Popular Astronomy

Share to Facebook Share to Twitter Stumble It More...

Solar Highlights for February 15

Solar Rotation Nos: 2160 to 2161

A quiet month for sunspots. Activity seen in Hydrogen-alpha and Calcium light has been very interesting as there was the appearance of a very long dark filament in mid-February and a fair bit of prominence activity to be seen.

The solar wind, which is the name that is given to the constant stream of energetic particles coming out in all directions from the Sun, has at times this month become very gusty. The increase in strength is the result of the appearance of coronal holes appearing on the Sun. While these events mostly go unnoticed it is something we cannot easily see directly, it has led the appearance of the northern lights at slightly lower geographical latitudes beyond the Arctic Circle and increases the possibility that we might see an aurora from the UK.

Here are the solar highlights for February 2015.

At the beginning of the month Active Regions (AR) 2268 and AR2277 were visible, the first was nearing the west (W) limb, the second moving away from the east (E) limb. Both were flare active. In addition, website mentioned that a coronal hole was active over the south pole of the Sun and this was making the Earth’s magnetic field unsettled. This time while there were displays of the northern lights none were seen from GB.

AR2268 went over the W limb on the 5th and this left AR2277 and farther east AR2280 and AR2281, having appeared over the E limb on the 8th. Of the two AR2280 was the larger and more complex of the two. The lead sunspot of AR2280 exhibited a clear light bridge through its umbra on the 9th. AR2281 on the 9th produced a single M-class solar flare at 2335UT. Farther eastwards at that time was AR2282 but as this group crossed the Sun it slowly decayed into two sunspots and reaching the W limb around the 19th.

Despite the low sunspots activity, aurora were once again seen at high latitudes on Earth brought about by the Earth passing through a strong solar wind stream.

On the 19th there were several small sunspots to be seen across the solar disk and this was reflected in the daily sunspot counts made by our members. We nearly had a blank solar disk on the 22nd with our members recording just 2 Active Regions that day. Yet again the solar wind was bringing energetic particles from a coronal hole towards the Earth raising the opportunity of seeing aurora at high geographical latitudes though sadly not down as far as the UK! This “gusty” solar wind stayed right up to the end of the month.  

AR2290 had appeared over the E limb by the 19th and we were watching it expectedly as it seemed to be developing as it neared the CM around the 24th , but it was not to be as this too became quiet and was last seen nearing the W limb on the 28th. In the last two days of the month AR2293 and AR2294, seen either side of the CM, were looking promising.

Well done to Brian Gordon-States who observed on 22 days and to Alan Heath and Jonathan Shanklin who made 18 and 16 observations this month. 

SPA Sunspot Mean Daily Frequency (MDF) for February: 2.51 
SPA Relative Sunspot Number for February: 39.48


There was plenty of bright plage activity seen around sunspot AR2277 on the 3rd and a much filament and prominence activity too seen to the east of AR2277 and along the whole of the E limb. This activity was seen again the next day and a dark filament, seen near to the E limb had grown by then too. Ian Lee reported seeing a solar flare close to the leading sunspot of AR2277. On the 5th bright plages were seen at the site of the solar flare the previous day and the dark filament was even longer. This filament persisted and was highlighted on the website on the 8th and 9th. Mark Beveridge imaged it on the 8th in Ha light and Calcium (CaK) light. The estimated length of this filament at that time was around 400,000km. Ian Lee observed and recorded this same filament on his drawing of the 14th. Julia Wilkinson then imaged it on the 15th as it was nearing the W limb. AT this time the filament was seen connected to a bright prominence on the W limb and also had bright plages along the length of it. Just to the north was a similar long dark filament starting at sunspot AR2282 and stretching eastwards nearly to the E limb. The other long filament (associated with AR2282) had dispersed somewhat by then.

On the 20th many small but very detached prominences were seen along the W limb, not far from AR2288 which was also heading towards the W limb by then. The next day and much of the prominence activity on the W limb had dispersed, or had been carried over the limb by the Sun’s rotation. There were numerous bright plages and small dark filaments across much of the northern hemisphere as were sunspots AR2287 and AR2290. A small detached prominence was seen by Ian Lee lying high above the SW limb at 0936UT on the 21st and Richard Bailey imaged an slowly changing prominence on the NE limb on the 24th.     


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, Julia Wilkinson and Brian Woosnam.

Geoff Elston
SPA Solar Section Director

Added by: