re Ulrich SAR arcs

[jan lameer]

Hi Ulrich !

Here are some links for information on SAR arcs.
It is quite a difficult subject.
To my idea a SAR arc is nothing more than the large red auroral displays that are seen over middle latitudes during severe storms.
I remember seeing a stable red arc forming on April 6/7 2000 and staying in the constellation of Leo for hours while in the northern hemisphere a "normal" aurora show was happening.

General info:

http://www.windows.ucar.edu/tour/link=/ ... l&edu=high

75 case studies of SAR arcs (Millstone Hill):

http://www.bu.edu/csp/imaging_science/a ... stats.html

and also:

http://www.haystack.edu/mhrobs/one-pagers/sar.html

Technical paper (Yakutsk):

http://eos.wdcb.rssi.ru/transl/gma/9405/pap11.htm

I hope that with your scientific knowledge you can make more sense of the subject than I can. I find it hard to get an ultimate idea of what a SAR arc is. I think the Hydrogen Lyman alpha radiation is only one aspect of the SAR arc but that normal 630 nm red is most of the radiation that we see.
By the way, the arc that I saw april 6/7 2000 was not very bright while I was at the darkest location on Terschelling. I remember one observer in Ireland reporting it also...