| Term: | Halo |
| Definition: | Group of optical phenomena, in the form of rings, arcs, pillars or bright spots around the sun or moon, produced by the refraction or reflection of light by ice crystals suspended in the atmosphere (cirrus clouds, diamond dust, etc.). |
| Term: | Halo |
| Definition: |
The part of an object or distributionsurrounding some central body or distribution. For example, the particlesabove the core energies that show enhancements above the thermal population.Typically, a "power law tail" shows a break from the core Maxwellian at aparticular energy. |