Effect of a coronal shock wave on the solar wind ionization state

Journal Article · Tue Nov 01 04:00:00 EST 1983 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/161457· OSTI ID:6593172

Owocki, S P; Hundhausen, A J

The solar wind ionization state is ''frozen'' within a few solar radii of photosphere, and measurements of the ions at 1 AU can therefore potentially yield information about conditions (e.g., electron temperature) at the base of the coronal expansion. In the active solar corona, intrinsic time variations can be as important as variations associated with flow through spatial gradients in determining the frozen-in ionization state. We illustrate that, by using a Lagrangian approach of following individual fluid parcels, the techniques used for calculating ionization state variations in a steady state case can be straightforwardly extended to time-varying flows, if the flow speeds of the different ion stages are the same. Sample calculations performed here for the specific case of a strong shock propagating at constant speed through the corona show that only fluid parcels shocked at or below the ambient freezing-in radius have their ionization state significantly modified by the shock. For fluid parcels shocked below this freezing radius, the degree of ionization initially increases sharply because of heating at the shock front, fut it then declines because of the adiabatic cooling with the outward expansion; the asymptotic degree of ionization for such parcels can actually be lower than for the unshocked ambient flow. Parcels shocked near the freezing-in radius show less of an initial response to the heating than those shocked lower, but they are already frozen-in during the cooling phase and thus have a moderately enhanced asymptotic degre of ionization. Time-dependent ionization effects for the sudden transition between two otherwise steady flows are thus likely to be limited to a narrow range of gas parcels which, having been shocked within the coronal freezing-in radius, pass a fixed interplanetary observer in an interval of a few times 10 minutes.

• Research Organization: Harvard-Smithsonian Center for Astrophysics
• OSTI ID: 6593172
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 274:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
FLUID FLOW
FLUID MECHANICS
HYDRODYNAMICS
IONIZATION
MAGNETOHYDRODYNAMICS
MECHANICS
SHOCK WAVES
SOLAR ACTIVITY
SOLAR CORONA
SOLAR WIND
STELLAR ATMOSPHERES
STELLAR CORONAE
WAVE PROPAGATION