People across the East End, and indeed much of the northern part of the United States, were treated to a vivid display of the aurora borealis on Thursday night, prompting many to look out their windows, pull over their cars, post pictures on Instagram, and wonder: Why?
Essentially, the northern lights, or aurora borealis, are created when high-speed particles from the sun "excite gases in the upper atmosphere," usually oxygen and nitrogen, said Jeffrey Katz, a member of the advisory board for the Hamptons Observatory. "So basically, the ionized gas causes the glow."
For the lights to be visible this far south, "you need a more intense reaction, and that usually means when you get a big solar storm," Dr. Katz said, and a solar flare is typically involved.
When there is a mass ejection from the sun, "those particles interact with particles in the earth's atmosphere, and it can give off the lights that we saw," said James Tomasini, a meteorologist with the regional branch of the National Weather Service, based in Upton. In fact, the colors can depend on which particles interact.
A coronal mass ejection was detected on Tuesday, Oct. 8, Mr. Tomasini said, and scientists determined that it was likely to arrive on Oct. 10.
As for whether the lights will be visible again Friday night, Dr. Katz was optimistic, but Mr. Tomasini had some doubts, based on the Space Weather Prediction Center's estimates.
"The geomagnetic storm we saw last night reached level 4, so the higher the level, the further south you can see the northern lights. Right now, they're predicting down to a level 2 for the rest of today," Mr. Tomasini said on Friday afternoon. Nonetheless, he said that he was not positive about the predictions.
"It's supposed to be possible again tonight," said Dr. Katz, who remembers seeing the northern lights in 1967.
