Lecture 2: Physical Processes In Astrophysical and Laboratory Plasmas Lecture 1: Temperature-Density regime Many physical processes Focus on Atomic+Plasma interactions Atomic properties are intrinsic, independent of external factors (temp, den, etc.) Plasma interactions are treated as extrinsic Approximation:  Isolated atoms perturbed by environment

Quantum Statistical Equilibrium Division between atomic and plasma physics Calculation of individual atomic parameters – Chs. 2-7  Hartree-Fock, Close-Coupling (R-Matrix), etc.  Radiative and collisional properties  Transition probabilities and cross sections External statistical equilibrium of particles Local-Thermodynamic-Equilibrium (LTE)  characterized by local temperature-density  Saha ionization balance, Boltzmann level population  Boltzmann-Saha distribution Non-LTE requires explicit particle-radiation coupling  Collisional-Radiative model (simple) – Ch. 8: Emission lines  Multi-level radiative transfer model (complex) – Ch. 9: Absorption

Collisional-Radiative (CR) Models Section 8.2 and Fig. 8.7 Need excitation and radiative parameters, viz.  Electron impact cross sections (E): Ch. 5 – EIE  Maxwellian averaged rate coefficients (T)  Eq. (5.31)  A-values and oscillator strengths  Ch. 4 – Radiative Transitions Other processes such as fluorescent excitation by background radiation field may be included

Coupled CR Rate Equations Level Populations, emissivity, line ratios  Section Examples: [O II], [S II] forbidden lines He-like X-ray lines: Section 8.4, Fig. 8.7 General time-dependent rate equation  Eq. (8.41) Transient emission spectra (e.g. black-hole accretion disk x-ray flares): Fig. 8.13

Non-LTE Radiative Transfer Models Ch. 9: Absorption lines and radiative transfer Consider radiation-matter coupling explicitly For each photon frequency, specify  monochromatic source function S  monochromatic opacity and emissivity Section 9.4: Radiative transfer

Optical Depth Definition: Fig. 9.9 and Eq. (9.118) Basic radiative transfer equation: Eq. (9.119) Absorption and emissivity coefficients Source function: Eq. (9.126) S  Einstein A,B coefficients