Solar flare radiation

The largest solar flare in four years erupted Monday. Its radiation is expected to reach Earth today and Friday and perhaps interfere with communication systems, power grids and navigation satellites. It might also enhance the northern lights.Radiation from the largest solar flare in four years is expected to reach the Earth Thursday and Friday, potentially interfering with communication and navigation satellites and disrupting ground-based communication networks and power grids.

The rain of charged particles from the so-called coronal mass ejections, or CMEs, should also enhance the northern lights, also known as the Aurora Borealis, making them both more prominent and visible farther south, perhaps even into the northern tier of the United States, experts said.

The solar flare, which erupted Monday, occurs when magnetic field lines on the sun's surface in effect get short-circuited, releasing large amounts of energy into space. Three such events occurred Monday, the largest of them a so-called class X event — the most powerful form of solar flare. Astronomers have been expecting the sun to ramp up its activity after several years of quiescence during its normal 11-year cycle of activity. Maximum solar activity is expected in 2013.