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Solar Rotation Nos: 2192 to 2193
Mostly quiet Sun with a decrease in the overall number of sunspots but there were still some surprises.
Here are the solar highlights of July 2017 together with a selection of images.
1st to 5th July
There was only one small Active Region (AR) visible in the first week of July and that was AR2664 at latitude N14°. This was a quiet sunspot and was at that time nearing the west solar limb. By the 4th AR2664 was over the west limb, leaving a blank solar disc for two days. There was a Coronal Mass Ejection (CME) on the 1st but it missed the Earth so no geomagnetic storms were seen. There was an M-class solar flare on the 3rd but it was right on the western solar limb and therefore hard to see clearly.
6th to 18th July
A large Coronal Hole appeared on the 6th but its effect on the Earth was quite small. Sunspot AR2665 appeared over the east solar limb on the 6th on the southern hemisphere (S06°). Over the following six days it developed rapidly into a highly active sunspot group visible to the protected naked eye. By the 9th it was estimated to be almost as wide as the planet Jupiter (more than 100,000km long) and flare active too. Also visible on the 9th was a pore, right on the Central Meridian (CM), but many missed it as it was quite small. This might have been AR2667. AR2665 on the other hand, was from the 11th at the CM and of type Ekc. Thereafter, AR2665 went into gradual decline and just north there appeared a new active region, AR2666. This was near the solar equator at N13°. AR2665 although disappearing by now, did survive until it reached the west solar limb on the 17th. By then AR2665 was type Dko and AR2666 was type Axx. Elsewhere, the Sun was spotless.
19th to 31st July
There was another Coronal Hole on the 19th but there was little effect on the Earth. A blank Sun was seen on the 19th and this spotless period lasted right up until the 25th/26th when AR2668 (N04°) came and went in about a day. We were then back to a spotless Sun and it was only on the 30th that this was broken by AR2669, a small Bxo type sunspot, at N18°.
SPA Sunspot Mean Daily Frequency (MDF): 0.69 (was 1.33).
SPA Relative Sunspot Number: 11.79 (was 17.70).
Solar Prominences, Plage, Filaments and Flares
There were some nice prominences and filaments throughout the month.
1st to 6th July
A highly curved filament was seen on its own on the 1st.It looked like it disintegrated into smaller parts by the 3rd but by the 6th the filament appeared to be back in a semi-circular form once again. Also seen on the 6th was a longer, straighter filament, near to the southwest limb, and a trio of point-like prominences on the northern limb.
7th to 17th July
The 8th and 9th saw a hedgerow type on the southeast limb, just behind sunspots of AR2665. As AR2665 developed, several areas of bright plage became visible around it together with several short dark filaments. By the 12th both disc and limb were active and AR2666 was just beginning to show. The south east and south west limb showed a number of prominences, especially the smoke-stack prominence on the SE limb.
18th to 31st July
As AR2665 and AR2666 neared the west limb, there were mainly small prominences visible. A lot of this activity was seen along the northwest limb on the 18th. By the 19th, with no sunspots on show, a hedgerow type was seen on the SE limb and another point-like prom on the west limb. Another hedgerow was seen on the SW limb on the 25th. The 28th saw a tall prom on the southwest limb and a dark filament near the northeast limb. On the last day of the month, several small proms lay along the north east and south west limbs but there was not much to be seen on the disc.
SPA Prominence Mean Daily Frequency (MDF): 3.30 (was 2.90).
Well done to Brian Gordon-States, who observed 31 days, and to Michael Fullerton who was not far behind at 29 days. Well done to Alan Heath who observed 28 days and to Jonathan Shanklin for reaching 27 days.
Detailed count records of Active Regions and Relative Sunspot Numbers came from: Brian Gordon-States, Michael Fullerton, Alan Heath, Mick Jenkins, Ian Lee, Lee Macdonald, Jonathan Shanklin, Bob Steele and the Director.
Images and drawings were supplied by: Carl Bowron, Paul Brierley, Mick Jenkins, Ian Lee, Ian Morrison, Cliff Meredith, Peter Paice and Julia Wilkinson.