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Solar Highlights for October 16

Solar Rotation Nos: 2181 to 2182

A quiet start, then more sunspots towards the middle of October, before it went quiet again. There was more to be seen in H-alpha light.

Despite the low sunspot activity, the Sun is still active in other ways. There were several high-latitude aurorae seen in October (10th, 16th, 23rd, 25th to the 27th) generally brought about by the interaction of the Earth’s magnetic field with the solar wind from the Sun. You had to be within the Arctic Circle to be able to see these displays as the UK is too far south.  

Here are the highlights for October 2016 together with a selection of images from members of the SPA Solar Section.


1st to 19th October
The only sunspot visible on the 1st was Active Region (AR)2597. This small type Hsx sunspot was seen the previous month and was situated on the southern hemisphere. It had gone on the 2nd leaving a nearly spotless Sun apart from AR2598, a northern hemisphere Bxo type sunspot group. AR2598 was quickly followed by a southern hemisphere type Hax sunspot, AR2599, on the 4th. Of the two, AR2599 was larger that showed signs of development over the following days until it reached the Central Meridian (CM) on the 9th. AR2600 then appeared on the 7th we then saw all three slowly travel across the solar disk (due to the Sun’s rotation) over the next few days. All three were quiet and stable in nature (so little chance of flares) though AR2599 did seem to develop slightly, forming a large slightly flattened triangle on the solar disk. Finally, on the 11th and 13th, AR2601 and AR2602 appeared. The first disappeared after two days but the second lasted longer.

20th to 31st October
The Sun then went back into almost a spotless period but there were two small sunspots, AR2603, a type Axx and on the northern hemisphere, and AR2604, a small Bxo type sunspot also on the northern hemisphere, that appeared on the disk on the 29th. Polar faculae were seen near the N solar pole on the 23rd. 

If you want to know more about the sunspot classification, see the guidance on our website.

SPA Sunspot Mean Daily Frequency (MDF): 1.73 (was 1.92) SPA Relative Sunspot Number: 24.73 (was 28.44)


There was some nice prominence activity this month. There were areas of bright plage and dark filament activity on the solar disk throughout October.

On the 2nd while there were no sunspots, there were several prominences along the NW limb and a collection of plage and filaments near the SE limb. By next day both NW and SE limbs had prominences along them and just on the disk running parallel with the SE was a long ribbon of bright plage and bordered by a long dark filament.

A tall prominence with one of two detached parts was seen on the N limb on the 5th and a hedgerow-type prominence with a pyramid-shaped prominence nearby on the W limb. The following days also saw plenty of prominence activity along the SE, N and W limbs. By then we had AR2598 and AR2599 on the solar disk. These had a small amount of plage activity around or near them.

On the 8th, 9th and 10th we saw quite extensive plage activity around the three sunspots crossing the disk (AR2598, AR2599 and AR2600) plus several dark filaments (some quite twisted) prominences along the SE, N and W limbs.

By the 16th there were fewer prominences but we had a pillar-type prominence on the NW limb and a filaprom (which is part filament- part prominence) on the SE limb that was still visible on the 17th. ON the same day there was also a long fragmented filament trailing AR2602 almost reaching the E limb. A small detached prominence was seen just off the NW limb on the 18th.

There were several interesting prominences on the 25th along the SE, N, W and SW limb. AR2603 was by then nearing the NW limb. By the last day of October the Sun appeared very quiet.

SPA Prominence Mean Daily Frequency (MDF): 5.01 (was 4.76)

Well done to Brian Gordon-States who observed on 30 days in October.  Alan Heath was close behind on 26 days and Jonathan Shanklin 24 days.

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

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

Sadly, I learned a few days ago that Richard Bailey, passed away in early October after a long battle against cancer. He was a kind and generous man as well as a dedicated solar astronomer. I am told that he continued to make solar observations right up until he went into hospital. Richard passed away five days later. He will be missed by us all. 

Geoff Elston


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