The Northern Lights are back once more, heralding summer with a beautiful light show along the U.S.-Canadian border. Here's how to watch the aurora borealis this week.
According to the U.S. National Oceanic and Atmospheric Administration's (NOAA) Space Weather Prediction Center (SWPC), the Northern Lights are expected to appear across northern U.S. states on June 1. The display may linger until June 2, but will be much weaker by then.
As always, your chances of viewing the aurora are better the further north you are. The SWPC states that the Northern Lights may be visible "as low as New York to Wisconsin to Washington state" on Sunday. Those along the U.S.-Canadian border may still be able to catch it on Monday if they're very lucky, however the aurora's area of visibility will have shrunk considerably.
This aurora borealis is the result of a coronal mass ejection which took place on the Sun's surface on Friday. The SWPC subsequently issued a severe G4 geomagnetic storm alert on Sunday, with conditions expected to weaken to minor G1 storm levels by Monday evening.
According to the NOAA Space Weather Scales, G4 geomagnetic storms can cause issues such as widespread interference with power systems, as well as prolonged disruption of radio and satellite navigation. In contrast, G1 storms may only cause weak power grid fluctuations, and might have a minor impact on satellite operations. Fortunately, the SWPC's warnings give us time to prepare for and mitigate disruptions.
However, auroras caused by G1 geomagnetic storms can't be seen in as many areas as those caused by more severe storms. While G4 storms have previously produced auroras visible as low as Alabama and northern California, auroras from G1 storms are typically only seen at higher latitudes such as northern Michigan and Maine.
How to get the best view of the Northern Lights
As always, you could just head outside at night and look up. Even if you're slightly outside the predicted visible zone, you may as well check since auroras can be visible from over 600 miles away in the right conditions. However, if you would like to optimise your chances of catching the aurora, there are a few factors to consider.
The SWPC states that the best time to see the Northern Lights is between 10 p.m. and 2 a.m., as the level of geomagnetic activity increases during this period. It's also the darkest time of night, which creates a strong contrast with the lights to make the aurora borealis become more visible.
Viewing the aurora borealis from an area with as little light pollution as possible will also help. Some of the best places to view the Northern Lights are likely to be Certified Dark Sky Places close to the U.S.-Canadian border, all of which have been assessed and recognised for having minimal light pollution.
What causes the Northern Lights?
Auroras are caused by activity on the surface of the Sun, specifically solar flares and coronal mass ejections. During these events, significant amounts of plasma and magnetic field are expelled from the corona, the outermost layer of the Sun's atmosphere.
Such expulsions create a solar wind, which travels through space to reach Earth. How long this takes depends on the type of event it was. While radiation from solar flares is capable of reaching Earth within eight minutes in some circumstances, winds from coronal mass ejections can take hours to days for the same trip.
Once the solar wind reaches Earth, the planet's magnetic field deflects the majority of it back into space. However, some charged ion particles enter the magnetic field instead, travelling to Earth's polar regions where this field is weakest.
These charged ions then collide with oxygen and nitrogen atoms, causing chemical reactions that create the spectacular coloured lights we know as auroras. Both the aurora borealis and aurora australis are caused the same way, the only difference being that the former is in the Northern Hemisphere and the latter is in the Southern Hemisphere.
