Zonnevlammen #2: Recht op aarde af

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Plasmawolk bereikt aarde
De plasmawolk die maandag de zon heeft verlaten, heeft vrijdagmorgen de aarde bereikt. De 'coronal mass ejection' botste omstreeks 02.00 uur Belgische tijd met het magnetisch veld van de aarde. De impact was niet zo hevig als enkele dagen eerder werd verwacht.

Donderdag had de Koninklijke Belgische Sterrenwacht al laten weten dat de plasmawolk hoogstwaarschijnlijk was vertraagd door de zonnewind en door twee voorafgaande minder snelle plasmawolken.

De wolk heeft hierdoor een deel van zijn energie verloren, wat verklaart dat de impact minder energetisch was. De voorspelling luidde dat er in België geen poollicht te zien zou zijn.
Zonnemassa

Een plasmawolk is een grote hoeveelheid zonnemassa die wordt weggekatapulteerd. Zo'n wolk bereikt meestal na twee tot vijf dagen onze planeet als ze onze richting uitvliegt. Een plasmawolk kan een magnetische storm veroorzaken.

Radiocommunicatie wordt bemoeilijkt of kan wegvallen, navigatiesystemen ondervinden nadeel, elektrische stromen kunnen geïnduceerd worden in elektriciteits- en pijpleidingen. Bij magnetische stormen is de breedtegraad belangrijk. Of het dag of nacht is, maakt niet uit.

Het magnetisch veld van de aarde beschermt ons tegen de impact van plasmawolken.

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Scientists warn for solar 'Katrina'
The sun is waking up from a long quiet spell. Last week it sent out the strongest flare for four years – and scientists are warning that earth should prepare for an intense electromagnetic storm that, in the worst case, could be a “global Katrina” costing the world economy $2,000bn.

Senior officials responsible for policy on solar storms – also known as space weather – in the US, UK and Sweden urged more preparedness at the annual meeting of the American Association for the Advancement of Science in Washington.
“We have to take the issue of space weather seriously,” said Sir John Beddington, UK chief scientist. “The sun is coming out of a quiet period, and our vulnerability has increased since the last solar maximum [around 2000].”

“Predict and prepare should be the watchwords,” agreed Jane Lubchenco, head of the US National Oceanic and Atmospheric Administration. “So much more of our technology is vulnerable than it was 10 years ago.”

A solar storm starts with an eruption of super-hot gas travelling out from the sun at speeds of up to 5m miles an hour. Electrically charged particles hit earth’s atmosphere 20 to 30 hours later, causing electromagnetic havoc.

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APPROACHING ACTIVE REGION: A significant active region is about to emerge over the sun's northeastern limb. The underlying sunspots are not yet visible from Earth, but the region's towering magnetic canopy is already in view. NASA's Solar Dynamics Observatory (SDO) took this picture during the early hours of Feb. 23rd:

A better view is had by NASA's STEREO-B probe, stationed over the sun's eastern limb where it can see the region from top down. Recent movies beamed back by STEREO-B show flashes of extreme UV radiation and hints of magnetic instability. This could herald a period of renewed solar activity when the region turns toward Earth in the days ahead. Or the action could peter out beforehand. Stay tuned for updates.
Bron: Spaceweather.com

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The quiet didn't last long. Earth-orbiting satellites detected an M3-class solar flare at 0735 UT on Feb. 24th. The source was an active region located just behind the sun's eastern limb. The eruption produced strong radio emissions, a coronal mass ejection (not Earth directed), and this spectacular picture taken by NASA's Solar Dynamics Observatory:

The active region responsible for this blast will emerge over the eastern limb during the next 24-48 hours, setting the stage for possible geoeffective solar activity. Stay tuned for updates.

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Another X-flare heading for earth?
X-FLARE: March 9th ended with a powerful solar flare. Earth-orbiting satellites detected an X1.5-class explosion from behemoth sunspot 1166 around 2323 UT. A movie from NASA's Solar Dynamics Observatory shows a bright flash of UV radiation plus some material being hurled away from the blast site:

A first look at coronagraph images from NASA's STEREO-B spacecraft suggests that the explosion did propel a coronal mass ejection (CME) toward Earth. This conclusion is preliminary, however, so check back later for updates.

After four years without any X-flares, the sun has produced two of the powerful blasts in less than one month: Feb. 15th and March 9th. This continues the recent trend of increasing solar activity, and shows that Solar Cycle 24 is heating up. NOAA forecasters estimate a 5% chance of more X-flares during the next 24 hours

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Solar activity heats up
April 14, 2011: If you've ever stood in front of a hot stove, watching a pot of water and waiting impatiently for it to boil, you know what it feels like to be a solar physicist.

Back in 2008, the solar cycle plunged into the deepest minimum in nearly a century. Sunspots all but vanished, solar flares subsided, and the sun was eerily quiet.

"Ever since, we've been waiting for solar activity to pick up," says Richard Fisher, head of the Heliophysics Division at NASA Headquarters in Washington DC. "It's been three long years."

Quiet spells on the sun are nothing new. They come along every 11 years or so—it's a natural part of the solar cycle. This particular solar minimum, however, was lasting longer than usual, prompting some researchers to wonder if it would ever end.

News flash: The pot is starting to boil. "Finally," says Fisher, "we are beginning to see some action."

As 2011 unfolds, sunspots have returned and they are crackling with activity. On February 15th and again on March 9th, Earth orbiting satellites detected a pair of "X-class" solar flares--the most powerful kind of x-ray flare. The last such eruption occurred back in December 2006.

Another eruption on March 7th hurled a billion-ton cloud of plasma away from the sun at five million mph (2200 km/s). The rapidly expanding cloud wasn't aimed directly at Earth, but it did deliver a glancing blow to our planet's magnetic field. The off-center impact on March 10th was enough to send Northern Lights spilling over the Canadian border into US states such as Wisconsin, Minnesota, and Michigan.