Line Transfer and Scattering

Line Transfer Modes

Variable: geo.line_mode

Python has a number of different line transfer modes, which affect the treatment of lines and scattering, and also whether we use indivisible packet constraints or allow photon weights to be attenuated by continuum absorption. These modes are selected with the question Line_transfer() as follows. The modes are described below, and the scattering modes at the bottom.

0 - pure absorption 1 - pure scattering 2 - single scattering 3 - escape probability, isotropic scattering 4 - escape probability, semi-analytic anisotropic scattering 6 - macro atoms, isotropic scattering 7 - macro atoms, numerical anisotropic scattering method

0: Pure Absorption

1: Pure Scattering

2: Single Scattering

3: Escape Probability, Isotropic Scattering

• Resonance scattering and electron scattering is dealt with isotropically.
• free-free, compton and bound-free opacities attenuate the weight of the photon
• wind emission produces additional photons, which have their directions chosen isotropically. The amount of radiation produced is attenuated by the escape probability.

4: Escape Probability, Semi-Analytic Anisotropic Scattering

• Resonance scattering and electron scattering is dealt with using the semi-analytic isotropic scattering routine.
• free-free, compton and bound-free opacities attenuate the weight of the photon
• wind emission produces additional photons, which have their directions chosen isotropically. The amount of radiation produced is attenuated by the escape probability.

5: Escape Probability, Semi-Analytic Anisotropic Scattering

• as mode 4, but we use scattering mode 2, the 'thermal trapping method' to choose an anistropic direction when an r-packet deactivation or scatter occurs.

6: Macro Atoms, Isotropic Scattering

• we use macro-atom line transfer.
• Packets are indivisible and thus all opacities are dealt with by activate a macro-atom, scattering, or creating a k-packet.
• the new direction for electron scattering or deactivation of a macro atom is chosen isotropically.

7: Macro Atoms, Anisotropic Scattering

• as mode 6, but we use scattering mode 2, the 'thermal trapping method' to choose an anistropic direction when an r-packet deactivation or scatter occurs.

8: Macro Atoms, Anisotropic Scattering, All simple ions

• as mode 7, but we treat all ions as simple

9: Macro Atoms, Anisotropic Scattering, All simple ions

• as mode 7, but we use scattering mode 1

Scattering Modes

Variable: geo.scatter_mode

0: isotropic Simply call the routine randvec every time you want to choose a new direction.

1: anisotropic semi-analytic

2: anistropic numerical

This is mainly used for the macro atom line transfer mode. The new direction for the photon is chosen by a rejection method according to the Sobolev escape probability along each direction. This is done in the routine scatter.