PHOIBOS: probing heliospheric origins with an inner boundary observing spacecraft

The earth is immersed in a hot, rarefied, energetic flow of particles and electromagnetic fields originating from the Sun and engulfing the entire solar system, forming the heliosphere. The existence of the solar wind has been established for almost 50 years now, and abundant data has been accumulated concerning both its average properties and the intermittent, violent energetic manifestations known as Coronal Mass Ejections which often impact the earth’s magnetosphere (causing geomagnetic storms and aurorae). The mystery of how the solar corona is heated and the solar wind is accelerated remains unsolved, however, because of the large gap in our knowledge of the inner region of the heliosphere, inside the orbit of mercury. The PHOIBOS mission, with a perihelion at 4 R s , by accessing the regions where energy in the coronal plasma is channeled from internal, magnetic and turbulent energy into bulk energy of the solar wind flow aims to solve the question of why the Sun has a hot corona and produces a solar wind. The PHOIBOS mission builds on previous Solar Probe studies, but provides an alternative orbit scenario avoiding a Jupiter encounter in favor of multiple Venus encounters and SEP systems to work its way close to the Sun in a gradual manner, providing a much vaster data return.