With skies becoming too bright by the end of May to see most auroral displays in the UK, we enter the noctilucent cloud (NLC) season. The first NLC reported this year was from Perm in Russia on 2012 May 25/26. There were further reports of NLC in May from the UK and Europe on three more nights. All except one report from Tyumen in Russia were of quite faint NLC but showing distinct forms. The Russian report of May 28/29 included an image which showed bright and extensive NLC between 18:00 and 19:00 UT.
June started with displays on 01/02, 02/03 and 03/04. The display of June 01/02 was widely seen in the UK while the 03/04 display was also seen in Europe. That on June 02/03 was only seen in Europe. There was then a gap of four nights before the next reports of a display on June 08/09. NLC has been reported frequently since the night of June 08/09 and poor weather conditions over UK and Europe may account for the lack of sightings on the four nights gap.
Following June 08/09, NLC has been seen frequently but by fewer observers than in previous years. The displays have generally been less dynamic than many of those in the past few years and the estimated brightness has also been lower. It is likely that a combination of widespread poor sky conditions and less bright NLC displays may account for fewer reports being received at the time of writing.
One of the best displays in June occurred on the night of 24/25 and, although bright and extensive for some time in the earlier evening, faded quite quickly after about 00:00 UT to leave fainter patches towards the northwest and northeast. NLC was reported on the following night, June 25/26, by several observers and Gordon Mackie, in Thurso, recorded images of NLC towards the south at about 23:00 UT.
In keeping with ground based sightings, the CIPS images from the AIM satellite first showed ice nucleation on 2012 May 25 and the extent of the ice in the mesosphere increased rapidly towards the end of May and into June.
Once again, may I thank all observers for their reports and images. Poor weather and sky conditions have not made this the easiest year to observe NLC. Thanks also go to Tom McEwan for his constant and rapid update of the NLC website, www.nlcnet.co.uk
Auroral activity in 2012 May and June
May 8/9: Kp 4, radio aurora in high latitudes. 21:44-01:06 UT, faint horizon light at Kelso, Co Mayo & the Derry coast, faint arc & weak rays at St Andrews. Homogeneous arc at Chapel of Garioch, Aberdeenshire, where Graeme Whipps observed & photographed the climax of the display at 23:45-00:07 when an active rayed band developed with moving purple rays up to 25[degrees] with fine structures below, then fading to homog. arc. Aurora also seen in Minnesota.
May 22/23: Kp 5, faint auroral light in Cumbria, no times given; aurora in Wisconsin & Minnesota.
June 17/18: Kp 5 following CME. Sky too bright or cloudy in UK, active rayed band aurora reported to Spaceweather from Melbourne (Australia); Invercargill, Te Anau, Dunedin & Southland (New Zealand); Oregon, Utah, Michigan, Minnesota, Washington State, Wisconsin, Iowa, N & S Dakota, Virginia & Kansas (USA).
Observers: A Boyko (Michigan), R. Cockman (Melbourne), T. Lloyd-Evans (St Andrews), M. McKenna (Derry), R. Newman (Mayo), D. Small (Kelso), G. Whipps (Garioch).
Ken Kennedy, Director
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|Title Annotation:||Notes and News|
|Publication:||Journal of the British Astronomical Association|
|Date:||Aug 1, 2012|
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