|dc.description.abstract||Development of a self-consistent theoretical model is of fundamental importance to the study of the solar wind. Such a model is necessary to understand the origin of the solar wind as well as observational and theoretical aspects. For instance, a complete description of the acceleration of solar wind particles, intrinsic velocity and magnetic field components, role of magnetic field in the solar wind's angular momentum loss, and so on has not yet been achieved. This thesis presents two data-driven solar wind models to provide more detailed pictures of the solar wind in the equatorial plane, to extract the solar wind plasma quantities from the direct observations at 1 AU, and to describe the underlying physics. It also provides a comprehensive comparison between analytic predictions, observations, and advanced MHD (magnetohydrodynamics) simulation outputs.
Chapter 1 provides a short literature review and a brief introduction for the thesis. Chapter 2 develops an analytic, self-consistent, theoretical model for the solar wind that includes conservation of angular momentum, frozen-in magnetic fields, and radial (r) and azimuthal (φ) components of velocity and magnetic field from the source surface/inner boundary to 1 AU. The solar wind model enforces corotation at the source surface (rs) assumes a constant radial speed at all heliolongitude, and applies near the equatorial plane. This model generalises previous models and reproduces the previous models in the appropriate limits. The model calculates the Alfvénic critical radius (ra) using the radial Alfvénic Mach number at 1 AU, and the predicted values agree with some recent observations. The predicted azimuthal velocity, which is only due to corotation is in the sense of corotation, but varies with, heliolongitudes (φ). Observations of the azimuthal velocity at 1 AU are usually much larger than predictions and not always in the corotation direction. These azimuthal velocities can not be explained by conservation of angular momentum alone. The standard interpretation involving stream-stream interactions and dynamical behaviour seems reasonable.
Chapter 3 develops an accelerating solar wind model that includes the following: conservation of angular momentum, deviations from corotation, and non-radial velocity and magnetic field components from an inner boundary (or source surface) to beyond 1 AU. The model includes an accelerating solar wind profile using a solution of the time-steady isothermal equation of motion and
predicts locations ra for the Alfvénic critical point which agree with recent observations. This model allows the flow velocity v to not always be parallel to magnetic field B in the corotating frame with the Sun, which results an electric field (E′) in the corotation frame. The resulting (E′ × B) drift may lead to enhanced scattering/heating of sufficiently energetic particles. The model demonstrates the existence of non-zero deviations δvφ from corotation at the source surface. These deviations of corotation are analogous to the transverse velocities caused by granulation and supergranulation motions. The abrupt changes in δvφ(rs,φs) are interpreted in terms of converging and diverging flows at the granulation cell boundaries and centers, respectively. Large range of variations of the angular momentum predicted and then are interpreted in terms of an intrinsic source in the solar wind of vorticity and turbulence from near the Sun towards 1 AU and beyond.
Chapter 4 presents a comprehensive comparison where the accelerating solar wind model's predictions, observations are compared qualitatively and quantitatively with Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) simulation's outputs for the solar rotation period from November 21 to December 17, 2013. The chapter compares simulation outputs in the ecliptic plane with the analytic model results in the equatorial plane. Comparisons between simulated plasma quantities for long run time and short run time demonstrate that the initial solar wind plasma is entirely swept out by the simulated wind. It appears that high order grid refinement helps the simulation to reach a steady-state MHD system. The current version of the BATS-R-US simulation code treats the solar corona (SC) and the inner heliosphere (IH) separately and discontinuities in simulation outputs remain in the intersection of two modules. Overall, the simulated magnetic fields agree quite well with model predictions, much better than the density, velocity, and temperature. Radial profiles of plasma quantities have some qualitative agreement along a plasma flux tube, but quantitative differences are apparent. Chapter 5 summarizes the results in this thesis and discusses future avenues for research.||en_AU|
|dc.publisher||University of Sydney||en_AU|
|dc.publisher||Faculty of Science||en_AU|
|dc.publisher||School of Physics||en_AU|
|dc.title||Generalized Theory of the Solar Wind||en_AU|
|dc.type.pubtype||Doctor of Philosophy Ph.D.||en_AU|
|Appears in Collections:||Sydney Digital Theses (Open Access)|