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Sun corona experiment12/8/2022 ![]() ![]() Here, we discuss some recent developments in the area. They deal with parameter inference, model comparison, and model averaging applications to gain information on the magnetic field and the plasma conditions in structures in the solar corona and in solar prominences. In the last decade, about 25 studies in coronal seismology have made use of Bayesian techniques. The first study that made use of Bayesian analysis in coronal seismology was by Arregui and Asensio Ramos (2011), who inferred coronal loop physical parameters from observed periods and damping times of their transverse oscillations. Initial solar applications were focused on statistical analyses of solar neutrino data ( Gates et al., 1995), followed by studies on solar flare prediction ( Wheatland, 2004), the analysis of solar global oscillations ( Marsh et al., 2008), and the inversion of magnetic and thermodynamic properties of the solar atmosphere from the analysis of spectro-polarimetric data ( Asensio Ramos et al., 2007). It took two more decades for the Bayesian approach to be adopted in solar physics. The first studies (already 50 years ago) dealt with both technical problems, such as the construction of image restoration algorithms ( Richardson, 1972), as well as with procedures for formalising the evaluation of astrophysical hypotheses by comparison between theoretical predictions and observational data ( Sturrock, 1973). Figure 1 shows the number of Bayesian astrophysics papers as a function of year. Since the values of the density and density contrast have probabilistic distributions, the derived magnetic field has a probabilistic distribution.īayesian analysis is increasingly being used in astrophysics. Only after assumptions about the loop plasma density and the density contrast one can derive the magnetic field. A prototypical example is the determination of the magnetic field strength in coronal loops from the observational measurement of the kink speed of transverse oscillations ( Nakariakov and Ofman, 2001). As a consequence, solar atmospheric seismology deals with inversion problems that are probabilistic in nature and our conclusions can only be probabilities at best. Because of our lack of direct access to the physical systems of interest information is incomplete and uncertain. Coronal seismology aims to infer difficult to measure physical parameters in magnetic and plasma structures, such as coronal loops and prominence plasmas, by a combination of observations of wave activity and theoretical models, usually under the MHD approximation ( Uchida, 1970 Roberts et al., 1984). Some coronagraphs are used with ground-based telescopes others are carried on satellites.The aim of this paper is to give a rationale for the use of Bayesian methods in the study of the solar corona and to show recent applications in the area of solar coronal seismology. A special instrument called a coronagraph allows astronomers to view the corona at other times. During a total solar eclipse the wispy corona briefly comes into view as the Moon blocks out the solar surface. The surface of the Sun is far too bright to allow a glimpse of the much fainter corona. We normally cannot see the solar atmosphere, including the corona. The density of plasma falls rapidly through the transition region moving upward from the chromosphere to the corona. ![]() Temperatures rise sharply in the transition region, from thousands of degrees in the chromosphere to more than a million degrees in the corona. A relatively narrow area called the transition region separates the corona from the chromosphere. The corona is above the Sun's lower atmosphere, which is called the chromosphere. The pressure and density in the corona is much, much lower than in Earth's atmosphere. The temperature in the corona is more than a million degrees, surprisingly much hotter than the temperature at the Sun's surface which is around 5,500° C (9,940° F or 5,780 kelvins). The material in the corona is an extremely hot but very tenuous plasma. It extends many thousands of kilometers (miles) above the visible " surface" of the Sun, gradually transforming into the solar wind that flows outward through our solar system. The corona is the outer atmosphere of the Sun. NCAR's High Altitude Observatory and NASA SDO< Two views of the Sun's corona: during an eclipse (top) and in ultraviolet light (bottom). ![]()
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