def beta(T: u.K, n: u.m**-3, B: u.T):
"""
The ratio of thermal pressure to magnetic pressure.
Parameters
----------
T : ~astropy.units.Quantity
The temperature of the plasma.
n : ~astropy.units.Quantity
The particle density of the plasma.
B : ~astropy.units.Quantity
The magnetic field in the plasma.
Examples
--------
>>> import astropy.units as u
>>> beta(1*u.eV, 1e20*u.m**-3, 1*u.T)
<Quantity 4.02670904e-05>
>>> beta(8.8e3*u.eV, 1e20*u.m**-3, 5.3*u.T)
<Quantity 0.01261482>
Returns
-------
beta: ~astropy.units.Quantity
Dimensionless quantity.
"""
thermal_pressure = parameters.thermal_pressure(T, n)
magnetic_pressure = parameters.magnetic_pressure(B)
return thermal_pressure / magnetic_pressure
def test_magnetic_energy_density():
r"""Test the magnetic_energy_density function in parameters.py."""
assert magnetic_energy_density(B_arr).unit.is_equivalent(u.J / u.m ** 3)
assert magnetic_energy_density(B).unit.is_equivalent('J / m3')
assert magnetic_energy_density(B).value == magnetic_pressure(B).value
assert_quantity_allclose(magnetic_energy_density(2 * B), 4 * magnetic_energy_density(B))
assert_quantity_allclose(magnetic_energy_density(B).value, 397887.35772973835)
assert_quantity_allclose(magnetic_energy_density(B), magnetic_energy_density(B.to(u.G)))
assert isinstance(magnetic_energy_density(B_arr), u.Quantity)
with pytest.warns(u.UnitsWarning):
magnetic_energy_density(5)
with pytest.raises(u.UnitConversionError):
magnetic_energy_density(5 * u.m)
assert np.isnan(magnetic_energy_density(np.nan * u.T))
with pytest.raises(ValueError):
magnetic_energy_density(5j * u.T)
assert np.isnan(magnetic_energy_density(B_nanarr)[-1])
with pytest.warns(u.UnitsWarning):
assert magnetic_energy_density(22.2) == magnetic_energy_density(22.2 * u.T)
assert_can_handle_nparray(magnetic_energy_density)
def test_magnetic_pressure():
r"""Test the magnetic_pressure function in parameters.py."""
assert magnetic_pressure(B_arr).unit.is_equivalent(u.Pa)
assert magnetic_pressure(B).unit.is_equivalent(u.Pa)
assert magnetic_pressure(B).unit.name == 'Pa'
assert magnetic_pressure(B).value == magnetic_energy_density(B).value
assert magnetic_pressure(B) == magnetic_energy_density(B.to(u.G))
assert np.isclose(magnetic_pressure(B).value, 397887.35772973835)
with pytest.warns(u.UnitsWarning):
magnetic_pressure(5)
with pytest.raises(u.UnitConversionError):
magnetic_pressure(5 * u.m)
with pytest.raises(ValueError):
magnetic_pressure(np.nan * u.T)
with pytest.raises(ValueError):
magnetic_pressure(5j * u.T)
with pytest.raises(ValueError):
magnetic_pressure(B_nanarr)
with pytest.warns(u.UnitsWarning):
assert magnetic_pressure(22.2) == magnetic_pressure(22.2 * u.T)
assert_can_handle_nparray(magnetic_pressure)
def time_magnetic_pressure(self):
magnetic_pressure(0.1*u.T)