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Physics 681: Solar Physics and Instrumentation – Lecture 4

Physics 681: Solar Physics and Instrumentation – Lecture 4. Carsten Denker NJIT Physics Department Center for Solar–Terrestrial Research. Solar Spectrum. The spectrum of the Sun: The dashed line is the curve of an ideal blackbody having the Sun’s effective temperature. Radiation Field.

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Physics 681: Solar Physics and Instrumentation – Lecture 4

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  1. Physics 681: Solar Physics and Instrumentation – Lecture 4 Carsten Denker NJIT Physics Department Center for Solar–Terrestrial Research

  2. Solar Spectrum The spectrum of the Sun: The dashed line is the curve of an ideal blackbody having the Sun’s effective temperature. Center for Solar-Terrestrial Research

  3. Radiation Field Center for Solar-Terrestrial Research

  4. Energy Transport • Radiation and convection • Energy flux (luminosity per unit area): • Mean free path of photons is small in the solar interior  local thermal equilibrium (LTE) • Radiative transfer equation • Total energy flux • Temperature gradient Center for Solar-Terrestrial Research

  5. Temperature Definitions Center for Solar-Terrestrial Research

  6. Opacity Any process that removes photons from a beam of light will be called absorption. Center for Solar-Terrestrial Research

  7. The optical depth may be thought of as the number of mean free paths from the original position to the surface, as measured along the ray’s path. Center for Solar-Terrestrial Research

  8. Radiative Transfer Equation Center for Solar-Terrestrial Research

  9. The intensity of the light tends to become equal to the local value of the source function. For the case of thermodynamic equilibrium, the source function is equal to the Planck function S = B. Center for Solar-Terrestrial Research

  10. Photon Interactions • Bound–bound transitions • Bound–free absorption • Free–free absorption (bremsstrahlung) • Electron scattering Center for Solar-Terrestrial Research

  11. Continuum Opacity Photoionization of H– ions The total opacity depends not only on the wavelength of the light being absorbed but also on the composition, density, and temperature of the stellar material. Rosseland mean opacity Center for Solar-Terrestrial Research

  12. Structure of Spectral Lines Center for Solar-Terrestrial Research

  13. Nuclear Reactions http://nobelprize.org/physics/articles/fusion/sun_pp-chain.html Center for Solar-Terrestrial Research

  14. CNO Cycle http://outreach.atnf.csiro.au/education/senior/astrophysics/stellarevolution_mainsequence.html Center for Solar-Terrestrial Research

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