After 3 a.m. on April 11, this year's strongest sunflare -- which are powerful bursts of radiation -- peaked.
Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, according to NASA. But when they're intense enough, they can disturb the atmospheric layer where GPS and communications signals travel, which disrupts radio signals for as long as the flare is ongoing -- anywhere from minutes to hours.
NASA also says that increased numbers of flares are common at the present time, since the sun's normal 11-year activity cycle is ramping up toward solar maximum, which is expected in late 2013. Humans have tracked this solar cycle continuously since it was discovered, and it is normal for there to be many flares a day during the sun's peak activity.