These types will be discussed in detail later in this chapter. Corpuscular radiation travels at lower velocity than light and arrives at the earth at a later time period.
Particles cause long-lasting ionospheric storm which disrupts long distance radio communication.
The usefulness of a radio signal is limited by the total noise in the receiver which may be either unwanted, external noise or the internal noise of the receiver. Atmospheric static is usually the limiting factor in receiver sensitivity at frequencies below 30 MHz, while receiver noise is the primary limitation at higher fre- quencies, especially those above 200 to 500 MHz. Static levels are generally stronger at night than in the daytime and the levels are higher in the warm tropical areas than in the cooler northern regions, which are far removed from most lightning storms. The average static level in the tropics may be as much as 15 decibels higher than for the temperate zones, while in the Arctic regions the static level may be 15 to 25 decibels lower. In all areas, typical summer averages are a few decibels higher than the winter values.