Fine Art Photography Prints & Images of New Zealand Landscapes & People
PERSUIT OF THE AURORA
Aurora Australis in a crowing glory from Alair, TImaru, New Zealand
Not often but anytime
The South Island of New Zealand is in a box seat for observing the Southern Austral is. While the polar regions have lively aural shows of swirling green ribbons and pulsations of light, stepping away a distance allows a far greater view. The vibrantly coloured rays reaching hundreds of kilometers into space become far more visible from side on.
The downside is that the Aurora reaches away for the poles less often and in TImaru we should only expect to see a phenomenal show once or twice a year - weather depending. Also the sun is now well into its 'solar minimum' further reducing the schedule for the greatest show on earth.
Despite this I must have seen about 20 reasonable auroras over the last couple of years, giving me plenty of opportunity to understand them, learn to chase them and succeed with photographic techniques. There is also a big lesson in patience which a good "talking book" and mp3 player helps.
I should also mention the perseverance and the need for warm clothing and hot coffee. It is the winter darkness with its chilly clear sky that offer the longest and clearest hours of observation.
What is it...
In simple terms the sun occasionally sends a burst of radiation our way and shakes up the earths magnetic field a bit more than usual. The field maintains a ring of light around the poles which can liven up and expand towards the equator during these shocks. If nearby we will see them a anything from ghostly glows over the horizon to billowing curtains of streaking gossamer.
An excellent full explanation is provided by the University Corporation for Atmospheric Research here.
This amazing shot of the aurora from the space shuttle helped my concept of how an aurora is structured.
This one from the skylab is not bad either and shows how much the structure can differ depending on location and stage of activity. Aurora can be seen on other planets and the Hubble Space Telescope (STIS) has captured these image of Jupter and Saturn. Below the the aurora even interacts as bright dots with the Jovian moons.
Aurora Crowns Jupiter's North Pole - Credit: NASA/ESA, John Clarke (University of Michigan)
Saturn Aurora — January 24, 2004 - Credit: NASA, ESA, J. Clarke (Boston University), and Z. Levay (STScI)
Where and when should we look?
They are common closer to the poles but the further away we are the less often they will reach our way. When they do they don't stay around too long adding to the reason why many people never see them..
Our probability of seeing an aurora is greatly lessened as we need night time with a clear sky and little other light from the moon or street lights. From a photographic point of view this doesn't matter as the camera is not affected by bright light away beyond the view of the lens. In fact even looking through a tube will help observation. Also our eyes are not so sensitive to colour in low light and if the aurora is close enough the camera is bound to capture amazing colours.
How can we find it?
Simple - just improve our probability. Know when the best time will be to look, and go to an area less likely to have cloud and street lights..
But first we need to appreciate what we are looking for and find some way of being notified when it is likely to be coming our way.
When I started to get interested I was absolutely ignorant of and asked Alan Gilmore of Mt John Observatory to give me a call whenever one could be viewed. With his help I soon got to see several great aurora.
I needed to have a better understanding to get the photos I desperately wanted. A quick search on the internet and I found SPACE WATCH and subscribed for Emails notifying you of major solar flares and auroral activities.
The Johns Hopkins University Applied Physics Laboratory
(JHU/APL)
has made significant advances in quantitatively understanding certain space physics processes. Here is a sample of a simulation they have created of the auroral ring form Polar UVI data.
If you are really interested you should get acquainted with them and also join the public forum to be in on all the speculation, and learn about the habits of aurora. To really get the full goings-on you can subscribe to SWIM and for an annual fee you can have all the monitoring information in the world (and beyond) on your own computer monitor. I find I get enough free information from various satellites and spacecraft. via a number of web sites including the SPACE ENVIRONMENT CENTRE and NASA
Now there some excellent tools for understanding what the aurora is. They would have saved me a lot of time had I found the at the begining of my quest. Try this one by NASA's sun-earth connection forum and hosted by UC Berkerley. With its animated visulisation and commentaries, II think it is excellent in showing up how it occurs and what observations are happening - right now!. Neat eh?
Watch for the solar flare
Whenever I get an Email alert about a major flare, I like to know more about its nature. GOES 12 Solar X-ray Imager, launched in 2001, produces images of the sun at 1 minute intervals. Sitting over the equator near middle of the Pacific Ocean it also gains a clear view of this side of the Earth. But as it rotates in a stationary position above the Earth, its view of the sun is briefly blocked by the earth.
In 1995 SOHO (Solar & Heliospheric Observatory) was launched and this spacecraft now sits away out in space (about 1.5 million km from Earth and 148.5 million km from the Sun) where it is held in a tug-of-war between the Earth's and Sun's gravitational pull. Here it enjoys a less interrupted study of the sun. SOHO also has a very good space weather page.Then I like to know where on the sun the activity is coming from. Basically the more the activity is towards the middle of the sun the greater the chance of a blast (Coronal Mass Ejection - CME) heading directly our way. Otherwise we may get a glancing blow only.
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This set of images from the sun are updated every minute and by pressing F5 this page will reload giving and almost instantaneous view. The bright area are the 'sun spots' and can vary depending on the sun level of activity.
If I am really curious I like to look at SOLARSOFT and even take a close up view of the flare in action. Experts can tell by the configuration of sunspots how big likely flares might be. A really active one may fire off every day or two. They rotate with the sun coming into view on the eastern shoulder (left had side), turn full-on to us and exit to the right. The odd ones are so persistent that they revolve right round to let off another passing volley. increasing our chances of seeing aurora off and on over over a 'season' of a few weeks.
Flares are not the only times the sun can give us a show. Sometimes the Sun's magnetic field stops looping back to its surface and breaks open letting it contents spew forward. This is known as a coronal hole and appears as a big black area on the suns surface. Also there can be a transitional effect every fortnight as the sun rotates and its magnetic field snaps from one direction to another. This is known as a boundary crossing. Solar flares can be enhanced (or diminished) by these two effects adding a lot of uncertainty to the auroral outcome on earth.
This site also gives an excellent idea of the magnetic field and the nature of any coronal holes and boundary crossings.
The speed of the ejection is also important. This can be measured by the distance the front of the CME (Halo) moves between difference images taken by the GOES Solar X-ray Imager. Then the GOES Solar X-ray Flux gives me an idea of the power and duration of the flare. At my 44deg latitude in New Zealand we need quite a flare to drive the aurora up from the Antarctic. A M8 tailing off over 6-12 hours does the job nicely. Larger ones can help.But this is still no assurance. Half the the time the shock waves may arrive in the daytime with all effect gone by nightfall. This is OK for the other half of the world. Winter time affords more hours of darkeners and increases the probability of seeing the aurora. Hopefully all the signs stack up and my excitement is eventually backed up by Email reports from SPACE WATCH.
Hope for clear weather
Next task is to check the local weather. The forecast charts and satellite imagery provided by James McGregor of Victoria University of Wellington are excellent.
This satellite image from a US Navy web site updates every hour and shows New Zealand in better proportions. Invariably the maritime climate of New Zealand and our coastal position means cloud, and many a potential night is totally ruined. If need be, I can get a good understanding of the cloud cover (and possibility of holes) from the finely manipulated NOAA images by Landcare Research. Fortunately we have very clear skies on many winter nights. But this also means very frosty nights, and reliance on many layers of fine marino wool clothing. Then if prospects still look good I can set about making myself available in 30-40 hours time, packing up a picnic for an all night vigil and getting some extra sleep. Also I trigger off alert messages to local friends. Making an intuitive guess on the estimated time of arrival, I log my computer onto data from another spacecraft and wait for an early warning, as I go about my normal work.
Wait for the shock
I prefer to access a simple set of data on the National Weather Service's Space Environment Centre website. A full set of Ace RSTW plots available here I am mainly looking for a sharp step up in velocity and and eventual climb to of anything upwards of 800kms/sec. Finally the other major factor is the magnetic orientation of the arriving wave. This is indicated by Bt and Bz. The Bz is the most influential and i am looking for a downward (southward) level of at least -10.
Sometimes this never occurs at all the the whole exercise is a fizzler. The best aurora seem to coincide with sharp upward (northward) trends.
This data comes from NASA's Advanced Composition Explorer (ACE) launched in 1997. This also sits away out with SOHO. From this far out we can get a 30-60min warning of a solar impact with earth. Ton's of time for me to pack up the camera gear, fill the thermos, and head out into the country for some dark sky.
Watch for the Aurora
In reality it may take several hours before the conditions for aurora truly set and now-a-days I leave the trip out till the last moment. Pin pointing the best time to head out is helped by going back to the
SPACE ENVIRONMENT CENTRE web site and watching the Satellite Environment Plot. Clicking on the GOES hp graph opens a window with better detail. When I see the blue line drop rapidly below normal, it is a good time to get moving as the aurora is most likely to be seen on the upswing. As our night fall coincides close to the bottom of the cycle any major movement below 50nt is enough to get me excited.
Despite such encouraging signs, strong magnetic disturbances still may not drive the hottest aurora. They simply may not nudge the earth's field at the right angle or in the right timing. This is like when to push a pendulum and which way.
For our latitude I find just a good old isolated M class flare will often do a better trick, especially if it is one of long duration. I think of this like seeing a flag in the wind: a steady wind and big undulating waves flow along the cloth; a stronger wind and the flag tightly ripples and freezes.
A typical 'sub-storm'
If we think of the whole event as a storm then within in this there is likely to one or more surges away from the poles. Because of the magnetic currents, each surge will have areas of local intensity known as sub-storms.
From my latitude you would first see a pale green eerie glow to the south brightening, as it approaches. A crest of a dull arc will rise above the horizon and thicken. And that may be all!
If lucky, the odd shaft of pale light may reaching and scan the lowest stars in the far distance. The glow may retreat or hang around for nights on end.
If the sub-storm has enough power (and we are talking gigawatts here - like multitudes of power stations) it will continue forward and at it furthermost advance suddenly break out into a crowning glory, a multitude of sweeping rays forming radiant multicoloured curtains across the sky lasting for up to half an hour before breaking up into what is known as the decaying phase. Occasionally you may see swabs of luminous light dab the southern sky or it may pulsate with enormous swishes of light rapidly running up from some tiny place, bursting apart to disappearing far and wide in the everness overhead.
Only once have I seen the arc go fully over head to watch it break into huge blobs of neon green to float silently North. Coming up behind was another wave this time already a broad wall of red covering half the sky. I just couldn't take it all in and stopped trying to photography it. It was all so large I had no lens that could take it all in.
Then bright red rays went overhead, penetrating up into an inconceivable space, dispersing way up there somewhere among the stars. Clouds forced a drive towards the hills and again no photo could ever convey the experience. I simply put it a way, gazed and gazed, with no further thought.
Someone can't have paid the power bill and there was sudden darkness.
How long to wait?
If I am having difficulty when the even is underway I find a another good real-time indicator of shock wave results is this OVATION simulator by
JHU/APL showing where the extent of the aurora is reaching.
By observing the rotational lag and 'cam' nature of the of the oval centered over the magnetic pole I found auroras would have to be more much more powerful to reach my latitude after midnight. There being less chance I find I have less argument with myself to stay out all night in vane hope. Probably a very good thing!
Here is another 'real time' Southern Hemisphere statistical oval extrapolated from NOAA-15
No show still a show?
If after all this the weather packs up it's nice to go home and watch this Alaskan WebCam on Mt Aurora near Fairbanks, and join their chat room (but only when Alaskan nighttime permits). The Alaskan Allsky Camera is very good at showing the trend of the Aurora in the Northern Hemisphere and as there is some mirroring effect with the south, it serves as a good indicator of what is happening down here too. And if the photography fails others will post their successes (and many other 'space things') on the Space Watch gallery.
Now I have a lap top computer I can take my work with me so all is not wasted if the show is rolls out to be a dud. Also there is always a shooting star or satellite to bee seen and the time spent musing over the stars has aroused much interest in astronomy. I now even have my own 'virtual' planetarium with me to assist.
Next will be the broadband internet connection for on-the-spot information and take my capabilities a step further.
Learn for the next time
After the event I report my observations to SPACE WATCH and study the charts to see if I can make any better sense of the jumble of information. Also there is a great need to humble yourself at this point. This is a very complicated phenomenon that scientists are grappling with. They have much to learn to improve predictions. That said, they believe Aurora predictions are more reliable that weather predictions. Going by this model of the earths magnetic from the Japanese Space Environmental Service (NiCT) site it does seem possible. It is certainly helping my understanding by showing an amazing simulation as the event happens.
World Wide Interest
As well as website visiting and emails forums I sometimes I join internet chat rooms, to swap enthusiasm and ideas along with website links. In all - join a world-wide community of buzzing people clamberig to vantage points to see skies of blooming colour.
Next I guess auroras will be getting TV coverage with commentator opinions and speculations over the real time simulator interspersed with, world-view snatches of events and even action replays.
So be it!