S K Y   I N F O R M A T I O N

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HOW TO PREDICT & WATCH AURORAS FROM SOUTHERLY LOCATIONS
 

Believe it or not, middle- and low-latitude locations (including much of the U.S., Europe and Asia) can receive one or two displays of the northern lights each year.  But if you're not under a dark, moonless rural sky you can't possibly see them.  This photo shows a display on May 14/15, 2005 from my front yard in the Anza-Borrego desert of Southern California!

There's no right or wrong way to determine when an aurora might appear in our sky, but the following steps outline what works for me.  They may seem confusing at first, but with a little practice you'll figure it all out. 

 
1.  Heads Up!

The first place I usually learn about an impending auroral display is SpaceWeather.  I visit this site daily―not only for all the cool photos, but also to learn if the sun's doing something that may lead to a auroral display. 

Also available are free subscriptions to auroral watches and warnings in which you can set your own parameters for being notified.  Because of my location in Southern California, I subscribe to low-latitude watches and warnings from Solar Terrestrial Dispatch and the University of Alaska.

2.  Is tonight the night?

If auroral activity seems possible as evening approaches, I begin to monitor conditions at the Earth itself.   

The auroral visibility oval shows the likelihood of seeing an auroral display.  Usually it's green and relatively small.  But as activity picks up over time, the oval can become yellow, orange or even red, and can swells over much of the continental U.S.  If my location is within, or near the edge of, the expanded oval, I'm definitely on the lookout.  

However, an even more straightforward graphic that shows the probability of seeing the aurora in your area is the OVATION Aurora.
If you have to choose only one indicator to watch for real-time activity in your location, this  is it!

Another indicator I watch is the Estimated Planetary Index (Kp)―a scale of global magnetic activity that runs from 0 to 9.  When Kp is low the vertical bars are green;  when Kp is moderate, they are yellow.  Only when the most recent Kp is 8 or 9 and the bars turn red am I ready for action.  Sky watchers farther north than Southern California might see a display when Kp is lower.

3.  Holy Moley... It's Showtime!

As darkness falls and a display seems imminent, I next turn my attention to real-time data from the ACE spacecraft (Advanced Coronal Explorer) which measures solar material heading our way.

First I watch the interplanetary magnetic field (Bz)―the red curve at the top. This is measured by ACE which lies between us and the sun, and usually gives a 20-40 minute preview of conditions heading our way.  Only when Bz is solidly negative (south) will auroras be likely in southerly areas.  Material density and velocity are also key indicators to watch. 

At the same time I'm watching the data from ACE, I'm online with other aurora watchers on the Southern U.S. Aurora Discussion Group.  A great forum to join, this group provides a nearly real-time exchange of information from those looking for, or actually seeing, the aurora in southerly locations around the U.S.  For a similar set of forums, check out the Space Weather Discussion Forum.

In addition I will occasionally check the Auroral Activity Observation Network map which shows a near real-time plot of reported observations.  Observations from other southerly locations are particularly encouraging.  

 

IS IT REALLY THE AURORA?

Conditions for an auroral display can change rapidly and, even though the numerical indicators suggest a display is likely, Mother Nature may have other ideas.

The lights might appear from here as only a faint gray smudge against the dark sky; sometimes we can see faint color or even some vertical rays dancing back and forth in the northern sky.  Moonlight can easily wash out any chance of seeing them.

Long exposure photos will often show red, green or blue in the lights. This is a good way to determine if it's auroral light or just distant light pollution.  If you have a digital camera, take several shots toward the north;  if you see evidence of any of these colors―or even signs of vertical rays―you may have an aurora brewing.  This photo was shot just before dawn on July 27, 2004 from Borrego Springs in the Anza-Borrego Desert of Southern California.

To photograph the lights, use a normal or wide-angle lens and open the aperture all the way, set your ISO to 400 or so and, with your camera on a tripod, take exposures of 15-60 seconds.  Of course this depends on their brightness and how fast they're moving.  Don't be afraid to experiment to get the best shots.

 

KEEPING WATCH UP NORTH

Seeing the lights from southerly latitudes is really a treat, but it's nothing like the show one gets from near latitude 65 degrees north.

While I'm waiting for those rare displays here in Southern California, I like to keep watch on the skies over Fairbanks, Alaska―the Aurora Capital of the World―with the Aurora Webcam at the Poker Flat Research Range.  During a good display in fall, winter or spring, the colors and movement of the aurora are stunning to watch.   The image refreshes every five minutes.  Unfortunately the webcam has lost its funding and is not operating at present.  There are others, however, in Sweden and Finland.

And for an all-sky review of the auroral activity earlier in the night or on previous nights, I check out the Poker Flat Real-Time Camera (be sure to select the Poker Flat Station).  It spreads the night's images across a horizontal axis to produce a single view of auroral activity, and offers some really cool all-sky time-lapse movies as well.  These provide terrific ways of studying how auroral substorms develop, break up and recover during the night. 

Occasionally the cameras are down for repairs or maintenance, but keep checking back!

 

SEEING THE REAL THING

It's fun to monitor the aurora from afar, or even to see it from southern latitudes.  But to experience the real thing, join me on my exciting and very popular public  aurora expeditions to witness and photograph the greatest light show on Earth!  Check out our offerings here!

 
Dennis Mammana