Tuesday, 9 December 2008

Subhorizon plate crystal halos

On the night of 7/8 December in Rovaniemi water fog was nucleated to diamond dust by snow machines, and a major display was observed in a spotlight beam for several hours. The photo above is from the end stage when plates dominated.

The lamp is downhill below the horizon (about 11.5 degrees), which shifts subhorizon halos above the horizon. Halos are named in the simulation which is made with Jukka Ruoskanen's program. Sub-Kern and sub-120° parhelia have not been documented before. By other means these are difficult to see. One needs to sit in an airplane which happens to pass through a high quality crystal cloud and sub-Kern is also located so low that one probably is not able be view it from small airplane window.

Crystals used in the simulation were plates which prism faces were allowed to variate freely in size within some limits. This produced the rather uniform stretch of subparhelic circle where sub-Liljequist parhelia are becoming hard to distinguish. Had there been solely regular hexagons in the air, the sub-Liljequist parhelia would have been better defined.

There was also circumnadir arc, which is another new feature. Les Cowley ( 1 ) has more on this and other subhorizon halos in the display.


  1. That night is set to go down in halo history as one of the greatest. Looking at the images, the mind just boggles. Congratulations Marko! (Oops, he did it again).

  2. Marko and his magic torch....
    I'm at a loss for words :)

  3. Unbelievable stuff.

    I've been thinking of how weird it is searching for subhorizon halos from above the horizon and whether or not they should be called subhorizon halos at all (of course it's undeniable that they are new halos because of their ray paths).

    I first looked at Les' site which didn't feature this image and was still puzzled of should they count as 120 subparhelia if they are seen against the sky.

    This however changes everything. If you simultaneously see "normal" 120 parhelia against the ground.. yeah, it counts!

    Congratulations again Marko!

  4. Marko, this is amazing!!! Making subhorizon halos in this way is a brilliant idea! Congrats again!!!
    I hope to meet you personally during Halo Meeting in Hungary.

  5. I like the idea more than the results, if possible! Very simple and smart! Congrats!

  6. Thanks again for congrats, folks. Yes, Hungary halo meeting is a must. See you there Jakub.

  7. Nice, nice. What else is there to say? Man of amazing arcs strikes again, well done.

  8. Jukka, that was well said :)
    I've been thinking recently that we could soon start calling the reflected lower sunvex Parry arc or the strange "M-arc" of the Lascar display "M-arc-o" ... I mean: "M-ark-o".

  9. Wow Marko CONGRADULATIONS!!!!! You did it!!! After seeing so many simulations it is wonderful that there are photos of the sub-120p sub-CZA and sub Kern arc!!! How much better could it get!! All I can say is you GOT R DONE!!!