Nonthermally

Nonthermally is an adverb used to describe actions, processes, or states that occur without reliance on thermal processes or thermal equilibrium. It is formed from the prefix non- (not) and the word thermal, with the -ly suffix to function as an adverb. In scientific writing, nonthermally indicates deviation from what would be expected under ordinary thermal conditions.

In physics and engineering, nonthermally describes phenomena that are not governed by temperature-based statistics or heat exchange. For example, nonthermally produced or excited particles and nonthermally generated radiation refer to energy distributions or emissions that do not follow a Maxwell-Boltzmann or Planck distribution. Common contexts include astrophysics, where nonthermal radiation such as synchrotron or inverse Compton emission arises from high-energy, non-Maxwellian particle populations; and condensed matter or plasma physics, where carriers or particles are energized by mechanisms other than heat, such as shocks, laser-plasma interactions, or rapid electric fields.

The term is often used alongside its adjective form nonthermal, with nonthermally serving as the corresponding adverb. While widely understood in technical disciplines, usage can vary by field, and some guides prefer more explicit phrasing like “nonthermally produced” or “nonthermally excited.” Overall, nonthermally helps distinguish processes that do not involve or reflect thermal energy distributions from those that do.