Article
Astronomy & Astrophysics
S. J. White, E. Verwichte
Summary: This study extends the modeling of wave coupling between transverse loop oscillations and slow magnetoacoustic waves, considering the effects of loop structuring and non-linearity. It demonstrates that transverse loop oscillations can generate propagating slow waves from the footpoints with the same periodicity but shorter wavelength, determined by the local sound speed. The degree of wave coupling is proportional to the square root of plasma beta, and the slow wave field is anti-symmetric in the direction of transverse wave polarization.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Llorenc Melis, Roberto Soler, Jaume Terradas
Summary: The fine structure of solar prominences consist of thin threads outlining magnetic field lines. Transverse waves of Alfvenic nature are commonly observed in these threads, which are driven at the photosphere and propagate to the coronal prominences. Energy balance between radiative losses, thermal conduction, and Alfven wave heating is explored to construct 1D equilibrium models of prominence threads. Equilibrium profiles of temperature, density, and ionisation fraction are computed along the thread using the energy balance equation, and the wave heating rate is calculated using the Alfven wave equation. The iterative process is repeated until a self-consistent thread model heated by Alfven waves is achieved.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Llorenc Melis, Roberto Soler, Jose Luis Ballester
Summary: Observational evidence shows the presence of small-amplitude transverse MHD waves in solar prominences, believed to be driven at the photosphere and dissipating as heat in the partially ionized plasma of the threads. The simple 1D model considered in this study suggests that MHD wave heating can play a significant role in energy balance within prominences, with further studies needed to explore this mechanism in more detail.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
M. Sieyra, S. Krishna Prasad, G. Stenborg, E. Khomenko, T. Van Doorsselaere, A. Costa, A. Esquivel, J. M. Riedl
Summary: The aim of this study is to understand the effect of projection on observed speeds by comparing them with those from a numerical model. The analysis of multi-wavelength data reveals a dominant period of 2-3 minutes for intensity disturbances at different heights of the atmosphere. Both observed propagation speeds and those calculated from the synthetic model exhibit an accelerated pattern.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Daria Shukhobodskaia, Alexander A. Shukhobodskiy, Robert Erdelyi
Summary: This study explores oscillations in a thin straight expanding magnetic flux tube, finding that cooling increases amplitude and is related to the expansion factor. Higher wave numbers lead to localized oscillations closer to the boundary.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
M. Geeraerts, P. Vanmechelen, T. Van Doorsselaere, R. Soler
Summary: The study focuses on investigating the quasimodes with resonant absorption in a straight cylinder using linearized ideal MHD, aiming to determine the frequency as a function of background parameters and analyzing the damping of these modes.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
P. Pagano, P. Antolin, A. Petralia
Summary: This study demonstrates the major role of the curvature of coronal loops in the asymmetry of reconnection jets, with inward directed jets being more likely to occur and more energetic than outward directed ones. Analytical and numerical models support the finding that post-reconnection magnetic tension is inherently stronger in the inward direction, leading to the disappearance of outward jets at large observable scales. The degree of asymmetry increases for small-angle reconnection and more localised reconnection regions.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
T. A. Howson, I De Moortel
Summary: This study investigates the atmospheric response to coronal heating driven by random velocity fields with different characteristic time scales and amplitudes. The results reveal that direct current (DC) driving leads to greater energy injection and higher temperatures compared to alternating current (AC) driving. AC driving results in more frequent but shorter duration energy release events, leading to asymmetric temperature profiles. Higher velocity driving is associated with larger currents, higher temperatures, and a larger corona volume. The majority of heating is associated with small energy release events.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
L. E. Fyfe, T. A. Howson, I De Moortel
Summary: The study shows that short timescale footpoint motions generate higher frequency perturbations, while long timescale footpoint motions produce lower frequency perturbations. Additionally, signatures of Alfvenic waves were identified, with fast wave signatures observable when short timescale driving is present.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
L. E. Fyfe, T. A. Howson, I. De Moortel, V. Pant, T. Van Doorsselaere
Summary: Studies have found that the ratio between non-thermal line widths and root mean squared wave amplitudes varies across different simulations due to factors such as line-of-sight angles, velocity magnitudes, wave interference, and exposure time. Therefore, the widely used method for estimating wave energy is not robust.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
P. Kohutova, P. Antolin, M. Szydlarski, M. Carlsson
Summary: To improve our understanding of coronal oscillations, it is necessary to consider the effect of a realistic magnetic field topology and the density structuring. A self-consistent 3D radiation-magnetohydrodynamics simulation was used to analyze the damping, dissipation, and physical processes of coronal oscillations. The observed oscillation parameters and evolution are consistent with typical values seen in observations of coronal loop oscillations.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
P. Kohutova, A. Popovas
Summary: Researchers studying solar coronal loops using 3D simulations found various types of oscillations present, including standing oscillations in both transverse and longitudinal velocity components, as well as rapidly decaying oscillations triggered by impulsive events and sustained small-scale oscillations.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
N. Magyar, T. Duckenfield, T. Van Doorsselaere, V. M. Nakariakov
Summary: This study investigates the properties of circularly polarized kink waves on straight plasma cylinders and compares them to linearly polarized kink waves. The research finds that the damping caused by resonant absorption is independent of the polarization state, although the morphology of the induced resonant flow differs for the two polarizations. There are no significant differences in the forward-modeled Doppler signals. Additionally, the growth rate of small scales in nonlinear oscillations is determined by the total energy of the oscillation, rather than the perturbation amplitude.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
V. S. Pandey, Ankit Kumar, M. K. Nayak
Summary: In this paper, the authors characterize the transverse oscillations in an incompressible non-ideal magnetohydrodynamic (MHD) fluid as either Alfvenic or Landau-type. They consider shear viscosity and magnetic diffusivity as dissipation mechanisms and derive a general dispersion relation for the incompressible MHD waves. The study finds that when magnetic tension dominates, the oscillations are of Alfvenic type, while when internal frictional forces dominate, the oscillations are of Landau type. The prediction of Landau-type transverse oscillations may help explain the heating of observed filamentary structures in the solar coronal plasma.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Sergio Diaz-Suarez, Roberto Soler
Summary: In nonuniform coronal loops, magnetic twist can trigger turbulence through phase mixing of Alfven waves, and the intensity of the magnetic twist can affect the development of turbulence.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
M. O. Archer, D. J. Southwood, M. D. Hartinger, L. Rastaetter, A. N. Wright
Summary: Global MHD simulations reveal that some predictions of large-scale MHD waves differ significantly from theoretical models in a realistic magnetosphere. Considering a non-uniform background magnetic field, the MHD equations result in reversed ordering of radial turning points and Alfven resonance locations, the presence of additional nodes, and opposite rotation directions between magnetic field oscillations and velocity close to the magnetopause.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
T. Elsden, A. N. Wright
Summary: Recent work has found that field line resonances (FLRs) can occur with intermediate magnetic field polarizations, referred to as 3-D. In the presence of a plasmaspheric drainage plume, strong field-aligned currents can form along asymmetric azimuthal contours of Alfven frequency. This study uses magnetohydrodynamic simulations to investigate the satellite signatures of non-toroidal FLRs under different magnetopause driving conditions, considering the impact of the 3-D nature on the amplitude and phase relations. The findings show that in the 3-D FLR regions of intermediate polarization, the FLR has contributions from both the radial and azimuthal field components, and their phase can be in or out of phase.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
F. Moreno-Insertis, D. Nobrega-Siverio, E. R. Priest, A. W. Hood
Summary: This study aims to calculate a set of theoretical self-similar solutions to the nonlinear diffusion equation with cylindrical symmetry, which can be used as tests for MHD codes incorporating ambipolar diffusion. The theoretical solutions are obtained using mathematical methods and are validated using the Bifrost code. The results show that the Bifrost code can reproduce the theoretical solutions with sufficient accuracy and can be used to test the performance of MHD codes.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
D. J. Pascoe, T. Van Doorsselaere, I De Moortel
Summary: We study the use of propagating kink waves as a diagnostic technique. The transverse structuring of the plasma can be inferred by the frequency-dependent wave damping. However, the classical model significantly overestimates the damping rate in coronal loops with low density contrast ratios.
ASTROPHYSICAL JOURNAL
(2022)
Review
Astronomy & Astrophysics
Sergey A. Anfinogentov, Patrick Antolin, Andrew R. Inglis, Dmitrii Kolotkov, Elena G. Kupriyanova, James A. McLaughlin, Giuseppe Nistico, David J. Pascoe, S. Krishna Prasad, Ding Yuan
Summary: The review discusses novel data analysis techniques developed or adapted for coronal seismology in the last decade, focusing on methods for EUV imaging observations and light curves, while also considering techniques for detailed investigation of MHD waves and seismological inference of physical parameters.
SPACE SCIENCE REVIEWS
(2022)
Article
Astronomy & Astrophysics
D. J. Pascoe, I De Moortel, P. Pagano, T. A. Howson
Summary: This study considers the behavior of Alfven waves propagating in a medium with random density perturbations. The interaction between the Alfven waves and the medium generates reflections most efficiently when their wavelength is comparable to the spatial scale of the density perturbations. This leads to the generation of quasi-periodic oscillations, and the periods of oscillation are no longer solely associated with the driver. Multiple wave reflections cause oscillatory power to be retained at low altitudes, increasing opportunities for heating at those locations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
I. De Moortel, T. A. Howson
Summary: The long-standing question of why the Sun's atmosphere is much hotter than its surface is investigated in this study, along with the potential role of magnetohydrodynamic waves. Through 3D MHD simulations, the researchers found that wave heating associated with resonant driving can balance radiative losses in the coronal loop, while nonresonant driving or higher density loops lead to cooling.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
J. Reid, J. Threlfall, A. W. Hood
Summary: Straightened cylindrical models of coronal loops have been commonly used to study heating processes, but the influence of geometric curvature on the heating has not been thoroughly examined. This study compares the heating and associated mechanisms in straightened models with those in curved loops. The analysis reveals bursty and aperiodic nanoflares resulting from processes initially triggered by magnetic reconnection, which are evenly distributed throughout the corona with a slight bias away from the footpoints. The independent occurrence of nanoflare-like events at separate sites along individual strands is an interesting finding.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
M. O. Archer, M. D. Hartinger, L. Rastaetter, D. J. Southwood, M. Heyns, J. W. B. Eggington, A. N. Wright, F. Plaschke, X. Shi
Summary: Surface waves on Earth's magnetopause have significant influence on the dynamics of the global magnetosphere. Due to limited in situ observations, it is desirable to use ground-based instruments in the polar regions to remotely sense these modes. Predictions of key qualitative features in auroral, ionospheric, and ground magnetic observations are provided. Monochromatic oscillatory field-aligned currents (FACs) are found throughout the magnetosphere, peaking at the equatorward edge of the magnetopause boundary. The currents exhibit slow poleward phase motion and may cause periodic auroral brightenings. Convection vortices circulate the poleward moving FAC structures in the ionosphere. Surface mode signals are also predicted in the ground magnetic field, with ionospheric Hall currents rotating perturbations by approximately 90 degrees. Implications in terms of ionospheric Joule heating and geomagnetically induced currents are discussed.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Physics, Multidisciplinary
Andrew Wright, Thomas Elsden
Summary: The paper discusses the importance of resonant excitation of Alfven waves using the fast magnetosonic mode in space plasmas. A numerical approach is used to study a 3D coronal arcade model and find that resonant coupling can occur in 3D, with new features compared to 2D. The polarization of Alfven waves can vary with position throughout the Resonant Zone and there are potentially infinite paths for the resonant waves to exist on.
Article
Astronomy & Astrophysics
G. Cozzo, J. Reid, P. Pagano, F. Reale, A. W. Hood
Summary: In this study, we used three-dimensional MHD simulations to explore the interaction of magnetic flux tubes in a stratified atmosphere. Our results show that avalanches can occur in realistic conditions and can result in the release of magnetic energy as a result of photospheric motions.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Kazue Takahashi, Tom Elsden, Andrew N. Wright, Alexander W. Degeling
Summary: Previous studies have found that magnetospheric ultralow frequency waves excited by interplanetary shocks have a strong toroidal component, indicating azimuthal displacement of magnetic field lines. However, observations of toroidal oscillations on the dayside by multiple spacecraft during an interplanetary shock event on 27 February 2014 revealed a strong poloidal component as well (radial field line displacement). Simulation results showed that the poloidal component is due to radially standing fast mode waves, while the toroidal component is a result of field line resonance driven by the fast mode waves, and their relative amplitudes and phases change with radial distance.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
R. Davies, A. N. Wright
Summary: A 2D Cartesian simulation is presented in this article to solve the ideal, low-beta, linear magnetohydrodynamics equations. The simulation investigates the propagation of Alfvén waves through inhomogeneities in Alfvén speed and density.
EARTH AND SPACE SCIENCE
(2023)
Article
Physics, Multidisciplinary
Thomas Howson, Ineke De Moortel
Summary: Recent studies have shown that coronal wave heating can balance radiative losses in low-density loops undergoing resonant absorption, phase mixing, and the Kelvin-Helmholtz instability. Broadband and multi-directional drivers with resonant and non-resonant frequencies were considered. Three-dimensional magnetohydrodynamic simulations were used to impose continuous velocity drivers on the footpoints of a dense coronal loop. The results indicated that the energy dissipation rates from the wave drivers are sufficient to balance average energy losses, but the loop core still cools due to local insufficiency in wave heating rates.