Contributed Talk - Splinter Magnetic

Thursday, 24 September 2020, 14:37   (virtual room H)

Growth-rates of electrostatic waves in double plasma resonance model of solar radio zebras

Jan Benáček, Marian Karlický
TU Berlin, Masaryk university, Astronomical Institute of the Czech Academy of Sciences

The solar radio zebras are found in spectral observations from Sun, Jupiter, and the Crab pulsar. They are classified as Type IV fine structures, and they are used for precise diagnoses of the magnetic field and density in the solar magnetic loops. The most commonly used model interpreting the radio zebras is based on the double plasma resonance instability. The model assumes a dense and cold isotropic background plasma and rare hot component with a loss-cone type of distribution function. At resonances between the plasma and cyclotron frequency, this constitution generates the electrostatic upper-hybrid waves. They are transformed into electromagnetic radiation and radiated in a narrow cone towards the observer. We used analytical theory for growth-rates and 3D electromagnetic relativistic Particle-in-Cell simulation for analyses of this instability. We analyzed the temperature shifts of the growth-rate maxima and conditions for the peak formation for different loss-cone distribution functions. From zebra observations, we estimated the brightness temperatures, the size of the emission region, the energy density in the double plasma resonance region, and the conversion rate to electromagnetic waves. We also calculated the growth-rates for loss-cone power-law and loss-cone kappa distribution functions.