### Shock microphysics (MSc/PhD

פורסם:

**19:26 14/11/2017**Collisionless shocks are one the most ubiquitous phenomena in the Universe and one of the most efficient accelerators of charged particles. They are present in virtually all plasma environments at the scales from 1 cm in the terrestrial labs to 1 Mpc in galaxy clusters. They accelerate particles up to energies five orders of magnitude higher than those achieved in the largest accelerator at Earth. A shocks is a multi-scale object: particle acceleration may occur at the million km length, while the transition itself from the un-shocked plasma to the shocked one typically occurs within several tens of kilometers. It is this narrow transition which is the true heart of the whole shock with all around. This small heart pumps all the energetic processes occurring at much larger distances. Therefore, understanding of what happens within this narrow region is crucial for understanding everything what happens in the shocks and around them.

Direct observations of collisionless shocks are possible only in the Solar System. Each planet has its own both shock and there plenty of interplanetary shocks as well. A rather large number of spacecraft pass through these shocks, measuring the electric and magnetic fields and also the parameters of electrons and various ions. Quality of these measurements is rapidly improving. The most advanced and most recent Magnetospheric Multiscale Mission (MMS) consists of four identical spacecraft that orbit around Earth and measure with the resolution of tens of meters. Such resolution is like using a microscope for the Earth bow shock.

The amount of the collected and streaming data greatly exceeds the current capabilities of the space plasma physicist society, and efforts are badly needed to extract physics. The least developed branch of shock physics is the shock theory, which is well behind the observations and even numerical simulations. The present situation is a rare chance for an ambitious physicist who seeks to achieve a breakthrough in our understanding of microphysics of collisionless shocks. The hot problems include time dependence of the shock front, development of three-dimensional structures, and the long standing problem of electron heating and acceleration.

Required knowledge: mechanics and electrodynamics. Mostly analytical work, supported with numerical model analysis and numerical simulations.

gedalin@bgu.ac.il

Direct observations of collisionless shocks are possible only in the Solar System. Each planet has its own both shock and there plenty of interplanetary shocks as well. A rather large number of spacecraft pass through these shocks, measuring the electric and magnetic fields and also the parameters of electrons and various ions. Quality of these measurements is rapidly improving. The most advanced and most recent Magnetospheric Multiscale Mission (MMS) consists of four identical spacecraft that orbit around Earth and measure with the resolution of tens of meters. Such resolution is like using a microscope for the Earth bow shock.

The amount of the collected and streaming data greatly exceeds the current capabilities of the space plasma physicist society, and efforts are badly needed to extract physics. The least developed branch of shock physics is the shock theory, which is well behind the observations and even numerical simulations. The present situation is a rare chance for an ambitious physicist who seeks to achieve a breakthrough in our understanding of microphysics of collisionless shocks. The hot problems include time dependence of the shock front, development of three-dimensional structures, and the long standing problem of electron heating and acceleration.

Required knowledge: mechanics and electrodynamics. Mostly analytical work, supported with numerical model analysis and numerical simulations.

gedalin@bgu.ac.il