What to know before getting excited about the aurora

As hype for the potential to see the aurora borealis this weekend increases, thousands of people are now eager to step outside around midnight tonight to glowing, moving multicolored lights in the night sky.

They’ll be disappointed.

There are a few things to know which will not only keep your expectations in check, but also keep you more knowledgeable regarding the phenomenon in the future.

During the middle part of this week, two solar flares occurred from the an Earth-facing sunspot. Solar flares are essentially eruptions from the sun which send energy, light, and high speed particles flying into space. If these flares occur on a part of the sun which is facing earth, eventually the energy, light and particles will reach our planet. These flares are often associated with magnetic storms called CME’s, or Coronal Mass Ejections. Although solar flares aren’t harmful to humans (thanks, atmosphere) they can create long-lasting radiation storms above our heads — and disrupt high frequency radio signals, GPS systems, and satellites. They also can produce beautiful aurora borealis in the night sky, especially in the Northern Latitudes.

Imagery showing the solar flare from Wednesday which registered as X-Class. Courtesy EuroGeosciences.

Two major solar flares occurred this week. The first, on Tuesday afternoon, was an M-Class flare, and the second on Wednesday was an X-Class flare. Solar flares are rated on a letter-scale for intensity. The classes (A,B,C,M,X,Super X) are meant to help categorize how strong solar flares are. The recent X-Class flare was obviously strong — but not one of the strongest in history.

What happens once the solar flare reaches Earth is what really matters to us — and that is wildly unpredictable, even with today’s technology. Space Weather models have made it much easier for us to anticipate what will occur, but even they struggle with the individual nuances of these events. And so, forecasting the impacts and the aurora event can be very difficult.

Small things like the exact position of earth relative to the solar flare, the tilt of the radiation once it arrives, and the speed and duration of the event, can greatly impact what occurs — and what is visible — to us on Earth. The M-Class flare from Tuesday reached Earth on Thursday Night, and produced aurora in the northern latitudes — especially Alaska. But this aurora event should be a good predecessor and lesson for the X-Class flare — the tilt of the event was unpredictable.

Aurora over Alaska on Thursday Night. Courtesy J.M Hall.

Making matters more difficult is the fact that our area lies to the south of the more common viewing area for Aurora. The last widespread visible aurora in New Jersey and Connecticut was years ago. Granted, the sun is in an active period and an X-Class flare which is Earth directed has not occurred in a while. But we need a relatively strong impact, and good southward tilt, to see the aurora in the suburbs of New York City.

An additional index, the planetary kP index, exists for understanding the horizontal component of the earths magnetic field — in our case, for viewing the aurora. Typically, a kP index between 7 and 9 is necessary to view the aurora in our area and the suburbs of NYC. Currently, the SWPC only anticipates a kP index of around 5 with some fluctuations. That would be too weak — and too far north — for our area to see.

KP index forecast from the Space Weather Prediction Center.

The fact of the matter, at this point, is that we don’t know exactly when (to the hour) the impacts from the X-Class flare will occur. We also don’t know the exact intensity of the solar storm itself. Recent space weather models indicate that the X-Class flare might have been pointed just slightly off-center toward Earth, and that our planet may miss the strongest impacts. In addition, the speed of the flare exiting the sun has some models thinking it will “fan out” a bit as it approaches, meaning the effects on our planet could be more moderate than strong.

Nevertheless, the Space Weather Prediction Center still has issued a G3 – Strong – Geomagnetic storm warning, with a heightened chance of mid-latitude aurora. They are still anticipating that the solar storm will reach earth tonight — with good timing for viewing an aurora if it does develop. It will likely come down to minute details, as the storm does reach Earth, before we can say with any confidence that some in our area will be able to view the aurora.

Light pollution map for our area. Head away from the Red and White colors and towards the Orange, Yellow and Green for better viewing. And look north.

If you’re planning on venturing out on the chance that the aurora will be visible, we strongly suggest getting away from the city lights. You’ll be best off in a suburb of New Jersey, Southeast New York or Connecticut. Northwestern New Jersey and Orange county are best, although the Pine Barrens aren’t bad either. You’ll have to look north — close to the horizon if possible — for the best chance at catching the green and pink hues from the solar storm.

Hopefully, we can all get a chance to see this wonderful phenomena. But for now, it’s best to stay educated — and keep expectations in check so we aren’t all disappointed tonight.