Are Coronal Loops Isothermal or Multithermal? Yes!

Abstract

Surprisingly few solar coronal loops have been observed simultaneously with TRACE and SOHO/CDS, and even fewer analyses of these loops have been conducted and published. The SOHO Joint Observing Program 146 was designed in part to provide the simultaneous observations required for in-depth temperature analysis of active region loops and determine whether these loops are isothermal or multithermal. The data analyzed in this paper were taken on 2003 January 17 of AR 10250. We used TRACE filter ratios, emission measure loci, and two methods of differential emission measure analysis to examine the temperature structure of three different loops. TRACE and CDS observations agree that Loop 1 is isothermal with Log T $=$ 5.85, both along the line of sight as well as along the length of the loop leg that is visible in the CDS field of view. Loop 2 is hotter than Loop 1. It is multithermal along the line of sight, with significant emission between 6.2 $<$ Log T $<$ 6.4, but the loop apex region is out of the CDS field of view so it is not possible to determine the temperature distribution as a function of loop height. Loop 3 also appears to be multithermal, but a blended loop that is just barely resolved with CDS may be adding cool emission to the Loop 3 intensities and complicating our results. So, are coronal loops isothermal or multithermal? The answer appears to be yes!

Cited by in corpus (19)

• Solar Corona Loop Studies with AIA: I. Cross-Sectional Temperature Structure
• Coronal Loops: Observations and Modeling of Confined Plasma
• On the Accuracy of the Differential Emission Measure Diagnostics of Solar Plasmas. Application to AIA/SDO. Part II: Multithermal plasmas
• Density diagnostics derived from the OIV and SIV intercombination lines observed by IRIS
• Is the High-Resolution Coronal Imager Resolving Coronal Strands? Results from AR 12712
• Heating of braided coronal loops
• Signatures of impulsive localized heating in the temperature distribution of multi-stranded coronal loops
• A simple model for the evolution of multi-stranded coronal loops
• Imaging and Spectroscopic Observations of a Transient Coronal Loop: Evidence for the Non-Maxwellian $\kappa$-Distributions
• X-raying hot plasma in solar active regions with the SphinX spectrometer
• Unravelling the components of a multi-thermal coronal loop using magnetohydrodynamic seismology
• The Coronal Abundances of Mid-F Dwarfs
• A nanoflare based cellular automaton model and the observed properties of the coronal plasma
• Electron Densities in the Solar Corona Measured Simultaneously in the Extreme-Ultraviolet and Infra-Red
• On the Area Expansion of Magnetic Flux-Tubes in Solar Active Regions
• Non-equilibrium ionization by a periodic electron beam. I. Synthetic coronal spectra and implications for interpretation of observations
• Temperature and Differential Emission Measure Profiles in Turbulent Solar Active Region Loops
• Multi-strand coronal loop model and filter-ratio analysis
• Anomalous cross-field motions of solar coronal loops