Speaker
Description
Over almost the past six decades, a fleet of space missions, strategically placed throughout the heliosphere at critical vantage points, have been devoted to the exploration of the interplanetary space, greatly advancing our knowledge of how the Sun influences the whole solar system, through the solar wind, a continuous flow of charged particles emitted by the outer layer of the solar atmosphere. The solar wind is the classical paradigm of a weakly collisional plasma for studying poorly understood fundamental phenomena that also occur in a variety of other astrophysical plasmas. Hence, the solar wind represents the best natural and accessible laboratory by interplanetary probes to directly study weakly collisional plasma phenomena. These include kinetic and fluid aspects of plasmas, such as plasma heating and acceleration, collisionless shock formation, particle acceleration and transport, magnetic reconnection, turbulence and waves.
Despite the low collisionality, the solar wind could present non-Maxwellian kinetic features in ion velocity distribution functions (VDFs), i.e. temperature anisotropies and beams, that carry important information about the kinetic processes that could determine the energy transfer between fluid and kinetic scales. These features have not yet been fully understood.
Moreover, during its journey through space, the solar wind interacts continuously with planets and other celestial bodies. In particular, it constitutes a coupled system with the Earth magnetosphere, playing a relevant role in the geomagnetic activity. Understanding the conditions in the solar system shaped by the Sun’s activity – known as Space Weather - is thus crucial, as they can affect satellite operations, communication systems, and even power grids on Earth.
This talk will try to give an overview on the solar wind characteristics observed at different heliocentric distances. In this context, a particular reference will be given to the Italian contribution to missions in operation (e.g. Solar Orbiter), highlighting new advances and issues that are still open.
