Observational Analysis of Solar Coronal Plasma Clouds and Theory for Their Persistence

The inner solar corona, when observed in X-ray emission, consists of loops and unstructured clouds. The emission from the clouds corresponds to temperatures about 2 - 3 MK. These ``hot clouds'' are variable, but persist for many days. An observational analysis is presented involving magnetic field, density, and temperature measurements. Using these observations, a theoretical model is proposed where the macroscopic stability of the clouds is provided by the ambient magnetic field. In this model, at the more ``microscopic'' level, the plasmas associated with the clouds are considered as dominated by transport processes including particle inflow processes [1,2] that counteract relevant outward diffusion processes and can explain the lifetime of these clouds.\\ $[1]$ B. Coppi and C. Spight, Phys. Rev. Lett. 41, 551 (1978).\\ $[2]$ B. Coppi, MIT (LNS) Report HEP 13/07, Cambridge, MA, 2013.