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Solar section.

2013 August

There was a slight upturn in solar activity in both hemispheres during August with the relative sunspot number (R) around the average for the year so far. Southern hemisphere activity remains dominant. An unusual spread in sunspot group latitudes was noted for this part of the solar cycle from N30[degrees] (AR1807) to N06[degrees] (AR1811).

AR1806 S15[degrees]/040[degrees] survived from the previous month straddling the CM, a collection of small sunspots type Dao. The group seemed to strengthen on Aug 2 showing complex detail but by Aug 4 the trailing sunspots had declined substantially. The group rotated over the SW limb on Aug 6.

AR1817 S20[degrees]/238[degrees] appeared as a small collection of pores trailing sunspot groups AR1814 and AR1816 on Aug 10. By the next day this group had grown dramatically to type Dsc with an estimated area of 140 millionths. The group developed the number of small penumbral sunspots within it as it passed the CM on Aug 13 before reducing by Aug 15, however the total area of the group increased to 240 millionths. As the group neared the western limb it became type Cao on Aug 17 and then a single Hsx sunspot when last seen on Aug 19.

AR1818 S05[degrees]/215[degrees] appeared over the SE limb on Aug 10 and the next day had grown to type Dso also with an estimated area of 140 millionths. The group continued to develop and was type Eac on Aug 14 with the leading and middle penumbral sunspots being the largest. The group was near the CM on Aug 15 when the leading penumbral sunspot became the largest in the group, the total area being 310 millionths. The main sunspot within the group changed slightly on each of the following days being reported visible with the protected naked eye on Aug 16, but lost all its following sunspots by the following day. The group was a single Hsx sunspot on Aug 20 and rotated around the limb on Aug 21.

AR1827 S17[degrees]/100[degrees] appeared over the SE limb on Aug 18 type Dso. By Aug 20 the group was type Dao consisting of several small penumbral sunspots but by Aug 22 had started to fade. As the group approached the CM on Aug 23 it was reduced to type Bxo and was barely visible on the disk on Aug 24. The group dissolved on the disk in the SW quadrant the following day.

AR1835 S09[degrees]/011[degrees] was a single Hsx sunspot on the SE limb on Aug 24 and just over the limb on Aug 25 & 26. The group then developed some small following sunspots on Aug 27 having a total area of around 350 millionths on Aug 28. The group was reported visible to the protected naked eye on Aug 29 before reducing to a single irregular Hax sunspot group on Aug 30. The next day the sunspot had split into two smaller more symmetrical sunspots with a few pores just to the east.

AR1836 N12[degrees]/343[degrees] appeared over the NE limb as a single Hsx sunspot on Aug 27. By Aug 28 the group was still a single sunspot but contained two umbrae. The group developed three small trailing penumbral spots on Aug 31 type Eao.

10 observers reported a Quality number of Q= 12.97

H-alpha

Prominences

16 observers reported a prominence MDF of 4.78 for August.

Few prominences of note were reported during the month. On Aug 7 a large arch prominence was on the NE limb. A multi arch prominence hearth was on the NW limb on Aug 10 rising to a height of around 47,000km. A double arch prominence was seen on the SE limb on Aug 11 also rising to 47,000km.

On Aug 12 a tall pillar was reported on the NE limb and later that day an incomplete arch was prominent on the same limb. The hearth persisted on Aug 13 and later that day was reported as a spectacular double arch extending some 233,000km around the solar limb. The hearth persisted during Aug 14 and rose to a height of approximately 65,000km.

A loop prominence was seen on the SE limb on Aug 20 which developed into a series of tall spikes on Aug 21. A tall tree prominence with a broad flattened top was reported on Aug 22 on the W limb. An arch prominence was on the NE limb on Aug 26.

Filaments & plage

11 observers reported a filament MDF of 4.99 for August.

Filaments were the main H-alpha feature during August with comprehensive reports received. On Aug 8 a spectacular 'horned' dark filament graced the SE quadrant which was still present the following day, matching the alignment of chromospheric disturbance in the SW quadrant.

On Aug 10 a very large 'feathered' filament was reported in the southern hemisphere, measuring approximately 250,000km in length. On Aug 11 this filament was estimated to cover some 30[degrees] of the solar disk and on Aug 12 was estimated at around 350,000km long and a similar length the following day. By Aug 14 the filament was in the SW quadrant and 'hanging like the sword of Damocles' as it rotated towards the limb. It started to decline on Aug 15.

On Aug 18 a similarly sized filament was seen in the southern hemisphere but much broader than its predecessor. It was broken up and displayed a complex structure. On Aug 19 the filament was estimated at 350,000km in length.

Another long southern hemisphere filament was seen on Aug 25 extending from the SE limb towards the centre of the disk. The following day, the filament was significantly longer and estimated to traverse around 40[degrees] of the solar disk. The filament appeared to have a break and was broader at the limb end. The feature began to fade on Aug 27.

CaK

An almost continuous line of CaK plage was observed for about 60[degrees] east-west at a latitude between S05[degrees] and S10[degrees] from Aug 17 to 20, linking plage around the sunspot groups in that region. On Aug 28 a large strong plage appeared centred at N15[degrees]/020[degrees] in the vicinity of a sunspot group AR1834.

Flares

On Aug 2 Kevin Kilburn reported a bright 'S' of plage in AR1806 which was associated with a modest Class B9.7 X-ray flare. On Aug 18 a C1.6 X-ray flare was observed near AR1818. On Aug 19 a 'hotspot', possibly a flaring region was seen preceding AR1818. This same sunspot group was responsible for another flare on Aug 21 reported by NOAA as C1.1 X-ray class from 11:25 UT to 11:48 UT.

Flares were also reported by Anthony Stone on Aug 11 x2 and Aug 12 x2; Athur Bowyer on Aug 23 at 07:55 UT and by Alan Heath on Aug 12 at 08:25 UT, 16 at 13:05 UT and Aug 28 at 09:30 UT.

2013 September

A decrease in activity particularly in the southern hemisphere resulted to the lowest relative sunspot number (R) since 2012 February. Activity approaching mid-month was particularly sparse for this point of the solar cycle. Few substantial sunspot groups were of note during September.

AR1835 S09[degrees]/011[degrees] remained on the disk from August, now in the SW quadrant type Dso with an area of 150 millionths, consisting of two small penumbral sunspots. It was last seen close to the W limb on Sep 4.

AR1836 N12[degrees]/342[degrees] also survived from August, was approaching the CM type Dso with an area of 140 millionths on Sep 2. By the next day the group was type Cso consisting of a single penumbral sunspot and two pores to the north of the main sunspot. The group did not develop further and was last seen on Sep 8 type Hsx on the NW limb.

AR1837 S16[degrees]/350[degrees] developed mid disk on Sep 2 as an arc of faint sunspots. The group had developed substantially by the next day to type Dso, the leading penumbral sunspot being the largest. The group further developed on Sep 4 to type Dsc but then started to decline as it approached the SW limb rounding the limb on Sep 7.

AR1841 S04[degrees]/145[degrees] appeared over the SE limb on Sep 11 type Hsx. Although this group never developed to a substantial active region it was persistent and during the period Sep 14 to 16 was the only sunspot group reported on the disk by the majority of observers. The group rounded the SW limb on Sep 22.

AR1846 S17[degrees]/059[degrees] appeared on the SE limb on Sep 17 and was seen as a substantial Hsx sunspot clearly on the disk the following day. By Sep 22 the group was type Hax with a total area around 190 millionths. The group progressed towards the SW limb as a substantial Hsx sunspot and was last seen on Sep 28.

AR1850 N11[degrees]/033[degrees] was first recorded on Sep 19 as a single Hsx sunspot very close to the NE limb. By the following day the group was type Cso but remained small until the group approached the CM when it underwent growth on Sep 24 & 25. By Sep 26 the group was type Dao in the NW quadrant comprising two penumbral sunspots at either end of the group with an area of 140 millionths. The group then started to decay to become a single Hsx sunspot on Sep 30 when it was close to the NW limb.

12 observers reported a Quality number of Q= 7.98

H-alpha

Prominences

18 observers reported a prominence MDF of 4.62 for September.

A notable arch prominence was on the NE limb on Sep 4 but was not present on Sep 5. On Sep 6, a large hedgerow prominence hearth was recorded on the NW limb stretching around the limb for about 102,000km.

A hedgerow prominence was on the NW limb on Sep 7. On Sep 8 a column type prominence was on the SW limb and reached an approximate height of 140,000km. Also on Sep 8, an eruptive prominence was reported on the SW limb with localised detached plasma clouds.

Four substantial mounds spanning the NW limb were reported on Sep 9 and also an active 'plant' like prominence on the S limb. This prominence consisted of a stem plus two drooping leaf like structures at 13:03 UT. By 13:28 UT the southern appendage had started to fade.

A substantial fila-prom graced the NE limb on Sep 10 accompanied by substantial prominence hearths on the SE limb, one being an arch that was also seen on Sep 12 & 13. On Sep 13, a prominence on the SW limb reach an approximate height of 149,000km whilst on the SE limb a prominence had ejected off the limb to about 168,000km.

On Sep 20 several observers reported a substantial hedgerow hearth on the NE limb stretching around the limb for approximately 410,000km; one observer noted this hearth developing from Sep 18. A prominence extending from the N limb on Sep 29 as a single spike at 10:45 UT released ejecta that closed to form a single spike prominence by 11:15 UT.

Filaments & plage

13 observers reported a filament MDF of 4.70 for September.

A filament in the NW quadrant on Sep 1 had an estimated length of 186,000km. The following day it had increased to about 251,000km. By Sep 6 this feature had reached the NW limb and formed the substantial hedgerow prominence reported above.

A long east-west filament was in the NE quadrant on Sep 3 well to the east of AR1836 but was not seen on Sep 4. A curving filament also trailed AR1834 on Sep 3 which was much shorter in length by the next day.

Two strong filaments accompanied AR1836 to the north and east on Sep 5. Two areas of plage were seen in the SE quadrant on Sep 8 associated with filaments but not with white light sunspot groups. On Sep 16 a long arc filament was seen with a broken structure.

On Sep 20 a filament near the north polar point resembled a inverted question mark extending to the limb. A long filament was seen in the southern hemisphere on Sep 25 laying across the CM. Also on Sep 25 the question mark-shaped filament of Sep 20 was now in the NE quadrant and resembled a butterfly in shape. A large filament was seen on Sep 27 with a length of approximately 372,000km but was not seen on Sep 29.

Plage was noted with ARs 1834 and 1837 on Sep 2 and around AR1843 and 1846 on Sep 20.

CaK

In addition to areas of CaK 'speckles', there were frequent areas of bright plage usually associated with sunspot groups but no sunspots, being within the CaK plage areas. A long train of activity accompanied sunspot AR1845 and stretched along the same latitude for about half the width of the solar disk.

CaK MDF for September 10.70 (1 observer).

Flares

Ken Medway reported a flare on Sep 3 importance Sn at S10[degrees]/032[degrees]W at 10:22 UT. On Sep 4, Alan Heath reported a flare at 07:25 UT.

Monty Leventhal observed a type 1B flare on Sep 19 on the NE limb associated with AR1850 starting at 23:00 UT, peaking at 23:05 and ending at 23:10 UT, X-ray class C1-2. Monty also reported a flare on Sep 24, type 2B, starting at 22:50 UT peaking at 22:55 and ending at 23:10, X-ray class C-1.

Brian Mitchell recorded a flare on the W limb on Sep 26 at N25[degrees]/100[degrees].

Lyn Smith, Director

BAA sunspot data, 2013
August-September

Day      August       September

         g    R       g   R

1        6    85      3   57
2        7    95      4   64
3        6    93      4   59
4        5    69      4   61
5        5    61      3   51
6        4    59      3   42
7        5    72      2   31
8        6    79      2   20
9        4    55      1   11
10       5    59      1   16
11       4    59      3   44
12       5    75      3   38
13       4    81      2   29
14       4    78      1   16
15       5    95      1   13
16       5    78      1   18
17       5    79      2   27
18       6    85      3   45
19       7   109      4   58
20       7   108      5   67
21       8   113      5   66
22       8   118      4   64
23       8   107      4   58
24       5    67      4   51
25       3    44      3   52
26       3    39      3   40
27       3    43      3   43
28       3    43      3   42
29       3    50      3   36
30       3    58      3   43
31       3    57

MDFg      5.13 (49)     2.99 (51)
Mean R   74.59 (44)   42.12 (47)

North & south MDF of active areas g

              MDFNg       MDFSg

August      1.90 (38)   3.18 (38)
September   1.38 (40)   1.71 (40)

g = active areas (AAs)

MDF = mean daily frequency

R = relative sunspot number

The no. of observers is given in brackets.
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Article Details
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Title Annotation:Notes and News
Author:Smith, Lyn
Publication:Journal of the British Astronomical Association
Geographic Code:4EUUK
Date:Dec 1, 2013
Words:2553
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