Lecture 5 - Free-Free emission and absorption and radio waves Flashcards
What is a cold plasma
A nonthermal plasma, cold plasma or non-equilibrium plasma is a plasma which is not in thermodynamic equilibrium, because the electron temperature is much hotter than the temperature of heavy species (ions and neutrals).
What is interplanetary scintillation?
They are random, second long, fluctuations in the intensity of radio waves.
Bremstrahlung with another name
Free-free emission
Are gaunt factors used for free-free transitions?
Yes, but not exclusively
For free-free emission, what happens with the absorption coefficient when the temperature or frequency is large?
It becomes small, making the cloud transparent
The emission measure, EM, is the integral of what?
number density electrons and protons (over line of sight in cloud)
Dispersion means that lower frequencies arrive…
later
The rotation measure depend on two things, what?
The number density of electrons and the parallel magnetic field
What is a scintillation?
A time variation of a signal
