Exploring the damping of Alfvén waves along a long off-limb coronal loop, up to 1.4 R${}_{\odot }$

Abstract

The Alfvén wave energy flux in the corona can be explored using the electron density and velocity amplitude of the waves. The velocity amplitude of Alfvén waves can be obtained from the non-thermal velocity of the spectral line profiles. Previous calculations of the Alfvén wave energy flux with height in active regions and polar coronal holes have provided evidence for the damping of Alfvén waves with height. We present off-limb Hinode EUV imaging spectrometer (EIS) observations of a long coronal loop up to 1.4~R${}_{\odot }$. We have obtained the electron density along the loop and found the loop to be almost in hydrostatic equilibrium. We obtained the temperature using the EM-loci method and found the loop to be isothermal across, as well as along, the loop with a temperature of about 1.37 MK. We significantly improve the estimate of non-thermal velocities over previous studies by using the estimated ion (equal to electron) temperature. Estimates of electron densities are improved using the significant updates of the CHIANTI v.8 atomic data. More accurate measurements of propagating Alfvén wave energy along the coronal loop and its damping are presented up to distances of 1.4 R${}_{\odot }$, further than have been previously explored. The Alfvén wave energy flux obtained could contribute to a significant part of the coronal losses due to radiation along the loop.

A&A, in press

References in corpus (9)

• Self-consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence
• Highly Efficient Modeling of Dynamic Coronal Loops
• Spectroscopic signature of Alfvén waves damping in a polar coronal hole up to 0.4 solar radii
• The Heating of Solar Coronal Loops by Alfven Wave Turbulence
• Evidence for Wave Heating of the Quiet Sun Corona
• Plasma parameters and geometry of cool and warm active region loops
• Spectroscopic Observations of a Coronal Loop: Basic Physical Plasma Parameters Along the Full Loop Length
• Fan Loops Observed by IRIS, EIS and AIA
• Spectroscopic evidence of Alfvén wave damping in the off-limb solar corona

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• Understanding the magnetic field and plasma-$\beta$ along umbral fan loops traced using 3-min slow waves
• Initiation of Alfvénic turbulence by Alfven wave collisions: A numerical study