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Solar Rotation Nos: 2161 to 2162
A few sunspots of interest and, of course, a total solar eclipse (partial from the UK) plus some very interesting prominence activity throughout the month, made up for the generally lower level of solar activity we are seeing at present.
Here are the highlights for March 2015.
At the start of April the two sunspot groups AR2293 and AR2294 were well on view and thought to be flare-active. It was while our attention was on these sunspots that another, AR2290, which was at that time nearly on the West (W) limb produced an M-class solar flare on the 2nd at 1530UT. This gave rise to a tall twisted prominence appearing on the W limb. Meanwhile, the solar wind was buffeting the Earth and creating bright displays of aurora confined to high geographical latitudes. AR2290 produced another stronger M-class flare on the 3rd at 0135UT.
By now all the sunspot activity was over by the W limb. As these were carried westwards by the Sun’s rotation the solar disk very nearly became blank right up until about the 7th when AR2297 came over the E limb. It was already the site of flares having produced an M-class flare on the 6th. AR2297 was from the 7th onwards the only sunspot group to be seen. It was active with solar flares the strongest being an X-class flare on the 11th at 1622UT. AR2297 reached the Central Meridian (CM) by the 13th having developed into a substantial sunspot group by then. There were other sunspots visible but they were much smaller. As AR2297 headed towards the W limb it produced a minor C-class flare on the 15th. There was a major geomagnetic storm on the 17th that led to widespread aurora here on Earth. The storm was the result of an earlier Coronal Mass Ejection (CME) impacting the Earth.
AR2297 finally went over the W limb just as we were getting ready to see the total solar eclipse on the 20th. The path of totality, stretched from the North Atlantic Ocean heading north and east passing over the Danish Faroe Islands, and then on towards the Norwegian island of Svalbard before coming to an end over the Arctic Ocean. Totality lasted longest from the Faroe Islands where the Moon hid the Sun for 2 minutes and 46 seconds. From the UK we did not see totality but saw a partial eclipse of 95% of the solar disk being covered by the Moon from northern Scotland reducing to 82% of the solar disk from southern England.
Some of our members were lucky to see part or all of the partial eclipse while others were less fortunate. A band of cloud was clearing from the northwest with clearer skies following behind. It seems that those located in northwest England and the Midlands saw most or all of the eclipse while those in south east England saw nothing but cloud. In my case, from Buckinghamshire, the sky was overcast until the eclipse ended and then the sky cleared completely! Thank you to everyone who sent in reports and images of the eclipse. These can be found on the SPA website and there were loads of tweets on SPA Twitter. The sunspot seen widely during the eclipse was AR2303 lying near the E limb at that time.
AR2303 remained much the same as it crossed the solar disk and was joined a few days later by AR2305, a slightly larger sunspot group plus some other smaller sunspots which brought up the sunspot number. AR2305 developed slightly as it headed towards the CM and was visible to the protected naked eye for a while but then went quiet again as it approached the W limb.
SPA Sunspot Mean Daily Frequency (MDF) for March: 2.91
SPA Relative Sunspot Number for March: 43.42
Well done to Brian Gordon-States who observed 28 days this month. Jonathan Shanklin was not far behind at 26 days and Alan Heath at 25 days.
PROMINENCES, PLAGE, FILAMENT AND FLARE ACTIVITY
As mentioned in the sunspot summary, AR2290 produced a tall twisted prominence as it went over the W limb in early March.
On the 3rd Ian Lee reported that on the NE limb there was “…a very dense and intricate forest of prominences stood out with a small filament leading away from it…”. AR2292, a cluster of 7 small spots was seen embedded in bright plage with an area of dark filaments just to the south. Many of these features were seen the following day.
Later on the month on the 11th AR2297 was accompanied by bright plages and an arched filament to the SE. Many long and elaborate filaments were also seen some with some breaks in their structure. A few days later and on the 15th and AR2297 still surrounded by bright plage with two filaments either side of it. Prominences were barely seen. By the 18th AR2297 was nearing the W limb but still had plenty of plage and prominence activity around it. Meanwhile, prominence activity had recovered with most of the NE limb and the SW limb populated with hedgerow prominences.
By the 19th, the day before the total solar eclipse, there was a lot of prominence activity along the NE limb while on the SW limb there had been a reduction in prominences.
On the 24th while prominences had declined, plage and filament activity associated with the sunspots had become visible especially clustered on the NE of the solar disk around sunspots AR2305 and AR2307.
On the 27th a huge and highly complex prominence was seen by many on the NE limb. Spaceweather.com website gave its dimensions as 6 times taller and 30 times wider than the Earth and capable of swallowing more than 180 Earth’s. This giant prominence was named “the Great Wall of Plasma”.
On the last day of the month, the W limb saw some prolific prominence activity and several dark filaments on the disk.
PROMINENCE MDF: 4.85
One solar flare was reported by Alan Heath on:
Detailed count records of Active Regions and Relative Sunspot Numbers came from: Richard Bailey, Michael Fullerton, Brian Gordon-States, Alan Heath, Mick Jenkins, Ian Lee, Jonathan Shanklin and Julia Wilkinson.
Images and drawings were supplied by: Richard Bailey, Mark Beveridge, Carl Bowron, Mick Jenkins, Ian Lee, Cliff Meredith, Peter Paice, Julia Wilkinson, Pete Williamson and Brian Woosnam.
SPA Solar Section Director