# EquationSystem¶

The EquationSystem class keeps track of settings for all unknown quantities which DREAM solves for. This class does very little work on its own and rather acts as a container for the objects representing specific unknown quantities.

Each unknown quantity which has specific settings is represented by its own Python class. The object is initialized with defaults when the EquationSystem class is created (which happens as soon as the parent DREAMSettings object is created) and can be accessed as a property of the equation system. The following unknown quantities are available in any EquationSystem object:

Quantity

Description

E_field

Electric field

f_hot

Hot electron distribution function

f_re

Runaway electron distribution function

ions

Ion densities and charge states

j_ohm

Ohmic current density

n_cold

Cold electron density

n_re

Runaway electron density

psi_p

Poloidal magnetic flux

spi

Shattered pellet shards

T_cold

Cold electron temperature

## Examples¶

Unknown quantities can be accessed in the following way:

ds = DREAMSettings()

ds.eqsys.E_field.setPrescribedData(0.3)  # Uniform electric field profile (V/m)
ds.eqsys.T_cold.setPrescribedData(1100)  # Uniform temperature profile (eV)

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