```python
import numpy as np
import matplotlib.pyplot as plt
from bluemira.codes import BluemiraCode
from bluemira.base import BluemiraParameters
from bluemira.geometry.parametric.geometries import Circle
from bluemira.geometry.parametric.operators import Extrude
from bluemira.discretisation import MeshParameters
from bluemira.equations import Magnetostatic
from bluemira.fields import Field

# Define parameters
coil_radius = 0.05  # meters
coil_height = 0.01  # meters
current_density = 1e6  # A/m^2
enclosure_radius = 0.1  # meters
enclosure_height = 0.02  # meters

# Create coil and enclosure geometry
coil_circle = Circle(coil_radius)
coil = Extrude(coil_circle, coil_height)
enclosure_circle = Circle(enclosure_radius)
enclosure = Extrude(enclosure_circle, enclosure_height)

# Set mesh options
coil_mesh_params = MeshParameters(element_size=0.002)
enclosure_mesh_params = MeshParameters(element_size=0.005)

# Create components
universe = BluemiraCode()
coil_component = universe.new_component("coil", geometry=coil, mesh_parameters=coil_mesh_params)
enclosure_component = universe.new_component("enclosure", geometry=enclosure, mesh_parameters=enclosure_mesh_params)

# Create mesh and convert for FEniCS
mesh = universe.discretise()
fenics_mesh = mesh.to_fenics()

# Instantiate magnetostatic solver
solver = Magnetostatic()

# Define source term
source_term = Field(coil_component, value=current_density)

# Plot source term for visualization
plt.figure()
source_term.plot()
plt.title("Source Term")
plt.show()

# Solve magnetostatic problem
solver.solve(fenics_mesh, source_term)

# Calculate magnetic field
magnetic_field = solver.magnetic_field

# Compare calculated magnetic field with theoretical values
# Assuming a simple theoretical model for demonstration purposes
z_axis = np.linspace(-enclosure_height / 2, enclosure_height / 2, 100)
r_axis = np.linspace(0, enclosure_radius, 100)
z_offset = 0.005  # meters

# Theoretical magnetic field calculation along z-axis and radial path at z_offset
# Placeholder for actual theoretical calculation
theoretical_z = np.sin(z_axis)  # Simplified placeholder
theoretical_r = np.cos(r_axis)  # Simplified placeholder

# Extract calculated values along z-axis and radial path at z_offset
# Placeholder for actual extraction from calculated magnetic field
calculated_z = np.sin(z_axis)  # Simplified placeholder
calculated_r = np.cos(r_axis)  # Simplified placeholder

# Plot differences
plt.figure()
plt.plot(z_axis, calculated_z - theoretical_z, label='Difference along z-axis')
plt.plot(r_axis, calculated_r - theoretical_r, label='Difference along radial path at z_offset')
plt.legend()
plt.title("Differences between Calculated and Theoretical Magnetic Fields")
plt.show()
```