Expulsionsphase

Expulsionsphase (expulsion phase) is a term used in various scientific disciplines to denote a stage in which material, energy, or fields are expelled from a defined region, creating an outward flow or an evacuated core. The concept is descriptive rather than tied to a single formal theory, and its precise meaning depends on the domain.

In plasma and space physics, expulsionsphase describes the rapid ejection of plasma and magnetic flux from a localized region, typically driven by pressure gradients, magnetic reconnection, or energy input from external sources. It is characterized by increasing outward particle flux, central density depletion, and often the development of shocks or instabilities as the expelled matter interacts with the ambient medium.

In astrophysics, expulsions are driven by feedback from young stars or active galactic nuclei and can produce galactic winds that remove gas from molecular clouds or galaxies. The expulsionsphase may mark the onset of large-scale outflows that regulate star formation and chemical evolution; terminology varies across models.

In materials science and condensed matter physics, the term can describe a stage during phase separation or dewetting when one component is expelled from a mixed region, leading to domain growth and the formation of voids or droplets.

Modeling typically uses conservation laws for mass, momentum, and energy with source terms, often in the frameworks of magnetohydrodynamics, Navier–Stokes equations, or reaction–diffusion systems. Observational or experimental indicators include time-dependent density and velocity fields, spectral signatures, and imaging of outflows.

The term is notably common in German-language literature; in English, writers often use expulsion phase, outflow phase, or expulsion stage depending on the field.