Size of 'whopping' solar flare scaled up by NZ scientists

5.00pm

The size of a "whopping" solar flare which hit Earth last November has been dramatically scaled up after research by Otago University physicists.

On November 4, the largest solar flare ever recorded exploded from the Sun's surface, sending an intense burst of radiation streaming towards Earth.

Scientists classify solar flares according to their brightness in the X-ray wavelengths. They had been forced to estimate the size of the flare because before the storm peaked, X-rays overloaded satellite detectors.

The United States National Oceanic & Atmospheric Administration Space Environment Centre estimated the flare as rating X28, the most powerful in recorded observational history.

However, the Otago University physicists used radio wave-based measurements of the X-rays' effects on Earth's upper atmosphere to dramatically revise the size of the flare, up to "a whopping X45".

The findings of Associate Professor Neil Thomson, Dr Craig Rodger and Emeritus Professor Richard Dowden will be published tomorrow in the American Geophysical Union's Geophysical Research Letters.

The trio's calculations showed the flare's X-ray radiation bombarding Earth's atmosphere was equivalent to that of 5000 suns, though none of it reached the Earth's surface.

"This makes it more than twice as large as any previously recorded flare," Prof Thomson said in a statement.

"If the accompanying particle and magnetic storm had been aimed at the Earth, the damage to some satellites and electrical networks could have been considerable."

Prof Thomson said the Otago research would not have been possible without data provided by the Space Environment Centre.

"We used their solar measurements to calibrate the response of the atmosphere to X-rays, so when this event overloaded the satellite detectors we were in a unique position to make this measurement," he said.

"Given that any future flares are unlikely to be large enough to overload the ionosphere, we believe that our new method has great advantages in determining their size in the event of satellite detector overloads."

- NZPA