This work involves ac and dc corona in air with heated discharge electrode, and breakdown streamers in corona in a crossed magnetic field. At first, the triggering of the breakdown streamers in positive and ac corona are governed by the temperature of the discharge electrode. In the negative corona, however, the breakdown streamers found to be practically independent of the temperature of the discharge electrode. Then, the transverse magnetic field, applied perpendicularly to the electric field, result in an improvement in pre-breakdown characteristic of the wire-tube gap. The application of the transverse field has the effect of increasing the corona onset voltage and the breakdown voltage. Also the transverse applied field has the effect of decreasing the corona current. It has been observed that triggering of the breakdown streamers in negative corona is affected appreciably by the transverse magnetic field.