The temporal evolution of coronal loops observed by GOES-SXI

Abstract

We study the temporal evolution of coronal loops using data from the Solar X-ray Imager (SXI) on board of GOES-12. This instrument allows us to follow in detail the full lifetime of coronal loops. The observed light curves suggest three somewhat distinct evolutionary phases: rise, main, and decay. The durations and characteristic timescales of these phases are much longer than a cooling time and indicate that the loop-averaged heating rate increases slowly, reaches a maintenance level, and then decreases slowly. This suggests that a single heating mechanism operates for the entire lifetime of the loop. For monolithic loops, the loop-averaged heating rate is the intrinsic energy release rate of the heating mechanism. For loops that are bundles of impulsively heated strands, it is an indication of the frequency of occurrence of individual heating events, or nanoflares. We show that the timescale of the loop-averaged heating rate is proportional to the timescale of the observed intensity variation. The ratios of the radiative to conductive cooling times in the loops are somewhat less than 1, putting them intermediate between the values measured previously for hotter and cooler loops. Our results provide further support for the existence of a trend suggesting that all loops are heated by the same mechanism, or that different mechanisms have fundamental similarities (e.g., are all impulsive or are all steady with similar rates of heating).

Accepted for publication in ApJ

References in corpus (4)

• On Solving the Coronal Heating Problem
• The Magnetic Structure of Coronal Loops Observed by TRACE
• Cooling Active Region Loops Observed With SXT and TRACE
• Analysis of a multi-wavelength time-resolved observation of a coronal loop

Cited by in corpus (19)

• Coronal Loops: Observations and Modeling of Confined Plasma
• Can Thermal Nonequilibrium Explain Coronal Loops?
• The Role of Type II Spicules in the Upper Solar Atmosphere
• Decay Phase Cooling and Inferred Heating of M- and X-class Solar Flares
• Statistical Signatures of Nanoflare Activity. I. Monte Carlo Simulations and Parameter-space Exploration
• A simple model for the evolution of multi-stranded coronal loops
• 2D cellular automaton model for the evolution of active region coronal plasmas
• The Magnetic Properties of Heating Events on High-Temperature Active Region Loops
• Effect of Coronal Loop Structure on Wave Heating by Phase Mixing
• Damping of longitudinal magneto-acoustic oscillations in slowly varying coronal plasma
• Physical processes involved in the EUV "Surge" Event of 09 May 2012
• Hot coronal loops associated with umbral brightenings
• Are the brightest coronal loops always rooted in mixed-polarity magnetic flux?
• Stereoscopic observations reveal coherent morphology and evolution of solar coronal loops
• Enthalpy-based modeling of tomographically reconstructed quiet-Sun coronal loops
• Dominance of Bursty over Steady Heating of the 4--8 MK Coronal Plasma in a Solar Active Region: Quantification using Maps of Minimum, Maximum, and Average Brightness
• Three-Dimensional Reconstruction and Thermal Modelling of Observed Loops
• Long-lived coronal loops in solar active regions
• The Effect Of Cooling On Driven Kink Oscillations Of Coronal Loops