# Plasma physics formulas (plasmapy.physics)¶

plasmapy.physics provides theoretical formulas for calculation of physical quantities helpful for plasma physics. The layout of the subpackage is still in flux, but for now we have settled on providing a single plasmapy.physics namespace for some of the most common functions. The actual functions are located in modules, subjectively grouped by topic, with sub-namespaces for larger sub-packages.

We thus have:

The subpackage makes heavy use of astropy.units.Quantity for handling conversions between different unit systems. This is especially important for electron-volts, commonly used in plasma physics to denote temperature, although it is technically a unit of energy.

Most functions expect astropy.units.Quantity as input, however some will use the plasmapy.utils.check_quantity decorator to automatically cast arguments to Quantities. If that happens, you will be notified via an astropy.units.UnitsWarning.

For a general overview of how unit-based input works, take a look at the following example:

Examples:

## Notes for developers¶

Values should be returned as an Astropy Quantity in SI units.

If a quantity has several names, then the function name should be the one that provides the most physical insight into what the quantity represents. For example, ‘gyrofrequency’ indicates gyration, while Larmor frequency indicates that this frequency is somehow related to a human (or perhaps a cat?) named Larmor. Similarly, using omega_ce as a function name for this quantity will make the code less readable to people who are unfamiliar with the notation or use a different symbol.

The docstrings for plasma parameter methods should describe the physics associated with these quantities in ways that are understandable to students who are taking their first course in plasma physics while still being useful to experienced plasma physicists.