ALBERT

Beschreibung: Solar Orbiter was launched in February 2020, and has now completed the first 3 perihelia of its nominal mission phase. Mission science goals include establishing and understanding the links between processes occurring at the Sun and their consequences for the nature of the inner heliosphere and solar wind, as well as furthering our knowledge of the physics of the solar wind and the solar atmosphere themselves. A significant volume of science data has been accumulated by the 10 payload instruments, including novel data recorded by the 3 separate sensors which, together with a central DPU, comprise the Solar Wind Analyser (SWA) suite. Between them, these sensors, the Electron Analyser System, the Proton-Alpha Sensor and the Heavy Ion Sensor, make measurements of 3D velocity distribution functions of solar wind electron, proton and alpha particle populations, together with abundant heavy ions such as O6+ and ion charge states such as Fe9+ or Fe10+. In this presentation we summarise recent key results of studies using data from one or more of the 3 SWA sensors, and illustrate the quality of the data and their contribution to achieving the mission science goals. These include the availability of high time cadence observations which offer unique possibilities for resolving plasma kinetic processes at small scales in the solar wind. Combining with observations from other instruments on the platform, and from other missions, we also report on work to establish the origin of the solar wind stream passing the spacecraft and the physical processes driving its release.

Beschreibung: Alfvénic fluctuations can be observed not only in the main portion of the high-speed solar wind streams, but also in the slow wind. The so called Alfvénic slow wind resembles the fast wind from many respects, including a similar solar source, identified as a region of strongly diverging open magnetic field. This super-radial expansion may slow down the slow wind, setting the conditions for the origin of the Alfvénic slow wind. The ESA/NASA Solar Orbiter mission, in particular, offers the unprecedented opportunity to perform in-situ observations of this solar wind regime at different heliocentric distances and to study its connection with the solar source, contributing to a better understanding of the general problem of solar wind acceleration. In this study, we focus on Alfvénic slow wind intervals, observed by Solar Orbiter, that will be compared with fast wind streams. A Potential Field Source-Surface (PFSS) model will be used to link in-situ measurements with solar sources while a spectral analysis will allow us to characterize the Alfvénic content of velocity and magnetic field fluctuations.Our results contribute to a better understanding of the evolution of the Alfvénicity in solar wind fluctuations, which is found to be very high close to the Sun also in slow streams, while it is rapidly lost at 1 AU in most cases (i.e. streamer slow wind), surviving instead in other cases (i.e. Alfvénic slow wind).