Proton event!

At last, another proton event in 2015! It is only the 4th event so far this year, the other three having occurred resp. on 18, 22 and 27 June (Note 1). With 23 pfu (Note 2), the greater than 10 MeV (Note 3) proton flux constituted only a minor radiation event (Note 4). The largest event this year took place on 22 June (1070 pfu), and the largest proton event so far this solar cycle was recorded on 8 March 2012 (6530 pfu, following an X5 flare from NOAA 1429 - Note 5).


No, this news item is not going to make publicity for a social network!... Instead, it will simply take a closer look at some sunspot groups that at first sight seem to be clearly separated, but upon examination of their magnetic field configurations, are connected to each other after all.

A swiftly blowing wind

On 04 October, a rather large transequatorial coronal hole (CH) transited the Sun's central meridian. According to LMSAL data, it had a surface area of nearly 150 times that of the Earth. For comparison: NOAA 2192, the largest sunspot group so far this solar cycle, was about 9 times smaller!

A two-stage CME

On 30 September, a prominence near the southwest solar limb got ejected into space. Prominences are clouds of plasma (charged particles) which are suspended in the corona, squeezed between large magnetic fields of opposite polarity, but denser and cooler than the surrounding coronal plasma. The structure had been visible during the last 2 weeks, before the surrounding magnetic field became unstable and ejected it into space starting around 07:30UT.

Rise and Shine!...

Rise and shine: That's exactly what active region NOAA 2422 did last week. From nothing, it started to emerge on 22 September as a simple bipolar sunspot region. Over the next few days, it developed into a fully mature sunspot group, gradually increasing its magnetic complexity. Until the 26th, it produced only a handful of C-class flares. However, by then, it had developed significant delta structures, i.e. spots of opposite magnetic polarity within the same penumbra, in its middle portion.

Another head-to-tail collision

NOAA 2415 started out as a rather quiet and dull sunspot group, until during the afternoon of 14 September a bipolar magnetic flux emerged right in front (to the southwest) of NOAA 2415's main leading spot. During the next few hours and days, the newly bipolar region developed further, with the positive (white) polarity spots drifting away to the west. However, its negative (black) trailing spots remained very close to the original main spot (white), and started to interact with each other.

PROBA2 observes an annular solar eclipse

This item was written by Matthew West and the PROBA2-team, and can also be read at their P2SC webpage.

Polar faculae near the Sun's south pole


NOAA 2403, an active region visible during the last 2 weeks of August, has been one of the largest and most complex sunspot groups so far this year. Its maximum surface area was 7 times that of the Earth, and its mixed magnetic polarities were the source of numerous small and moderate solar flares. No wonder that many astronomers took the time for a photoshoot of this marvellous sunspot group!

Holy loopiness!

Solar activity has been very low over the last few weeks, with the last big solar flare already dating back to 25 June. That day, NOAA 2371 produced the last and strongest of its series of 6 M-class flares. The M7.9 flare peaked at 08:16UT and its space weather effects were extensively discussed in the 3 July 2015 Newsletter.



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