Subtract two field componentsยง
Let's assume we have the data for two components of the electromagnetic fields, \(E_r\) and \(B_\theta\), in a 2D cylindrical simulation.
import ozzy as oz
e2_ds = oz.open('osiris', 'path/to/file/MS/FLD/e2/e2-000010.h5')
b3_ds = oz.open('osiris', 'path/to/file/MS/FLD/b3/b3-000010.h5')
print(e2_ds)
import ozzy as oz
e2_ds = oz.open('lcode', 'path/to/file/er00200.swp')
b3_ds = oz.open('lcode', 'path/to/file/bf00200.swp')
print(e2_ds)
import ozzy as oz
import numpy as np
# Create some dummy data
x1 = np.linspace(0, 10, 100)
x2 = np.linspace(-5, 5, 50)
e2_data = np.random.rand(50, 100)
b3_data = np.random.rand(50, 100)
# Create the Datasets
e2_ds = oz.Dataset({'e2': (['x2','x1'],e2_data)}, coords={'x1': x1, 'x2': x2}, pic_data_type='grid', data_origin='ozzy')
b3_ds = oz.Dataset({'b3': (['x2','x1'],b3_data)}, coords={'x1': x1, 'x2': x2}, pic_data_type='grid', data_origin='ozzy')
print(e2_ds)
Right now we have two datasets (one for each field component). Since these data variables share the same axes ("coordinates" in xarray nomenclature), we can easily merge both datasets.
import xarray as xr
fields = xr.merge([e2_ds,b3_ds])
print(fields)
In this example we want to obtain the radial force associated with the electromagnetic fields of an axisymmetric plasma wave. In the normalized units used in most PIC codes, the radial force (on a positive particle) is defined simply as \(W_r = E_r - B_\theta\). We can perform the subtraction and store the result as a new variable in the same dataset.
fields['wr'] = fields['e2'] - fields['b3']
print(fields['wr'])
Afterwards, we can save the result as an HDF5 file.
# We're leaving e2 and b3 aside
fields['wr'].ozzy.save('wr.h5')