Active region transition region loop populations and their relationship to the corona

Abstract

The relationships among coronal loop structures at different temperatures is not settled. Previous studies have suggested that coronal loops in the core of an active region are not seen cooling through lower temperatures and therefore are steadily heated. If loops were cooling, the transition region would be an ideal temperature regime to look for a signature of their evolution. The Extreme-ultraviolet Imaging Spectrometer (EIS) on Hinode provides monochromatic images of the solar transition region and corona at an unprecedented cadence and spatial resolution, making it an ideal instrument to shed light on this issue. Analysis of observations of active region 10978 taken in 2007 December 8 -- 19 indicates that there are two dominant loop populations in the active region: core multi-temperature loops that undergo a continuous process of heating and cooling in the full observed temperature range 0.4-2.5 MK and even higher as shown by the X-Ray Telescope (XRT); and peripheral loops which evolve mostly in the temperature range 0.4-1.3 MK. Loops at transition region temperatures can reach heights of 150 Mm in the corona above the limb and develop downflows with velocities in the range of 39-105 km/s.

15 pages, 8 figures. Accepted for publication in ApJ

References in corpus (6)

• Observations of Active Region Loops with the EUV Imaging Spectrometer on Hinode
• Transition region features observed with Hinode/EIS
• Observation and Modeling of Coronal "Moss" With the EUV Imaging Spectrometer on Hinode
• Modeling X-ray Loops and EUV "Moss" in an Active Region Core
• Multiresolution analysis of active region magnetic structure and its correlation with the Mt. Wilson classification and flaring activity
• Observations of Transient Active Region Heating with Hinode

Cited by in corpus (64)

• Heating of the Solar Chromosphere and Corona by Alfven Wave Turbulence
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• A Systematic Survey of High Temperature Emission in Solar Active Regions
• Establishing a Connection Between Active Region Outflows and the Solar Wind: Abundance Measurements with EIS/Hinode
• Solar ultraviolet bursts
• The multi-thermal and multi-stranded nature of coronal rain
• Using a Differential Emission Measure and Density Measurements in an Active Region Core to Test a Steady Heating Model
• High Spatial Resolution Observations of Loops in the Solar Corona
• Asymmetries of solar coronal extreme ultraviolet emission lines
• Patterns of Nanoflare Storm Heating Exhibited by an Active Region Observed with SDO/AIA
• Can Thermal Nonequilibrium Explain Coronal Loops?
• Evidence for evaporation-incomplete condensation cycles in warm solar coronal loops
• The Temperature Dependence of Solar Active Region Outflows
• On-disk coronal rain
• Evidence for Steady Heating: Observations of an Active Region Core with Hinode and TRACE
• Modeling the Line-of-Sight Integrated Emission in the Corona: Implications for Coronal Heating
• Long-Period Intensity Pulsations in Coronal Loops Explained by Thermal Non-Equilibrium Cycles
• Flows and Motions in Moss in the Core of a Flaring Active Region: Evidence for Steady Heating
• The Coronal Monsoon: Thermal Nonequilibrium Revealed by Periodic Coronal Rain
• Observational Signatures of Coronal Loop Heating and Cooling Driven by Footpoint Shuffling
• Continuous upflows and sporadic downflows observed in active regions
• The Coronal Veil
• EUV spectral line formation and the temperature structure of active region fan loops: observations with Hinode/EIS and SDO/AIA
• Temporal Variability of Active Region Outflows
• Cool transition region loops observed by the Interface Region Imaging Spectrograph
• A closer look at a coronal loop rooted in a sunspot umbra
• Multi-scale observations of thermal non-equilibrium cycles in coronal loops
• Determining heating time scales in solar active region cores from AIA/SDO Fe XVIII images
• The Evolution of the EM Distribution in the Core of an Active Region
• A simple model for the evolution of multi-stranded coronal loops
• Signatures of the slow solar wind streams from active regions in the inner corona
• Properties and Modeling of Unresolved Fine Structure Loops Observed in the Solar Transition Region by IRIS
• Observations of Plasma Upflow in a Warm Loop with Hinode/EIS
• Can Large Time Delays Observed in Light Curves of Coronal Loops be Explained by Impulsive Heating?
• Fan Loops Observed by IRIS, EIS and AIA
• The Magnetic Properties of Heating Events on High-Temperature Active Region Loops
• Active Region Moss: Doppler Shifts from Hinode/EIS Observations
• Formation of coronal rain triggered by impulsive heating associated with magnetic reconnection
• Prevalence of Thermal Non-Equilibrium over an Active Region
• EUV fine structure and variability associated with coronal rain revealed by Solar Orbiter/EUI HRIEUV and SPICE
• Doppler shift of hot coronal lines in a moss area of an active region
• Heating and cooling of coronal loops observed by SDO
• Coronal Heating Topology: the Interplay of Current Sheets and Magnetic Field Lines
• Heating Mechanisms for Intermittent Loops in Active Region Cores from AIA/SDO EUV Observations
• Damping of longitudinal magneto-acoustic oscillations in slowly varying coronal plasma
• Chromospheric counterparts of solar transition region unresolved fine structure loops
• Emission Measure Distribution for Diffuse Regions in Solar Active Regions
• Dark Post-Flare Loops Observed by Solar Dynamics Observatory
• Electron Densities in the Solar Corona Measured Simultaneously in the Extreme-Ultraviolet and Infra-Red
• Further Evidence for Looplike Fine Structure inside "Unipolar" Active Region Plages
• On the spectroscopic detection of periodic plasma flows in loops undergoing thermal non-equilibrium
• On the Area Expansion of Magnetic Flux-Tubes in Solar Active Regions
• Observations and modeling of the emerging EUV loops in the quiet Sun as seen with the Solar Dynamics Observatory
• Undetected Minority-polarity Flux as the Missing Link in Coronal Heating
• EUV Observational consequences of the spatial localisation of nanoflare heating within a multi-stranded atmospheric loop
• The Role of Magnetic Topology in the Heating of Active Region Coronal Loops
• Model fitting of kink waves in the solar atmosphere: Gaussian damping and time-dependence
• Direct Observations of Plasma Upflows and Condensation in a Catastrophically Cooling Solar Transition Region Loop
• Hot coronal loops associated with umbral brightenings
• Characteristics and Evolution of the Magnetic field and Chromospheric Emission in an Active Region Core Observed by Hinode
• EUV Analysis of a Quasi-Static Coronal Loop Structure
• Heating of quiescent coronal loops caused by nearby eruptions observed with the Solar Dynamics Observatory and the Solar Upper Transition Region Imager
• Properties of EUV Imaging Spectrometer (EIS) Slot Observations
• Thermal Non-equilibrium Cycles in a Non-eruptive Pseudo-Streamer