Space weather researchers say a series of strong solar flares could disrupt communication satellites, GPS and short-wave radio around the world over the next few days.
Solar flares are large eruptions of electromagnetic radiation from the Sun. They can expose Earth to masses of ejected protons and other charged particles.
Officials with Japan's National Institute of Information and Communications Technology say solar flares of the most intense class were observed five times between Wednesday and early Friday local time.
They say the geomagnetic storm could reach Earth as early as Friday night.
The director of the NICT's Space Environment Laboratory, Tsugawa Takuya, says it is extremely rare for five strong solar flares to occur in such a short period.
He says the ejected particles are unlikely to affect human health, but warns that GPS location data and some radio communications could be disrupted over the coming days.