HALO3 simulation of the rare UK display. The sun is below centre inside the bright circular 22° halo.
30 million virtual light rays were traced through mathematical representations of the cloud ice crystals to
make this view as would be photographed by a wide angle camera.
Halos, produced by hexagonal shaped ice crystals in clouds, are visible once
or twice a week on average.
These are usually sundogs and fragments of a 22° radius circular halo around the sun. In complex displays
a whole variety of bright and colourful arcs spread across the sky including ones rarely seen. In the UK
these displays are few and far between but one was visible over the Midlands and Northern England on
Friday 9th February .
The sightings of common and rare halo arcs were:
|Malcolm Garland||Sheffield||12.40 - 13.10||1 2 4 5 6 7 8|
|Malcolm Goldsmith||Prestwich, Manchester||10.30 &13.30||2 10|
|Judith Proctor||Leicestershire||- 1330||1 2 3 5 10 11|
|Gill Smith||Ashberry near Rievaulx Abbey, Yorkshire||13.30 - 14.00||1 2 3 4 5 7 9|
|Bruce Thomas||Castleford near Pontefract, Yorkshire||1 2 3 4 5 7 8 9 10|
|Ant Veal et.al.||Birmingham||11.45 - 12.40||1 2 3 4 5 9 10|
|Tony Young||Derby||12.00 - 13.15||1 2 4 5 6 7|
Weak in display
|2||22° sundogs (parhelia)||hexagonal
|4||Upper tangent arc||horizontal
|Extremely bright and coloured|
|6||Sun pillar||plates & columns||
Not often seen when the sun is so high. Probably
made by the large numbers of column crystals.
|7||46° halo||poorly oriented||
Rare and colourful halo - see supralateral arc.
Produced by multiple reflections inside plate crystals.
|9||Parry arc||Parry columns||
Rare halo first seen by Parry in 1820 while icebound
in the Arctic.
The sun was 18 to 22° high and these altitudes it
can be difficult to distinguish between partial supralateral
arcs and 46° halo fragments. Crystals capable of
generating each were present but the hexagonal columns
which generate supralateral arcs were most abundant.
Coloured arcs beneath the parhelic circle at this solar
elevation. Produced by the reverse ray paths through
column crystals to those which create supralateral