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  • Monty Leventhal OAM

Solar Observations for September 2017

Solar activity overall remained quite low in September but there were a few extraordinary observations. Activity began to increase on the 1st of September with a Bxo group in AR 12675 and an Hsx spot in AR 12673. A much larger Eki group developed in AR 12674 and produced type 2N Flare. By the 3rd the group in AR12673 had grown to a Dki and the group in AR 12674 had grown to a CV of Fkc. On the 4th the group in AR 12673 had grown to an Fkc and produced a type 10N Flare and again on the 7th it produced a type 3B Flare. The last of these groups were seen close to the western limb on the 9th.producing Post Flare Loops reaching a height of about 93,000km and stretching across the limb for about 261,000km.

As shown in the photograph above and drawn in the map below a double Post Flare loop was also observed on the 10th also reaching an approximate height of 93,000km on the western limb possibly emanating from another Flare in AR 12673.

From the 12th on, until the 19th only one single Cki group could be seen. On the 20th it had reduced to a single Hsx spot. Close to the SE limb a new single Hsx spot was observed in AR 12681. By the 23rd it had grown to a CV of Cki.

On the 24th another new Csi group appeared close to the SE limb in AR 12682 and a further new Cki appeared close to the NE limb in AR 12683.

These 3 groups of Sunspots were the only ones on the solar disc until the 30th. At that time the group in AR 12683 grew to a CV of Dki.


Most Prominence activity remained fairly small & constant, though mostly faint. On the 9th some Post Flare loops were observed on the NW & SW limb. As shown in the map below, on the 10th a large double looped Post Flare loop emanating from an X-9 Flare on the western limb was observed reaching a height of about 93,000km.No further significant Prominences were observed for the rest of the month. All were small and faint.

Photograph Monty Leventhal X-class Flare


On the 1st September a type 2N Flare erupted in AR 12674. It started at 23.45 UT, peaked at 23.50 & ended at 00.00 on the 2nd September. It had an X-ray class of C1.5.

Another type 10N Flare was observed on the 4th in AR 12673 as shown in the photograph on the right. It started at 16.00 UT, peaked at 16.40 & ended the following day at 02.35. It had an X-ray class of M5.

On the 7th the group in AR12673 became very active and produced a type 3B Flare. This one started at 23.50, peaked 00.00 hrs on the 8th and ended at 00.50 the following day. It had an X-ray class of M4.


For the month of September 2017 all activity once again on the Sun remained very low.

A total of 24 Observations were made for the month with the remaining days being cloud covered and/or rain. A total of 10 groups were observed. This included 5 groups in the north and 5 in the south, comprising of 24 spots in the north and 28 spots in the south, giving a total of 52 Sunspots.

The average Relevant Sunspot number for the month was 34 and the average CV was 60. The average Q CV was 8.

Monty Leventhal OAM



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