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SWAP carrington rotation movies

Differential rotation

When observing the Sun for a prolonged period of time, it soon becomes evident that features on its surface, and in its outer atmosphere do not rotate at the same rate. This is because the Sun is not a solid body, but a big ball of magnetised plasma, whose rotation is variable with position and height in the solar atmosphere.

A sunspot accident!

Once more, two sunspot groups have collided with each other. Indeed, NOAA 2497 was minding its own business when, starting on 11 February, the trailing part of a smaller sunspot group suddenly emerged right in front (to the west; "right") of it. It was unavoidable that the leading part of NOAA 2497 would bump into the trailing part of this new magnetic bipolar region, and it was easy for the space weather forecasters to predict that these developments could result in the production of low-level M-class ("medium") solar flares.

NOAA 2494's growth spurt

Once again, solar flaring activity has been pretty low. The strongest flare was a C5.1 peaking on 4 February at 18:22UT. The region responsible for this event was NOAA 2494, a sunspot group that was developing near the centre of the solar disk at that time. The region already reached its maximum sunspot area about a day later. It was always smaller than two times the total surface area of the Earth, so considerably smaller than e.g. NOAA 2192.

A filament erupts

Solar filaments are clouds of charged particles ("plasma") above the solar surface squeezed between magnetic regions of opposite polarity. Being cooler and denser than the plasma underneath and their surroundings, they appear as dark lines when seen on the solar disk and as bright blobs when seen near the solar limb (then they are called "prominences"). Special filters are required to observe these features, and one such a filter is the Hydrogen-alpha (H-alpha) line in the red part of the solar spectrum.

Phoenix

The phoenix is a large mythological bird with red and gold plumage, which has the most startling ability to regenerate itself. Indeed, when its body becomes old, it disintegrates in a fiery flash, soon to rise from its ashes as a newborn chick. Recently, it was most impressively featured in the Harry Potter movies as Professor Dumbledore's pet.

The Polar Faculae are back!

The STCE Newsitem of 9 September 2015 discussed some peculiarities of polar faculae, the relatively bright points that sometimes can be seen near the solar poles. On the highly contrasted SDO/HMI image from 11 January 2016 underneath, two red arrows point out some of these polar faculae. There is a significant difference in outlook between these puny dots and the much brighter main zone faculae (dashed blue), as well as the much bigger and darker sunspots (green).

The duration of solar flares

In several previous news items, solar flares are often tagged as impulsive or long duration events, meaning they last resp. only a few minutes or more than one hour. This news item will focus on the typical duration of a solar flare, thus providing a reference to appreciate the extreme duration of some solar flares.

M-class brothers

The two strongest events that occurred during last week were two M-class flares. They were both born from active region (AR) NOAA 2473, which was also responsible for most of the M-class flaring the week before. This region was declining in sunspot area, but remained magnetically complex throughout its entire transit over the solar disk. So how do these two medium flares compare to each other?

New Years Eve Sun

credits Mark Brennan, Belgium


Farside eruption


Last week was -once again- a nice example of a relatively inactive Sun. It was quite a surprize when CACTus detected a partial halo coronal mass ejection (CME) in SOHO's coronagraphic imagery on 07 December. Indeed, starting at 15:12UT, a CME having a width of about 210 degrees could be seen emanating from the Sun's east limb travelling at a plane-of-the-sky speed of about 650 km/s.

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