Add Plasma Environment

The plasma environment contributions are used to surround the model geometry in ambient plasma to recreate the target environment the model will experience. CHARGE allows you to customize these inputs by varying the species of the plasma, its density and temperature (eV) along with the distribution function used to describe it. It also allows for time variation of the individual contribution parameters to emulate shadowing effects, entering sheaths etc. Individual plasma environments are often stacked to simultaneously irradiate your model to simulate your final environment.

Plasmas are initialized as a distribution of density or current as a function of energy. Depending on the orbit of choice, various distributions are needed to initialize the plasma. Typical distributions for lower energy plasmas (GEO, LEO, Lunar) are defined based on density such as a Maxwellian, Double Maxwellian, or Kappa distribution. For slightly higher energy plasmas (auroral environments) the distributions are defined based on current such as a Gaussian, Power Law, or a Maxwellian distribution. We can model all these distributions in EMA3D Charge, both as an analytical current for the BEM or as a particle species in the PIC. For PIC, we added a mono-energetic particle source. We labeled distributions that take in a current instead of a density as a Zeta distribution, where Zeta is the current in A/m^2.

This page discusses adding a plasma environment from scratch, there are built in GEO environments as well, which can be viewed by clicking here.

Instructions

Click on Plasma in the Environments section of the CHARGE tab to see the option to add a custom Plasma Environment or one of two built in GEO environments.
Expand the properties window sections in the HUD to reveal the options which can be adjusted for your simulation.
Adjust the values to your liking to match the simulation which you want to run. When finished, click the OK button to complete the plasma environment definition.
The plasma environment definition can be viewed in the EMA3D stage by navigating through the SID at the bottom of the Discovery window,where you can find it under Environments.

General

Options

Entry	Meaning
Name	Plasma environment name.
Color	Plasma environment color.
Type	This will dictate the charge of the plasma, Electron having negative charge and Proton positive charge association
Plasma Model	[NOTE: PIC Plasma Environment Models MUST HAVE a body assignment to work, surface environments do not.]Choose between a plasma model that is solved with analytical currents at the surface of the geometry or with the particle-in-cell solver. All plasmas have to be defined with the same model. For the PIC plasmas, some or all geometries with a vacuum internal charging material have to be selected by the user.
Plasma Model	Sets the analytic model for the plasma space charge. Laplacian assumes no space charge, Barometric is used when the charging is expected to be only negative, Nonlinear when positive charging can occur such as when using biased solar panels.
Plasma Model	[NOTE: PIC Plasma Environment Models MUST HAVE a body assignment to work, surface environments do not.]Choose between a plasma model that is solved with analytical currents at the surface of the geometry or with the particle-in-cell solver. All plasmas have to be defined with the same model. For the PIC plasmas, some or all geometries with a vacuum internal charging material have to be selected by the user.
Plasma Model	[NOTE: PIC Plasma Environment Models MUST HAVE a body assignment to work, surface environments do not.]Choose between a plasma model that is solved with analytical currents at the surface of the geometry or with the particle-in-cell solver. All plasmas have to be defined with the same model. For the PIC plasmas, some or all geometries with a vacuum internal charging material have to be selected by the user.

Ion Options

Entry	Meaning
Charge Multiplier	Defines the charge in multiples of the characteristic charge of an electron.
Mass	Mass of the ion species in amu.
Is Excited	If this is set to true, this allows relaxtion to be turned on.

Distribution Settings

Distribution Settings Options

Entry	Meaning
Distribution	Set the analytic distribution model. The Zeta models are current weighted distributions.
Temperature	Set the temperature for the Plasma Environment.
Density	Set the density for the Plasma Environment.
Kappa	----
Zeta	Current Density amplitude.
Width	The standard deviation of the energy spread.
E-Zero	Peak energy of the distribution.
E-Lower	The minimum energy cutoff for the distribution.
E-Upper	The maximum energy cutoff.
Alpha	Power law index. Slope in a log-log plot.

Fluid Properties

Fluid Properties Options

Entry	Meaning
Kinematic Viscosity	A measure of a fluid’s resistance to flow under the influence of internal momentum. It quantifies how momentum difusses through the plasma. Typical values are 1E-4 to 10.
Thermal Diffusivity	Characterizes the rate of thermal energy transport due to temperature gradients. Typical values are 1E-4 to 10.
Temperature	Defines the initial temperature of the plasma species.
Density	Defines the initial mass density of the plasma species.
X	Define the initial velocity in the X direction
Y	Define the initial velocity in the Y direction
Z	Define the initial velocity in the Z direction

PIC Advanced Settings

PIC Advanced Settings Options

Entry	Meaning
Boundary Type	Select the boundary type for this plasma, it will be applied to all bodies in which that species will be simulated
Boundary Loss	[0 <= Percentage <= 1]Select the percentage of macro-particles lost through the boundary for this plasma, it will be applied to all bodies in which that species will be simulated
Model Wake	Determines whether or not to model an analytic wake for this species. This should generally be set to false for electrons, and true for ions in situations where the ion speed is on the same order as the satellite.

Background Options

Entry	Meaning
Neutral Density	Sets an analytic background density for a neutral species to be used in reactions.

Time Varying Settings

Time Varying Settings Options

Entry	Meaning
Import Temperature Collection	Import Temperature Collection
Import Density Collection	Import Density Collection
Import Kappa Collection	Import Kappa Collection