye. This was quite something considering where we are in the Sunspot Cycle! As AR2671 neared the CM we had a total solar eclipse lasting up to 2 minutes 40 seconds at the centre line of totality and visible right across North America. Sadly, none of the eclipse could be seen from the UK or Europe. As if this was not enough, AR2672 appeared at the east limb on the 21st AR2672, a type Dao sunspot group, and north of the solar equator at: N05°. By the 24th AR2871 was type Fsi and nearing the west limb while AR2672, now at the CM, was type Esi. AR2671 was over the west limb by the 29th having decayed beforehand. At the end of August AR2672 was near the west limb, but two more sunspots had appeared over the east limb. AR2673 was another southern hemisphere sunspot at S08° and AR2674 was at N14°. The latter developed into type Eko by the 31st and was solar flare active. Also on the 31st AR2675 appeared at S07°, and was sunspot type Dro.

SPA Sunspot Mean Daily Frequency (MDF): 1.56 (was 0.69).
SPA Relative Sunspot Number: 23.36 (was 11.79).

Solar Prominences, Plage, Filaments and Flares

There were several interesting prominences seen (and imaged) in H-alpha light throughout the month. AR2671 and AR2672 brought more disc activity later in the month.

1st to 12th August
A lovely detailed image of AR2670 in H-alpha using a DayStar Combo Quark by Carl Bowron on the 5th. A lovely arch type prominence was seen on the east limb on the 10th imaged by Carl and drawn by Ian Lee.

13th to 31st August
A few days later there were several prominences along the southeast and northwest limbs on the 13th. A long column type prominence appeared on the east limb on the 18th just as AR2671 was on the disc. In H-alpha AR2671 showed several short filaments and bright areas of plage around it. The same was true as AR2671 reached the centre of the solar disc on the 20th. By the 25th AR2671 was nearing the west limb and AR2672 was near the CM. Along the west limb were several high prominences. By the following day filament and prominence activity seemed to decrease. The 27th and 28th showed more in the way of prominences as did the 31st but by then there was more disc activity due to AR2672-75. In particular was a tangled and complex filament near the CM on the 30th and 31st.

SPA Prominence Mean Daily Frequency (MDF): 3.51 (was 3.30).

Well done to Brian Gordon-States, who observed 29 days, to Ian Lee and Jonathan Shanklin who both observed 27 days and to Alan Heath for reaching 26 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 the Director.

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

My thanks to Srinath Sudunagunta, who provided images of the total solar eclipse on the 21st from Menan Butte, Idaho.

Geoff Elston


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