In the early hours of this morning (Monday, 02:17 UT), the sun exploded to life with an X1.7 flare. X-class flares are the most energetic type of flare the sun can generate. Although this flare was at the lower end of the the X category, it was the most powerful of the year, so far.
Although the Earth has a pretty hefty atmosphere that can shield us against the X-ray radiation generated by flares of this type, this morning’s event occurred beyond the limb of the sun, meaning that the bulk of the energy generated was directed away from Earth. A coronal mass ejection (CME) was also generated, but that too was fired safely away from Earth. No other planets are thought to be in the path of the expanding bubble of magnetized plasma, although NASA’s Spitzer space telescope and Epoxi comet chaser are in the line of fire, according to Spaceweather.com.
The flare site may be facing away from the Earth, but NASA’s Solar Dynamics Observatory was able to see the eruption, imaging it across an array of extreme ultraviolet wavelengths. With the SDO’s awesome resolution, wonderful detail of the unfolding flare could be observed.
Starting in the lower corona, solar flares are a product of extreme magnetic pressure; as magnetized loops of plasma push up from the sun’s interior, creating active regions (and sunspots), the conditions may be right for magnetic reconnection to occur. During such events, massive quantities of energy are generated by the rapidly-accelerated coronal plasma, generating huge quantities of radiation. Through the SDO’s high-definition eye, the accelerated plasma from this flare event can be seen propagating around a huge loop of magnetism — known as a coronal loop.
We may have avoided feeling the full force of this flare, but the active region that generated it probably hasn’t finished yet. Over the next few days, the active region will rotate into view, potentially generating more flares, some that may impact Earth.
The sun is currently undergoing a very exciting phase of its approximate 11-year cycle. Known as “solar maximum,” this is a time when an increased frequency of flares and CMEs can be expected. Although this cycle’s solar max is “below average,” it can still surprise us, generating some very powerful eruptions like today’s event.
Image credit: NASA/SDO