engleski

Solar Differential Rotation Determined by Tracing Low and High Brightness Temperature Regions at 8 mm

At the wavelength of 8 mm absorption features (Low brightness Temperature Regions, LTRs) and emission features (High brightness Temperature Regions, HTRs) can be traced for determination of solar rotation. From earlier studies it is known that about two thirds of LTRs are associated with H$\alpha$ filaments. The goal of the present analysis is to determine the heights of these solar structures and their rotational velocities. We used the method for the simultaneous determination of the solar synodic rotation velocity and the height of tracers. The rotation velocities were determined by the linear least-square fit of their central meridian distances as a function of time. The mean value of the low brightness temperature regions' heights is about 45 600 km. The results of solar rotation determined by tracing LTRs and HTRs are mutually compared and also compared with the results using other tracers and methods. The method for the simultaneous determination of the solar synodic rotation velocity and the height of the tracers could be applied properly only on LTRs, since a wide distribution over latitudes and central meridian distances of a large data set is necessary, which was not available for HTRs. Observational findings that HTRs rotate systematically faster than LTRs and the possibility that they can be observed at and outside the solar limb are consistent with relatively high altitudes of HTRs. It was concluded that the radiation mechanism of HTRs is thermal bremsstrahlung, probably associated with flaring active regions.

Sun - rotation

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