Coming our way - yet another powerful solar flare
12 April 2001
An angry Sun fired off another powerful X-class flare on Tuesday, 10April. X-class flares are the most powerful classification, andthis flare, rated X-2, was the most recent in a series that includedan X-20 flare, one of the most powerful flares in 25 years. Aneruption of electrified gas, called a Coronal Mass Ejection (CME),was observed shortly after Tuesday's flare and is heading our way.Depending on the orientation of the magnetic field carried by the CMEcloud, it may cause a magnetic storm when it impacts the Earth's ownmagnetic field.Tuesday's flare, which occurred at about 5:25 UT, came from a region on the Sun designated active region 9415. This region is rotating with the Sun and currently points towards Earth. Active region 9415 includes a sunspot group and has generated three X-class flares this month, including an X-5 flare on Friday, 6 April.
The CME associated with Tuesday's flare was expected to arrive at Earth Tuesday evening or early Wednesday morning, between 0100 and 0600 UT. Moderate to strong storm levels (rated G2 - G3) will be possible during 11 - 12 April as the CME passes Earth, according to the National Oceanic and Atmospheric Administration's Space Environment Center (NOAA SEC), Boulder, Colorado.
"This is another in an exciting series of solar events during this maximum epoch of the current solar activity cycle," said Dr Ernie Hildner, Director of the NOAA SEC. The NOAA SEC classifies flares according to their power and estimates, tracks, and evaluates the effects of solar activity on the space environment near Earth.
Solar flares, among the solar system's mightiest eruptions, are tremendous explosions in the atmosphere of the Sun capable of releasing as much energy as a billion megatons of TNT. Caused by the sudden release of magnetic energy, in just a few seconds flares can accelerate solar particles to very high velocities - almost to the speed of light - and heat solar material to tens of millions of degrees.
CME eruptions, often associated with flares, are clouds of electrified, magnetic gas weighing billions of tons ejected from the Sun and hurled into space with speeds ranging from 20 to 2000 kilometers per second. The CME associated with Tuesday's flare was thrown from the Sun at the high end of this scale, estimated at 1600 kilometers per second. CMEs can be even more powerful than flares - the total energy in a good-sized CME is about 100 times greater than that of the largest flares.
Depending on the orientation of the magnetic fields carried by the CME cloud, Earth-directed CMEs cause magnetic storms by interacting with the Earth's magnetic field, distorting its shape and accelerating electrically charged particles (electrons and atomic nuclei) trapped within. Severe solar weather is often heralded by dramatic auroral displays (northern and southern lights), but magnetic storms are occasionally harmful, potentially disrupting satellites, radio communications, and power systems.
Active region 9415 is expected to produce more solar outbursts because it has a complex magnetic field structure. Active regions are areas near the Sun's visible surface where a concentration of distorted magnetic fields exists. Sunspots are often found in active regions because the strong magnetic fields there slow the flow of heat from the Sun's interior, keeping part of the region slightly cooler than its surroundings, which causes it to appear as a dark spot on the solar surface. Active regions frequently generate stormy solar activity as the distorted magnetic fields generate flares and CMEs via the sudden release of magnetic energy.
