Saturday, 7 December 2013

'Great' Flares of SC24

The plot shows all 27 solar flares of SC24, stronger than GOES class X1 - my definition of 'great' flares. We see no definite trend yet - and since the strongest flares occur some years after cycle maximum - we may have quite a wait for the flaring peak. When is/or was maximum? A hard question. The flares tend to occur in short bursts when very complex sunspot groups appear. These are currently in short supply. Stay posted.

Monday, 25 November 2013

Enigmatic Returnee

The big spot appearing around the Sun's eastern limb may, sometimes, be a 'relic' of an earlier group. 'Helio' freeware (c) Peter Meadows left no doubt that giant AR11899 was the return of the 'front end' or preceding (p) spot of October's giant AR11875: it had moved a little westwards while on the Sun's far-side. New (red) spots arose near it on Nov 13 and a C3 flare erupted along the filament (arf) to its north. The 'smiley face' (lhs) shows most of what remained of the AR11875 (p) spot in late Oct. This very large earlier group had two X-class flares during it disc passage, one at the western limb (see below). Renamed AR11899, it grew to 600 area units in size during Nov with fields in the big spot's umbra reaching a SC24 record of 2700G.

Friday, 15 November 2013

X2.3 in AR11875

Five logs showing a GOES X2.3 flare in AR11875 (Nov 29 UT)- we see the flare arcade above the limb: the spot group is now behind the limb. Over the next 30min the flare arcade evolves into post flare loops while surges erupt nearby. Big surge s1 is retracting in log5 - causing a splash, it seems, in the chromosphere.

Monday, 4 November 2013

C5.7 flare in AR11875


This small but bright flare was seen while much stronger GOES M-class and even X-class were erupting. The polarities of spots have been added (c) Mt Wilson. They show a complex mingling of unlike polaries and red polarities 'ahead' of the great preceding spot - little wonder that strong flares were active in this complex group. It would host an X2.3 when at the Sun's western limb a week later.

Friday, 18 October 2013

Brief Glory!

A giant of its kind, this huge prominence was glimpsed through heavy cloud. Over 100Mm high it was clearly erupting off the disc - and did so some hours later - resulting in a small CME that was not 'geoeffective'. The logs from 14 days earlier showed a hedgerow at the western limb with the same coordinates as shown above. The eruption caused the two foreground filament to vanish also.

Friday, 4 October 2013

Big Filament Ejects

Five NSO GONG images (c) show September's big filament as it crosses the sun - for the second time!
These five GONG views show the filament tilted from our line-of-sight in views 1, 3, 4 and 5. Note how different it looks as the l-o-s changes: showing complex details of the footpoints.View 2 shows it crossing the central meridian: we see it from directly overhead. Fig 5 shows it at the moment of lift off. It ejected at 900km/s, causing widespread aurorae on planet Earth. Heliocentric positions show it had made almost 2 complete rotations of the Sun at the time of liftoff! A very long-lived filament. In the process, H-alpha users saw some great prominences. Will the filament reform at the site?

Tuesday, 24 September 2013

An active Prominence

This tall, bright prominence adorned the eastern limb on Sept 19 (18 UT). Small scale motions continued throughout the session - how I wish for an inline webcam. Sketching such complex motions is a challenge.

Thursday, 5 September 2013

current activity is very low! And getting lower?

Solar activity - sunspot areas - are now lower than even SC16 in the early 20th century. Where to next! Stay posted.

Friday, 26 July 2013

AR11785

Watching big spot groups develop in both while light (the continuum) and H-alpha (hydrogen emission band) hints at the magnetic complexity of sunspots. Add the umbral magnetic field data posted daily by Mt Wilson Observatory (c) Regents of the University of California, and we have enough material for a PhD! Understanding current spots is further complicated by the steady weakening of spot magnetic fields. Late 20thC authors all agreed that average sunspot fields were 3000G - well, they arent any more! They currently average <2000G, and falling. And the Mt Wilson archive published in 2006 (Livingston, Harvey et al, "Sunspots with the Strongest Magnetic Fields" Sol. Physics) of a century of umbral field data showed clearly that the era of 3000G fields was short-lived: from ~1950 to 1992.
   Translation: current spots are pale and small in area compared with earlier decades. Nevertheless, spot groups like this one showed interesting details and some nice surges on the western edge of the preceding spots. Sadly, this group had no flares stronger that GOES C9. A glance at the bargraph below shows that SC24 flaring, so far, is well behind that of the past three cycles - with no sign of a dramatic turn-around any time soon.
    Southern group AR11785 had an irregular separation of spots with unlike polarities, making it Hale magnetic class Beta-Gamma; we would have expected much stronger flaring. Watch the site when it returns around July 30 - will any spots remain? Or maybe just a large patch of H-alpha plage with some filaments.

Saturday, 22 June 2013

Flaring in SC24

It is too early to say much about flaring in Solar Cycle 24, as the sunspot maximum has, it seems, not yet been reached. There are signs that the northern sunspot maximum of SC24 was reached in 2011. This plot shows all flares greater than or equal to GOES X5.7. The data used is from Jan Janssens website (see link below). Just one flare of SC24 so-far has reached that required flux, while there have been 14 class-X less than X5.7. The graph shows that flaring in SC23 not only reached an historic peak, but that peak was a year or two after the cycle's two sunspot peaks. The strongest flare yet recorded was the well-known GOES X28 in AR 10486 on Nov 4, 2003, an unforgettable event well-observed in Sydney. Here are two of nine sketches made of the flare, and the post flare loops. The first was made 36m after flare peak - the entire event covered nine hours.

         http://users.telenet.be/j.janssens/Flares/Powerflare.html




Saturday, 25 May 2013

Great flare in AR11748

AR11748 hosting an X3 flare - and its aftermath. The sketches show flare ribbons and flare loops ( the brightest parts of a flare arcade) the latter developing into an unusually compact cluster of post flare loops above the Sun's NE limb. Dates and times are UT. The spot group was, it seems, much reduced as a result of the weakened umbral fields of SC24. The event was sited at lat. +12, long. 290. A particularly elegant display though it rose only ~40Mm above the limb during the session.

Tuesday, 14 May 2013

Homunculus Nebula

Perhaps the strangest object in the night sky, the "Homunculus", contains the giant star Eta Carinae. This is a 'rough' sketch made with the 25" Mike Kerr Telescope at ASNSW's dark sky site, Wiruna. This is the raw sketch - though I have erased some notes etc. Key points of interest are the billows of cumulus-like gas at the right-lobe, and the central 'jet' of the left-lobe The latter has a dimmer cloud of ejecta. The right-lobe showed distinct gaps in places - and an equatorial 'jet' is seen below the star. A second 'jet' was suspected above the star. Magnification was 350. Many thanks to Chris Ross for pointing the huge 'scope at the target, I look forward to a longer session with, maybe, steadier 'seeing'. The prime spectrum of Eta Car clearly showed the hydrogen-alpha and beta lines in emission! I suspect it's the only object to do so with amateur telescopes.
     For complex reasons the bright emission points in this spectrum will soon disappear (~2014) when an unseen WR companion to Eta Car reaches periastron. "Watch this space" if, like us on the night, you have a diffraction grating in front of the 'scope's eyepiece; a rare event in practical astrophysics.

Tuesday, 7 May 2013

SPSP Challenge: IC2966 - can you see it?

Is IC2966 in fact Dunlop 266, 267?  He described two small hazy spots very near the Index Catalogue (IC) object. He was using a nine inch speculum - perhaps he did! IC2966 is one of the 'missing' Dunlop Objects that scholars do not credit to Dunlop. SPSP attendees might like to tackle the object with eight to ten inch telescopes. Report what you see to me (Harry) - I hope to be there. And the forecast is for clear-ish skies.

Where is IC2966? Its on the Musca/Centaurus border at 11h50m -64deg52min - overhead near the Southern Cross during the South Pacific Star Party. Good luck!
      Happy to report the two faint nebulae were fairly easy with the Mike Kerr 25" F5 telescope - pointed by Chris Ross. A 15m exposure by Joe Cauchi with his 16" reflector shows a pair of stars embedded in a blue reflection nebula - just as Dunlop described. How did he see it in a nine inch speculum: or was it then brighter?

Joe's great shot approximates the view in the 25". It seems the embedded stars are spectral type B or A as they excite no H-alpha emission - just a faint blue reflection nebula. Here's an idea: 180y ago the nebula was denser and scattered more light - but has now 'cleared' and little scattering occurs. Any thoughts?

Friday, 3 May 2013

AR11726 at the Limb

AR11726 was a large spot group of great complexity. When it reached the limb it revealed some fine H-alpha features. Here we see post flare loops after a GOES C5.7 flare at 22:25UT. The site showed no activity at 22:00, when white light viewing began. Returning to H-alpha at 23:03 showed these events. View 1: above the site we see the PFL ~40Mm high. Below are bright surges and some tiny  loops of the C5.7 flare. View2 shows the flare loops still present, now with larger surges - the latter are still strong in View3, while the PFL are fading. View4: crossing the flare loops are parts of a tall surge, in the process of recoiling back into the solar surface. Only the following spot of the active region was seen the time; the rest was concealed behind the limb

Thursday, 25 April 2013

Big flare in AR11718

AR11718, a northern hemisphere group, was a simple entity at first. Around April 9, half way across the disc, it had a burst of new spots: a close count showed about 30, many in curved chains. It seemed  two spot groups were intertwined - and the complexity implied fireworks! On the 10th and 11th it was almost too complex to sketch. Here we see it on the 12th when it had an M3.3 flare. The peak was at local sunrise (20:38UT) and I had this view at 20:49UT when the GOES flux had dropped to M1.  It was a great flare - bright and of large area: ~450 area units, roughly the size of the spots themselves. The group stretched across nine degrees of longitude, and at the time lay some 40 degrees from the western limb.      This was one of the few great flares in AR11718. Nearby, AR11719 had an M6.5 on the 11th at 07:16UT, not seen in Sydney.

Tuesday, 19 March 2013

Graceful eruption

This quiescent prominence lifted off the sun's SW limb on February 20th (UT) .There was plenty of time to sketch it since the ejection velocity was a low 25km/sec : fairly typical for a quiet region filament (QRF). Active region filaments (ARF) under special circumstances can eject at over 3000km/sec - an incredible velocity even given the very low density of the material involved. This filament was formed by plumes or 'streaks' of low-power magnetic fields, the relics of decayed sunspot groups.
   While the sun is abnormally quiet at present, from time to time it still hosts a range of interesting and beautiful transients.

Wednesday, 23 January 2013

AR11654: when groups collide!

Two views of a complex spot group - perhaps the result of a new group emerging directly below an older one. The result was a triple grouping of spots stretching over 21 degrees. Huge! Despite sunspot motion, the emergence of new flux and magnetic complexity there were no great flares, only a few to GOES M1.7. The dotted lines suggest magnetic configuration of the blended groups. Fascinating!