Propagation of Surface Magnetohydrodynamic Waves in Asymmetric Multilayered Plasma

Investigation of magnetohydrodynamic wave propagation in different equilibrium configurations is important for the development of solar magnetoseismology. In the present work, a magnetized plasma slab sandwiched between an arbitrary number of nonmagnetic layers is considered and an analytical approach is used for the derivation of its dispersion relation. This work is a natural generalization of the symmetric slab model studied by Roberts and the asymmetric magnetic slab model, considered by Allcock & Erdélyi. Similar to the dispersion relation for an asymmetric slab, and unlike a symmetric slab, the dispersion relation for an asymmetric multilayered plasma cannot be decoupled into sausage and kink eigenmodes. The waves that permitted us to propagate in multilayered slabs have mixed characters; therefore, the notion of quasi-sausage and quasi-kink waves is more appropriate. Here, we focus on how a multilayered structuring affects the eigenmodes. The amplitudes of the eigenmodes depend on the equilibrium structuring and the model parameters; this motivates an application as a solar magnetoseismology tool. Finally, specific cases of two- and three-layered slabs are studied in detail and their potential applicability to magnetic bright points is discussed

Significance of Cooling Effect On Comprehension of Kink Oscillations of Coronal Loops

Kink oscillations of coronal loops have been widely studied, both observationally and theoretically, over the past few decades. It has been shown that the majority of observed driven coronal loop oscillations appear to damp with either exponential or Gaussian profiles and a range of mechanisms have been proposed to account for this. However, some driven oscillations seem to evolve in manners which cannot be modeled with purely Gaussian or exponential profiles, with amplification of oscillations even being observed on occasions. Recent research has shown that incorporating the combined effects of coronal loop expansion, resonant absorption, and cooling can cause significant deviations from Gaussian and exponential profiles in damping profiles, potentially explaining increases in oscillation amplitude through time in some cases. In this article, we analyze 10 driven kink oscillations in coronal loops to further investigate the ability of expansion and cooling to explain complex damping profiles. Our results do not rely on fitting a periodicity to the oscillations meaning complexities in both temporal (period changes) and spatial (amplitude changes) can be accounted for in an elegant and simple way. Furthermore, this approach could also allow us to infer some important diagnostic information (such as, for example, the density ratio at the loop foot-points) from the oscillation profile alone, without detailed measurements of the loop and without complex numerical methods. Our results imply the existence of correlations between the density ratio at the loop foot-points and the amplitudes and periods of the oscillations. Finally, we compare our results to previous models, namely purely Gaussian and purely exponential damping profiles, through the calculation of χ2 values, finding the inclusion of cooling can produce better fits in some cases. The current study indicates that thermal evolution should be included in kink-mode oscillation models in the future to help us to better understand oscillations that are not purely Gaussian or exponential

Unusually long path length for a nearly scatter-free solar particle event observed by Solar Orbiter at 0.43 au

Context: After their acceleration and release at the Sun, solar energetic particles (SEPs) are injected into the interplanetary medium and are bound to the interplanetary magnetic field (IMF) by the Lorentz force. The expansion of the IMF close to the Sun focuses the particle pitch-angle distribution, and scattering counteracts this focusing. Solar Orbiter observed an unusual solar particle event on 9 April 2022 when it was at 0.43 astronomical units (au) from the Sun. // Aims: We show that the inferred IMF along which the SEPs traveled was about three times longer than the nominal length of the Parker spiral and provide an explanation for this apparently long path. // Methods: We used velocity dispersion analysis (VDA) information to infer the spiral length along which the electrons and ions traveled and infer their solar release times and arrival direction. // Results: The path length inferred from VDA is approximately three times longer than the nominal Parker spiral. Nevertheless, the pitch-angle distribution of the particles of this event is highly anisotropic, and the electrons and ions appear to be streaming along the same IMF structures. The angular width of the streaming population is estimated to be approximately 30 degrees. The highly anisotropic ion beam was observed for more than 12 h. This may be due to the low level of fluctuations in the IMF, which in turn is very probably due to this event being inside an interplanetary coronal mass ejection The slow and small rotation in the IMF suggests a flux-rope structure. Small flux dropouts are associated with very small changes in pitch angle, which may be explained by different flux tubes connecting to different locations in the flare region. // Conclusions: The unusually long path length along which the electrons and ions have propagated virtually scatter-free together with the short-term flux dropouts offer excellent opportunities to study the transport of SEPs within interplanetary structures. The 9 April 2022 solar particle event offers an especially rich number of unique observations that can be used to limit SEP transport models

Model of Dirac field interacting with material plane within Symanzik’s approach

The model for the interaction of a spinor field with a material plane is constructed in the framework of the Symanzik’s approach. The characteristics of scattering process of Dirac particles on the plane are calculated. The bounced states localized near the plane are investigated.The model can find application to a wide class of phenomena arising by the interaction of quantum electrodynamics fields with two-dimensional materials

Flute oscillations of cooling coronal loops with variable cross-section

We consider fluting oscillations in a thin straight expanding magnetic flux tube in the presence of a background flow. The tube is divided into a core region that is wrapped in a thin transitional region, where the damping takes place. The method of multiple scales is used for the derivation of the system of governing equations. This system is applicable to study both standing and propagating waves. Furthermore, the system of equations is obtained for magnetic tubes with a sharp boundary. An adiabatic invariant is derived using the Wentzel-Kramer-Brillouin (WKB) method for a magnetic flux tube with slowly varying density, and the theoretical results are then used to investigate the effect of cooling on flute oscillations of a curved flux tube semi-circlular in shape. We have analysed numerically the dependencies of the dimensionless amplitude for a range of values of the expansion factor and the ratio of internal to external plasma densities at an initial time. We find that the amplitude increases due to cooling and is higher for a higher expansion factor. Higher values of the wave number lead to localisation of the oscillation closer to the boundary. Finally, we show that the higher the value of the ratio of internal to external plasma densities, the higher the amplification of oscillation due to cooling. Therefore, we conclude that the wave number, density ratio, and the variation of tube expansion are all relevant parameters in the cooling process of an oscillating flux tube

Bound states in a model of interaction of Dirac field with material plane

In the framework of the Symanzik approach model of the interaction of the Dirac spinor field with the material plane in the 3 + 1-dimensional space is constructed. The model contains eight real parameters characterizing the properties of the material plane. The general solution of the Euler-Lagrange equations of the model and dispersion equations for bound states are analyzed. It is shown that there is a choice of parameters of the model in which the connected states are characterized by dispersion law of a mass-less particle moving along the material plane with the dimensionless Fermi velocity not exceeding one

Symanzik approach in modeling of bound states of Dirac particle in singular background

In the model of interaction of spinor field with homogeneous isotropic material plane constructed in framework of Symanzik approach, the bound states are studied. For localized near plane Dirac particle the expression for current, charge and density are presented. For bound state with massless dispersion law the current, charge and density are calculated for simplified model with 2 parameter exactly.The model can find application to a wide class of phenomena arising by the interaction of fields of quantum electrodynamics with two-dimensional materials

Bound states in a model of interaction of Dirac field with material plane

In the framework of the Symanzik approach model of the interaction of the Dirac spinor field with the material plane in the 3 + 1-dimensional space is constructed. The model contains eight real parameters characterizing the properties of the material plane. The general solution of the Euler-Lagrange equations of the model and dispersion equations for bound states are analyzed. It is shown that there is a choice of parameters of the model in which the connected states are characterized by dispersion law of a mass-less particle moving along the material plane with the dimensionless Fermi velocity not exceeding one

Model of Dirac field interacting with material plane within Symanzik’s approach

The model for the interaction of a spinor field with a material plane is constructed in the framework of the Symanzik’s approach. The characteristics of scattering process of Dirac particles on the plane are calculated. The bounced states localized near the plane are investigated.The model can find application to a wide class of phenomena arising by the interaction of quantum electrodynamics fields with two-dimensional materials

Symanzik approach in modeling of bound states of Dirac particle in singular background

In the model of interaction of spinor field with homogeneous isotropic material plane constructed in framework of Symanzik approach, the bound states are studied. For localized near plane Dirac particle the expression for current, charge and density are presented. For bound state with massless dispersion law the current, charge and density are calculated for simplified model with 2 parameter exactly.The model can find application to a wide class of phenomena arising by the interaction of fields of quantum electrodynamics with two-dimensional materials