October 2014 – SPACE – At 17:09 UT (12:09 p.m. EDT) today (Saturday), active region (AR) 2192 erupted with another X-class flare directed at Earth. This is the second powerful eruption in less than 24 hours to be triggered from the large sunspot that occupies the region. Today’s flare registered at X1 on the solar flare Richter Scale, the most powerful class of flare, but weaker than Friday’s X3-class flare. Further radio black-outs have been recorded on the daytime side of the Earth, but, once again, today’s flare did not generate a significant coronal mass ejection (CME). There was already a high probability that active region (AR) 2192 was going to erupt with a powerful solar flare, so it came as little surprise when, yesterday, the huge sunspot fired a powerful X-class flare right at Earth. And we sure did feel its impact.
The sun has a myriad of effects on Earth during intense solar activity. When a flare erupts in the lower solar corona, the radiation generated can cause extreme ionization in the upper atmosphere, interfering with the propagation of high-frequency radio waves, meddling with global communications. Signals from global positioning satellites (GPS) can be interrupted, air traffic communications can get patchy and the interference can even be measured by amateur radio operators. On Friday at 21:40 UT (4:40 p.m. EDT), AR2192 erupted with an X3-class flare as the huge sunspot was facing Earth. Like looking down the barrel of a solar gun, the region crackled with X-ray and extreme-utraviolet (EUV) radiation that immediately washed over the Earth’s ionosphere. A “radio blackout” was reported across the sun-facing side of our planet, including much of the US. With the immediate effects of the X-class flare (which is the most powerful class of flare) subsiding, solar scientists monitored the region for any trace of a coronal mass ejection that may have been associated with the flare.
Coronal mass ejections, or CMEs, are magnetic bubbles of highly-energetic particles that are hurled into space from the sun’s lower corona. They may take hours or days to reach Earth orbit, but their impact on our planet’s magnetosphere can be dramatic. However, it appears that yesterday’s flare did not launch a CME. In fact, none of the dozens of flares (all of lesser energies than yesterday’s event) AR2192 has produced have generated a CME, which is interesting. Although CMEs and flares are thought to be triggered by a common phenomenon (magnetic reconnection in the lower corona), they are not necessarily triggered at the same time. A flare may occur without a CME and vice versa. But for an active region not to generate any significant CMEs, and yet still generate a large number of flares, is rare. Needless to say, space weather forecasters will be studying this large sunspot — the largest sunspot seen on the sun for 24 years — until it rotates out of view to understand what is going on. –Discovery