Update, 7:20 A.M. ET,06 November 2003: NOAA's Space Environment Center (SEC) has classifiedthis flare as an X28, making it in fact the strongest ever recorded. A sourcetold SPACE.com that the SEC is aware other scientists still think theflare was even stronger. The article below remains as it originally appeared. -RRB
A flare released by theSun on Tuesday could be the most powerful ever witnessed, a monster X-rayeruption twice as strong as anything detected since satellites were capable ofspotting them starting in the mid-1970s
The strongest flares on record, in 1989 and 2001, were rated at X20. This oneis at least that powerful, scientists say. But because it saturated the X-raydetector aboard NOAA's GOES satellite that monitors the Sun, a full analysis hasnot been done.
The satellite was blinded for 11 minutes.
Craig DeForest, a solar physicist at the Southwest Research Institute, saidothers in his field are discussing the possibility that Tuesday's flare was anX40.
"I'd take a stand and say it appears to be about X40 based onextrapolation of the X-ray flux into the saturated period," DeForest told SPACE.com.
That estimate may even be conservative, he said.
The flare leapt from a sunspot that is rotating off the visible face of theSun, so its effects were not directed squarely at Earth. Nonetheless, a radioblackout occurred at many wavelengths as the storm's initial radiation arrivedjust minutes after the eruption. Radio blackouts are ranked from R1 to R5 byNOAA's Space Environment Center, the space counterpart to the National WeatherService.
"This is an R-5 extreme event," said SEC forecaster Bill Murtagh."They don't get much bigger than this."
Paal Brekke, deputy project scientist for the SOHO spacecraft, which monitorsthe Sun, also told SPACE.com the outburst could be as strong as X20"or much higher."
At least X20
The SEC is still evaluating the flare's ranking.For now, they are calling it an X20+, indicating that it is indeed the mostpowerful on record. The only known event that might outrank it is an 1859solar storm that zapped telegraph linesin an era when solar monitoring could not provide an evaluation of a flare'sstrength.
The radiation flare was accompanied by a coronal mass ejection (CME), anexpanding cloud of charged particles -- actual matter that moves at supersonicspeeds but not as fast as light. Had this CME been aimed at Earth, scientistswould have feared a potential space storm unlike anything seen in the Space Age.
As it is, the expanding cloud is expected to provide a glancing blow sometimeThursday.
The storm, if it arrives, will not likely be major, forecasters say. But aswith all space weather, satellites and communication systems will be at risk ofdisruption or damage. Colorful sky lights called auroras may be active at highlatitudes and possibly into northern U.S. states and Europe.
More to come?
Tuesday's flare was generated by Sunspot 486, which is about 15 times thesize of Earth.
Sunspots are dark, cooler regions of the solar surface, areas of pent-upmagnetic activity. They're a bit like caps on a shaken soda bottle, andupwelling matter and energy can blow at any moment. Scientists cannot predictwhen a flare will occur.
During the past two weeks, number 486 and two other large sunspots set offnine other major flares. It was one of the stormiest periods of activity everwitnessed, all experts agree. The number of intense flares, some shooting outwithin a day of another, was unprecedented. Auroras were seen as far south asTexas and Florida.
The second strongest flare in this historic two-week series was an X17 eventon Oct. 28. It was aimed at Earth and generated severe geomagnetic storming whenit blew past the planet less than 24 hours later.
A period of relative calm is now expected on the solar surface. But anotherround is possible.
The Sun spins once on its axis once every 25 days at its equator, carryingsunspots around. Sunspots can last days or weeks. Any of the three that haverotated off the right side of the Sun could return in about two weeks on theleft side and, possibly, send more major storms toward Earth.