Interplanetary magnetic clouds

The Sun is producing a steady outflow of plasma, known as the solar wind. This is a stream of high charged particles, which takes along the magnetic field of the Sun. Regular structures of the solar wind, resulting from the solar rotation and slower and faster flows, are interacting with occasionally present explosive eruptions from the Sun`s corona, so called Coronal Mass Ejections (CMEs). When these structures reach the Earth, they can be source of disturbances within the Earth`s magnetosphere, and they can have harmful effects, e.g., on satellite missions. Therefore there exists a need to forecast the arrival of such structures at the Earth, which is part of the so called space weather. In our work we study a very special kind of CMEs: magnetic clouds. They can be identified in satellite data because of their very specific characteristics, which are present over hours when passing a spacecraft. To obtain the features of magnetic clouds, as their magnetic field configuration and their large-scale geometry, we will make improvements to a model, which considers the magnetic clouds having a constant alpha, force-free, and locally cylindrical magnetic field topology. It will be a major part of the study to extend the model to time-varying phenomena, expansion processes, magnetic barrier effects (i.e., plasma depletion), to a flux-rope like geometry, and others. The theoretical model is then least-square fitted to the observations. Thus, we have knowledge about the main characteristics of the magnetic cloud, which are then linked with phenomena related to the propagation of the cloud, as the existence of a shock front, the thickness of the sheath region, and others. We will analyse as much as possible magnetic cloud observations from a variety of satellites (Wind, Helios 1 and 2, Voyager, IMP 8, ACE, SOHO, Ulysses, and others). A very special and important topic are in-line observations, i.e., the same magnetic cloud observed by different spacecraft at different distances to the Sun. These examples, and also the other observations at different heliocentric distances, will allow us to answer questions concerning the evolution of magnetic clouds.