Combined study of solar magnetic flux tubes eruptions and their interplanetary manifestation

NAKWACKI, M. S.

São Paulo

Seminario; Seminários do Departamento de Astronomia IAG/USP; 2010

The interplanetary medium is filled with a low density plasma that flows from the Sun and is called the solar wind. This wind transports the magnetic structures that are ejected from the solar corona (e.g. coronal mass ejections, CMEs). In this Thesis, we study from a theoretical and observational point of view some aspects of the evolution of CMEs in the interplanetary medium; in particular, of a subset called magnetic clouds (MCs). We model the dynamical evolution of several events that occurred between 1997 and 2004, we quantify their expansion and we compute, using models developed as part of this Thesis, the global invariant quantities (flux and magnetic helicity) that are relevant to a combined analysis of solar events and their interplanetary counterparts. The models we develop are based in a magnetohydrodynamic description of the plasma. We propose a self similar evolution for the cloud structures with different expansion rates in each of their main directions (radial and axial). We start considering only a radial expansion and we proceed to include an axial expansion. Finally, we broaden the description towards a more general formalism, based on observations, that is derived in a hierarchical order and can be applied to more general structures. We show the robustness of global invariants when computed using different expansion models. We quantify for the first time the typical amount of energy lost per unit time in the evolution of a MC. For some of the studied MCs we also analyze observations of the associated solar event and of its source active region. We identify the characteristics of the eruptive regions that allow us to quantify the global invariants in the Sun. We quantify the magnetic flux involved in the ejection and the magnetic helicity variation of the source active region. Finally, we study the evolution of a particular MC from its observation close to Earth until farther than 5 astronomical units using data from two spacecraft aligned with the Sun. We quantify the global invariants in both observational points. We compare these quantities and we provide an interpretation for the origin of the magnetic structure distorted because of its interaction with the solar wind far from the Sun. We extend this comparison to the Sun and we identify the solar source, in this way we achieve a complete description of the MC evolution along the heliosphere.