The rise and fall of space plasma instabilities

The Sun sends out a stream of particles and a magnetic field, which, together, are called the solar wind. The planets of our solar system, and also comets, and their atmospheres are obstacles to this wind, and an interaction takes place. First of all, a bow shock is created around the obstacle, where the wind is braked, and particles from the extended planetary atmosphere, mainly hydrogen, can lose an electron and are added to the solar wind. These extra particles make the region behind the bow shock unstable, and waves are created. These waves make the magnetic field become very weak, and the particles fall and collect, as it were, into this magnetic field hole. These are called mirror mode waves, because particles trapped inside these structures bounce back and forth in a way similar to light trapped between two glass mirrors. Another kind of wave can be created by the solar wind protons that are circling around the magnetic field. This motion makes waves in the magnetic field have a period equal to the particles orbital period around the field. These waves are called cyclotron waves. It is interesting that these waves and the mirror modes are created by the same kind of particles, raising the question of when and how one or the other wave is created. This study is done with data from different spacecraft that visited or orbited Venus, Mars and comets. We have chosen planets without a magnetic field, because then we do not have to worry about the different strengths of planetary magnetic fields, nor about the interaction that can happen between the solar wind magnetic field and the planetary magnetic field. We would like to study in detail how these waves and particles behave at Venus, Mars and comets. As these three obstacles are very different in size, with radii 6052 km, 3390 km and 10 to a few 100 km in the same order as mentioned, we might expect some differences there. The questions that need to be answered are: do these mirror mode waves have the same size across planets and between them?; how deep does the hole in the magnetic field get?; and what is the temperature of the particles that fall into the hole? And, very importantly, when do we get these mirror mode waves and when do we get the cyclotron waves, and what effects do these waves have on their surrounding environment? Because the size of the obstacles is so different, it can well be that the characteristics of these two types of waves are also different.