Evolution of Elemental Abundances During B-Class Solar Flares: Soft X-ray Spectral Measurements with Chandrayaan-2 XSM

Abstract

The Solar X-ray Spectrometer (XSM) payload onboard Chandrayaan-2 provides disk-integrated solar spectra in the 1-15 keV energy range with an energy resolution of 180 eV (at 5.9 keV) and a cadence of 1~second. During the period from September 2019 to May 2020, covering the minimum of Solar Cycle 24, it observed nine B-class flares ranging from B1.3 to B4.5. Using time-resolved spectroscopic analysis during these flares, we examined the evolution of temperature, emission measure, and absolute elemental abundances of four elements -- Mg, Al, Si, and S. These are the first measurements of absolute abundances during such small flares and this study offers a unique insight into the evolution of absolute abundances as the flares evolve. Our results demonstrate that the abundances of these four elements decrease towards their photospheric values during the peak phase of the flares. During the decay phase, the abundances are observed to quickly return to their pre-flare coronal values. The depletion of elemental abundances during the flares is consistent with the standard flare model, suggesting the injection of fresh material into coronal loops as a result of chromospheric evaporation. To explain the quick recovery of the so-called coronal "First Ionization Potential (FIP) bias" we propose two scenarios based on the Ponderomotive force model.

arXiv commentAccepted for publication in the Astrophysical Journal, 19 pages, 12 figures

References in corpus (31)

• An Observational Overview of Solar Flares
• CHIANTI -- an atomic database for emission lines -- Paper XVI: Version 10, further extensions
• Impulsive phase flare energy transport by large-scale Alfven waves and the electron acceleration problem
• The FIP and Inverse FIP Effects in Solar and Stellar Coronae
• Solar UV and X-Ray Spectral Diagnostics
• A Unified Picture of the FIP and Inverse FIP Effects
• RHESSI Microflare Statistics II. X-ray Imaging, Spectroscopy & Energy Distributions
• Non-WKB Models of the FIP Effect: Implications for Solar Coronal Heating and the Coronal Helium and Neon Abundances
• Non-WKB Models of the FIP Effect: The Role of Slow Mode Waves
• The Thermal Properties of Solar Flares Over Three Solar Cycles Using GOES X-ray Observations
• Measurements of Absolute Abundances in Solar Flares
• Accelerated electrons observed down to <7 keV in a NuSTAR solar microflare
• The First Ionization Potential Effect from the Ponderomotive Force: On the Polarization and Coronal Origin of the Alfven Waves
• Solar Flare Element Abundances from the Solar Assembly for X-rays (SAX) on MESSENGER
• Solar X-ray Monitor On Board the Chandrayaan-2 Orbiter: In-flight Performance and Science Prospects
• The FIP and Inverse FIP Effects in Solar Flares
• Ponderomotive Acceleration in Coronal Loops
• NuSTAR Detection of X-Ray Heating Events in the Quiet Sun
• Inverse FIP Effects in Giant Solar Flares Found from Earth X-Ray Albedo with Suzaku/XIS
• Solar Flare Composition and Thermodynamics from RESIK X-ray Spectra
• The Evolution of Plasma Composition During a Solar Flare
• 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
• RESIK Solar X-ray flare element abundances on a non-isothermal assumption
• FOXSI-2 Solar Microflares I : Multi-instrument Differential Emission Measure Analysis and Thermal Energies
• NuSTAR Observation of a Minuscule Microflare in a Solar Active Region
• NuSTAR Observation of Energy Release in Eleven Solar Microflares
• Coronal Elemental Abundance: New Results from Soft X-ray Spectroscopy of the Sun
• Observations of the Quiet Sun During the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM -- Elemental Abundances in the Quiescent Corona
• Solar microflares: a case study on temperatures and the Fe XVIII emission
• Data Processing Software for Chandrayaan-2 Solar X-ray Monitor
• Nanoflare Heating: Observations and Theory

Cited by in corpus (3)

• Role of small-scale impulsive events in heating the X-ray bright points of the quiet Sun
• Delayed Development of Cool Plasmas in X-ray Flares from kappa1 Ceti
• Aditya-L1 and SDO Observations of a Confined X-Class Flare with an EUV Late Phase: Thermal and Nonthermal Emission, Magnetic Topology, and Flux Rope Confinement