Turbulence, magnetic reconnection, shocks and particle acceleration: nonlinear processes. (co-organized)
|Convener: Giovanni Lapenta | Co-Conveners: Alex Lazarian , A. Retino , Francesco Valentini , Luca Sorriso-Valvo , Ilias Sibgatullin|
Magnetized plasmas are frequently turbulent in astrophysical systems, as well as in space and laboratory. The turbulence is known to change many properties of fluids, in particular their transport properties. Does it change the properties of magnetic reconnection? What is the back reaction of magnetic reconnection on turbulence in magnetized plasmas? These two interrelated questions are the focus of the proposed session. We aim at creating a forum of experts to summarize the recent significant advances in both the field of turbulence and magnetic reconnection and provide the forum for discussing new directions.
In many situations, e.g. in the Solar wind case, the properties of turbulence are affected by the properties of the energy injection scale. Therefore it is essential to search for the signatures of how the properties of turbulence and the measured properties of magnetic reconnection are related.
The aims of the proposed session are twofold. First of all, reconnection is usually assumed to be slow, unless special conditions are satisfied, e.g. magnetized plasma is collisionless. Is it always true? While a lot of the research in the area of reconnection deals with collisionless processes, many important questions are left unaswered. Is Sweet-Parker reconnection stable for large Lundquist numbers? Do we expect collisional gas, which constitutes most of the Sun's interior, Sun's photosphere, interstellar media etc. to exhibit slow reconnection? The latter would mean that the entire crop of simulations of magnetized collisional media are in error. Second, the discussion of magnetic turbulence is usually is disconnected from the fundamental property of magnetic field to reconnect. At the same time, one should realize that the phenomenon of slow reconnection, if it takes place in turbulent systems, must substantially modify the properties of turbulence and may potentially make the simulations with the present diffusive codes not representative of the turbulence in actual astrophysical environments of high conductivity.
Magnetic reconnection is a universal energy dissipation mechanism occurring in magnetized plasmas. Such plasmas are frequently in a turbulent state, raising the fundamental topological question of how reconnection and turbulence are related to each other. In addition, many key processes, e.g. particle acceleration, may be driven both by magnetic reconnection and magnetic turbulence, but it is difficult to find reliable ways to distinguish the causes and the effects in the context of vortical, wave and helical forcings.