file: radtrans-notes.txt = Rob Rutten notes MSU rad-trans course July 2003
last: Aug  1 2003 
init: Jul  3 2003 
site: /home/rrutten/radtrans-course @ mithra.physics.montana.edu 
todo: update this file 


material
========

  lecture notes
    GTR  = undergraduate course (computer translation; 1 paper copy here)
      GTR Chapts 2-5 = extended version of Rybicky & Lightman Chapt 1
      GTR Chapt 6 = summary of Rybicky & Lightman Chapts 2-7

    RTSA = graduate course (clickable pdf at http://www.astro.uu.nl/~rutten)
      RTSA Chapt 2 = summary GTR Chapts 2-5 
      RTSA Chapt 3-4 = roughly similar to Mihalas 1st edition (but easier)

  IDL-based exercises
    SSA = Stellar Spectra A exercises (basic line formation, Rob website)
    SSB = Stellar Spectra B exercises (LTE line formation, Rob website)
    SSC = Stellar Spectra C exercises (NLTE line formation, Alfred file)


people 
======

  Rob Rutten          R.J.Rutten@astro.uu.nl
  Alfred de Wijn      A.G.deWijn@phys.uu.nl

  Brandon Anderson    phoenix7799@hotmail.com
  Jonathan Cirtain    jcirtain@mithra.physics.montana.edu
  Blane McCracken     mccrack@solar.physics.montana.edu
  Michael Hahn        hahn@solar.physics.montana.edu
  Brian Hurlbutt      hurlbutt@solar.physics.montana.edu
  Mike Obland         obland@physics.montana.edu 
  Brian Larsen        larsen@mithra.physics.montana.edu
  John Macaluso       quantuumcosmo@yahoo.com
  Piet Martens        martens@physics.montana.edu
  Andres Munoz        an-munoz@uniandes.edu.co
  Joe Shaw            jshaw@montana.edu
  Karen Wilson        wilson@physics.montana.edu


planned contents = mainly Chapts 2, 4, 8 RTSA
=============================================

  introduction (Chapts 1, 8 GTR)
    Fraunhofer lines in solar irradiance: nonlocal
    Kirchhoff-Bunsen versus solar photosphere: thin versus thick
    white light corona: local nonthermal thin
    EUV corona bright: local thermal thin
    EUV corona dark: bound-free non-monofrequent scattering 
    Zanstra emission nebulae: non-local in space and wavelength

  photon-particle interactions (Chapt 2 RTSA)
    bb, bf, ff, Thomson, Rayleigh
    pairs: photon creation, destruction, scattering, conversion
    TE: Planck function, Boltzmann, Saha distributions
       # exercise: SSA2 = Cecilia Payne = Saha-Boltzmann partitioning

  radiation quantities (Chapt 2 RTSA)
    definitions I, J, F; j, alpha; tau, tau_radial; S 

    local thermal (LTE) versus nonthermal nonlocal (scattering, conversion)  
    2-level scattering: S = (1-eps) J + eps B

  basic radiative transfer (Chapt 2 RTSA)
    differential transport equation
    line formation for homogeneous thin/thick medium
    integral solution, Eddington-Barbier approximation
    schematic line formation in plane-parallel atmosphere
       # exercise: SSA3 = Marcel Minnaert = curve of growth

  spectral line quantities
    Einstein coefficients, Einstein relations
    line emissivity, extinction, source function in Einstein coefficients
    redistribution versus coherence
    <line broadening>
  
  plane-parallel radiative transfer (Chapt 4 RTSA)
    Lambda and Phi operators and kernel weighting
    diffusion approximation
    demonstration: scattering in Eddington approximation
       # exercises: SSC (partial) 

  solar continua (Chapt 8 RTSA)
    VAL3C continua formation
    VAL3C radiative heating/cooling budget
       # exercises: SSB1 = Gene Avrett = VAL3C stratification
                    SSB2 = Chandrasekhar = H-minus extinction 



============================================================================
                              daily logs
============================================================================

Jul  3 2003 introduction (Chapts 1, 8 GTR)
===========

    overview material (see above)
      2 lecture-note "books" undergraduate (paper) - graduate (WWW)
      3 IDL exercise sets  idem, WWW 

    Fraunhofer lines in solar irradiance (from Dana's nose)
      nonlocal
      any sunlight-illuminated solar-system object shows solar spectrum
      even when you don't even see the sun - indirect source, transfer 

    major photon-particle interactions
      5x bound-bound, bound-free, free-free (atoms, ions, molecules, hadrons)
      Thomson scattering off free electrons (hot star continua)
      Rayleigh scattering off bound electrons (blue sky, red sunset)

    Kirchhoff-Bunsen Na D lines from sodium in flame
      emission = collisonal excitation + spontaneous deexcitation
      absorption = scattering out of beam toward observer

    coronal radiation 
      inner white-light corona at eclipse 
        Thomson-scattered photospheric light (white color)
        Fraunhofer lines washed out by Doppplershifts (=> T = 1 MK)
      EUV emission from loops
        collisional excitation + spontaneous deexcitation + photon escape
        local thermal photon creation, no radiative transfer
      EUV absorption by cooler foreground gas
        H, He, He II bound-free scattering with frequency redistribution 
        TRACE: wavelength shift outside passband, so black


Jul 10 2003 basic quantities (Chapt 2 RTSA) 
===========

    repeat 5 processes bb, bf, ff; Thomson scattering; Rayleigh scattering

           pairwise bb, bf, ff combinations
             thermal photon-in-beam creation, destruction
             scattering into beam, out of beam (same as TS and RS) 

    scattering also has stimulated part, but with perfect cancelation
      between emission and extinction in non-relativistic conditions

    quantities
      I_nu intensity = basic quantity expressing that photons do not decay
      J_nu angle-averaged intensity = "radiation field": photon availability 
      F_nu flux = net energy stream in given direction 
        e.g. stellar surface energy loss
             irradiance at earth
             energy on pointed telescope mirror/antenna 
             brightness of an unresolved star (= NOT intensity!)

      j_nu = emissivity: local addition of photons into beam
      alpha_nu = extinction: local attenuation of beam 

      transport equation: d I_nu = + j_nu ds - I_nu alpha_nu ds
        linear differential equation but becomes integro-differential eq.
        if scattering contributes so that J_nu goes into j_nu
       

Jul 17 2003 transport equation, TE laws (Chapt II RTSA)
===========
   
     definition tau = optical thickness or optical depth
     defintion source function = emissivity/extinction coefficient

     plane-parallel stellar atmosphere transport equation
     mu dI/dtau = I - S    or integral "formal solution"

     TE = thermodynamic equilibrium (detailed balancing) laws:
       matter     Maxwell    velocity distribution
                  Boltzmann  level partitioning within ion stage
                  Saha                          between ion stages
       radiation  Planck, Wien, Stefan Boltzmann
     Boltzmann-Saha explained apparent spectral types (OBAFGKM, Annie
     Cannon) as temperature scale (Cecilia Payne)

     TE: I=S=B    
     LTE: S=B (= TE laws with local temperature)


Jul 24 2003 RT, LTE, EB, H-min (Chapt 2 RTSA)
===========

  source function nature   
     2-level atoms: S = (1-eps) J + eps B
     linear combination of scattering into beam and thermal production
     eps = collisional photon destruction fraction per extinction
         = alpha_abs / (alpha_abs + alpha_scat)
     LTE: Boltzmann valid => S_nu = B_nu (T)
     
  homogeneous medium, say LTE so S=B and isothermal
    thick: no spectral lines, just B
    thin: emission lines if no irradiation I_0 from behind
          absorption lines if S < I_0

  stellar atmospheres
    formal solution transport equation I^- and I^+
    Eddington-Barbier approximation for emergent radiation:
      I^+(0,mu) \approx S_nu (tau_nu=mu)
      I^+(0,1) \approx S_nu (tau_nu=1)
    in words: value S at tau=1 is predictor for emergent radiation
              NOT: "the photons come from tau=1"
    in LTE: 
      I^+(0,mu) \approx B_nu [T(tau_nu=mu)]
      I^+(0,1) \approx B_nu [T(tau_nu=1)]

  solar optical and infrared continuum
    differences from Planck funxtion = different sampling tau=1
    difference behavior = location tau=1 = extinction coefficient
    minima 400 and 1600 nm, hump in optical, increase beyond 1600 nm
    Wildt: H-minus ion, confimed by Chandrasekhar + Green
    H-min bf = up to ionization limit 1.6 mum, nearly LTE
    H-min ff = beyond, exactly LTE
    below 400 nm dominance by Mg I bf, Al I bf, Fe I bf, Si I bf
      all scattering, out of LTE, small eps

Jul 31 2003 LTE and NLTE line formation stellar atmospheres
===========

   Eddington Barbier: map source function at tau=mu
   emergent line profile
     large peak in extinction
     mapping over considerable height range
     sampling of mapping set by varying tau scale through line profile
     mapping = temperature (height)
               Planck function (temperature)
               epsilon-dependent linear combination with J if NLTE 
               epsilon \propto collision frequency \propto density
               tau with height per frequency
               extinction with frequency 

   absorption line = outwards declining source function
   emission line = outwards increasing source function
   Ca II H & K self reversals
     peak in source function = mapped in two emission features
     line center dark due to scattering
     peak = some following of chromospheric temperature rise before 
            scattering decouples source function from Planck function

     but NB: acoustic shocks, gravity waves, magnetism, Wilson-Bappu...