The following is speculation: * Perhaps those are higher resistance (drier) zones in the air. Increased resistance could lead to increased heating, * Conversely, air that has been heated by the arc into plasma is highly conductive, perhaps the low resistance of the plasma "funnels" the arc into hot zones causing localized heating (bright spots). Perhaps the arc is more spread out outside of these bright spots resulting in less localized heating (and a less visible arc). On Thu, Apr 2, 2015 at 7:52 PM, David VanHorn wrote: > Something that I've been wondering about, as I look at high voltage spark= s. > > Within a single spark, along its length, there are sometimes zones that a= re > much brighter than the rest of the spark. A given spark might have three > or four of these, or none. > > Any ideas what causes this? Could it be my eye rather than the spark? > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 Jason White --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .