Solar Activity:

The number of sunspots is not stable though changes from year to year. The variation is dramatic and periodic. This disparity of sunspot numbers is termed as the sunspot cycle. It has a period of around 11 years. The increase in the number of sunspots is normally faster than the refuse, and the maximum & minimum sunspot count differ from cycle to cycle.

The sunspot cycle affect propagation circumstances at frequencies up to around 70 MHz for F1- and F2-layer propagation and 150 to 200 MHz for E-layer propagation. Whenever there are not much sunspots, the maximum usable frequency (MUF) is comparatively low since the ionization of the upper atmosphere is not intense. At or close to the time of a sunspot peak, the MUF is higher since the upper environment is more ionized.

The solar flare is an aggressive storm on the surface of the Sun. Solar flares cause an rise in the level of radio noise which comes from the Sun and cause the Sun to emit an raised amount of high-speed subatomic particles. Such particles travel via space and enter at the Earth a few hours after the primary appearance of the flare. Since the particles are electrically charged, they are accelerated through Earth's magnetic field. At times geomagnetic storm outcomes. Then we see the "northern lights" or "southern lights" (i.e., aurora borealis or aurora australis, frequently known simply the aurora) at high latitudes during the night and experience a rapid deterioration of ionospheric radio-propagation situations. At several frequencies, communications can be cut off in seconds. Even wire communications circuits are at times affected.

Solar flares can take place at any time, though they seem to occur most frequently close to the peak of the 11-year sunspot cycle. The scientists do not know accurately what causes solar flares, however the events appear to be connected with the associative number of sunspots.