High-resolution observations of active region moss and its dynamics

Abstract

The \textit{High resolution Coronal Imager (Hi-C)} has provided the sharpest view of the EUV corona to date. In this paper we exploit its impressive resolving power to provide the first analysis of the fine-scale structure of moss in an active region. The data reveal that the moss is made up of a collection of fine threads, that have widths with a mean and standard deviation of $440\pm 190$~km (Full Width Half Maximum). {The brightest moss emission is located at the visible head of the fine-scale structure and the fine structure appears to extend into the lower solar atmosphere.} The emission decreases along the features implying the lower sections are most likely dominated by cooler transition region plasma. These threads appear to be the cool, lower legs of the hot loops. In addition, the increased resolution allows for the first direct observation {of physical displacements of the moss fine-structure in a direction transverse to its central axis. Some of these transverse displacements demonstrate periodic behaviour, which we interpret as a signature of kink (Alfvénic) waves. Measurements of the properties of the transverse motions are made and the wave motions have} means and standard deviations of $55\pm 37$~km for the transverse displacement amplitude, $77\pm 33$~s for the period and $4.7\pm 2.5$~km/s for the velocity amplitude. The presence of waves in the transition region of hot loops could have important implications for the heating of active regions.

arXiv comment34 Pages, 10 Figures, 1 Table - accepted in ApJ

References in corpus (30)

• Self-consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence
• Heating of the Solar Chromosphere and Corona by Alfven Wave Turbulence
• High Resolution Observations and Modeling of Dynamic Fibrils
• Observing the fine structure of loops through high resolution spectroscopic observations of coronal rain with the CRISP instrument at the Swedish Solar Telescope
• On the nature of kink MHD waves in magnetic flux tubes
• Persistent Doppler shift oscillations observed with HINODE/EIS in the solar corona: spectroscopic signatures of Alfvenic waves and recurring upflows
• Quantifying Spicules
• Propagating waves along spicules
• Selective spatial damping of propagating kink waves due to resonant absorption
• Structure of solar coronal loops: from miniature to large-scale
• Observing coronal nanoflares in active region moss
• On active region loops: Hinode/EIS observations
• Observational evidence of resonantly damped propagating kink waves in the solar corona
• 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
• Evidence for the photospheric excitation of incompressible chromospheric waves
• The Magnetic Structure of Coronal Loops Observed by TRACE
• Transverse oscillations in chromospheric mottles
• The generation and damping of propagating MHD kink waves in the solar atmosphere
• Hi-C & AIA observations of transverse MHD waves in active regions
• Anti-parallel EUV flows observed along active region filament threads with Hi-C
• Characteristics of transverse waves in chromospheric mottles
• Solar Dynamics Observatory discovers thin high temperature strands in coronal active regions
• Flows and Motions in Moss in the Core of a Flaring Active Region: Evidence for Steady Heating
• Active Region Moss: Basic physical parameters and their temporal variation
• The Transparency of Solar Coronal Active Regions
• Coronal fuzziness modelled with pulse-heated multistranded loop systems
• Estimating the Chromospheric Absorption of Transition Region Moss Emission
• Small-scale Hα Jets in the Solar Chromosphere
• Characteristics and Evolution of the Magnetic field and Chromospheric Emission in an Active Region Core Observed by Hinode

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• Flows and Waves in Braided Solar Coronal Magnetic Structures
• Power distribution of oscillations in the atmosphere of a plage region: Joint observations with ALMA, IRIS and SDO
• 3D WKB solution for fast magnetoacoustic wave behaviour around an X-line
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