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The Aurorae Returns

posted Mar 2, 2014, 12:35 AM by Stephen Chadwick   [ updated Mar 2, 2014, 3:40 AM ]
Blog post by Ian Cooper

Some of you may have heard that the sun is experiencing the lowest activity in many wavelengths for almost 100 years. This manifests itself firstly in fewer and often smaller sunspots than we have grown accustomed to in our lifetimes. One of the main consequences of this is lower levels of auroral activity. Many people are surprised to learn that the aurora australis can be seen from our region, but during the peak activity period of the sun known as Solar Max we have in the past been able to see up to 20 displays at each maxima.

Some of these auroral displays have been full blown storms that have lasted all night and covered half of the sky while many are short lived sub-storms that range from 5 or 10 minutes up to around 40 minutes in duration. With the drop off in solar activity there have been NO major storms during the solar max of SunSpot Cycle 24 (SSC 24) that has been occurring over the past 24 months or so. This solar max is expected to last only another 12 months or so. Since the maximum started there have been a few good displays that we would have seen from here if the weather had been kinder. A good example of this was the St Patrick’s Day aurora of 2013. Well seen on the east coast up around Gisborne but missed here.


from Opiki (Ian Cooper)

Perhaps because the activity levels on the sun are so low trying to determine if a display is going to be good enough to be seen from here is quite tricky. The best predictions don’t always pan out and one can spend a lot of time patrolling the southern horizon waiting for something that doesn’t come.

On the night of February 19th 2014 we were treated to the best display the writer has seen for nearly ten years. I had only been home for 30 minutes and hadn’t seen any alerts online myself when a member of the P.N. Astronomical Society rang me and said he was detecting a hint of red in shots taken with his digital camera. I went outside with my camera and confirmed that indeed there was some weak activity in progress around 9.50 p.m.

I had time to just ring two people then I was off on a drive to get behind a few pesky clouds in the south. I had to stop about 5km from home when the first burst of rays sprang up and I took some pictures from there before pushing on to south of Opiki where I caught the last 20 minutes of the activity which ended not long after moonrise.

Although the camera picked up the colour I couldn’t detect any with the eye. This was a sign that the energy wasn’t sufficient to excite the different molecules such that we can see their individual colours as happens during stronger displays. Having said that, it was a good display for a maximum that hasn’t produced many. South Islanders had a better view as they always do and when we are likely to see another such display is anyone’s guess.

 

from Himatangi Beach (Stephen Chadwick)


Ian Cooper


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