Astrophysical and Laboratory Plasmas Lecture 1 TemperatureDensity regime Many physical processes Focus on AtomicPlasma interactions Atomic properties are intrinsic independent of external factors temp den etc ID: 242345
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Slide1
Lecture 2: Physical Processes InAstrophysical 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 environmentSlide2
Quantum Statistical Equilibrium
D
ivision 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: AbsorptionSlide3
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
includedSlide4
Coupled CR Rate Equations
Level Populations, emissivity, line ratios
Section 8.1.3
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. 8.13Slide5
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
transferSlide6
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