2018 PDG seminars

Fast MHD modes of a two (and three) shell semi-cylindrical waveguide

The modelling of coronal loop structures has long been pursued as a means of determining physical properties of the sun's corona.

Here, a 3D semi-cylindrical waveguide is proposed, representing a coronal loop arcade anchored in the photosphere.

By considering the eigenfunctions formed at the interface of a sharp density discontinuity (represented by "two-shell" and subsequently "three-shell" density structures), we show that waves are elliptically polarised, and that small changes in density contrast between shells can drastically affect the presence of eigenmodes.

Since observational information has restrictions on resolution, the implication is that two similarly determined density structures may produce vastly different estimations of potential eigenmodes.

Introduction to multiple scaling methods to solve differential equations with applications to plasma physics. Part II: Nonlinear partial differential equations

In the second part of my seminar, I will focus on nonlinear partial differential equations that can be obtained from the MHD equations.

Using the multiple scale technique I will present a method to obtain the Korteweg-de Vries-Burgers equation in a non-ideal plasma in the presence of Hall currents.

Using simple methods, I will find solutions to the limiting cases of shock waves and solitons.

Introduction to multiple scaling methods to solve differential equations with applications to plasma physics. Part I: Ordinary linear differential equations

Many of the equations we encounter in our research on solar and space plasma physics dynamics contain essential physical constraints (nonlinearity, singularities, complex domains of interest, complex boundary conditions, etc) that makes it difficult to find exact solutions.

Therefore, in order to obtain information about solutions of equations, we are forced to use approximative methods, numerical solutions, or both. The most important approximation methods are the perturbation methods, where the solutions are represented by the first few terms of an expansion.

In this seminar I will review the perturbation methods used to solve ordinary differential equations, highlighting their advantages and shortcomings. The presentation will revolve around simple examples of differential equations, presenting the method of finding approximative solutions of a differential equation we can derive in plasma physics.

Properties of Alfvénic waves in the solar chromosphere

In the first part of my talk, I will discuss the results of investigation of the properties of transverse waves existing in spicules using the automated wave tracking code NUWT.

Analysing a distance-time diagram at an altitude of 7 Mm relative to the solar limb produces the measured distribution of properties such as wave amplitude, period and velocity amplitude.

In the second part of the talk I will provide an overview of the recent studies on the effect of initial flow profiles on the dynamics of solar jets.

Introduction to the sun

This talk will be an introduction to the science required to understand the sun and its atmosphere.

It is primarily intended for students starting their postgraduate research in plasma, solar, or magnetospheric physics.

Due to the introductory nature of the talk, it would also be suitable for any interested non-specialists.