Cooling flow regime of a plasma thermal quench

- A large class of Laboratory, Space, and Astrophysical plasmas is nearly collisionless. When a localized energy or particle sink, for example, in the form of a radiative cooling spot or a black hole, is introduced into such a plasma, it can trigger a plasma thermal collapse, also known as a thermal quench in tokamak fusion. Here we show that the electron thermal conduction in such a nearly collisionless plasma follows the convective energy transport scaling in itself or in its spatial gradient, due to the constraint of ambipolar transport. As a result, a robust cooling flow aggregates mass toward the cooling spot and the thermal collapse of the surrounding plasma takes the form of four propagating fronts that originate from the radiative cooling spot, along the magnetic field line in a magnetized plasma. The slowest one, which is responsible for deep cooling, is a shock front.

Automated summary

A localized energy or particle sink introduced into a nearly collisionless plasma can trigger a plasma thermal collapse, known as a thermal quench. We demonstrate that electron thermal conduction in such a plasma follows the convective energy transport scaling due to ambipolar transport, resulting in a robust cooling flow and the formation of four propagating fronts along the magnetic field line. The slowest front is a shock front responsible for deep cooling.