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Tour de France


The Sun had its own mountain stage this month, with soaring sunspot numbers during the first week, then a fast decline until sea-level values (that is: zero sunspots) were reached on the 17th, followed by a gradual recovery to more moderate sunspot numbers. This can be seen in the evolution of the estimated daily sunspot number as compiled by SILSO, and shown in graph underneath.

Sunspot Summer Festival


Coinciding with the traditional summer festivals, the Sun started a party on its own by producing a flurry of relatively large and complex sunspot groups. While on 29 June, the daily sunspot number was only 62, by 5 July it was at an estimated 152. The 10.7cm radio flux happily joined the festivities, by rising over the same time period from 126 to 193 solar flux units.

Backside eruption


Late on 26 June, an eruption took place in an active region just behind the Sun's east limb. The event led to some spectacular images of the associated coronal mass ejection (CME) and post-flare coronal loops.

The eruption started around 21:00UT, and the expanding CME can be seen in extreme ultraviolet (EUV) in SDO, STEREO-B and PROBA2 imagery, as indicated with the dashed orange lines in the images underneath.

Up, up and away!...


Solar filaments are clouds of ionized gas above the solar surface squeezed between magnetic regions of opposite polarity. Being cooler and denser than the surrounding plasma, they appear as dark lines when seen on the solar disk using special filters. On 19 June, a filament north of sunspot region NOAA 2093 became unstable and swirled away from the Sun.

The 3 X-class flares from NOAA 2087


On 10 and 11 June, the not so big but complex sunspot group NOAA 2087 produced three X-class flares in less than 24 hours. On 10 June, there was an X2.2 peaking at 11:42UT, followed by an X1.5 at 11:52UT. On 11 June, an X1.0 peaked at 09:06UT. This brings the X-class flare counter for the current solar cycle to 34. The associated coronal mass ejections (CME) were not directed to Earth, though from the second CME a glancing blow was expected. In the end, no obvious CME-signature was observed in the solar wind data.

A snaky filament lifts off


Solar filaments are clouds of ionized gas above the solar surface squeezed between magnetic regions of opposite polarity. Being cooler and denser than the surrounding plasma, they appear as dark lines when seen on the solar disk using special filters. At the solar limb, the same features shine bright and are called prominences.

STEREO: News from the other side...


Launched on 25 October 2006, STEREO (Solar TErrestrial RElations Observatory) consists actually of two nearly identical spacecraft. One of the spacecraft is ahead of Earth in its orbit (STEREO-A), the other trailing behind (STEREO-B), and both are at distances from the Sun similar to Earth's.

Our 12 points go to... NOAA 2056!


From 5 till 18 May, sunspot Group NOAA 2056 made its transit over the solar disk. This group was not especially big, but initially had a complex trailing sunspot section that resulted in an M5 flare on 8 May (see previous Newsletter). Over the next few days, the group gradually simplified and almost completely disintegrated.

Prelude to a solar flare


On 8 May, an M5 flare took place in sunspot region NOAA 2056. This active region was part of a cluster of sunspot groups that had appeared from behind the Sun's east limb between 4 and 6 May.

A movie of the event can be seen here.

Lunar eclipses and solar cycles


On 15 April, a total lunar eclipse was visible from the America's and the Pacific. Some websites were buzzing about the "Blood Moon", as if werewolves and witches were going to team up and unleash a veritable apocalypse upon us. Fortunately, reality was a lot less dreadful and a lot more beautiful.

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