Constraining Hot Plasma in a Non-flaring Solar Active Region with FOXSI Hard X-ray Observations

Abstract

We present new constraints on the high-temperature emission measure of a non-flaring solar active region using observations from the recently flown Focusing Optics X-ray Solar Imager sounding rocket payload. FOXSI has performed the first focused hard X-ray (HXR) observation of the Sun in its first successful flight on 2012 November 2. Focusing optics, combined with small strip detectors, enable high-sensitivity observations with respect to previous indirect imagers. This capability, along with the sensitivity of the HXR regime to high-temperature emission, offers the potential to better characterize high-temperature plasma in the corona as predicted by nanoflare heating models. We present a joint analysis of the differential emission measure (DEM) of active region 11602 using coordinated observations by FOXSI, Hinode/XRT and Hinode/EIS. The Hinode-derived DEM predicts significant emission measure between 1 MK and 3 MK, with a peak in the DEM predicted at 2.0-2.5 MK. The combined XRT and EIS DEM also shows emission from a smaller population of plasma above 8 MK. This is contradicted by FOXSI observations that significantly constrain emission above 8 MK. This suggests that the Hinode DEM analysis has larger uncertainties at higher temperatures and that >8 MK plasma above an emission measure of 3x10^44 cm^-3 is excluded in this active region.

7 pages, 2 figures, published in PASJ

References in corpus (4)

• High energy resolution hard X-ray and gamma-ray imagers using CdTe diode devices
• Hinode X-Ray Telescope Detection of Hot Emission from Quiescent Active Regions: A Nanoflare Signature?
• Non-equilibrium of Ionization and the Detection of Hot Plasma in Nanoflare-heated Coronal Loops
• Fine-pitch semiconductor detector for the FOXSI mission

Cited by in corpus (22)

• Solar UV and X-Ray Spectral Diagnostics
• Non-Equilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind \textit{(Invited Review)}
• Inference of Heating Properties from "Hot" Non-flaring Plasmas in Active Region Cores I. Single Nanoflares
• The Instruments and Capabilities of the Miniature X-ray Solar Spectrometer (MinXSS) CubeSats
• The first X-ray imaging spectroscopy of quiescent solar active regions with NuSTAR
• IRIS observations of short-term variability in moss associated with transient hot coronal loops
• FOXSI-2: Upgrades of the Focusing Optics X-ray Solar Imager for its Second Flight
• Inference of Heating Properties from "Hot" Non-flaring Plasmas in Active Region Cores. II. Nanoflare Trains
• Spectroscopy of very hot plasma in non-flaring parts of a solar limb active region: spatial and temporal properties
• FOXSI-2 Solar Microflares I : Multi-instrument Differential Emission Measure Analysis and Thermal Energies
• Hard X-Ray Constraints on Small-Scale Coronal Heating Events
• Solar microflares: a case study on temperatures and the Fe XVIII emission
• The First Flight of the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS)
• Estimate of the Upper Limit on Hot Plasma Differential Emission Measure (DEM) in Non-Flaring Active Regions and Nanoflare Frequency Based on the Mg XII Spectroheliograph Data from CORONAS-F/SPIRIT
• High-speed X-ray imaging spectroscopy system with Zynq SoC for solar observations
• Fine-pitch CdTe detector for hard X-ray imaging and spectroscopy of the Sun with the FOXSI rocket experiment
• A New Component from the Quiet Sun: Synchrotron Radiation from Galactic Cosmic-Ray Electrons
• Quantifying the Influence of Key Physical Processes on the Formation of Emission Lines Observed by IRIS: I. Non-Equilibrium Ionization and Density-Dependent Rates
• Hot plasma in a quiescent solar active region as measured by RHESSI, XRT, and AIA
• Yet Another Sunshine Mystery: Unexpected Asymmetry in GeV Emission from the Solar Disk
• Thermal Evolution of an Active Region through Quiet and Flaring Phases as Observed by NuSTAR XRT, and AIA
• White paper of the "soft X-ray imaging spectroscopy"