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.
The observation on the 2nd showed that all but one of the eight groups seen were in the southern hemisphere. Indeed the southern hemisphere dominated during the month – a trend that has persisted since April 2013. The largest group on the 2nd was AR 2253 at 5°S/1° of type Eac with an area of 460 millionths. The main sunspot was in the leading part of the group – there were a couple of smaller nearby sunspots and additional penumbral sunspots in the following part of the group. AR 2253 was seen with the protected naked eye.
The next observation on the 10th also had eight groups. AR 2257 was at 8°N/320° of type Dac with an area 210 millionths and it comprised of a collection of several penumbral sunspots spread out in both latitude and longitude. AR 2259 was also present at 15°S/241° of type Eao and area 360 millionths – here the larger of the two sunspots was at the following position. In addition four small Axx/Bxo were seen the northern hemisphere to the east of AR 2257. By the 11th AR 2257 had grown slightly to 300 millionths while AR 2259 was slightly smaller. The following sunspot of AR 2259 had split by the 14th when the group was near the central meridian.
From the middle of month the number of groups reduced with just three being seen on the 17th, 23rd and 24th. During this period the largest group was AR 2266 of type Dao at 5°S/163° with an area of 190 millionths on both the 19th and 20th when near the central meridian. It then decayed as it was last seen as an Hsx sunspot on the 25th close to the western limb. On the 23rd AR 2268 had appeared around the eastern limb at 9°S/47°. By the following day it was seen a type Fko with an area of 410 millionths. It was of a similar form on the 25th but by the 27th it was of type Fac through the addition of a few penumbral sunspots and many pores between the leader and follower sunspots. The number of groups seen on the 27th had increased to seven.
The most notable prominences based on 4 observations was on the 11th when two detached prominences were visible – the one on the SW limb was quite rectangular in shape while the other on the NE limb comprised a slim band of hydrogen separate but parallel to the limb stretching for over 10°. A small bright prominence appeared at 13h 15m UT close to the solar equator on the W limb but cloud prevented further observation. Several medium length filaments were seen on each observation including a semi-circular one near the middle of the disk on the 24th. Plage was seen around AR 2257 on the 10th and 11th.
Activity during the month showed quite a reduction compared to previous months – in fact R at 60.0 was at its lowest since September 2013. As well as fewer sunspots groups, the size and complexity of sunspot group was also lower. There was also a dominance of the northern hemisphere over the southern hemisphere for the first time since April 2013.
On the 2nd two northern groups were seen, one at 8°N/337° of type Dsi just approaching the central meridian. It was comprised of two small nearby penumbral sunspots and a few surrounding pores (the total area being just 90 millionths). With a gap of 15° to the east of this group was a Cao group at 12°N/316° where the irregular penumbral sunspot had an area of 200 millionths. NOAA classified these two groups as just one active area (AR 2277): examination of the Solar Dynamic Observatory MDI magnetogram, showing the magnetic polarity of the solar surface, for the 2nd does indeed suggest that both two observed sunspot groups have opposite polarity thus confirming a single active region. On the 5th there was still a lack of sunspots for 10° in the middle of AR 2277 which increased to 15° on the 6th due to the decay of sunspots. Just the following part of AR 2277 was seen on the 8th and 9th.
The largest group of the month, AR 2280, was initially seen as a Bxo group on the 2nd at 7°S/282° near the eastern limb. By the 5th it was type Dac with an area of 120 millionths. More sunspots appeared within the group by the 6th which appeared slightly larger by the 9th when the total area was 330 millionths and type Eac – the largest sunspot was in the leading part of the group. The group had rotated off the disk by the next observation on the 15th.
On the 8th a small penumbral sunspot was seen near the eastern limb at 13°N/191°. On the following day another group was seen slightly to the south and east. By the 15th the northern of these group was a single Hax sunspot and size 90 millionths, while the southern was of type Cso, size 60 millionths and at 8°N/189°. Again NOAA classified these two groups as one active area, AR 2282. However, the SDO magnetogram seems to indicate that these sunspots should not be classified as one AR as there are distinct north and south magnetic polarity for both groups. When seen on the 18th just two penumbral Hsx sunspots were seen at 13°N/191° and 8°N/189° respectively.The last observation of the month on the 23rd just showed three small groups, two in the north of type Cso at 40 millionths and Bxo and one in the south of type Hsx.
There was further reduction in activity compared to previous months and with higher activity in the south once again. No sunspots were seen in the northern hemisphere on each day between the 7th and 14th inclusive.
The largest of three groups seen on the 1st was AR 2293 at 6°N/339° of type Dac and area 80 millionths. At this group neared the western limb it became type Dao on the 4th with an area of 140 millionths. It was last seen on the 6th as an Axx group. On the 7th a compact but complex group was seen close to the eastern limb. This was AR 2297 at 16°S/195° which comprised of several penumbral sunspots, the largest being the following sunspot. Over subsequent days, this group grew slightly to have an area of 360 millionths on the 12th and 13th. It extended in longitude to become type Eac on the 14th when the follower was still the largest sunspot and when there were many smaller sunspots in the leader portion of the group. AR 2297 was seen with the protected naked eye on the 12th and 14th.
On the next observation on the 20th showed just one sunspot, AR 2301 at 18°N/65° of type Hax. However by the 23rd six groups were present. The largest was AR 2305 at 7°S/6°, type Eac and area 330 millionths. When seen on the 27th it was close to the central meridian when it comprised of an irregular leading penumbral sunspot, one small following penumbral sunspot and several pores. There were still six groups visible on the 27th.
Although it was totally cloudy in Chelmsford during the eclipse, a dip in the 23.4 kHz VLF signal from the DHO38 transmitter in German was detected. This is shown in the plot below. One characteristic of DHO38 is that the transmitter is switched off for an hour between 7 and 8 UT. Around the time of maximum eclipse there was a symmetrical dip in VLF signal strength. The start and end times of the dip were 09:22 and 09:59 UT with the minimum strength being at 09:41 UT.
The minimum strength time did not correspond to maximum eclipse here at the receiver (09:31 UT) but to the maximum eclipse time at the transmitter site near Rhauderfehn, Germany at 09:41 UT. The average of the start and end dips times is also 09:41 UT. I’m not sure why this should be the case, as I expecting the minimum time to correspond to the mid-point between here and the transmitter.
There was an increase in activity compared to March, especially in the northern hemisphere. On the 1st, one of the two groups seen was AR 2305 which was an Eac group on March 27 – now it was just a single Hkx penumbral sunspot at 10°S/10° approaching the western limb. It was last seen on the following day. On the 5th, the larger of two groups seen was AR 2320 at 13°S/211° of type Dso and 140 millionths: a compact bipolar group. Over subsequent days, more small penumbral and pores appeared within the group as it became type Eac on the 8th and 9th when it crossed the central meridian. AR 2320 then decayed and it was last seen as type Cao on the 12th.
Activity began to increase from the 11th with the appearance of more groups including the rotation on to the disk of AR 2321 of type Eac at 11°N/90°. On the 12th this group was of type Ekc through the presence of a very elongated penumbral sunspot in latitude. By 14th this sunspot must have split as the group now consisted on several medium sized penumbral sunspots spread over quite a large area in both latitude and longitude. AR 2321’s area was 540 millionths. The size of the group began to reduce as it became more of a typical bipolar group. For example on the 16th it was of type Eac with an area of 210 millionths. As the group progressed towards the western limb, it decayed such that on the 20th it was of type Cso with an area of 80 millionths. It was last seen as type Hsx on the 21st and 22nd. From the 15th to 18th a small group was seen just to the north of AR 2321: AR 2326 of type Bxo on the 16th and 18th.
Another of the five groups seen on the 14th was AR 2324 of type Hkx at 18°N/62°. On the following day a following penumbral sunspot appeared to make the group type Dkc – it had an area of 330 millionths. By the 20th, the main penumbral sunspot decayed to leave a collection of small penumbral sunspots. The number of sunspots reduced as this group neared the western limb and it was last seen on the 24th as an Hsx sunspot. Between the 18th and 28th AR 2331 was seen at 9°S/17°. Initially it was of type Cso before developing to type Esc with an area of 140 millionths on the 22nd (when near the central meridian). It remained type E as it progressed towards the limb and also developed a central penumbral sunspot.
From the 22nd onwards the number of groups reduced from eight to just one Axx group on the 29th and 30th (AR 2334 at 20°S/260°).
Activity was quite variable during the month with lower activity at the start and end of the month compared with the middle portion. The southern hemisphere was the more dominant once again.
The only group seen on the 1st was the Dso group AR 2335 at 15°S/193° and close to the eastern limb. By the 3rd it has developed two small penumbral sunspot between the leader and follower and it had an area of 250 millionths. The number of penumbral sunspots had increased again by the following day and it also became type Eac with an area of 320 millionths. However by the 7th with the group just past the central meridian the number and size of sunspot reduced such that the total area was an estimated 110 millionths. The next observation on the 11th showed that AR 2335 was an Axx group close to the western limb.
One of the other six groups from the 7th was the largest of the month, AR 2239 at 12°N/129°. On this date it was seen as type Fkc, comprising several medium sized sunspots spread throughout the group. It had an area of 250 millionths which had increased to 590 millionths on the 11th when the group was near the central meridian. It comprised several irregular penumbral sunspots mainly at the leader and follower positions of the group with several other smaller sunspots and pores spread throughout the group. AR 2239 was seen at its largest on the 12th at 700 millionths and by the following day it was seen smaller at 430 millionths through a reduction in the size of the penumbral sunspots. This decay continued as the group progressed towards the limb and it was last seen as type Eac on the 17th. AR 2239 was seen with the protected naked eye on the 11th as two sunspots and as one sunspot on the 12th.
With the passage of AR 2239 over the limb, the number of groups seen reduced from a peak of six on the 18th to one on the 27th and 28th. All of these were small groups.
A total of seven groups were seen on the 6th but all were fairly small: the largest being AR 2362 at 6°N/100° and of type Dao with an area of 180 millionths. As this group progressed across the disk it lost its leading penumbral sunspot and it was last seen on the 11th as a small Cso group with an area of 30 millionths. One of the three southern groups on the 6th was AR 2365 near the eastern limb at 13S/80 and of type Hsx. On the 10th a few small surrounding pores could be seen around the single penumbral sunspot which had an area of 70 millionths. It was last seen close to limb on the 17th as a single penumbral sunspot once again.
The observation on the 15th revealed a complex bipolar group, AR 2367 at 19°S/1° of type Eac and area 300 millionths. The main sunspots comprised of an almost symmetrical leader with two nearby penumbral followers. By the following day, the leader had almost split into two and more followers had appeared. As AR 2367 began to decay the leader became more complex while the followers reduced in size and number. By the 21st the group had reduced to 170 millionth even though it was still of type Eac. It was last seen close to the western limb on the 23rd. AR 2367 was seen with the protected naked eye on the 18th.
The largest group of the month, AR 2371 appeared around the limb on the 16th as a complex Ekc group at 12°N/302°. Further sunspots in this group could be seen on the following day as they rotated onto the disk. Many of the followers had merged together by the 18th so that the group comprised mainly of large leader and follower sunspots – the total area being 860 millionths. The shape of the follower had changed again by the 19th as it became more irregular. By the 21st both the leader and follower become less elongated in latitude with both sunspots containing several umbrae. Again the shape of both main sunspots changed shape by the 23rd when the group’s total area was 1040 millionths. Subsequent observations showed a decaying group with an area of just 280 millionths on the 25th and AR 2371 was last seen as type Eko on the 27th. This group was seen with the protected naked eye on the 18th, 19th, 20th (as two sunspots), 21st (two sunspots), 22nd (two sunspots) and 23rd (two sunspots).
From the 25th to 27th AR 2371 was the only group on the disk. The next observations on the 29th and 30th showed several small groups near the eastern limb.
On the 16th at 18h 05m a bright region of plague was seen around AR 2371 near the eastern limb - over the next 15 minutes this formed into two bright spots. At the start of the Hα observation on the 29th at 18:00 UT, three bright spots were seen around AR 2373 but these had faded by 18:20UT (this being a C2 flare peaking at 18:07 UT).
All four groups seen on the 1st were in the east, the largest being AR 2373 at 16°N/143° of type Dao. It comprised a leading asymmetrical penumbral sunspot and a few small followers and it had an estimated area of 180 millionths. Over subsequent days further groups appeared such that on the 5th seven were seen in the central and eastern part of the Sun. By this date AR 2373 had lost its following penumbral sunspots to become a smaller Hsx group – it remained of type when last seen close to the limb on the 9th.
One of the groups that had rotated onto the solar disk on the 4th was AR 2381 of type Dso at 14°N/73°. By the following day, several penumbral sunspots had formed to make the group of type Dsc with an area of 250 millionths. It was of a similar form and size on the 6th. However on the 8th it had become a bipolar group with asymmetrical sunspots in the leading and following positions. Its area had also increased to 440 millionths and it was now of type Eai near the central meridian. By the 9th the following penumbral sunspot had reduced in size slightly. The longitudinal extent of AR 2381 lengthened on the 10th and 11th to become an F type group, although the group’s size continued to reduce such that on the 11th it was 260 millionths. AR 2381 was seen with the protected naked eye on the 8th and 9th.
The next observation on the 19th showed a much reduced level of activity which continued until almost the end of the month. For example on the 21st, 22nd and 23rd only two small groups were seen in the northern hemisphere and no sunspots in the southern hemisphere. Similarly on the 25th only two small southern groups were on the solar disk. One of these was AR 2390 of type Bxo at 14°S/197°. By the 27th it had rapidly developed into a Dac group with an area of 180 millionths. On the following day, the leading sunspot appeared to split into several penumbral sunspots. As AR 2390 progressed towards to limb on the 31st, it reverted back to type Bxo. On the 30th six groups were seen and five on the 31st.
Activity during the month was dominated by the presence of two naked eye sized groups: AR 2396 and AR 2403.
AR 2396 at 16°S/37° was first seen on the 4th as a Dso group with an area of 150 millionths – nothing was seen at this location on the previous day. By the 6th this group had developed to type Eac through the appearance of a asymmetrical leading sunspot which included several umbrae. There were also several smaller follower sunspots. Over subsequent days AR 2396 continued to grow to type Ekc such as on the 8th when its area was estimated to be 760 millionths – it was also near the central meridian. By the 9th several penumbral sunspots in the following part of the group had increased in size to give an overall size of 820 millionths. The last observation of AR 2396 on the following day showed that the group had started to decay through a reduction in the size of the leading sunspot – it was now 660 millionths. AR 2396 was seen with the protected naked eye on the 6th, 7th, 8th and 9th.
Activity reduced in the days leading up the appearance of AR 2403 around the eastern limb on the 19th of type Dsc. For example on the 17th there was just one small Hsx group on the disk. Between the 19th and 21st, AR 2403 at 14°S/191° had developed into a collection of many small penumbral sunspots and pores. It was of type Eac and area 350 millionths. By the 22nd a more substantial leading sunspot was beginning to form. This rapid development continued such that on the following day a more substantial follower had also developed – AR 2403 was now a substantial bipolar group of type Ekc and area 660 millionths. When next seen on the 25th the group had almost doubled in size to 1110 millionths of now type Fkc: there were now two substantial leading and following penumbral sunspots each containing many umbrae but only a few pores between. The next two observations on the 27th and 28th showed that the leader had started to split with a couple of small penumbral sunspots appearing the break away while the follower also splitting with the main follower being very elongated in latitude. When the group was last seen close to the western limb on the 29th the leader was quite reduced in size while the follower had broken into small penumbral sunspots. AR 2403 was seen with the protected naked eye on the 21st, 22nd, 23rd, 25th (as two naked eye spots) and 26th (as two naked eye spots with the darkest being nearest to the limb).
Other groups seen were modest in size – the largest being AR 2394 at 13N/77 of type Cso of the 7th with an area of 130 millionths.
Many filaments were seen on most of the 10 observations, particularly on the 8th & 9th and the 28th and 29th. Of particular note was a V shaped filament on the 28th which had lost it distinctive shape by the following day. Also on the 28th were two quite extensive filaments which had the appearance of blobs of hydrogen rather than the more normal thin elongated filaments. Both were still present on the 29th, although of slightly different shapes.
In particular plage was seen around the naked eye sunspot group AR 2403 on the 21st to 23rd On the 22nd and many small plage regions were seen within the group (see Hα images below which were taken before, during and after a C5.1 flare which occurred between 09:09 and 09:39 UT, peaking at 09:21 UT).
Activity was quiet during the first half of the month before increasing particularly through the development of naked eye sized group AR 2422. Just two small northern groups were seen on the 2nd, 5th and 6th. Additional southern groups were seen on subsequent observations. Of particular note was AR 2414 at 9°S/319°. It was initially seen as an Axx sunspot on the 9th and 10th before developing into type Cai on the 11th, where the penumbral sunspot was at the following position. This penumbral sunspot had increased in size by the following day as well as two small leader penumbral sunspot making the group type Eac with an area of 270 millionths. On the last observation on the 13th it had lost some of its pores to become type Eao.
Also on the 13th an Hsx sunspot was seen close to the eastern limb at 14°S/201°. By the next observation on the 19th AR 2418 had become type Hhx with an area of 270 millionths and still a single sunspot – it was also near the central meridian. It had become more asymmetrical and slightly reduced in size to 220 millionths. When next seen on the 24th it was type Hsx again and close to the western limb. AR 2418 was seen with the protected naked eye on the 19th and 20th.
One of the six groups seen on the 24th was AR 2422 at 19°S/103° which appeared as a Dac group with an area of 140 millionths. By the following day it had developed into an Eac group with many penumbral sunspots, the largest being the follower – its area was 330 millionths. Further development continued over subsequent days such that by the 27th, with the group near the central meridian, it attained an area of 630 millionths. It now comprised two main leader and follower sunspots, the leader being the more symmetrical. On the 28th further changes occurred within AR 2422 and it changed from being type Eac to Fkc. On the 29th and 30th, with the group approaching the western limb, it could be seen that the leader and follower sunspots had split into several smaller penumbral sunspots. AR 2422 was seen with the protected naked eye as two sunspots on the 27th, 28th and 29th and as one naked eye sunspot on the 30th.
Overall activity was lower than during recent months: both the number of groups MDF and R are lower than since January 2011 – an indication that activity is now declining.
The naked eye group from September, AR 2422 at 19°S/103°, was seen progressing towards at the limb at the beginning of the month. On the 1st it was of type Fac while by the 3rd on a single Hsx sunspot was seen near the western limb from the following part of the group. The only other significant sunspot group on the 1st was AR 2427 of type Dai at 18°N/37° with an area of 110 millionths. The two leading penumbral sunspots merged to form a Cai group when seen on the 2nd, 3rd and 4th. Observations on the 8th, 9th, 11th and 14th only showed a few small sunspot groups.
The next observation on the 20th showed four sunspot groups, the largest being AR 2436 at 9°N/110 of type Eac and area 160 millionths. This group decayed to type Cai and 90 millionths when next seen on the 25th. The most significant group of the month, AR 2443, was seen on the 31st as a Fac group at 7°N/313° near the eastern limb. It had an area of 530 millionths and it comprised of a string of many penumbral sunspots where the larger ones were towards the leading part of the group.
The particularly cloudy weather restricted observing to 6 days where the majority of the activity was in the northern hemisphere. The most significant of the three groups seen on the 1st was AR 2443 at 7°N/313°. It was of type Fac comprising a collection of medium to small penumbral sunspots throughout the group and it had an area of 510 millionths. It was also seen with the protected naked eye. This group was not seen on the next observation on the 13th when four small or Axx groups were seen. The most significant group seen on the 20th was a Dsc group near the eastern limb (AR 2457) at 10°N/30°. On the 22nd it was of the same type and it had an area of 110 millionths. AR 2457 had reduced to a small Hsx sunspot by the 28th. The other two groups from the 28th were AR 2458 at 6°N/358° of type Dao and area 140 millionths and AR 2459 at 4°N/329° of type Hsx and area 100 millionths.
A second month of particularly cloudy weather restricted observing to 7 days. The larger of two groups seen on the 1st was AR 2458 at 8°N/359° of type Dsc and size 110 millionths. It had rotated off the disk by the next observation on the 4th but three small groups had rotated around the eastern limb. Two additional small groups had appeared on the 7th – the largest of these five groups was AR 2463 at 8°S/213°, type Hsx and size 60 millionths. On the next observation on the 9th AR 2465 at 4°S/166° had developed from type Hsx to Dso with an area of 190 millionths, the largest group on this date.
Page created on 20 December 2014.