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.
January
2013
Although
only
eight observations
were possible during the month, it was clear that activity during the
first
half of the month was much higher than the second half (which was more
typical of
that from previous months). The
largest
of seven groups seen on the 1st was AR 1640 of type Dac at
28°N/319° near the
central meridian with an area of 260 millionths.
On
the next observation, on the
8th, the largest of eight groups, which were evenly distributed between
the
northern and southern hemispheres, was AR 1652 of type Eac at
21°N/183° and
area 270 millionths. The largest sunspot within this group was the
leader with
two small penumbral followers and a few pores in between. By the
following day
the leader had become quite elongated and an additional penumbral
sunspot had
developed in the middle of the group – the group’s
size had
increased slightly to
300 millionths. By the next observations on the 16th and 17th, AR 1652
had
reduced to a single Hsx group approaching the western limb.
Also
on the 8th an Hhx sunspot
was close to the eastern limb but on the following day it could be seen
that
this group, AR 1654 at 7°N/147° was in fact of type Fko
with a
quite irregular
leader and symmetrical follow. When next seen on the 16th this group
was now of
type Fkc with three irregular penumbral sunspots spread throughout the
group –
its total area was 800 millionths. By the following day, the area of
the group had
reduced to an estimated 470 millionths.
On
the 16th and 17th only three groups were seen.
The
final observations on the
month on the 26th, 27th and 30th showed a reduced number of groups and
group
sizes compared to earlier in the month.
Hydrogen Alpha:
The
three observations made during the month, on
the 1st, 26th and 27th, showed many prominences on each date but all
were
fairly small. There
was, however,
quite
a contract between the hemispheres, with the majority being in the
southern
hemisphere. Similarly the filaments seen were all small. On
the 1st plage was seen around AR 1640
while on the 26th and 27th plage was seen around AR 1663.
February
2013
On
the 2nd only
four small groups
were seen, the largest being AR 1665 of type Hax at
11°N/241°
with an area of
120 millionths. When next seen on the 5th it was of similar size and
the other
two groups seen were also in the northern hemisphere. On the 8th three
northern
groups were seen – again all small as the largest groups at
100
millionths each
were AR 1667 of type Cso at 23°N/194° and AR 1670 of
type Dai
at 18°N/160°.
The
next set of observations on
the 17th, 18th and 19th showed an almost equal number of northern and
southern
groups. Again all
were small in size.
The largest of these, AR 1678, was initially seen as an Axx group on
the 17th
at 12°N/68° before disappearing on the 18th but then
re-appearing on the 19th
as a Dao group consisting of a bipolar group with irregular penumbral
sunspot
at either end of the group giving a total area of 140 millionths. Note
that AR
1671 was just to the north-west of AR 1678 at 16°N/73°
which
was of type Cao on
the 19th and area 120 millionths.
Hydrogen Alpha:
The
only
observation on the 17th
showed five prominences including several spikes on the SE limb.
Several
filaments were also seen included one extending about 40° in
longitude in the
eastern hemisphere. Plage was seen around AR 1675 and AR 1673.
March
2013
The
largest of
the five groups
seen on the 4th, all in the southern hemisphere, were AR 1686 at
14°S/261° of
type Dsc with an area of 110 millionths and AR 1683 at
17°S/202° of type Dac
and an area of 120 millionths. Each of these groups consisted of three
penumbral sunspots. By
the 5th AR 1686
had grown slightly to 140 millionths and a few pores were also seen:
this group
was also nearing the western limb.
AR
1683 had decayed into a Cso group with an area of 40 millionths: this
group was
nearing the central meridian.
The
next observation on the 12th
showed more activity in the northern hemisphere, with four groups
compared with
one in the south. The
largest were AR
1696 at 4°N/92° of type Dac with an area of 190
millionths
– it consisted of
several small penumbral sunspots and just to its east was AR 1692 at
9°N/76° of
type Hhx with an area of 240 millionths. As its type suggests it was a
large
symmetrical single penumbral sunspot.
Due
to the poor weather
conditions, the next observations were not until the end of the month
on the
28th, 29th and 30th. On
the 28th just
three groups were seen where as five were seen on each of the following
days. Of
particular
note were an Axx group
at the
high southern location of 31°S/268° (AR 1709) on the
29th only
and an extended
Dko group on the eastern limb at 20°S/157° (AR 1711)
seen on
the 30th.
Hydrogen Alpha:
The
only Hα observation on the 28th showed several
prominences around the solar limb, with the largest being in the NE
quadrant
near the North Pole in the form of a hedgerow – although it
was
not
particularly high, it was quite extended along the limb. Also
nearby on the solar
disk was an
extensive filament which had a large extent in latitude.
April
2013
AR 1711 of type
Dko at 18°S/156° was the largest of four groups seen on
the 1st – it had an
area of 420 millionths (this group rotated around the eastern limb on
30th
March). The following penumbral sunspot had reduced in size by the next
day
while the total area was similar.
By
the
6th the group was near the central meridian and how a single asymmetric
penumbral sunspot of type Hkx. By
the
10th it was still of a similar size, 440 millionths and now approaching
the
western limb. AR
1711 was seen with
the
protected naked eye on the 2nd, 6th and 7th. Also on the 6th a small
Cao group,
AR 1718, was seen at 22°N/108° (area 90 millionths)
– it was of a similar form
and size on the 7th but by the 10th it has developed into a complex Dao
group
with an area of 420 millionths: both the leading and following
penumbral
sunspots were quite irregular with several small umbra within each
sunspot. The
third largest of six groups seen on the 10th was AR 1719 of type Dao at
10°N/76°
with an area of 120 millionths: this group was initially seen near the
eastern
limb on the 6th and an Hax sunspot before forming into a small Dac
group on the
7th.
The
next
observation on the 20th showed an Eac group near the central meridian
at 14°N/326°,
AR 1726: it had an area of 150 millionths. By the following day it had
grown to
400 millionths and now comprised a string of penumbral sunspots
surrounded by
several pores. On the 22nd the leader and middle penumbral sunspots had
both
become larger - although the number of penumbral sunspots had reduced,
the
total area of the group had increased to 500 millionths. As the group
approached the western limb, its area continued to grow such that by
the 24th
it had an area of 670 millionths.
Only
the following penumbral sunspots was seen close to the limb on the 26th
as an
extended Hkx sunspot.
On
the 25th AR
1731 had rotated onto the disk as a small Dao group at
8°N/188°. Further
small penumbral
sunspots had
developed within the group by the following day to make the group type
Esc.
Further development continued such that by the 28th the group was of
type Ekc
and an area of 410 millionths – the group was quite complex
with a particularly
irregular sunspots towards the following part of the group. Further
pores appeared within the group on
the 29th while on the 30th a quite irregular penumbral sunspot was seen
within
the middle portion of the group. It was also now near the central
meridian. Finally
on the 29th and
30th,
a Dko group was seen near the eastern limb, AR 1734 at
20°N/187°: on the 30th
it comprised a pair of irregular sunspots with the follower being the
more
irregular.
Hydrogen
Alpha:
One of the most
striking prominences seen from 9 observations was on the 1st when a
series of
nearby spike prominences were seen on the NE limb. Also on the 28th a
detached
prominence was seen on the E limb.
Filaments
were seen on all observing days but they were particularly
numerous on the 6th while the largest was seen on the 1st as two part
circular
filament in the W portion of the solar disk. AR 1711, the largest
sunspot group
on the disk on the 1st and 6th was seen with a noticeable penumbra in
Hα. Extensive
plage was
seen
around the active sunspot groups during the month including AR 1726 on
the
20th, 21st and 26th. Two flares were seen during the month –
a C1.1 flare
within AR 1718 on the 6th between 09h 35m and 09h 50m which appeared a
small
number of small bright regions and a C4.4 limb flare on the 26th
between 15h
55m and 16h 05m – this was within AR 1726 and appeared as a
bright and active
portion of the solar limb.
May
2013
AR
1731 at
11°N/188° was one of
five groups seen on the 1st having just passed the central meridian. It
was
still a complex Eac type group with many small penumbral and other
sunspots and
a total area of 290 millionths. On
the
2nd and 3rd AR 1731 was still of type Eac but it had less sunspots
visible on
each day such that by the 4th it was of type Cso and a single Hsx
sunspot on the
5th. It was not visible on the 6th having rotated around the limb. A
larger
group seen on the 1st was AR 1734 at 17°S/152° with an
area of 660 millionths –
this was of type Dko which consisted two irregular penumbral sunspots
with the
following sunspot being the smaller but more irregular. As this group
rotated
towards the central meridian it remained type Dko but it reduced
slightly such
that when it crossed the meridian on the 5th it had an area of 440
millionth
and it had developed several pores within the group. This group then
continued
to decay so that by the 9th it was just a single irregular Hkx sunspot
– it was
last seen close to the western limb on the 11th. AR 1734 was seen with
the
protected naked eye on the 7th.
On
the 10th and 11th ten groups
were seen, with six in the north and four in the south. The largest of
these
was AR 1745 which appeared on the eastern limb as an Hsx sunspot at
13°N/335°
on the 10th. By the
13th it had
developed into a Dkc group with an area of 390 millionths –
the follower penumbral
sunspot was the largest. On subsequent days the leading sunspots
decayed so
that by the time the group passed the central meridian on the 16th it
comprised
a single Hkx sunspot at 210 millionths. When next observed on the 19th
it was a
Hax sunspot at 170 millionths – it was last seen on the 22nd
as a small Hsx
sunspot close to the western limb.
By
the 25th the number of groups
had reduced to five – the largest being AR 1755 at
10°N/200° of type Dao and
1756 at 19°S/212° of type Dac.
Both
groups were of a similar size of just over 300 millionths. By the 27th
AR 1755
had become type Dsi with a reduced size of 60 millionths while AR 1756
had
elongated to become type Fai with a reduced size of 150 millionths. By
the 31st AR 1755 must have decayed on the
disk while AR 1756 was a single Hsx sunspot on the eastern limb. It
was one of three groups seen on this date.
Hydrogen Alpha:
There were notable
Hα events on
the 3rd and 13th. On
the 3rd between 14h
50m and 15h 15m UT a compact flare was seen within AR 1734 (type C1.7).
Later the
same day two other flares were seen, the first of type M1.3 within AR
1731 was
seen from 17h 15m UT which appeared as several bright ribbons while the
second
of type M5.7 was seen from 17h 30m UT very close to the eastern limb
within AR
1739 (the group was first seen in white light on the following day). The
latter flare appeared as a bright region
with a nearby bright and active prominence. The appearance of this
prominence
changed rapidly over the next 25 minutes with a jet of hydrogen moving
away
from the limb before breaking up into several blobs of hydrogen which
stretched
up to an estimated height of 200,000 km.
By
17h 45m UT these
blobs had started to disappear before the base of
the prominence reduced in height and intensity.
With
the strength of
the flare reducing, the prominence began to
disappear.
On
the 13th at 17h 30m UT a very
bright compact loop prominence was seen on the eastern limb –
this had been the
site of an X2.8 limb flare which had peaked at 16h 05m before decayed
to an M1
flare by the time of the observation. The flare occurred in AR 1748
which was
first seen in white light as an irregular Dko group on the following
day.
However a very spectacular prominence was also seen on the almost
opposite limb. It
comprised a hearth
near the limb with
several blobs and a broken jet higher above the limb up to an estimated
height
of 300,000 km. Just
10 minutes later
only the hearth and a small jet were all that remained of this very
dynamic
prominence.
June
2013
The
largest of
the three
groups
seen on the 1st was AR 1762 which had just passed the central meridian
at 28°S/128°:
it was of type Dsc with an estimated area of 130 millionths. Over the
next two
days the follower developed into a quite elongated asymmetrical sunspot
(with
the longest axis being in latitude). By the 4th all the pores between
the
leader and follower had disappeared while the follower continued to
grow. By
the 5th this group had a total area of 480 millionths. On the 7th, with
the
group nearing the western limb, just a single Hsx was seen. On the 5th
AR 1765
developed on the disk at 8°N/51° as a small Cao group.
By the 8th, with the
group just passed the central meridian, it was of type Dao and area 120
millionths - it was also the only group seen on the disk.
The
next observation on the 14th
showed one group in the west and four others in the east (all were in
the
south). The western group was AR 1768 at 9°S/354° of
type Dac and area 260
millionths. It was still of this type on the 16th when seen near the
western
limb. Two further eastern groups appeared on the 15th.
Yet
another southern group, AR 1775, appeared
around the eastern limb on the 16th to give a total of seven groups on
the
disk. AR 1775 at 25°S/223° was the largest group seen
on the 19th at 210
millionths as a single Hax sunspot. By the 23rd it had decayed into a
small Dac
group and then to type Cso on the 25th. On the 29th and 30th just three
small
groups were seen with two out of three being in the south (the dominant
hemisphere throughout the month).
Hydrogen Alpha:
Several prominences and
filaments
were seen on each of 7 Hα observing days. The most notable
prominence was seen
on the 3rd and 4th as a combined filament/prominence on the NW limb
with the
filament shortening between the two dates due to it rotating off the
disk. A
particularly long filament was seen in the SE quadrant on the 8th
– it covered
about 40° on the solar disk. Plage was seen around AR 1762 on
the 3rd, around
AR 1766 and 1765 on the 5th, around AR 1781 and 1778 on the 29th and an
unusual
looking plage region around new group AR1780 on the 30th (this appeared
as a
string of circular plages).
July
2013
During
the
month
activity was
higher in the south than the north.
Indeed
on the 4th all
three groups were in the south including an Fkc
group, AR 1785, at 9°S/6° – it comprised a
collection of irregular penumbral
sunspots together with a string of pores located in the leading part of
the
group. By the
following day
many of the
penumbral sunspots appeared to have merged to form a ribbon following
the main
penumbral sunspot. The
leading pores had
disappeared to make the group type Ekc.
By
the 6th the ribbon
had broken into many penumbral parts.
The
shape and size of the penumbral sunspots
within AR 1785 continued to change daily as the group passed the
central meridian
on the 8th. By the
9th fewer pores
were
seen and by the 11th with the group approaching the western limb, the
group had
decayed to an Eao type with an area of just 180 millionths. It
was last seen on the 12th as a small Dso
group. AR 1785 was seen with the protected naked eye on the 6th, 7th,
8th and
9th.
One
of two groups seen on the
14th was an Hsx sunspot close to the eastern limb.
By
the following day further sunspots had
rotated onto the disk to form an Esc group at
21°N/192°. When next seen on the
19th this group, AR 1793, was still of the same type with an area of
340
millionths and it had the appearance of a typical bipolar group. By the
21st
with the group just pass the central meridian it had reduced in size to
120
millionths due to a contraction of both the leading and following
sunspots. On the
22nd, 24th and
25th
just two penumbral sunspots were seen.
It
was not seen on the
26th.
On
the 29th and 30th six groups
were seen on each date with an even spread between the north and south
but all
were fairly small.
Hydrogen Alpha:
The most notable
prominences from
9 observations were seen on the 13th, 19th and 26th. The first of these
was a
fine hedgerow prominence on the SE limb, the second was seen on the NW
limb as
an irregularly shaped tree prominence while the third were several
detected
strips of hydrogen running parallel to the limb at an estimated height
of
110,000 km on the SW limb. Filaments were seen for each observation
– these
included a pair of almost straight filaments on the NE limb on both the
6th and
7th. Plage was seen
around
the main
sunspots groups.
August
2013
Although
several groups were seen
on each observation during the first 10 days of the month, all were
fairly
small. There was also an almost equal spit between both the northern
and
southern hemispheres. However there was quite a spread in group
latitudes for
this part of the solar cycle with, on the 1st, AR 1807 at
30°N/89° (type Bxo) and
AR 1811 at 6°N/7° (Axx).
On
the 11th just three southern
groups were seen: two of these were AR 1817 at
20°S/238° of
type Dsc which
comprised a few small penumbral sunspots and AR 1818 at
5°S/215° of type Dso
(both had an estimated area of 140 millionths).
Over
subsequent days both groups developed. AR 1817
increased the number
of small penumbral sunspots as it passed the central meridian on the
13th
before the number of sunspot started to reduce by the 15th although its
total
area increased slightly to 240 millionths.
As
this group neared the western limb it became type Cao
on the 17th and
then a single Hsx sunspot when last seen on the 19th.
Meanwhile
AR 1818 was type Eac on the 14th with
the leading and middle penumbral sunspots being the largest. It was
near the
central meridian on the 15th when the leading penumbral sunspot became
the
largest in the group when the total area was 310 millionths. The main
sunspot
within AR 1818 changed slightly on each of the following days while it
lost all
the following sunspots by the 17th – this group also became a
single Hsx
sunspot when last seen on the 20th.
By
the 25th the number of groups
seen reduced back to just three (there had been up to 8 on the 19th,
21st and
23rd). One of these was AR 1835 which was initial seen as an Hsx
sunspot near
the eastern limb on the 25th and 26th (at 9°S/11°). It
then developed some small following
sunspots on the 27th, having an area of 350 millionths on the 28th,
before
becoming a single irregular Hax sunspot on the 30th.
By
the following day this sunspot had split
into two smaller more symmetrical sunspots.
Hydrogen Alpha:
The most notable Hα features seen
from 10 observations were some particularly long filaments. One
on the 11th a filament stretched some
30°
in the SW quadrant. A
similarly sized
filament was seen in the southern hemisphere on the 18th but it was
much
boarder than the one seen on the 11th as well as having a break. A
similar long
filament, again in the southern hemisphere, was seen on the 25th and
26th –
this one was about 40° in length and again it appeared to have
a
break when it
was seen further on the disk on the 26th.
September
2013
Activity
has
reduced quite
significantly compared to previous month in both the number of groups
seen and
their size and that some of the groups were close to the solar equator
(see the
Butterfly Diagram below). On the 1st the largest of three groups was AR
1835 of
type Dso at 9°S/11° with an area of just 150 millionths
–
it consisted of two
small penumbral sunspots. It
was last
seen close to the western limb on the 4th. On the 2nd AR 1836 at
12°N/342° was
near the central meridian of type Dso with an area of 140 millionths.
Although
a few pores were seen around this group on the 3rd, now type Cso, it
did not
develop further and it was last seen as an Hsx sunspot on the 8th. This
and AR
1838 were the only group seen on this date (AR 1838 was a small Cso
group at 4°S/224°
at 70 millionths.
On
the 15th only one small Hsx
group (AR 1841 at 4°S/145°) was seen while on the 18th
an Hsx
sunspot had
appeared around the eastern limb.
This
group, AR 1846 at 17°S/59° had a size of 190 millionths
on the
22nd (type Hax).
It was seen again as an Hsx sunspot as it progressed towards the
western limb
and it was last seen on the 28th.
The
only other group seen on the 26th was AR 1850 at
11°N/33°
– this was initially
seen on the 20th as an Cso group before becoming type Dao on the 26th
when it
comprised two penumbral sunspots at either end of the group and it had
an area
of 140 millionths. Afterwards it started to decay to become a single
Hsx
sunspot on the 30th when it was close to the western limb.
Hydrogen Alpha:
The most notable prominences seen
from 4 observations were on the 7th when a nice hedgerow prominence was
on the
NW limb and on the 20th when another long hedgerow prominence was on
the NE
limb. Several long
filaments
were seen
on each of the 4 observations. Plage was seen around AR 1834 and 1837
on the
2nd and around AR 1843 and 1846 on the 20th.
|
Butterfly
Diagram for
Solar Cycles 23 and 24 (groups coloured red are for areas greater than
1000 millionths, purple for between 500 and 1000 millionths, green for
between 100 and 500 millionths and yellow for less than 100 millionths).
|
October
2013
This
solar
cycle continues to
surprise with a significant increase activity during the month. This
was due to both an increase in the
number of groups seen and the presence of four moderately sized sunspot
groups
– ARs 1861, 1875, 1877 and 1884.
The
first of these, AR 1861, was initially
seen as an Axx sunspot near the eastern limb on the 7th. It was still
just an
Hsx on the 8th before becoming type Dao on the 10th at
9°S/168°
with an area of
130 millionths (it comprised a leading irregular sunspot followed by
several
pores and a small penumbral sunspot). When the group was near the
central
meridian on the 12th it had grown to 290 millionths and it was of type
Dkc and
looking more like a typical bipolar group. By the following day many of
the
sunspots between the leader and follower had disappeared. On the 15th
with the
leader reducing in size it obtained a size of 380 millionths. The
size of all sunspots had reduced when
last seen on the 17th and close to the western limb although the number
of
sunspot had increased once again.
The
17th saw the first appearance
of AR 1875 as a small Hsx sunspot on the eastern limb. When next seen a
few
days later on the 24th AR 1875 was just past the central meridian at
9°N/28°
and of type Ekc with an area of 700 millionths. The main sunspots were
at the
leading and towards the following part of the group: there were many
other
smaller sunspots within the group. By the 25th, the leading sunspot had
increased in size while the other main penumbral sunspot had decayed. Despite
this the overall size of the group
increased to 790 millionths and it became type Fkc. As this group
neared the
limb on the 28th it reverted back to type Ekc and then to type Dso when
last
seen on the 29th.
The
24th revealed AR 1877 at 10°S/9°
of type Dkc with an area of 470 millionths through the presence of one
main
irregular penumbral sunspot. It was also nearing the central meridian
and to
the south and east of AR 1875. It was of similar appearance on the
following
day before it decayed to type Dao on the 28th with an area of just 190
millionths. It continued to decay to become a small Hsx sunspot close
to the
western limb on the 30th.
The
final moderately size group
was AR 1884 which was first seen on the 28th as a small Dso group at
12°S/261°.
On the following day it was an Eac group with an area of 290 millionths
where
the latest sunspot was the follower. It has grown again such that it
was 400
millionths on the 30th and now of type Ekc.
This
was one of seven groups seen on the 30th.
Three
sunspots were seen with the
protected naked eye on the 24th (2 for AR 1875 and one for AR 1877),
two on the
25th (one each for AR 1875 and 1877) and one on the 28th (AR 1882 which
was at
7°S/293°, of type Dko and with an area of 320
millionths).
Hydrogen Alpha:
On the 6th several prominences
were seen along the eastern limb including a combined
filament-prominence.
Plage was seen around ARs 1857 and 1856.
The
other Hα observation on the 28th showed several
small prominences
including a blob of hydrogen suspected above the eastern limb. Several
small
filaments were also seen. A
bright
region of plage was seen around AR 1875 close to the western limb. The
decay of two flares (M4.4 at 15:15 UT and
M2.7 at 15:01 UT) within AR 1882 was seen from 15:35 to 15:45 UT as two
bright
ribbons together with two bright blobs of hydrogen (these had subsided
at the
end of the observing session).
VLF
Receiver:
Many solar flares were detected during
the month using a 23.4 kHz VLF receiver – the most striking
was
the X2.1 flare
at 15:03 UT on the 25th from AR 1882.
The
impact of this flare on the ionosphere was detected
until just after
17:00 UT when the usual dip in signal strength occurs are sunset.
|
VLF
23.4 kHz flare detections. 2013 October 25 (UT).
|
November
2013
Based
on
observations made up to
the 19th, the increased activity seen in October continued. Of
particular
interest during this period were AR 1890 and 1899.
The
first of these groups was initially seen
on 2nd as a single Hsx sunspot on the eastern limb.
On
the following day further irregularly
shaped penumbral sunspots had rotated onto the disk – the
group
was at 10°S/169°
and of type Ekc. It was most likely the return of AR 1861 seen in
October. By
the 4th AR 1890 was of similar form as on the 3rd: it comprised of
several
penumbral sunspots where the leader was the largest while the follower
was of the
greatest latitude extent. On the 5th the leader had almost split into
two while
more small sunspots had appeared in the middle portion of the group. The
group had an estimated area of 790
millionths. When
next seen on the
10th
the group was still of type Ekc but it had reduced in size to 430
millionths
through the decay of all but the leader sunspot.
The
size and complexity of the group
continued to reduce by the 13th when it was seen as a small Eac group
nearing
the western limb. AR
1890 was seen with
the protected naked eye on the 5th.
Also
on the 13th an Hkx sunspot
was seen near the eastern limb at 7°N/38° (AR 1899). By
the
15th it was of type
Dko through the presence of a small follower – the leader was
the
dominant
sunspot which was irregularly shaped and the total area was 730
millionths. By
the following day the group returned to type Hkx.
AR
1899 was last seen just past the central
meridian on the 19th as a much more circular penumbral sunspot with an
area of
540 millionths. AR
1899 was seen with
the protected naked eye on the 15th, 16th and 19th.
Hydrogen Alpha:
On the 3rd several small prominences
were seen together with quite a few filaments. Plage was seen around
ARs 1884,
1887 and 1890. The
other Hα
observation
on the 10th was similar in that there were many small prominence, the
largest
being a spike prominence on the south-west limb and many filaments on
the solar
disk. Plague was
seen around
AR 1890.
December
2013
The
recent
moderately high
activity continued throughout the month. The largest number of groups
was ten
on the 10th when the sunspot number was 128. The majority of activity
was in
the southern hemisphere.
The
most complex of the five
groups seen on the 1st was AR 1909 at 17°S/205° near
the
central meridian – it
was a complex group of type Eac comprising several penumbral sunspots,
some of which
were irregularly shaped. Its total area was 360 millionths. On the next
observation on the 8th AR 1909 was seen just as a single Hsx sunspot
and near
the western limb. Also on the 8th another complex group was seen
– AR 1916 at
11°S/168°. This was of type Dac with an area of 340
millionths
– the leader was
the largest with many small followers some of which had penumbra. Two
days
later AR 1916 was nearing the limb as a collection of small penumbral
sunspots
– almost all the pores had disappeared.
Two
groups from the 14th were
seen with the protected naked eye. AR 1917 at 12°S/76°
was
initially seen as
type Cao on the 8th near the eastern limb before becoming type Dao on
the 10th
and type Dac on the 14th with an area of 320 millionths. On this date
it
comprised of several small penumbral sunspots and pores together with a
larger
penumbral sunspot to the south and middle portion of the group. It was
last
seen on the 19th as an Hsx sunspot close to the western limb. The other
naked
eye group from the 14th, AR 1921, was initially seen on the 10th as an
irregular Hax sunspot at 6°N/42° and near the eastern
limb. By
the 14th it had
developed into an Hkx sunspot of area 270 millionths. By the 19th and
20th AR 1921
was seen as a close pair of penumbral sunspots due, presumably, to the
splitting
of the irregular penumbral sunspot.
Another
complex southern group
was seen just past the central meridian on the 19th – this
was AR
1928 at 15°S/5°
of type Eac. On the following day the leader penumbral sunspot had
grown to make
the group type Ekc and give a total area of 500 millionths. There were
many
small follower penumbral sunspots. By the 22nd the group, now nearing
the
western limb, was of a similar form and size although there were fewer
pores.
Observations
from the 25th to
28th showed either five or six small groups, all in the southern
hemisphere.
Hydrogen Alpha:
On the 22nd several small prominences
were seen around the limb including a small ‘tree’
type on
the SW limb and a
twisted spike type on the NE limb. Several
small filaments were also seen together with plage around AR 1928.
Page
created on 31 December 2012.
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