Excerpt from mashable.com
The northern tier of the U.S., from Washington State to Michigan, as well as parts of Europe and Asia saw the colorful phenomenon on Monday night, just as the G4 solar storm was hitting Earth's magnetic field. The solar storm intensified on Tuesday, and if it remains at a high intensity through much of the night, which scientists say is possible, locations all the way south to Washington, D.C. may have a decent chance at catching the lights.
Mostly clear skies from the Upper Midwest into the Ohio Valley and eastward to the Mid-Atlantic will aid in creating favorable viewing conditions. For the best chance to see the Northern Lights, formally known as the Aurora Borealis, try to get away from any light pollution in large cities or streetlights in rural areas, and look north, particularly in the wee hours of the morning.
If you're reluctant to head out into the cold air at 2 a.m., there are some Internet resources to check first that will help you determine how high a chance there is that you'll see the Aurora.
There is no precise way to predict the Aurora (even the forecast for the geomagnetic storm was off in both intensity and timing), but real-time monitoring, plus Twitter, can provide a good idea of how likely it is that a widespread event is occurring.
The Space Weather Prediction Center, which is part of the National Oceanic and Atmospheric Administration (NOAA), has a variety of tracking tools on its website.
One index to check out is the Planetary Kp-Index, which measures the magnitude of geomagnetic storms. NOAA also has realtime maps of Aurora probabilities and short-term model forecasts.
So far, the Kp Index has peaked at an eight on a nine-point scale, although as of 6 p.m. ET it had declined to a seven. Those readings are typically associated with Northern Lights displays as far south as Northern California, as far east to Delaware, and points northward. However, NOAA scientists told the media on Tuesday that solar storms of this intensity can result in Aurora displays that reach all the way into the Southeast, including states such as Alabama and Tennessee.
Reports of a vivid Aurora display on Tuesday night have been coming in from Northern Europe, with more to come as night falls across the U.S. and Canada.
The geomagnetic storm, which is just one notch below the highest category of solar storm, began at about 10 a.m. ET on Tuesday, according to the Space Weather Prediction Center. The geomagnetic storm is the result of a pair of coronal mass ejections, or CMEs, that left the Sun on March 15 and are now interacting with Earth's atmosphere and geomagnetic field.
In a press briefing on Tuesday, NOAA scientists said the two CMEs may have unexpectedly combined as they sped toward Earth, which could explain why the geomagnetic storm has been so strong.
Coronal mass ejections, which are essentially magnetic clouds ejected at high velocity from the sun, can affect the electricity grid, radio transmissions and GPS signals, among other things, when they interact with the planet's magnetic field. According to NOAA, there had not been any reported abnormalities in the U.S. power grid as of noon eastern time on Tuesday.
In the Southern Hemisphere, unusually vivid displays of the Southern Lights, or Aurora Australis, also were observed on Monday, and may occur again Tuesday.