Active Region 1302 (September 2011)

Each of the dark cores in this image is larger than Earth and the entire active region stretches more than 100,000 km from end to end.

(NASA/SDO/HMI)

Without the Sun there would not be life on Earth. However, the Sun occasionally acts up in the form of solar storms; the dangerous effects of which can sometimes be felt here.

The subject of space weather deals with the impacts of these solar storms on Earth and, like the "regular" weather we normally cover, space weather can at times be unpredictable.

The amount of solar storm activity cycles about every 11 years. We still don't fully understand the solar cycle. In fact, the current cycle began later than and the peak of the cycle - known as solar maximum - is , more than a year later thanpredicted.

The effect on Earth of solar storms can be grouped into three categories:

Radio blackouts - occur shortly after solar stormRadiation - occur within hours of solar stormGeomagnetic storms - occur one to four days after solar storm

Strong geomagnetic storms like the one in September 2011, can occur several hundred times per solar cycle but fortunately for us, the effects on Earth from most storms are not directly felt.

This particular storm was caused when a coronal mass ejection from Sunspot 1302 lashed but fortunately only sideswiped the Earth's magnetic field.

A coronal mass ejection, or CME, is a massive chunk - up to billions of tons - of charged particles or plasma violently launched from the Sun’s outer atmosphere during solar storms. CMEs can eject at speeds of up to millions of miles per hour.

These charged particles then travel millions of miles toward Earth and interact with the Earth's magnetic field. It's this interaction between the energized particles and the magnetosphere that goes on to cause sometimes very serious problems on Earth.

The most obvious impact from a storm is usually increased aurora, more commonly known as the northern (or southern) lights.

Other effects of geomagnetic storms are temporary degradation of high-frequency radio communication and satellite navigation. Commercial aircraft that fly over the poles often have to change routes during strong solar storms to avoid communication or navigation problems.

Satellites in Earth's orbit can also be affected by geomagnetic storms. Sensitive electronics on satellites can be damaged by solar radiation and geomagnetic storms. With much of our daily lives dependent on satellite communication, interruptions to everyday conveniences can occur with the most intense storms.

The most significant threat posed by severe geomagnetic storms is on the power grid. Changes in the Earth’s magnetic field can induce electrical current in transmission lines, which could damage transformers and other equipment. Warnings of impending geomagnetic storms can allow power companies to take steps to minimize damage.

The worst geomagnetic storms, especially ones that occur at a time of heavy power grid usage, could cause widespread and possibly long lasting power outages.

The federal government is working with partners in industry and academia to develop plans to deal with the increase in solar activity as solar maximum approaches.

The Space Weather Prediction Center, part of the National Weather Service, is responsible for monitoring and forecasting space weather. Just like NWS issues watches and warnings for tornados and hurricanes, SWPC issues watches and warnings for solar storms that can impact us here on Earth.

SWPC noted that the CME on September 26, 2011 largely missed Earth (see CME Ejection Animation), so the intensity and duration of the associated geomagnetic storm was less than it could have been with a more direct hit.

Even though we have likely passed the peak of the current solar cycle, strong solar storms are still possible. As a result, we will likely see more CMEs affecting Earth in the coming years.

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