Observations of the Quiet Sun During the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM -- Elemental Abundances in the Quiescent Corona

Abstract

Elements with low First Ionization Potential (FIP) are known to be three to four times more abundant in active region loops of the solar corona than in the photosphere. There have been observations suggesting that this observed "FIP bias" may be different in other parts of the solar corona and such observations are thus important in understanding the underlying mechanism. The Solar X-ray Monitor (XSM) on board the Chandrayaan-2 mission carried out spectroscopic observations of the Sun in soft X-rays during the 2019-20 solar minimum, considered to be the quietest solar minimum of the past century. These observations provided a unique opportunity to study soft X-ray spectra of the quiescent solar corona in the absence of any active regions. By modelling high resolution broadband X-ray spectra from XSM, we estimate the temperature and emission measure during periods of possibly the lowest solar X-ray intensity. We find that the derived parameters remain nearly constant over time with a temperature around 2 MK, suggesting the emission is dominated by X-ray Bright Points (XBPs). We also obtain the abundances of Mg, Al, and Si relative to H, and find that the FIP bias is ~2, lower than the values observed in active regions.

arXiv commentAccepted for publication in ApJL; 10 pages, 5 figures; All figures of figure set 5 available in the tar file

References in corpus (21)

• The FIP and Inverse FIP Effects in Solar and Stellar Coronae
• Solar UV and X-Ray Spectral Diagnostics
• CHIANTI - an atomic database for emission lines - Paper XV: Version 9, improvements for the X-ray satellite lines
• A Unified Picture of the FIP and Inverse FIP Effects
• Non-WKB Models of the FIP Effect: Implications for Solar Coronal Heating and the Coronal Helium and Neon Abundances
• Measurements of Absolute Abundances in Solar Flares
• Hinode/Extreme-Ultraviolet Imaging Spectrometer Observations of the Temperature Structure of the Quiet Corona
• The Instruments and Capabilities of the Miniature X-ray Solar Spectrometer (MinXSS) CubeSats
• New Observations of the Solar 0.5-5 keV Soft X-ray Spectrum
• Solar Flare Element Abundances from the Solar Assembly for X-rays (SAX) on MESSENGER
• A Twenty Year Decline in Solar Photospheric Magnetic Fields: Inner-Heliospheric Signatures and Possible Implications?
• A Solar cycle correlation of coronal element abundances in Sun-as-a-star observations
• Solar X-ray Monitor On Board the Chandrayaan-2 Orbiter: In-flight Performance and Science Prospects
• Ponderomotive Acceleration in Coronal Loops
• The EUV spectrum of the Sun: quiet and active Sun irradiances and chemical composition
• Observations of the Quiet Sun During the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM -- Sub-A Class Microflares Outside Active Regions
• Coronal Elemental Abundance: New Results from Soft X-ray Spectroscopy of the Sun
• Soft X-Ray Observations of Quiescent Solar Active Regions using Novel Dual-zone Aperture X-ray Solar Spectrometer (DAXSS)
• Data Processing Software for Chandrayaan-2 Solar X-ray Monitor
• Ground Calibration of Solar X-ray Monitor On-board Chandrayaan-2 Orbiter
• Analysis of Quiescent Corona X-ray Spectra from SphinX during the 2009 Solar Minimum

Cited by in corpus (11)

• NuSTAR observations of a repeatedly microflaring active region
• Observations of the Quiet Sun During the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM -- Sub-A Class Microflares Outside Active Regions
• Coronal Elemental Abundances during A-class Solar Flares Observed by Chandrayaan-2 XSM
• The First Flight of the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS)
• Coronal Densities, Temperatures and Abundances During the 2019 Total Solar Eclipse: The Role of Multi-Wavelength Observations in Coronal Plasma Characterization
• Role of small-scale impulsive events in heating the X-ray bright points of the quiet Sun
• Multi-wavelength observations by XSM, Hinode and SDO of an active region. Chemical abundances and temperatures
• New Solar Flare Calcium Abundances with no Surprises: Results from the SMM Bent Crystal Spectrometer
• Nanoflare Heating of the Solar Corona Observed in X-rays
• Evolution of Elemental Abundances During B-Class Solar Flares: Soft X-ray Spectral Measurements with Chandrayaan-2 XSM
• Limits on the axion-photon coupling from Chandrayaan-2 observations