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Thursday, 11 September 2014

Extreme solar storm approaches Earth



A powerful solar flare sparked on an Earth-facing section of the sun. A subsequent coronal mass ejection is expected to reach our planet later in the week, possibly causing disruptions of communication and power grids.

The flare was unleashed by the sun on Wednesday and was estimated at X1.6, putting it in the strongest ‘extreme’ class of solar flares. It was launched from a sunspot called Active Region 2158 and was caught on camera by NASA’s Solar Dynamics Observatory spacecraft, reports Space.com. The same region produced a smaller flare a day before that.

The flare was accompanied by the release of superhot plasma, a coronal mass ejection, with the cloud expected to reach Earth later on Friday. Luckily, most of it is expected to pass north of Earth, causing a relatively week solar storm. Power grids may experience some fluctuations, as the plasma would affect the planetary magnetic field, but it poses little danger either to anyone down here or to crew members of the International Space Station.

"We're not scared of this one," Tom Berger, director of the Space Weather Prediction Center in Boulder, Colorado told AP.

On the bonus side, the space weather events may trigger colorful aurora borealis in regions usually too far from the North Pole to produce them, which is good news for enthusiasts.

The frequency and intensity of solar flares depends on the phase of the 11-year solar cycle. The sun is currently close to the peak of Cycle 24. But our star was relatively quiet this cycle, with the maximum phase measured in the weakest in about 100 years.

The Wednesday flare was strong, but far from being the strongest this year. In February a monster flare was measured at X4.9. The absolute record in solar flare recorded was an X28 in November 2003, while the Carrington Super Flare of 1859, which fired telegraph systems at the time and would cause catastrophic damage if it happened in modern times, is estimated at well over X40.

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Coronal Mass Ejections

Large flares are often associated with huge ejections of mass from the Sun, although the association is not clear. These coronal mass ejections (CMEs) are balloon-shaped bursts of solar wind rising above the solar corona, expanding as they climb. Solar plasma is heated to tens of millions of degrees, and electrons, protons, and heavy nuclei are accelerated to near the speed of light. The super-heated electrons from CMEs move along the magnetic field lines faster than the solar wind can flow. Rearrangement of the magnetic field, and solar flares may result in the formation of a shock that accelerates particles ahead of the CME loop. Each CME releases up to 100 billion kg (220 billion lb) of this material, and the speed of the ejection can reach 1000 km/second (2 million mph) in some flares. Solar flares and CMEs are currently the biggest "explosions" in our solar system, roughly approaching the power in ONE BILLION hydrogen bombs!

Fast CMEs occur more often near the peak of the 11-year solar cycle, and can trigger major disturbances in Earth's magnetosphere, known as space weather.

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Update 12/09:

The shock front now crossing interplanetary space should reach Earth on Friday morning. SWPC forecasters are predicting a moderate G2 geomagnetic storm on Friday and more robust G3 levels through Saturday. These could trigger displays of auroras over locations roughly northward of latitude 45° north (Oregon, Illinois, New England, and northern Europe).

Although the "northern lights" can appear anywhere in the sky, would-be aurora watchers should look first toward north. Most displays appear as shimmering greenish curtains of light suspended in the sky. Stronger auroras can appear tinged with blue or red.

It is interesting that a Swift X-ray spike alert was sent out that same day just over 15 hours earlier.  The X-ray spike was detected on the 10th at 1:02 AM Univeral Time, while the solar outburst occurred at 6:48 PM Universal Time.  Here is some information about it from Sky and Telescope website.

An abrupt spike in X-ray emission was detected September 10th coming from the Galactic center, Sgr A*.

One possibility is that this gamma ray signal may have been associated with the core outburst and this could have somehow triggered the subsequent solar outburst.  But this is just speculation.
New data shows that the X-ray emission from the Galactic center has stayed at its pre burst level, which is good news.



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Space.com
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Related:
Evidence of superwave propagation in a nearby galaxy