Cosmic physics 1

A.Y. 2020/2021
Overall hours
Learning objectives
The course aims at providing theoretical knowledge concerning interaction of radiation and matter and astrophysical fluid dynamics. Several radiation processes will be covered, such as dipole radiation, scattering Thomson and Compton, bremsstrahlung, and fundamentals of radiative transport. Then, the cours will consider the fluid equations, discussing astrophysically relevant equilibrium configurations (such as polytropic spheres), wave phenomena and instabilities, siuch as the gravitational instability
Expected learning outcomes
At the end of the course the student will:
1. Recognize the spectrum and emission features of the most important radiative processes in Astrophysics.
2. Solve the radiative transfer equation in simple geometries.
3. Apply when encessary the appropriate approximations, such as the radiative diffusion one.
4. Recognize and describe hydrostatic balance configurations in astrophysical context.
5. Derive the dispersion relation for sound waves and other dispersive waves.
6. Solve the shock conditions.
7. Recognize the fluid processes at play in the dynamics of astronomical systems, such as stars, the interstemmar medium and gas orbiting compact objects.
Course syllabus and organization

Single session

Lesson period
First semester
In an emergency, lectures will be held synchronously via Zoom, using a virtual chalkboard. Lectures wil be recorded and made available on the Ariel website of the course.
Course syllabus
-) Fundamental physical processes
-) Interaction of radiation and matter:
> The electromagnetic field. Radiation from moving charges: Larmor's formula, dipole approximation.
> Thomson scattering, Rayleigh scattering.
> Bremsstrahlung radiation: single charge spectrum, spectrum from a thermal population of electrons.
> Cyclotron and synchrotron radiation. Compton scattering. Inverse Compton scattering.
> Absorption and emission coefficients. Radiative transport equation. Optical depth. Radiative transport for plane parallel geometry: Rosseland approximation.
> Black body radiation. Kirchhoff theorem. Einstein's coefficients.
-) Astrophysical fluid dynamics:
> Fluid equations. Eulerian and Lagrangian approaches.
> Continuity equation, Euler's equation, Equation of state. Poisson's equation. Energy equation.
> Hydrostatic balance: isothermal atmosphere, self-gravitating isothermal slab. Polytropic spheres, Bonnor-Ebert spheres.
> Waves and fluid instabilities: sound waves, shock waves. Thermal instability. Gravitational instability. Outline of Rayleigh-Taylor and Kelvin-Helmholtz instabilities.
> Viscous flows: Navier-Stokes equation. Vorticity: Kelvin's theorem on vorticity. Helmholtz equation. Bernoulli equation.
> Turbulence: Kolmogorov theory.
Prerequisites for admission
1. Fundamentals of mechanics (e.g. the two body problem, Kepler's laws)
2. Fundamentals of electrodynamics (e.g. Maxwell's equations)
3. Findamentals of special relativity (Lorenza trasformations)
4. Elents of calculus, in particular differential equations in one and more variables, Fourier transforms.
Teaching methods
Chalkboard lectures.
Teaching Resources
1) Rybicki-Lightman, "Radiative processes in Astrophysics", Wiley-Vch.
2) Clarke-Carswell, "Astrophysical Fluid Dynamics", Cambridge University Press.
Assessment methods and Criteria
The exam is an oral discussion related to both broad topics of the course (interaction of radiation and matter and fluid dynamics).
FIS/05 - ASTRONOMY AND ASTROPHYSICS - University credits: 6
Lessons: 42 hours
Professor: Lodato Giuseppe
Educational website(s)
Monday 14.00-15.00 (upon appointment)
Teacher's office