Specific and interesting type of fine-structured radio bursts - "zebras" - are known from spectral observations of the Sun, Jupiter, and the Crab-Nebula pulsar. In the solar case, they are classified as 'Type IV' fine structures and quite frequently observed also by the Ondřejov solar radiospectrographs. Assuming a model of their emission they can be used for the otherwise difficult diagnostics of plasma density and magnetic field in the solar atmosphere. The most commonly used zebra-emission model is based on the double plasma resonance (DPR) instability of the upper-hybrid (UH) waves and their subsequent conversion into the escaping electromagnetic radiation. In order to make detailed calculations of the DPR model-predicted radio emission, we use analytical theory for the UH-waves growth rates in conjunction with a 3-D electromagnetic relativistic Particle-in-Cell (PIC) code. We calculate the plasma and wave dynamics for specific velocity distribution function of hot-electron component (DGH, loss-cone, kappa,...) superimposed over the colder Maxwellian background plasma. We analyze how the frequencies of the growth-rate maxima change with the temperature (a new result unexpected by the so-far models) and conditions for the emission-peak formation. The results are combined with the zebra observations: From them we can estimate the zebra-source brightness temperature, the size of the emission region, the energy density of the electrostatic waves in this region, and the conversion rate of the electrostatic (UH) waves into electromagnetic ones. It is shown that such detailed calculations of radio emission from solar/astrophysical plasmas represents the necessary ground for reliable diagnostics based on radio bursts observations.

Exoplanet group was officially created in 2018. We became a member of ESA PLATO Space mission hunting for exoplanets with a launch date in 2026. Furthermore, activities and results of the group with OES spectrograph on Perek telescope will be presented with a latest surprise discovery among TESS space mission objects. Finally, plans for new projects and a long term vision for exoplanetary research in the Czech Republic will be introduced.