Each month a summary of sunspot activity is written and forms part of a report sent to the Solar Section of the British Astronomical Association (BAA) and to The Astronomer. Follow the links below to read a page summary of sunspot activity. The McIntosh Sunspot Group Classification is used for sunspot group descriptions.
Another particularly cloudy month restricted observing to 8 days. The largest of the six groups seen on the 8th was AR 2480 of type Eac near the eastern limb at 3°N/123° and area 180 millionths. The largest sunspot within the group was the leader. By the 10th a few additional pores were seen within the group. When next seen on the 15th and 16th AR 2480 had become type Hsx with an area of 100 millionths and now approaching the western limb. To the north of AR 2480 was AR 2483 initially seen as an Axx sunspot at 17°N/126° on the 8th before developing into a small Dso group on the 10th with an area of 60 millionths. Like AR 2480, AR 2483 was seen as an Hsx sunspot on the 15th and 16th.
On the 23rd a small Dai group, AR 2488, was seen approaching the central meridian at 4°N/320° and area 90 millionths. Although the number of follower sunspots had reduced by the following day, the leader had enlarged and contained several umbrae – the total area of this now Cai group had increased to 190 millionths. AR 2488 was of a similar type and size on the 28th but of type Hsx close to the limb on the 30th. An Eac group was also seen on the 28th – this being AR 2489 at 10N/252 and area 210 millionths. The main sunspot was the leader. By the 30th most of the followers had disappeared to leave a Cai group where the leader had an area of 230 millionths. AR 2488 and 2489 were the only groups seen on the 30th.
None of the groups seen during the month were particularly large. Of particular note were AR 2494, 2497 and 2506. AR 2494 was initially seen on the 7th as a Dac group at 11°S/163° with an area of 180 millionths – the follower was the largest sunspot. By the 9th, with the group approaching the western limb, AR 2494 the follower had split but the group was of the same type and similar size. A small Hsx sunspot was all that remained by the 11th when it was close to the limb.
One of the other groups seen on the 7th was AR 2497 at 13°N/84° of type Dsc and close to the eastern limb – it comprised several small penumbral sunspots and several pores. When seen on the 9th it now resembled a normal bipolar group of type Dsi with an area of 70 millionths. The longitudinal extent of AR 2497 had increased by the 11th to make the group type Eac and it was also near the central meridian. None of the several penumbral sunspots were particularly large as the total area was just 180 millionths. By the 14th it has reverted back to a Dsc group and it appeared as a collection of small penumbral and other sunspots. It was also the only group seen on this date. AR 2497 was last seen close to the limb on the 17th a three small penumbral sunspots.
One of the three groups seen on the 23rd was an Axx group, AR 2506, close to the eastern limb at 8°S/222°. It was still of type Axx on the following day before developing into a small Cso group on the 25th and 26th. On the 28th with the group near the central meridian it became type Dsc with an area 110 millionths. On the 29th most of the pores between leader and follower had disappeared to leave a Dso group with a total of area 80 millionths.
Activity reduced slightly compared to previous months and again none of the groups were particularly large. The northern hemisphere was still dominant. The number of groups seen varied from seven on the 4th the one on the 22nd & 23rd and between the 29th and 31st. Groups of particular note were AR 2513, AR 2519, AR 2524 and AR 2526.
The largest group seen during the start of the month was AR 2513 – it was initially seen on the 3rd as a single Hsx sunspot at 10°N/101° near the eastern limb. It remained of the same form during its passage across the solar disk although it had a peak size of 120 millionths on the 5th and it was last seen nearing the western limb on the 13th. Another single Hsx sunspot appeared close to the eastern limb on the 11th – AR 2519. This sunspot, at 5°N/12°, had a couple of attendant pores on the 16th when its area peaked at 120 millionths. These pores had decayed by the 20th when AR 2519 was near the western limb.
Yet another Hsx sunspot was seen close to the eastern limb on the 16th. However by the following day a following penumbral sunspot was also seen – AR 2524 at 14°N/277° was of type Eso. By the 20th two pores were seen between the leader and follower and the group has a total area of 210 millionths. When seen on the 22nd and 23rd AR 2524 was just past the central meridian and the only group seen. As the group approached the limb it began the decay with being type Cso on the 25th and type Hsx on the 27th and 28th.
The final group seen during the month was AR 2526. It was initially seen as a moderately sized Hsx sunspot at 4°S/176° on the 25th. As it moved away from the eastern limb, a small number of attendant sunspots appeared. AR 2526 was in the middle of the disk on the 30th of size 250 millionths. It appeared as a single Hsx sunspot on the 31st. AR 2526 was seen with the protected naked eye on each day between the 27th to 31st inclusive (despite it being smaller than the nominal 500 millionths required for sunspot to be visible by the protected naked eye).
Although activity in terms of the number of active areas and sunspot number was similar to previous months, there was particular interest because of the moderately sized group AR 2529 seen between the 8th and 19th and an unusual bipolar group at the end of the month. The number of groups seen during the first three weeks were either one or two but during the last week up to six groups were seen. As during recent months the northern hemisphere was dominant. Several groups were seen close to the solar equator, an indication of activity during the declining part of solar cycles.
The largest group seen during the first week was AR 2526 at 3°S/176° which on the 2nd was of type Hax and area 140 millionths. It was last seen very close to the western limb on the 5th.
The observation on the 8th showed that AR 2529 had rotated around the eastern limb at 9°N/340° and of type Dko. The dominant sunspot was the leader. On the 10th the group was now of type Ekc with an estimated area of 830 millionths. The dominant leader was asymmetric in shape while there were two much smaller followers. It was also the only group seen. On subsequent days the leader became more symmetrical while the followers reducing in size. The shape of the umbrae also changed from day to day. The total area was slightly reduced at 740 millionths on the 12th. When next observed on the 16th, with AR 2529 now past the central meridian, the size of the group had reduced the 600 millionths and the followers were all small. As the group neared the western limb, its reduced in size such that on the 17th it was 490 millionths and no followers were seen on the 18th and 19th. AR 2529 has rotated around the limb on the 20th. AR 2529 was seen with the protected naked eye on the 10th, 11th, 12th, 16th, 17th and 18th.
On the 23rd AR 2533 was the only group seen – it was of type Hsx, of size 100 millionths and very close to the solar equator at 2°S/182°. By the 26th, five groups were seen which increased to six on the 27th and 28th. These additional groups were spread across the solar disk. All were small in size but one was of particular interest. This was AR 2536, initially seen as a small single Hsx sunspot at 14°N/118° close to the eastern limb. On the following day two small sunspots had developed towards the south of the penumbral sunspot. One of these southern sunspots developed further into small penumbral sunspot of similar size to the northern penumbral sunspot. Thus AR 2536 had the appearance of a bipolar Dsi group which was highly inclined to the solar equator – quite unusual given that most bipolar groups have the line between the leader and follower inclined by only a few degrees. By the 30th, the northern penumbral sunspot increased in size towards the direction of the southern penumbral sunspot. The total area was 150 millionths (SDO HMI Magnetogram images indicated that the northern and southern ends of AR 2536 has different polarity thus indicating that this was indeed a bipolar group with a high inclination angle).
Hydrogen Alpha: Images:
One of the five groups seen on the 1st was the unusual bipolar group AR 2536 at 14°N/118° now just past the central meridian. The northern penumbral sunspot has reduced in size to be more like the southern penumbral sunspot and several pores were seen within the group as shown in the image. By the following day the leading southern sunspot had become more asymmetrical and the northern follower had reduced in size. The number of pores had also reduced. On subsequent days the group continued to decay such that on the 4th it was of type Csi with an area of 60 millionths but still highly tilted. When last seen on the 5th just a single Axx sunspot remained (no observations were made on the 6th and 7th when the group would have been close to the western limb).
On the 4th and 5th a Dso group was seen close to the eastern limb – this was AR 2542 at 11°N/358°. By the next observation on the 14th it was approaching the western limb still of type Dso with an area of 160 millionths. A single Hsx sunspot was all that was seen of this group very close to the limb on the 16th. One of the other five groups on the 14th and near the central meridian was of type Csi with many pores following a small penumbral leader – this was AR 2544 at 21°N/295°. By the 16th the leader penumbral sunspot had grown from 30 to 130 millionths but there were fewer followers. When last seen on the 17th, the group, still of type Cai was reduced at 70 millionths and again few pores being present.
The 14th also showed a moderately sized group, AR 2546, close to the eastern limb at 7°S/223° and of type Hhx. On the 16th it had an estimated area of 370 millionths before slowly increasing to 650 millionths on the 23rd. Thereafter it slightly reduced to 530 millionths on the 24th and it was last seen close to the western limb on the 26th. It remained of type Hhx on all observing days and it was the only group seen on the 22nd, 23rd and 24th. AR 2546 was seen with the protected naked eye on the 17th, 22nd, 23rd and 24th. The last observation of the month, on the 29th, only showed two small Hsx sunspot groups.
On the 22nd a flare was seen to the west of the moderately sized AR 2546 (the sunspot umbra was easily seen in Hα). At the start of the observing period at 09:15 UT a bright compact blob was seen together with a slightly fainter elongated bright region to its west. Over the next 15 minutes the elongated region faded to leave two smaller brighter regions. The compact blob also reduced in brightness during these 15 minutes. NOAA indicates that this was a B5.9 flare peaking at 09:21 UT. During the same observation an extensive region of plage was seen to the east of AR 2546. Plage was also seen around AR 2546 on the 15th, 16th and 23rd.
There was quite a reduction in activity compared to recent months and the lowest since May 2010. No sunspots were seen during the beginning and end of the month – in particular for observations between the 4th and 7th inclusive, between the 24th and 28th inclusive and the 30th.
The first observation with sunspots was on the 8th with the appearance of AR 2552 at 16°N/358° of type Cro having appeared on the solar disk. By the following day this group had developed into an irregular Hax penumbral sunspot of size 120 millionths which included several umbrae. On the 12th another group has developed in the western hemisphere – AR 2554 of type Dso at 8°N/316° and area 110 millionths. The only other group on the 12th was AR 2553, an asymmetrical penumbral sunspot of type Hax at 6°S/226° with an area of 230 millionths. On the 15th AR 2554 was close to the western limb while AR 2553 was approaching the central meridian with a similar appearance and size. AR 2553 was seen again on the 19th to 21st still type Hax and of a similar size. Also on the 19th were AR 2558 at 12°N/215° of type Dai and size 70 millionths and AR 2556 of type Hax at 5°N/135° and area 90 millionths. AR 2558 had disappeared by the following day while AR 2556 started to reduce in size as it approached the central meridian. On the 21st, the last observation with sunspots, AR 2556 was just 30 millionths in size.
There was an increase in activity compared to the previous month but there were still several spotless days at the beginning and end of the month. Between the 1st and 6th inclusive only one groups was seen on the 3rd only – an Axx sunspot near the centre of the disk at 11°N/°9. Observations on the 25th, 26th and 31st also showed spotless disks.
On the 16th four groups were seen including two nearby groups AR 2565 and 2567: these were at 5°N/175° of type Cao & size 170 millionths and at 6°N/165° of type Dac & size 270 millionths (the other two groups were of type Axx and Bxo). AR 2565 increased in size slightly over subsequent days such that it was 340 millionths on the 19th and still of type Cao. With this group approaching the western limb on the 22nd and 24th it was of type Hax. AR 2567 also increased in size to 340 millionths on the 18th when it was of type Dkc with several pores between the larger leader and a couple of follower penumbral sunspots. It then continued to grow through the leader between the 19th and 20th to 600 millionths – the group was now of type Dkc. The two followers had also merged. Subsequent observations showed that AR 2567 reverting back to type Dac and it was seen close to the limb on the 24th. A single Axx sunspot, AR 2566, was seen to the north of AR 2565 on the 18th only. One protected naked eye sunspot was seen on the 16th (AR 2567) and two on each day between the 17th to 20th (AR 2565 and 2567).
Although overall activity was at its highest since 2016 February, there were no notable sunspots groups. Based on 25 observations there was only one spotless day on the 3rd. The northern hemisphere was the more dominant while in the southern hemisphere there were several days without any sunspots.
One of the two groups seen on the 4th was AR 2571 at 14°N/268° of type Axx. It was of type Bxo on the 5th before developing into a small compact Dsc group on the 7th with an area of 90 millionths when near the central meridian. When last seen on the 9th the two leading penumbral sunspots had merged while the following sunspots had almost disappeared to leave a Cao group of area 100 millionths. On the 8th a group with an extended latitudinal extent had appeared around the eastern limb – this was AR 2574 at 5°N/172°. It had an irregular penumbral sunspot to the north and a more regular penumbral sunspot to the south. Observations on the 9th and 12th showed AR 2574 of type Dao and area 160 millionths. As AR 2574 progressed across the disk, the northern sunspot reduced in size and became more circular in size. Hence on the 17th it had an area of 80 millionths while it was last seen on the following day as just two similarly sized small penumbral sunspots. By the 12th AR 2574 was accompanied by a following group at a similar latitude. This was AR 2577 at 4°N/164° of type Csi and size 30 millionths. It obtained a size of 90 millionths and type Dao on the 13th before being last seen on the disk as a type Axx group on the 17th. During the period 9th to 18th a southern group, AR 2576 was seen. This was of type Hax and area 100 millionths on the 12th before developing a couple of follower spots on the 14th and then reducing to a pair of close small penumbral sunspots on the 18th.
On the 20th only one group was seen – AR 2578 at 10°N/87° of type Cso and area 30 millionths. It had disappeared by the 22nd when the larger of two groups was AR 2579 at 12°N/34° of type Dsi with an area of 60 millionths. Subsequent observations showed that this group decaying as it passed through the central meridian and it was last seen as an Axx group on the 26th. AR 2581 had formed in the disk between the 25th and 26th as a small Cso group at 14°N/337°. The leader penumbral sunspot increased in size such that by the 27th the group had an area of 120 millionths. Although the leader became more symmetrical as it progressed across the disk, it was still of a similar size when last seen on the 31st.
of two new groups that
appeared near the eastern limb on the 31st was AR 2585 at
8°N/222° of type Dkc.
It comprised of an irregular leader penumbral sunspots and two follower
penumbral sunspots – a promising group for September. Hydrogen Alpha:
A fine wispy prominence was seen on the 15th extending above the NE limb. It comprised of several parts and it had an estimated height of about 220,000 km. Another notable feature was a combined prominence and filament seen on the 30th and 31st on the NE limb. On the 30th only a small portion of this was seen as a prominence and the rest as a thin filament extending. By the 31st no prominence was seen and there was a gap between the filament and the limb caused by solar rotation.
Plage was seen around combined AR 2570 and 2571 on the 6th and 7th around AR 2574 on the 12th, 14th and 15th and around AR 2581 on the 27th, 30th and 31st.
There was a slight reduction in activity compared to the previous month and once again the northern hemisphere was the more dominant with no sunspots in the south on 9 or the 12 observing days.
The highlight group of the month was AR 2585 initially seen close to the limb on August 31 as a Dkc group at 8°N/222°. By the 3rd it was of type Eac with an area of 500 millionths comprising four irregular penumbral spots and a few pores – the largest sunspot was the leader. By the following day two of the follower sunspots had merged to form the largest sunspot and the change the group to type Ekc. When next seen on the 7th AR 2585 was just past the central meridian when it consisted of two penumbral sunspots and a few pores – the irregular follower was still the largest sunspot – the total area had reduced to 380 millionths. On the 8th the follower became more irregular which became much smaller and had split into two when AR 2585 was last seen near the limb on the 11th. AR 2585 was seen with the protected naked eye on the 3rd, 4th, 7th and 8th. A small Axx group was seen following AR 2585 on the 3rd and 4th – this being AR 2587 at 10°N/212°.
During the period 3rd to 11th the other five groups seen (i.e. in addition to AR 2585 and 2587) were all small. No sunspots were seen on the 15th. On the 18th three groups were seen. One of these was AR 2593 of type Axx at 8°N/47°. When next seen on the 21st it was bipolar of type Dsi with an area 60 millionths with a few pores seen in addition to the small symmetrical leading and following penumbral sunspots. By the 23rd it was if type Csi comprising a small leading penumbral sunspot and a fan shaped collection of following pores. On the following day AR 2593 was of type Bxo approaching the western limb. Also on the 23rd a southern small group, AR 2597, had developed on the disk of type Cai at 13S/347 and area 90 millionths (it was not seen on the previous day). It was of the same type on the 24th while by the last observation of the month on the 25th it had become type Dac with an area of 100 millionths.
There was a further slight reduction in activity compared to the previous months and once again the northern hemisphere was the more dominant with no sunspots in the south on all 7 observations made in the latter half of the month.
The first observation, on the 2nd, showed no sunspots. On the 3rd one group, AR 2598 developed on the disk while another, AR 2599 appeared around the eastern limb. AR 2598 at 14°N/175° was initially of type Cai before developing into type Dso on the 4th and then Dai on the 6th when it comprised of two irregular penumbral sunspots and several pores to the south; the total area was 140 millionths. When next seen on the 9th AR 2598 was of type Cai with a string of pores following the penumbral leader which had an area of 100 millionths. On the 11th and approaching the western limb only a single Axx sunspot was seen. AR 2599, the largest group seen during the month, was an irregular penumbral sunspot of type Hkx on the 4th, 5th and 6th at 14°S/146° and with an area of 300 millionths on the 6th. By the 9th AR 2599 was near the central meridian and the main sunspot had almost split and small following penumbral sunspots developed to form a Dki group of area 270 millionths – it was also seen with the protected naked eye. By the 11th AR 2599 was of type Cao with the surrounding pores disappearing by the 13th to give a Hax group with area 200 millionths. This group was last seen on the 15th very close to the western limb.
Three other groups were seen during the first half of the month – the largest of these was AR 2600 at 12°N/104° as an Hax or Hsx sunspot which attained a maximum area of 150 millionths on the 15th. During the second half of the month only one or two groups were seen on each observation. The largest of these was AR 2603 at 13°N/337° which obtained an area of 100 millionths when it was of type Dso and approaching the western limb.
Page created on 24 January 2016.