Solar wind ionization state as a coronal temperature diagnostic

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

DOI:https://doi.org/10.1086/161538· OSTI ID:5016652

Owocki, S P; Holzer, T E; Hundhausen, A J

The solar wind ionization state is ''frozen'' within a few solar radii of the 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. We examine the nature of this freezing-in process, first employing a straightforward interpretation of the interplanetary ionization state to estimate the electron temperature of the coronal freezing-in region by making traditional simplifying assumptions about the coronal expansion, namely, that the electron temperature decreases monotonically with height, that the bulk flow speeds of all charge stages of a given ion species are equal (at a given location) to the proton speed, and that the ion outflow is spherically symmetric. We then investigate the consequences of relaxing these simplifying assumptions and find: (1) The traditional, straightforward interpretation of the interplanetary ionization state tends to underestimate the magnitude of a temperature maximum occurring near the freezing-in radius. (2) The tradional interpretation tends to overestimate (understimate) the actual coronal electron temperature if ion flow speeds in the coronal freezing-in region increase (decrease) with ionization stage. (3) Because it is associated with high-speed, low-density flow, an areal divergence that is faster than that in spherical outflow lowers the ionization state freezing-in level relative to that typical in spherically symmetric expansion, but the ionization states of all species should still freeze above the coronal base.

• Research Organization: Harvard-Smithsonian Center for Astrophysics
• OSTI ID: 5016652
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 275:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
CHARGED PARTICLES
ELECTRON DENSITY
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
INTERPLANETARY SPACE
ION MOBILITY
IONIZATION
IONS
LEPTONS
MATHEMATICAL MODELS
MOBILITY
PARTICLE MOBILITY
PLASMA
RADIATIONS
SOLAR ACTIVITY
SOLAR CORONA
SOLAR ELECTRONS
SOLAR PARTICLES
SOLAR RADIATION
SOLAR WIND
SPACE
STAR MODELS
STELLAR ATMOSPHERES
STELLAR CORONAE
STELLAR RADIATION