Diagnostics of magnetic field strength for gyrosynchrotron radiation regions of the lower harmonics

A diagnostic formula of magnetic field strength of gyrosynchrotron radiation regions of the lower harmonics (5⩽S⩽10) is presented based on their emissivity , absorptivity , and the turnover frequency of radio spectrav _p . Their diagnostic error is estimated. And an accurate relation between electron energy spectral indexδ and brightness temperature spectral indexβ is also given.