Circular ion waves in the inner heliosphere and their role in solar wind heating

Most of the visible Universe is in a highly ionized plasma state.

Plasma processes are operating work everywhere, from radio galaxy jets and supernova explosions to solar flares and planetary magnetospheres.

The Sun is our nearest star and the most important to our life, but it is the only star we have a chance of understanding how it works in detail and how it interacts with the surrounding environment.

The outer part of the Sun´s atmosphere, called the corona, is formed of plasma which is much hotter than the layers underneath it.

It also constantly expands, forming a flow of plasma with embedded magnetic fields called the solar wind, which fills all the space around the Sun.

This wind creates a plasma bubble that extends for over 100 astronomical units and has all the solar system´s planets within it.

The physical processes responsible for heating the plasma of the corona and accelerating the solar wind are a subject of active debate. This project concerns circularly polarized waves near the proton cyclotron frequency.

Due to their frequency, such waves can effectively interact with solar wind protons, potentially playing an important role in solar wind heating.

Despite numerous observations of such waves, it is still unclear to which plasma wave mode they correspond and, therefore, how they interact with the plasma ions.

Here, we study the waves at varying heliospheric distances and understand their role in the heating of the solar wind Solar Orbiter using data and simulations.