Bernanke was asked at his news conference whether the flare-up in Cyprus signals that the U.S. financial system might be more vulnerable than bank "stress tests" have shown.
The latest flare-up in the bilateral relationship comes as the U.S. is withdrawing its forces and negotiating with Mr. Karzai what American military presence, if any, will remain in Afghanistan after the coalition's mandate ends next year.
Radiation from the flare was so intense it saturated the X-ray detectors on two spacecraft used by the U.S. government to determine the strength of the solar blasts.