Coronal Temperature Profiles Obtained from Kinetic Models and from Coronal Brightness Measurements Obtained During Solar Eclipses

Abstract

Coronal density, temperature and heat flux distributions for the equatorial and polar corona have been deduced by Lemaire [2012] from Saito's model of averaged coronal white light (WL) brightness and polarization observations. They are compared with those determined from a kinetic collisionless/exospheric model of the solar corona. This comparison indicates rather similar distributions at large radial distances (> 7 Rs) in the collisionless region. However, rather important differences are found close to the Sun in the acceleration region of the solar wind. The exospheric heat flux is directed away from the Sun, while that inferred from all WL coronal observations is in the opposite direction, i.e., conducting heat from the inner corona toward the chromosphere. This could indicate that the source of coronal heating rate extends up into the inner corona where it maximizes at r > 1.5 Rs well above the transition region.

Exospheric Solar Wind Model Based on Regularized Kappa Distributions for the Electrons Constrained by Parker Solar Probe Observations

“…At the exobase, the VDF is also truncated due to the absence of incoming protons. The absence of incoming protons at the exobase leads to T p⊥ > T p// proton temperature anisotropies at low radial distances before an inversion occurs after several solar radii in agreement with observations [51]. At 17.2 Rs, the distribution is highly focused in the direction parallel to the magnetic field by conservation of the magnetic moment.…”

Coronal heating and solar wind acceleration for electrons, protons, and minor ions obtained from kinetic models based on kappa distributions

“…Figure shows typical radial profiles of the solar wind obtained with the exospheric model for the electrons at the exobase level 2 R S , where the temperature of the electrons is assumed to be T e = T p = 10 6 K. It can be seen that the density continues to decrease, while the temperature reaches a maximum and begins to decrease. Note that the maximum of electron temperature is obtained around 2 R S even when the exobase is located at lower altitudes, corresponding well to the temperature inversion profiles deduced from coronal observations during solar eclipses [ Pierrard et al ., ].…”