A pair of flares seen on the sun on Tuesday (May 9) may display the northern lights for parts of the northern and central United States tonight.
Late Tuesday, a satellite known as the Sun and Heliospheric Observatory, or SOHO, detected a large coronal mass ejection (CME) that was likely caused by the double flare explosion that afternoon. The associated subatomic matter appears to be heading straight for Earth, and as a result, the Space Weather Prediction Center at the National Oceanographic and Atmospheric Administration (NOAA) has I issued a geomagnetic storm watch (Opens in a new tab) for a possible G3 event today (May 11).
Such a geomagnetic storm would allow the aurora to be visible as far south as the Oregon border, northern California, Denver, Colorado, and the Outer Banks of North Carolina.
Related: Northern lights (aurora borealis): what they are and how to see them
For most of the past week, the Sun has been behaving in a very disturbing manner. Since May 5, a sunspot cataloged as AR3296 has been slowly making its way across the sun’s disk and in the process has fired at least nine magnetically charged “M” class solar flares toward Earth. These flares have caused frequent disruptions or even blackouts in shortwave radio communications around the world. Compass needles swung back and forth, while utility companies braced for stray surges of current that might even cut their power lines.
But on Tuesday (May 9), within a time span of less than two hours, two significant solar flares erupted from sunspot AR3296. Large streams of subatomic particles shot out from these solar disturbances at staggering speeds of 2.2 million miles per hour (1.3 million km/h). When these particles encounter Earth’s magnetic field, some of them may be accelerated and directed to regions around the North and South Poles.
The Magnetic Storm Watch is now in effect
Forecasting space weather events, like terrestrial weather, has its uncertainties. The expected magnetic storm may be stronger or weaker than expected. The time of her arrival is also highly uncertain; Some computer models have suggested this will happen as early as this morning, but as of this writing, we are still waiting for the subatomic matter released from Tuesday’s double flare event to reach Earth.
Projections indicate that this electrified material will reach Earth sometime on Thursday afternoon (May 11), eventually colliding with oxygen and nitrogen molecules, as well as rarefied gas atoms in the upper atmosphere. These atoms are temporarily stripped of some of their electrons by collision or near collision. Atoms absorb energy in the process. Within a millionth of a second, the atoms regain their lost electrons and re-emit this energy in the form of light of different colors in the same physical process that the light from a neon sign emits.
We call this display in the night sky the aurora borealis, more commonly known as the northern lights.
When and where to look
Usually confined to Alaska, northern Canada, and Iceland, the Northern Lights appear in various forms up to 200 or more nights annually. But sometimes when a particularly intense turbulence erupts in the sun, the area of view to see the lights can be pushed farther south.
Skywatchers hoping to catch a glimpse of the northern lights should make a concerted effort to go to a location well away from the bright city lights and check the northern sky as soon as it gets dark enough and then do periodic sky checks at regular intervals. Auroral activity can be dormant, then suddenly erupt at any moment. The most common shape appears low on the northern horizon and is called a homogeneous arc. If the activity is increasing, the arc may appear to pulsate as rays of light appear and shoot up into the sky. Others take the form of specks, spots of light, or flames.
As for colors, green and white are the most common, although blue and red aurora are also observed.
Smoke can obstruct vision
One drawback that could seriously hinder viewers over the North and Northeastern United States is the presence of airborne smoke from wildfire activity over western Canada. Upper level winds were blowing this smoke in an east-southeast direction, creating a clear haze in the sky. This haze produced sunrises and sunsets of a deep red color, but it also dimmed or even subdued completely, views of the faint stars in the night.
For the best possible views of the aurora borealis, the sky must be clear and transparent. But the smoky skies currently affecting much of southern Canada and the northern United States could either mute or obscure the potential display of the Northern Lights tonight.
Joe Rao is a teacher and guest lecturer in New York Hayden Planetarium (Opens in a new tab). He writes about astronomy for Natural History Journal (Opens in a new tab)the Farmers’ almanac (Opens in a new tab) and other publications. Follow us on Twitter @tweet (Opens in a new tab) and on Facebook (Opens in a new tab).
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