Electromagnetic Ion-Cyclotron waves
Waves are disturbances of a medium that propagate in it, carrying information and energy. In plasmas, the combination of their electromagnetic properties with their fluid nature allow the propagation of a great variety of waves. Among the myriad of plasma waves, electromagnetic ion-cyclotron (EMIC) waves are deemed to play a key role in the dissipation of energy at scales smaller than the ion gyroradius, that is, the radius of the helix that the movement of an ion describes in presence of a uniform magnetic field. Such dissipation could contribute to heat the solar wind and coronal plasma, and explain other plasma features.
EMIC waves propagate mostly parallel to the magnetic field, are left-handed polarized in the frame of the plasma and have frequencies close to the ion cyclotron frequency. While solar wind plasma measured at Earth's distance from the Sun is mainly made of electrons and protons, it also contains a small percentage of heavier positive ions, mainly helium nuclei (alpha particles). This percentage of heavy ions is even larger in other plasma environments, like at closer distances from the Sun or in Earth's magnetosphere. In such environments, EMIC waves are excited at different energy bands, each one near the gyrofrequency of an ion species. Wave-particle interactions lead to particle energization, hence EMIC waves can accelerate ions and even create a differential velocity between their populations.
Our group uses numerical simulations to study the propagation of waves in inhomogeneous plasmas and data from Parker Solar Probe (PSP), Solar Orbiter (SolO) and Magnetospheric MultiScale (MMS) spacecraft missions. One of our main objectives is to use the in-situ data provided by the former missions to detect EMIC waves in the solar wind, so we can discover what conditions are more favorable to their generation and how their occurrence and evolution change with the distance from the Sun. We also aim to gain a better understanding on the relation of EMIC waves with other plasma processes, particularly turbulence and magnetic reconnection.
Figure: Detection of EMIC waves with Solar Orbiter data