33 research outputs found
Resonant Absorption of Transverse Oscillations and Associated Heating in a Solar Prominence. II- Numerical aspects
Transverse magnetohydrodynamic (MHD) waves are ubiquitous in the solar
atmosphere and may be responsible for generating the Sun's million-degree outer
atmosphere. However, direct evidence of the dissipation process and heating
from these waves remains elusive. Through advanced numerical simulations
combined with appropriate forward modeling of a prominence flux tube, we
provide the observational signatures of transverse MHD waves in prominence
plasmas. We show that these signatures are characterized by thread-like
substructure, strong transverse dynamical coherence, an out-of-phase difference
between plane-of-the-sky motions and LOS velocities, and enhanced line
broadening and heating around most of the flux tube. A complex combination
between resonant absorption and Kelvin-Helmholtz instabilities (KHI) takes
place in which the KHI extracts the energy from the resonant layer and
dissipates it through vortices and current sheets, which rapidly degenerate
into turbulence. An inward enlargement of the boundary is produced in which the
turbulent flows conserve the characteristic dynamics from the resonance,
therefore guaranteeing detectability of the resonance imprints. We show that
the features described in the accompanying paper (Okamoto et al. 2015) through
coordinated Hinode and IRIS observations match well the numerical results.Comment: This is part 2 of a series of 2 papers. Part 1 corresponds to Okamoto
et al. (2015, accepted). 36 Pages (single column), 10 figures. Accepted for
publication in The Astrophysical Journa
Resonant Absorption of Transverse Oscillations and Associated Heating in a Solar Prominence. I- Observational aspects
Transverse magnetohydrodynamic (MHD) waves have been shown to be ubiquitous
in the solar atmosphere and can in principle carry sufficient energy to
generate and maintain the Sun's million-degree outer atmosphere or corona.
However, direct evidence of the dissipation process of these waves and
subsequent heating has not yet been directly observed. Here we report on high
spatial, temporal, and spectral resolution observations of a solar prominence
that show a compelling signature of so-called resonant absorption, a long
hypothesized mechanism to efficiently convert and dissipate transverse wave
energy into heat. Aside from coherence in the transverse direction, our
observations show telltale phase differences around 180 degrees between
transverse motions in the plane-of-sky and line-of-sight velocities of the
oscillating fine structures or threads, and also suggest significant heating
from chromospheric to higher temperatures. Comparison with advanced numerical
simulations support a scenario in which transverse oscillations trigger a
Kelvin-Helmholtz instability (KHI) at the boundaries of oscillating threads via
resonant absorption. This instability leads to numerous thin current sheets in
which wave energy is dissipated and plasma is heated. Our results provide
direct evidence for wave-related heating in action, one of the candidate
coronal heating mechanisms.Comment: 28 pages, 9 figures, accepted for publication in ApJ. Part II by
Patrick Antolin et al. will appear soo
First High-resolution Spectroscopic Observations of an Erupting Prominence Within a Coronal Mass Ejection by the Interface Region Imaging Spectrograph (IRIS)
Spectroscopic observations of prominence eruptions associated with coronal
mass ejections (CMEs), although relatively rare, can provide valuable plasma
and 3D geometry diagnostics. We report the first observations by the Interface
Region Imaging Spectrograph (IRIS) mission of a spectacular fast CME/prominence
eruption associated with an equivalent X1.6 flare on 2014 May 9. The maximum
plane-of-sky and Doppler velocities of the eruption are 1200 and 460 km/s,
respectively. There are two eruption components separated by ~200 km/s in
Doppler velocity: a primary, bright component and a secondary, faint component,
suggesting a hollow, rather than solid, cone-shaped distribution of material.
The eruption involves a left-handed helical structure undergoing
counter-clockwise (viewed top-down) unwinding motion. There is a temporal
evolution from upward eruption to downward fallback with less-than-free-fall
speeds and decreasing nonthermal line widths. We find a wide range of Mg II k/h
line intensity ratios (less than ~2 expected for optically-thin thermal
emission): the lowest ever-reported median value of 1.17 found in the fallback
material and a comparably high value of 1.63 in nearby coronal rain and
intermediate values of 1.53 and 1.41 in the two eruption components. The
fallback material exhibits a strong () linear correlation between
the k/h ratio and the Doppler velocity as well as the line intensity. We
demonstrate that Doppler dimming of scattered chromospheric emission by the
erupted material can potentially explain such characteristics.Comment: 12 pages, 6 figures, accepted by ApJ (Feb 15, 2015
Resonant absorption of transverse oscillations and associated heating in a solar prominence. I. Observational aspects
Transverse magnetohydrodynamic waves have been shown to be ubiquitous in the solar atmosphere and can, in principle, carry sufficient energy to generate and maintain the Sun's million-degree outer atmosphere or corona. However, direct evidence of the dissipation process of these waves and subsequent heating has not yet been directly observed. Here we report on high spatial, temporal, and spectral resolution observations of a solar prominence that show a compelling signature of so-called resonant absorption, a long hypothesized mechanism to efficiently convert and dissipate transverse wave energy into heat. Aside from coherence in the transverse direction, our observations show telltale phase differences around 180° between transverse motions in the plane-of-sky and line-of-sight velocities of the oscillating fine structures or threads, and also suggest significant heating from chromospheric to higher temperatures. Comparison with advanced numerical simulations support a scenario in which transverse oscillations trigger a Kelvin–Helmholtz instability (KHI) at the boundaries of oscillating threads via resonant absorption. This instability leads to numerous thin current sheets in which wave energy is dissipated and plasma is heated. Our results provide direct evidence for wave-related heating in action, one of the candidate coronal heating mechanisms.Publisher PDFPeer reviewe