Virtual Packet Logging

If virtual_packet_logging is set to True in either the spectrum configuration or as an argument to the run_tardis function, then TARDIS will log information about the simulation’s virtual packets.

The parent-interaction fields are populated from the real-packet histories used by virtual-packet spectrum post-processing. Virtual packets spawned at the inner boundary have last_interaction_type NO_INTERACTION, before_nu 0, radius equal to the inner boundary radius, and -1 for shell_id and the line ids.

After running the simulation, the logged virtual packets are available from the spectrum solver as a DataFrame with one row per escaping virtual packet. For a TARDIS simulation sim, run sim.spectrum_solver.vpacket_tracker_to_df(); workflows provide the same method on workflow.spectrum_solver. The interaction columns use the same names and types as the real-packet transport_state.tracker_last_interaction_df. Each row describes the real-packet event that spawned the virtual packet.

Column	Type	Description
`last_interaction_type`	Categorical	Type of the real-packet event that spawned the virtual packet; `NO_INTERACTION` for virtual packets spawned at the inner boundary
`radius`	Float	Radius of the spawning real-packet event [cm]
`shell_id`	Integer	Shell of the spawning real-packet event
`before_nu`	Float	Frequency of the real packet before the spawning event [Hz]
`line_absorb_id`	Integer	Absorbing line of the spawning event, or -1 if it was not a line interaction (see How to Access Physical Quantities)
`line_emit_id`	Integer	Emitting line of the spawning event, or -1 if it was not a line interaction (see How to Access Physical Quantities)
`nus`	Float	Escaping virtual packet frequency [Hz]
`energies`	Float	Escaping virtual packet energy [erg]
`initial_mus`	Float	Propagation direction the virtual packet was launched at
`initial_rs`	Float	Radius the virtual packet was launched at [cm]

When a simulation is saved to HDF, this DataFrame is stored at /simulation/spectrum_solver/vpacket_tracker_df, with last_interaction_type stored as InteractionType integer codes.