Advanced Fieldline Rendering for Space Weather Visualization

Abstract: The Sun is vital for life on Earth, but its life-giving powers can just as well be threatening. It is constantly bombarding the solar system with dangerous radiation and plasma, which Earth’s magnetic field is protecting us from. The Sun also possesses a strong magnetic field which interacts with Earth’s magnetic field in what is called the Dungey cycle. This master’s thesis project aims to find a method to visualize the Dungey cycle using moving magnetic fieldlines. This project is a continuation of a previously developed fieldline rendering project. The prior method uses a velocity vector field to trace a pathline around Earth, saving vertices at discrete steps; magnetic fieldlines are then traced from each vertex. These magnetic fieldlines are called key frames and are not visualized. They are instead used to interpolate the position of a rendered fieldline over time. The main issue with this prior method occurs when the Sun’s magnetic field links with Earth’s magnetosphere in what is called reconnection. Then, the topology of the fieldlines changes which makes them instantaneously jump to a new position. The developed method in this thesis is built upon the prior method, where both pathlines and key frames still are used. The concept of matching fieldlines is introduced to solve the issue with jumping fieldlines. It is implemented by using seed points close to critical points. Critical points are found externally and are used to trace fieldline pathlines to points where reconnection occurs, as reconnection always happens at critical points. The pathline to a critical point is created by tracing backward through the vector field. It then continues from the critical point by tracing it forward. A pair of matching fieldlines is created for each critical point; one fieldline represents the Sun’s magnetic field and the other represents Earth’s magnetic field. The starting positions of the fieldlines are adjusted to account for time differences to traverse their respective pathlines, to ensure that they meet at the critical point at approximately the same time. The two fieldlines interact and mix with each other as reconnection occurs, resulting in a smooth interpolation through the changing topology. This solves the issue with jumping fieldlines in the prior project and allows for smooth visualization of the Dungey cycle.