Electromagnetic radiation from negative corona discharge in air

In order to obtain spectra of electromagnetic (EM) radiations from the negative corona discharge in air, the radiation field was measured in a needle-to-ring configuration under different gas conditions. The experiments show that some characteristic EM radiations emit from the negative corona whose frequency is of tens megahertz. The characteristic radiations have fixed position and amplitude on the spectrum-meter which does not depend on the applied voltage or the discharge current under given gas conditions. These radiations do not change their characteristic spectra when the gas condition changes, but have different amplitudes in various air pressures or airflows. The characteristic EM radiations of the negative corona discharge in air are supposed to relate to the Trichel pulse. The rising edge of the pulsed current determines the frequency as well as the amplitude of the EM radiations.