When to look for Aurora

[Terry Richardson]

Predicting Aurora.

Predicting Aurora uses science, but like the weather forecast, it is not an exact predicter.

What we as astronomers need to know is when aurora is likely, and in real time find out if it is worth looking outside or going somewhere there is good viewing.

Prediction is in 3 phases.

1.      Looking at the sun for flares or Coronal Mass Ejection (CME)

This data travels at the speed of light and arrives at sensors on (or around) earth in 8 minutes.

2.      Predicting the speed of the consequent solar wind (Particle Radiation) and its arrival time to earth’s magnetic field. And measuring it.

3.      Looking at local data (magnetogram) to check current activity in your locality to see if there is sufficient activity to tell you when to look up.

A flare or CME can be seen in visible spectrum and will indicate that Radiation is on its way. The velocity of that radiation is variable, such that it may arrive at earth within hours, or up to 2 days later. The larger the outburst and the higher the velocity generally means more magnetospheric disturbance and more likelihood of Aurora. This in itself does not guarantee visible aurora as it depends on a number of factors, not the least of which is the time of day. The best chance of seeing it is the few hours around midnight.

Since the earths magnetic field (and the effect of solar wind on it) is variable from place to place, the best data is local data.

 

Some helpful places to get predictions.

1 The Aurora Australis forecast centre.   http://www.aurora-service.net/aurora-forecast/

This is a service run by volunteers based in Tasmania. It gives short term (hourly) forecast of likely distribution of visual aurora and Kp index. Kp index is a scale of “strength”, based on the degree of disturbance of the magnetogram. K4 and above means aurora is likely. A 3 day forecast is also displayed.

This site also gives Gauges For Bz (The north/south strength of the interplanetary magnetic field), solar wind velocity and density.

This site will also send text alerts for a subscription of $7.50 per month.

 

2. Dunedin Aurora.  http://dunedinaurora.nz/index.php

This is a site run by Ian Griffin with engineering by Vaughn Malkin and Chris Campbell in Dunedin

This has a real time view of the sun and sunspot maps.

There is also real time data on solar wind speed and density and a 4 day solar wind forecast as well as real time and historical magnetograms.

There is useful comparison of predicted with actual data.

They also have a skycam to visualise the sky for aurora.

Since this is more local for our purposes, I regard it as highly relevant.

 

3. Local Magnetometer.

If there is indication on the above websites you can check my magnetometer.

http://richardson.geek.nz/christchurchmagnetometer/

This will tell you what is happening in West Melton at this moment. If this is very active (above K5) then there will almost certainly be Aurora on our horizon. (even if not very bright).

The Graeme Kershaw camera at the observatory may show activity but not necessarily because of the angle of view. It is worth a look though.

 

These tools are what I use for clues for aurora watching. There may be other sites that members use. I believe there are facebook pages which will give real time information and images. Since I don’t subscribe to facebook I cannot advise. Maybe another member may be able to post some sites.

 

This is an example of my magnetogram fron 31 August 2019. Note the activity from 6pm (0600 UTC) to about 2am. This is the sort of pattern you are looking for.

 

Happy hunting.

[Dale Kershaw]

thanks Terry for this information,

I also look at the facebook pages you mentioned and links are here below

https://www.facebook.com/groups/auroranzalert/

and the other one is

https://www.facebook.com/groups/NZaurora/

Cheers

Dale

[Anonymous]

Thanks Terry and Dale

[Anonymous]

Another FB page

New Zealand Auroa Australis Group

One doesn’t actually need to get one’s feet wet with the amount of photos coming in this weekend.

[Author]

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