Exploring Relationship between Solar X-ray Irradiance and Magnetic Flux

Advisor: Aki Takeda

Our Sun is a G type star with the surface temperature at around 6000(K), but its thin atmosphere called corona is known to be more than 300 times hotter than the surface. The heating mechanism of the corona above the cooler surface is not fully understood, but the magnetic flux penetrating the surface from Sun's interior is believed to play a crucial role. This project explores the possible heating mechanism by closely comparing the brightness of the corona (measured as soft X-ray intensity) with the magnetic field strength (obtained from spectral information of visible light) underneath.

We will use data acquired in space. As soft X-ray data, we will use X-Ray Telescope(XRT) aboard the Hinode satellite (an international mission among Japan/US/UK), As magnetic field data we will use Helioseismic and Magnetic Imager(HMI) aboard the Solar Dynamic Observatory (a NASA mission). Student will first learn about these instruments and basic calibration of the data. The data analysis will be performed using IDL (Interactive Data Language) software. Experience with IDL programming would be favorable, but not required, as the basic programs will be provided.

This REU project started in 2024 as an extension of the study described in Yoshimura et al (2025) , which uses the full-Sun integrated signals of soft X-ray and magnetic field images. In the past two years, students investigated the X-ray vs magnetic flux relation for the sunspots. This year, this project will further expand the object of research to other solar structures like coronal bright points and quiet Sun.

Reference: K. Yoshimura, A. Takeda & D.W. Longcope, Astrophysical Journal (2025) vol.992, p.165, "Re-examining the power-law relationship between global solar X-ray luminosity and total unsigned magnetic flux"