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Sun-as-a-star Spectral Irradiance Observations: Milestone For Characterizing The Stellar Active Regions

Presentation #205.03 in the session “Solar Physics Division (SPD): Corona & ARs and Photosphere/Chromosphere”.

Published onJun 18, 2021
Sun-as-a-star Spectral Irradiance Observations: Milestone For Characterizing The Stellar Active Regions

For understanding the physical mechanism behind the solar flares, it is crucial to measure the magnetic fields of active regions (ARs) from the photosphere to the corona and investigate their scale, complexity, and evolution. This is true for the stellar flares. However, it is still difficult to spatially resolve the starspots, and one possible way to probe their evolution and structure is to monitor the star in multiple wavelengths. To test this possibility with the solar data, we perform multi-wavelength irradiance monitoring of transiting solar ARs by using full-disk observation data from SDO, Hinode, GOES, and SORCE. As a result, we find, for instance, that the near UV light curves show strong correlations with photospheric total magnetic flux and that there are time lags between the coronal and photospheric light curves when ARs are close to the limb, which together may enable one to discern how high bright coronal loops extend above stellar ARs. It is also revealed that the sub-MK (i.e. transition-region temperature) EUV light curves are sometimes dimmed because the emission measure is reduced owing to the heating over a wide area around the AR. These results indicate that, by measuring the stellar light curves in multiple wavelengths, we may obtain information on the structure and evolution of stellar ARs.


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