Report and photographs by Peter Dick GM4DTH.

 

Dr. David Gavine talking at the LRS meeting.

At the LRS meeting on 8th February 2012 Dr David Gavine gave a most interesting talk "Aurora Explained". Dr Gavine is retired from teaching astro-navigation and meteorology at Leith Nautical College (where LRS member Colin Wright GM4HWO was one of his students!) then maths at Jewel & Esk College. He is a Past-President of the Astronomical Society of Edinburgh, former Director of the Aurora Section of the British Astronomical Association, and an amateur astronomer. His talk was very timely as there had been a number of visible aurorae in the UK in the previous weeks.

Dr Gavine has a longstanding interest in the phenomenon Aurora Borealis, also known as the Northern Lights (Borealis being derived from the Greek for north wind). He opened with various references to aurorae from Biblical times through to the present era. He along with many amateur observers has been recording auroral events for many years and illustrated his talk with a number of photographs taken from his home in Joppa which is to the east of Edinburgh. He gave descriptions of the many structures and forms the display takes and how its latitude varies with solar activity. The energy that drives the auroral display is from the charged particle stream that radiates from the sun. This stream interacts with planetary magnetic fields resulting in atmospheric ionisation near the magnetic poles. Aurorae have also been observed on some other planets in the solar system. The magnetic effects can be seen using a home made magnetometer with light being reflected from a mirror mounted on a magnet suspended in a coffee jar. To assist seeing the aurora a narrow band filter can be employed which passes the oxygen emission line on 557.7 nm (green) while rejecting optical interference. The auroral ionisation also has significant effects on radio propagation. Some examples were given of how aurorae have affected military and civilian operations in unexpected ways. Although having no direct connection Dr. Gavine also gave a short resume of noctilucient clouds, also well supported by photographs. Again, this was timely as a beautiful display of noctilucent clouds was observed by LRS members at VHF NFD 2011 (see report with photographs in Society Activities). 

Peter Bates gave a vote of thanks for this fascinating wide ranging talk. I must take this opportunity to thank David for an informative and enjoyable evening - Peter Dick GM4DTH.

 

Title slide showing one of many beautiful examples of visual aurorae. 

 

The aurora is caused by the impact of charged particles in the solar wind with gas molecules in the upper atmosphere and drawn towards the poles by the earth's magnetic field.

 

A home-made magnetometer can give warnings of impending aurorae. 

 

The final slide says it all!