The number of sunspot groups increased slightly on the previous month with the upsurge emerging in the northern hemisphere. Overall solar activity remained similar to that recorded in May, June and July with the relative sunspot number (R) actually falling slightly. Sunspot groups were recorded on all days of the month. Many small groups peppered the disk early in the month, declining mid-month, with activity resurging again as the month closed.
AR1532 S21[degrees]/176[degrees] remained on the disk from the previous month type Fkc, but with a reduced area of 320 millionths. The group was now straddling the central meridian, the leading sunspot still being the largest. By Aug 2 the group was type Fac through a further reduction in size of the leader. The group was of similar appearance the following day but by Aug 4 had lost many of its followers to become type Cao. The group was last seen on the SW limb on Aug 6.
AR1538 S22[degrees]/108[degrees] was on the disk near the SE limb on Aug 1 type Dso. By Aug 2 the follower had a curved umbra which persisted the following day. Several small sunspots also developed between the leader and follower. By Aug 8 the group had returned to just two penumbral sunspots and was now in the SW quadrant. The group continued unchanged towards the SW limb rounding the limb on Aug 12. Although this group was not particularly notable in white light, a significant feature in H-alpha accompanied its transit of the solar disk (see prominence report).
AR1542 S14[degrees]/031[degrees] rounded the SE limb on Aug 6 and was type Dao on Aug 8, consisting of nine sunspots exhibiting a distinct penumbral leader and follower. By Aug 9 the following penumbral spot had dissolved and the group was now type Csi but regained a small penumbral follower the next day to become type Dsi. By Aug 14 the group had declined significantly to a single small penumbral sunspot type Hsx and was the only activity seen on the disk along with AR1543. The group was last seen on Aug 15 in the SW quadrant and appears to have dissolved on the disk.
AR1543 N20[degrees]/020[degrees] On Aug 7 this sunspot group was seen on the NE limb and by the following day the group was fully on the disk type Dho. It was the same type on Aug 9 before the leader became asymmetric to make the group type Dko on Aug 10. Several other sunspots were seen within the group on Aug 12. By Aug 14 the group had passed the CM and was type Hkx with an area of 320 millionths. The group was type Hax on Aug 17 & 18 before extending to type Dao as it approached the western limb on Aug 19. The group was seen with the protected naked eye on Aug 11 & 13.
AR1548 N18[degrees]/236[degrees] first appeared over the NE limb on Aug 18, a small penumbral spot with 3 small umbrae preceding it. By the following day the penumbral spot had declined and the group was type Bxo containing 4 small sunspots. The small penumbral sunspot reformed on Aug 20 with one accompanying pore and was of similar appearance on Aug 21. On Aug 22 only a small Hsx sunspot remained which declined to just 2 small umbrae on Aug 23. The group subsequently dissolved on the disk.
AR1553 S23[degrees]/192[degrees] appeared over the SE limb on Aug 22, a single Hsx sunspot. The spot was slightly larger on Aug 23 but still type Hsx. The group developed to type Cso on Aug 25 and type Dso by Aug 27. When seen on Aug 30 the group was in the SW quadrant, type Dso consisting of 3 small penumbral sunspots in a triangular formation and a small sunspot without any penumbra. The group was still present at the close of the month.
10 observers reported a Quality number of Q = 15.14.
17 observers reported a prominence MDF of 4.92 for August. Few prominences of note were seen during the month.
A filaprom was seen on the W limb near to AR1529 on Aug 3 and also a small but distinctive loop was seen on the SE limb just south of AR1539.
On Aug 4, 5 & 6 a prominence was seen at 0[degrees]W, described as a large 'tooth' and as a 'witch's hat' on Aug 4. A strong spike was on the SW limb on Aug 15 to the west of AR1542 and two tall spikes were seen on the NW limb ahead of AR1543 on Aug 17 & 18.
An incomplete arch was on the SE limb rising to 65,000km on Aug 20 and a fine filaprom graced the NE limb on Aug 21. A series of arches were on the SE limb on Aug 24 & 25 from S35[degrees] to S50[degrees] which was also seen as a multiple arch hearth on Aug 26.
Several observers reported an unusual prominence on the NE limb on Aug 27 & 28. The prominence consisted of a large block of hydrogen, the top of which was quite flat and parallel to the limb; there was also a slight extension from the middle of the northern side of the prominence that on Aug 28 was seen extending onto the limb as a short filament. The overall height of the feature had also reduced.
Filaments & plage
12 observers reported a filament MDF of 4.73 for August.
A long spectacular filament graced the disk near the equator right from the start of the month. By Aug 2 it was a long snaking line extending from north of AR1538 eastwards north of AR1539 and onto the eastern limb. The filament persisted the following day and extended eastwards from AR1538 north of AR1539 and new group AR1540 near the eastern limb. The feature was recorded near the CM on Aug 5 and over the centre of the disk on Aug 6 (see image). By Aug 8 the filament appeared snake-like with a triangular head north of AR1538 and still extending eastwards through AR1539 and north of AR1540. The filament was still of similar appearance on Aug 9 and was still seen on Aug 10 but had lost its triangular head and the leading section of the filament appeared detached from the rest. The feature was last reported on Aug 11 as a long curved filament near the W limb.
A multi-segment semi-circular filament was observed in the southern hemisphere on Aug 17, 18 & 19 with AR1549 appearing in white light within the semi-circle of the filament on Aug 19 with the loop of the filament appearing to widen. On Aug 20 & 21 the loop widened further and the filament was last seen on Aug 22 as a north-south curve near the SW limb.
On Aug 20 a straight east-west filament was south of AR1548 in the NE quadrant which appeared stronger and barbed in appearance on Aug 21. By Aug 22 the filament was breaking up and consisted of three short filaments in a line.
On Aug 21 a fuzzy mass was on the disk over the SE limb to the NE of AR1552. By Aug 22 the filament was a thick east-west arc extending from AR1552 eastwards to AR1553 on the SE limb. The arc filament was still present on Aug 23 but much fainter.
Strong plage was seen from the rear element of AR1538 on Aug 8 in association with a short filament and strong plage was also seen dissecting the rear element of AR1543. This plage was still present on Aug 9 to the front of the follower ofAR1543 and covered a larger area on Aug 10 engulfing the active region.
On Aug 14 plage was seen to the rear of AR1543 and a short dark filament and also streamed eastwards behind AR1542 to engulf the following filament. On Aug 15 plage surrounded the filament dissecting AR1542. Plage was also recorded in association with AR's 1532, 1535, 1539, 1546 and 1555.
Activity was slightly down on the previous month in both solar hemispheres, overall activity returning to that seen in July this year. Multiple sunspot groups were seen on all days throughout the month although complex active regions were rare.
AR1560 N04[degrees]/129[degrees] was mid-disk as the month opened, type Eac with an area of 190 millionths, comprising a collection of small penumbral and other sunspots. On subsequent days the number and size of sunspots within this group reduced so that by Sept 6, when the group was last seen nearing the western limb, it was just a Bxo type group.
AR1564 S13[degrees]/069[degrees] was seen near the SE limb on Sept 2 type Dsi consisting of 9 sunspots. By Sept 3 the group was Eac with an area of 250 millionths. Similar to AR1560, although larger in total area, the group was a collection of penumbral and other sunspots. As the group progressed towards the meridian, the number of penumbral sunspots reduced whilst the number of pores increased. On Sept 7 the group had passed the CM and just two penumbral sunspots remained, however by the following day there was a resurgence of penumbral spots. The group was last seen on Sept 11 approaching the limb, type Bxo.
AR1569 S11[degrees]/297[degrees] was first seen on Sept 11. The following day the group was type Dsi and type Eac with an area of 220 millionths by Sept 13. As the group progressed towards the CM, it lost its following sunspots and by Sept 18 was a single penumbral sunspot followed by a solitary pore. The group was last seen on Sept 21 near the SW limb type Hsx.
AR1571 S12[degrees]/280[degrees] was first seen on Sept 12 close to the SE limb, a Cso group comprising a small penumbral leader and two following pores. By Sept 15 the leader had developed a double umbra and only a single pore was following. The pore had disappeared by Sept 18 and the group was type Hsx, the leader being a single penumbral sunspot with an area of 60 millionths. The group was declining on Sept 21 and was type Bxo. The group was not seen on Sept 22 and had dissolved on the disk nearing the SW limb.
AR1575 N09[degrees]/181[degrees] was first seen on Sept 18 rounding the NE limb, two penumbral sunspots. By the following day, the extent of the group was more obvious and comprised of two penumbral sunspots linked by an asymmetrical penumbra with a smaller penumbral sunspot following. By Sept 21 the leading sunspot was complex containing two main umbrae and several smaller umbrae underneath, all within the same penumbral area. The following day the leader had changed appearance again and contained just two umbrae within an asymmetrical penumbra. The group had a total area of 270 millionths. By Sept 25 the main sunspot was now the follower with a small penumbral sunspot leading. On Sept 29 the group was type Hsx close to the western limb.
10 observers reported a Quality number of Q = 13.38.
18 observers reported a prominence MDF of 5.11 for September.
On Sept 1 three large prominences were seen, one on the NW limb reaching an approximate height of 74,000km, another on the SW limb reaching 84,000km and the third on the SE limb reaching about 112,000km in height.
A large prominence at NW 50[degrees] persisted on Sept 3, 4 & 5. Also on Sept 4 an arching prominence was seen on the NE limb and ejecta was reported at 1300 UT reaching a height of between 250,000 and 300,000km.
A column type prominence had ejected off the limb on Sept 6 to an approximate height of 196,000km and on the SE limb another had reached a height of about 112,000km.
A short but strong prominence accompanied the appearance of AR1575 on Sept 18 which extended in length on Sept 19 although it didn't gain any height. Another short intense prominence was seen on the SW limb on Sept 21 just ahead of the approaching AR1574.
A fine hearth was observed on the SE limb consisting of 4 separate elements on Sept 22 with another prominence further south. Three prominences were counted on Sept 29, one being a complex structure on the SE limb with a maximum height of 100,000km.
Filaments & plage
13 observers reported a filament MDF of 3.77 for September.
A straight east-west filament was south of the rear element of AR1560 on Sept 2, 3 & 4. On Sept 3 a curving north-south filament was to the south of AR1564 and associated with it. The following day a short filament was just north of the group and an arching north-south filament trailed the group.
On Sept 9 a curving filament was imaged around AR1564 with associated plage. This area also produced a M1.2 class flare later that day.
Two north-south aligned filaments were following AR1566 on Sept 12 and on Sept 15 a filaprom was seen over the SE limb. On Sept 16 a semi-circular filament was obvious in the SW quadrant. By Sept 18 the filaprom seen on Sept 15 was a long broken east-west filament in the SE quadrant which shortened the next day but re-established itself by Sept 21. The following day two filaments were seen in this area and on Sept 23 they had merged into a long east-west filament which was forked at the western end.
A short dark east-west filament was seen between the leader and follower of AR1575 on Sept 21 and was accompanied by plage. This plage became extensive on Sept 22 & 23. A patch of plage was also seen to the NE of the spot group on Sept 21, 22 & 23.
Plage was recorded around AR1560 and 1564 on Sept 3 and around AR1569 on Sept 14. Plage also accompanied AR1574 on Sept 16 and was seen around AR1577 and AR1583 on Sept 29.
Lyn Smith, Director
BAA sunspot data, 2012 August-September Day August September g R g R 1 8 117 7 110 2 8 113 7 110 3 10 144 6 119 4 9 122 6 108 5 7 97 5 90 6 6 81 5 91 7 7 96 4 72 8 7 103 4 70 9 8 122 5 74 10 7 104 5 62 11 7 90 4 54 12 5 72 4 53 13 3 52 3 47 14 2 26 3 42 15 2 24 4 49 16 2 27 3 45 17 3 40 3 44 18 3 43 4 52 19 4 57 4 56 20 5 61 5 68 21 4 58 5 63 22 4 54 3 48 23 5 57 4 58 24 4 63 5 82 25 5 63 7 111 26 4 64 7 108 27 4 58 6 82 28 4 60 5 65 29 4 65 4 58 30 6 95 5 68 31 7 112 MDFg 5.38 (49) 4.78 (50) Mean R 75.47 (44) 71.97 (45) North & south MDF of active areas g MDFNg MDFSg August 2.66 (36) 3.02 (36) September 2.06 (37) 2.67 (37) g = active areas (AAs) MDF = mean daily frequency R = relative sunspot number The no. of observers is given in brackets.