自由落下中に成長する人工雪の結晶一凍結撒水滴からの成長(<特集>結晶のモルフォロジー)

抄録

By using large cloud chambers small snow crystals were grown in free fall from frozen water droplets. When a frozen water droplet grows in a supercooled cloud, 20 facets, {0001}, {101^^-0} and {101^^-0}, appear on its spherical surface at first. Pyramidal faces, {101^^-0}, gradually disappear and it changes to a hexagonal short column with gas enclosures. At temperatures about -15℃ it grows to a double-plate via a solid hexagonal plate. One of two plates of the crystal grows larger than the other and it grows to a hexagonal dendrite. In a larger plate some markings indicating comparatively thick parts are observed ; it is possible to infer a growth history by analyzing such markings. When a plate-like snow crystal grows, the most rapidly growing part extends or pushes out parallel to one of <112^^-0> directions ; the part may be indicated by an edge formed by neighboring two prism faces. This is also applicable to every branch and this occurs because a plate-1ike snow crystals grows by two dimensional nucleation occurring at <(101^^-0) (101^^-0)> edges.