Solar microflares: a case study on temperatures and the Fe XVIII emission
arXiv:1905.08579 · doi:10.1051/0004-6361/201834856
Abstract
In this paper, we discuss the temperature distribution and evolution of a microflare, simultaneously observed by Hinode XRT, EIS, and SDO AIA. We find using EIS lines that during peak emission the distribution is nearly isothermal and peaked around 4.5 MK. This temperature is in good agreement with that obtained from the XRT filter ratio, validating the use of XRT to study these small events, invisible by full-Sun X-ray monitors such as GOES. The increase in the estimated Fe XVIII emission in the AIA 94 Å band can mostly be explained with the small temperature increase from the background temperatures. The presence of Fe XVIII emission does not guarantee that temperatures of 7 MK are reached, as is often assumed. We also revisit with new atomic data the temperatures measured by a SoHO SUMER observation of an active region which produced microflares, also finding low temperatures (3 - 4 MK) from an Fe XVIII / Ca XIV ratio.
arXiv comment12-13 pages, 17 figures (22 eps-files), 4 tables, accepted by Astronomy and Astrophysics
References in corpus (23)
- The chemical composition of the Sun
- On Solving the Coronal Heating Problem
- CHIANTI - An atomic database for Emission Lines. Version 8
- Heating of the Solar Chromosphere and Corona by Alfven Wave Turbulence
- Solar UV and X-Ray Spectral Diagnostics
- RHESSI Microflare Statistics II. X-ray Imaging, Spectroscopy & Energy Distributions
- A Systematic Survey of High Temperature Emission in Solar Active Regions
- Structure of solar coronal loops: from miniature to large-scale
- Constraints on the Heating of High Temperature Active Region Loops: Observations from Hinode and SDO
- A revised radiometric calibration for the Hinode/EIS instrument
- Microflare Heating of a Solar Active Region Observed with NuSTAR, Hinode/XRT, and SDO/AIA
- Coronal Temperature Diagnostic Capability of the Hinode/X-Ray Telescope Based on Self-Consistent Calibration
- Benchmarking atomic data for astrophysics: a first look at the soft X-ray lines
- The first X-ray imaging spectroscopy of quiescent solar active regions with NuSTAR
- Hot Plasma in Non-Flaring Active Regions Observed by the Extreme-ultraviolet Imaging Spectrometer on Hinode
- Constraining Hot Plasma in a Non-flaring Solar Active Region with FOXSI Hard X-ray Observations
- Plasma heating in solar microflares: statistics and analysis
- The Evolution of the EM Distribution in the Core of an Active Region
- Coronal-Temperature-Diagnostic Capability of the Hinode/X-Ray Telescope Based on Self-Consistent Calibration. II. Calibration with on-Orbit Data
- Spectroscopic Observations of Fe XVIII in Solar Active Regions
- Spectroscopy of very hot plasma in non-flaring parts of a solar limb active region: spatial and temporal properties
- Calibrating Data from the Hinode/X-Ray Telescope and Associated Uncertainties
- Wave-like Formation of Hot Loop Arcades
Cited by in corpus (5)
- Solar X-ray Monitor On Board the Chandrayaan-2 Orbiter: In-flight Performance and Science Prospects
- NuSTAR observations of a repeatedly microflaring active region
- Impulsive coronal heating from large-scale magnetic rearrangements: from IRIS to SDO/AIA
- Multi-wavelength observations by XSM, Hinode and SDO of an active region. Chemical abundances and temperatures
- Evolution of Elemental Abundances During B-Class Solar Flares: Soft X-ray Spectral Measurements with Chandrayaan-2 XSM