The breakdown of atmospheric pressure air in mode of generation of runaway electrons beam terms was investigated. A beam of runaway electrons was registered with nanosecond pulse duration voltage negative polarity on coaxial electrodes, which corresponded to the first phase breakdown on the runaway electrons. It is shown that at voltage pulse duration of 2 ns, its amplitude is 300 kV and the gap in coaxial air line is 8 cm, first generation of runaway electrons does not lead to the breakdown, and that the form of discharge in line corresponds to a corona discharge. It is shown that the FWHM of the pulse of the runaway electron beam during corona discharge is not longer than 100 ps.
breakdown of atmospheric pressure air, development of discharges before breakdown, mode of runaway electrons, pulse duration of e-beam