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.
Two small groups were observed based on 7 observations. These were AR 2696 on the 19th as a single Axx sunspot at 15°S/124° and AR 2697 on the 30th as a Bxo group comprising four sunspots at 5°S/265°. The other observations on the 7th, 22nd, 25th, 27th and 28th were all spotless.
Only one group was observed based on 15 observations. This was AR 2699 at 7°S/166° – it was first seen on the 5th as an Hsx sunspot near the eastern limb. By the following day a small follower penumbral sunspot appeared to make the group type Dao. On the 7th the follower has increased in size and several pores were seen within the group. The follower grew again by the 8th to make the leader and follower of approximately the same size – the total area of the group was 200 millionths. When next seen on the 11th, with the group just past the central meridian, it was still of type Dai and similar size. On the 12th several small penumbral sunspots had appeared within the group and its size had increased to 240 millionths. By the 15th all the follower penumbral sunspots had disappeared to leave a Cso group of 110 millionths. With the group near the western limb on the 16th just an Hsx sunspot was seen. AR 2699 was not seen on the following day having rotated around the limb.
Observations on the 1st, 4th, 17th, 18th, 22nd, 24th and 25th were all spotless.
Only one group was observed based on 11 observations. This was on the 31st when AR 2703 was seen at 11°S/194° as a single Axx sunspot. Observations on the 10th, 13th, 14th, 16th, 19th, 20th, 21st, 23rd, 25th and 29th were all spotless.
Overall activity was slightly higher compared to the previous month through the presence of two small groups seen during the latter part of the month. Observations on the 5th, 6th, 7th and 14th revealed spotless solar disks. A small Axx sunspot was seen on the 18th only at 14°S/2° (no NOAA number). AR 2706 was initially seen as an Axx sunspot near the eastern limb on the 19th within a region of faculae. By the following day this group was of type Cso at 4°N/280°. On subsequent days it remained of type C and it obtained an area of 70 millionths on the 22nd. It straddled the central meridian on the 25th when of type Cao. The follower pores has disappeared by the 26th to make the group Hax with an area of 60 millionths. No further observations were made during the remainder of the month.
Activity increased slightly again with five small groups seen throughout the month. After three spotless days on the 1st, 2nd and 3rd, AR 2708 appeared near the eastern limb on the 4th as a Bxo group consisting of three pores at 10°S/100°. A small leading penumbra appeared on the 5th to make the group type Cso and area 30 millionths. On subsequent days AR 2708 reverted to type Bxo before not being seen on the 8th and then re-appearing as a single Axx sunspot on the 9th when near the central meridian. Also on the 9th AR 2709 appeared as an Axx sunspot near the eastern limb at 4°N/34°. By the 11th it appeared as a Hrx sunspot before becoming type Axx on the next two days. No sunspots were seen on the 14th and subsequent days (no observation on the 16th) until the 21st when AR 2710 was seen on this date only at 18°N/222° as a type Axx group near the eastern limb surrounded by a region of faculae.
The next observation on the 24th shows AR 2711 and 2712 on the disk at 6°N/289° towards the west and 15°N/175° on the eastern limb respectively. AR 2711 was of type Cso with an area of 30 millionths before decaying to type Axx on the 26th (it was not seen on the following day). AR 2712 was a single Hsx sunspot which had an area of 50 millionths on the 26th before becoming type Cso with a few leading pores on the 28th and then an extended Bxo group on the 30th when just past the central meridian. AR 2712 was last seen on the 31st as a small Dso group with an area of 60 millionths.
There was a further slight increase in activity during the month but all five groups seen were in the northern hemisphere. In during recent months there were several days which were spotless: 5th, 8th to 11th inclusive, 29th and 30th.
On the 1st AR 2712 was still on the disk at 14°N/175° as a Cri group. Fewer pores were seen on the 2nd when it was of type Cso with an area of 30 millionths. With the group nearing the western limb on the 3rd just a single Axx sunspot was seen (no observation was made on the 4th). On the 6th only a Hrx sunspot was seen at 10°N/109° (no AR number).
On the 12th an Axx sunspot was seen near the eastern limb surrounded by faculae. By the 13th, AR 2713 at 6°N/287°, had developed into type Cso before decaying to type Bxo on the 14th and then to type Axx on the 16th. Unusually this group then developed back into type Bxo with several sunspots on the 18th when it was near the central meridian. It then continued to develop into type Dao on the 20th with an area of 70 millionths and then type Dso on the 21st with an area of 80 millionths.
Also on the 18th AR 2714 had developed on the disk to the west of AR 2713 as a Cso group of area 30 millionths. It was of the same type and nearing the western limb when seen on the 20th. Another group developed on the disk to the east of AR 2713 on the 20th – AR 2715 at 8°N/230° of type Dao with an area of 120 millionths. The leading and following penumbral sunspots had increased in size slightly by the 21st to an area of 200 millionths. No observations were made until the 29th when there was a blank disk.
Several regions of plage were seen during the month associated with sunspot groups: on the 2nd & 3rd associated with AR 2712, on the 14th associated with AR 2713, on the 18th associated with AR 2713 & 2714, and on the 21st associated with AR 2714 and 2715.
sunspots were seen from 27
observing days. Hydrogen Alpha:
Four groups were seen during the month as well as many blank days. On the 1st, 2nd and 3rd an Axx group, AR 2717, was seen at 6°S/26° with two sunspots on the 1st, one on the 2nd and two faintly on the 3rd when the group was approaching the central meridian. Spotless disks persisted until the 14th when a Hrx sunspot was seen near the eastern limb (AR 2718) at 8°S/191° and of size 60 millionths. It was of type Cso on the 16th and then type Hrx on the 17th. It had disappeared on the disk by the 19th when another group was seen at a similar latitude but on the eastern limb. This was AR 2719 at 6°S/132° which was of type Axx before becoming type Bxo on the 21st and then type Cso of size 30 millionths when past the central meridian. It has decayed to type Bxo by the 25th and it was not seen on the 27th. A northern group AR 2720 had appeared on the disk between the 21st and 24th at a similar longitude as AR 2719. On the 24th AR 2720 at 9°N/136° was type Cso with area 30 millionths and then type Dso on the 25th with area 100 millionths. This group had decayed to type Cso and area 50 millionths as it approached the western limb on the 27th. Blank disks resumed on the 29th and 31st.Hydrogen Alpha:
Overall Hα activity was low during the month and indeed on the 31st no features were seen. A collection of prominences were seen on the eastern limb on the 3rd. A small mound prominence was on the SW limb on the 3rd and 4th. On arch prominence was seen on the SW limb on the 11th. The most striking prominence was on the NE limb on the 27th when several nearby spikes were seen. Some moderately size filaments were seen throughout the month, particularly on the 5th, 6th, 8th, 11th, 19th (orientated north-south near the CM), 25th and 27th. Plage was seen associated with AR 2717 between the 1st and 4th (no sunspots were seen on the 4th). It was also seen associated with AR 2718 on the 17th and AR 2719 on the 19th, 21st and 25th when plage was also seen around AR 2720.
Observations on the 1st, 2nd, 3rd, 6th and 7th revealed blank disks. On the 8th a collection of pores in the form of a Bxo group were seen just past the central meridian at 10°N/285°. This group, AR 2721, was seen as an Hsx group on the 9th while nothing was seen on the following day. Another Bxo group, AR 2722, appeared on the disk on the 11th at 8°S/212°. No observation was possible on the 12th but the disk was blank again on the 13th and on subsequent observations on the 14th to 16th. Further observations on the 23rd, 24th, 27th to 29th also revealed blank disks. The final observation of the month, on the 30th, showed a small Dso group, AR 2723, at 8°S/356° just past the central meridian.Hydrogen Alpha:
Some prominence activity occurred during the month. On the 2nd an arch and spike prominences were seen on almost opposite side of the solar disk – on the NW and SW limb. On the 7th a collection of spike prominences were seen on the SW limb. On the NW limb on the 13th several prominences were spread out for some 20° along the limb. Prominences were seen at several positions around the limb on the 14th. On the 29th and 30th a hedgerow prominence was seen on the SE limb. Very few filaments were seen during the month. Plage was seen associated with AR 2723 on the 30th.
AR 2723 at 8°S/356° was seen on the 1st as a Dao group with an area of 60 millionths. This group had disappeared by the next observation on the 5th when the disk was devoid of sunspots. All 17 other observations of the month were also blank (7th to 11th, 16th & 17th, 19th to 22nd, 24th & 25th, 27th to 29th and 31st).
The first four observations of the month, on the 2nd, 3rd, 8th and 11th were all blank. On the following day, 12th, a Bxo group at 6°N/136° appear near the central meridian. This group, AR 2726, was seen as an Axx on the next 2 days. The next observation on the 17th revealed a Cso group near the equator at +1°/110° mid-way between the central meridian and the western limb. On the 18th AR 2727 was now of type Dso and area 60 millionths. The final observation of the month showed a further blank disk.Hydrogen Alpha:
The three Hα observations during the month on the 2nd, 11th and 18th showed very little activity. An arch prominence was seen on the SW limb on the 11th – no prominences were seen on the 18th. Plage was seen around AR 2727 on the 18th.
The first observation of the month, on the 7th, showed a small Cso group approaching the western limb at 6°S/231° (AR 2729). This group was not seen on the 8th when the disk was blank as was the case on the 9th. The next observations on the 11th revealed AR 2730 – a Bxo group at 7°N/95° mid-way between the eastern limb and the central meridian. Further observations on the 16th, 17th, 19th, 20th, 22nd and 24th were all blank.
Page created on 30 December 2017.