A possibility of the electron phase transition into cyclotron superradiance mode in a vicinity of the Io flux tube foot in the Jovian magnetosphere has been considered. A high power of cyclotron superradiance allows it to be considered as the main mechanism of decameter Jupiter radiation generation in the form of S-bursts. It was found that the downward electron beams emitted by Io are able to create electric double layers in the form of shock waves. Such waves, when moving along the flux tube, accelerate electrons in the magnetosphere. As a result, the temperature of the electron plasma component decreases considerably. The emerging upward electron beams create conditions favorable for the phase transition into the cyclotron superradiance mode to take place. K e y w o r d s: magnetosphere, superradiance, double layer, plasma.

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The process of the e−e+ pair photoproduction in a strong magnetic field through the polarization cascade (the creation of an e−e+ pair from a single photon and its subsequent annihilation to a single photon) has been considered. The kinematics of the process is analyzed, and the expression for the general amplitude is obtained. A radiation correction to the process of pair creation at the lowest Landau levels by a single photon is found in the case where the energy of this photon is close to the threshold value. A comparison with the process of e−e+ pair production by one photon is made.