ABSTRACT
This chapter describes noise generated by various sources, and considers factors that affect the propagation and generation of the noise. It also considers the information provided by intensity, polarization, and spectrum of the noise, and by maps of the source. The phrase noise due to natural causes is used to denote a class of electromagnetic disturbances that are caused by natural phenomena such as lightning and solar storms and by accelerated charges, often relativistic electrons, that occur in space. The characteristics of the receiver and those of its antenna, the operating frequency, and the place where the receiver is operated all determine whether noise from a particular source will be important. Noise usually has a wide spectrum, and for that reason electric field strengths inferred from receiver responses depend also on the bandwidth of the receiver. The bandwidth lay in the region 100 to 300 kHz.
