Conventions in this package¶

We chose our conventions to align as much as possible with NuRadio.

Coordinate system¶

We use a right-handed coordinate system, with the z-axis pointing upwards. The x-axis points to magnetic East and the y-axis to magnetic North. This is essentially the CORSIKA coordinate system rotated by 90 degrees.

Furthermore, we also use arrival direction instead of travel direction. Hence, \(\phi = 0^{\circ}\) in our system means that the shower is _coming_ from the East, not travelling towards it. In the same vein, \(\phi = -90^{\circ}\) means that the shower is coming from the South (which in CORSIKA would be azimuth equal to 0) and setting \(\phi = 90^{\circ}\) implies that the shower comes from North.

Units¶

To keep track of the units in this package, we use the same unit system as NuRadio. Just like in that package we provide a units module that can be used to give each variable physical units. Each input is multiplied by its corresponding unit. To retrieve a value in a specific unit, you divide the output by the unit. For example, to retrieve a distance in centimeters, you can divide the variable by units.cm. Of course the output will only make sense if the the variable is divided by a unit of the same dimension.

Caution

As of April 2025, there are two notable exceptions to the use of the unit system, both related to atmospheric grammages. The first is the longitudinal profiles of the Shower objects. The first column contains the grammages values, but these are not in the internal unit system. Rather they are in g/cm2 directly. The same goes for the grammage values of the SliceSynthesis objects in the Numpy version of the package. The reason for this is that the g/cm2 unit is an awkward value, which makes it difficult to work with. Rather than adapting the internal unit system, which would make it incompatible with NuRadio, we simply do not convert some values for now.