```python
from pyaedt import Maxwell2d
import os

# Set non-graphical mode
os.environ["PYAEDT_NON_GRAPHICAL"] = "True"

# Create a Maxwell 2D project
maxwell_2d = Maxwell2d(solution_type="TransientXY", specified_version="2023.1", new_desktop_session=True)

# Insert a Maxwell 2D design and save the project
project_path = os.path.join(maxwell_2d.working_directory, "Maxwell2D_Transient_Example.aedt")
maxwell_2d.save_project(project_path)

# Create a rectangle and duplicate it
rectangle1 = maxwell_2d.modeler.primitives.create_rectangle([0, 0, 0], [10, 20], name="Conductor1", matname="copper")
rectangle2 = maxwell_2d.modeler.primitives.duplicate_and_mirror(rectangle1.id, [0, 10, 0], [10, 10, 0], is_3d_comp=False)[0]

# Create an air region
airbox = maxwell_2d.modeler.create_air_region(x_pos=-50, y_pos=-50, z_pos=-50, x_size=100, y_size=100, z_size=100, name="AirRegion")

# Assign windings to the sheets
maxwell_2d.assign_current([rectangle1.id], amplitude=1, name="Winding1")
maxwell_2d.assign_current([rectangle2.id], amplitude=-1, name="Winding2")

# Assign a balloon to the air region
maxwell_2d.assign_balloon([airbox.id], name="AirBalloon")

# Plot the model
maxwell_2d.plot(show=False, export_path=os.path.join(maxwell_2d.working_directory, "model_plot.png"), plot_air_objects=True)

# Create a transient setup
transient_setup = maxwell_2d.create_setup(setupname="TransientSetup")
transient_setup.props["StopTime"] = "1ms"
transient_setup.props["TimeStep"] = "10us"
transient_setup.update()

# Create a rectangular plot
maxwell_2d.post.create_rectangular_plot(expression="Mag_B", setup_name="TransientSetup", domain="Sweep")

# Solve the model
maxwell_2d.analyze_all()

# Create output and plot it using PyVista
# Note: PyVista code is not included as it requires a separate environment setup and is not directly related to PyAEDT operations.

# Generate the same plot outside AEDT
# Note: This step would typically involve exporting field data from AEDT and using an external plotting library like matplotlib or PyVista.

# Close AEDT
maxwell_2d.release_desktop()
```