Relaxation of the Turbulent Magnetosheath
Presentation Type
Talk
Presenter Format
In Person Meeting Talk
Topic
Dayside Science
Start Date
10-5-2022 1:45 PM
Abstract
The large-scale phenomena that involve plasmas can be adequately described by using magnetohydrodynamics equations. Such a set of equations consists of several nonlinear terms that are responsible for driving the energy contained in the large-scale eddies to small scales through the so-called energy cascade. A turbulent state is a state in which the nonlinear terms are of the order of (or greater) than the linear terms. It has been shown that space plasma turbulence (e.g., described by three-dimensional magnetohydrodynamics) tends to relax toward equilibrium states that minimize the energy; these states, in principle, are considered global. However, turbulence can locally relax toward such equilibrium states, creating patches where the magnitude of the nonlinear terms is reduced and the energy cascade impaired. Boundaries between such patches are expected to have a stronger unimpaired cascade. We argue that this “cellularization” of turbulence can happen in strongly turbulent environments (large fluctuations' amplitude) such as the Earth's magnetosheath, as we demonstrate here by analysis of MMS observations.
Relaxation of the Turbulent Magnetosheath
The large-scale phenomena that involve plasmas can be adequately described by using magnetohydrodynamics equations. Such a set of equations consists of several nonlinear terms that are responsible for driving the energy contained in the large-scale eddies to small scales through the so-called energy cascade. A turbulent state is a state in which the nonlinear terms are of the order of (or greater) than the linear terms. It has been shown that space plasma turbulence (e.g., described by three-dimensional magnetohydrodynamics) tends to relax toward equilibrium states that minimize the energy; these states, in principle, are considered global. However, turbulence can locally relax toward such equilibrium states, creating patches where the magnitude of the nonlinear terms is reduced and the energy cascade impaired. Boundaries between such patches are expected to have a stronger unimpaired cascade. We argue that this “cellularization” of turbulence can happen in strongly turbulent environments (large fluctuations' amplitude) such as the Earth's magnetosheath, as we demonstrate here by analysis of MMS observations.
