Evolution of elemental abundances in hot active region cores from Chandrayaan-2 XSM observations

TL;DR

This study investigates the elemental abundance variations in hot active region cores on the Sun using Chandrayaan-2 XSM data, revealing consistent FIP bias patterns and rapid establishment after active region emergence.

Contribution

It provides new insights into the temporal evolution and stability of FIP bias in solar active regions based on soft X-ray spectroscopic observations.

Findings

Low FIP elements have higher abundances than photospheric values.

FIP bias for Mg and Si is around 3, for S around 1.5.

FIP bias for Al exceeds 3, indicating FIP dependence.

Abstract

The First Ionization Potential (FIP) bias, whereby elemental abundances for low FIP elements in different coronal structures vary from their photospheric values and may also vary with time, has been widely studied. In order to study the temporal variation, and to understand the physical mechanisms giving rise to the FIP bias, we have investigated the hot cores of three ARs using disk-integrated soft X-ray spectroscopic observation with the Solar X-ray Monitor (XSM) onboard Chandrayaan-2. Observations for periods when only one AR was present on the solar disk were used so as to ensure that the AR was the principal contributor to the total X-ray intensity. The average values of temperature and EM were ~3 MK and 3.0E46/cm3 respectively. Regardless of the age and activity of the AR, the elemental abundances of the low FIP elements, Al, Mg, and Si were consistently higher than their photospheric values. The average FIP bias for Mg and Si was ~3, whereas the FIP bias for the mid-FIP element, S, was ~1.5. However, the FIP bias for the lowest FIP element, Al, was observed to be higher than 3, which, if real, suggests a dependence of the FIP bias of low FIP elements on their FIP value. Another major result from our analysis is that the FIP bias of these elements is established in within ~10 hours of emergence of the AR and then remains almost constant throughout its lifetime.