SOLAR AFFECTS AND DEFINITIONS -  PART 2

 

Last article described The Sun, Solar Wind, Earth's Magnetic Field, Sunspots, Sunspot Numbers and Smoothed Sunspot Numbers. Is there more? Plenty, more than I can tell you. However, we can look at a few more items.

 

SOLAR FLUX. This is an interesting one. It can get quite involved, but knowing the basics will give you an idea of our propagation performance.

 

This measurement has been in use since the late 1940s. It can also be called Solar Radio Flux. The quiet Sun emits radio energy across a broad frequency spectrum, with a slowly varying intensity. Solar Flux is a measure of energy received per unit time, per unit area, per unit frequency interval. There is a degree of correlation between solar flux values and sunspot numbers.

 

Energy measuring solar flux is in joules. Solar flux is measured daily at 2800 MHz (10.7 CM). This is a standard used for predictions. However the Sun emits more energy at higher frequencies up to 15.4 GHz. However, the daily 10.7 CM value is sent to WWV where it makes its propagation bulletins. This is more accurate a prediction than counting sunspots.

 

IONOSPHERE. This area is from 25 to 200 miles out. You can't live up there without protective gear.

 

The atmosphere is at such a low pressure that the gases break up into electrons and positively charged ions. The amount of charge is affected by the Sun's variety of radiations.

 

This in turn results in fairly distinct layers of ionization, each with different characteristics. These layers are parallel to the earth's surface and are regularly changing.

 

THE D LAYER. This lies between 37 to 57 miles out. This is a relatively low dense part of the atmosphere. The atoms at this altitude break up into ions by the Sun and recombine quickly. Therefore, ionization starts at sunrise, peaks at noon and disappears at sundown. Energy going through this section can be used up as heat. One of the reasons our longest wavelength bands, 160 and 80 meters are quiet during the day.

 

The D layer is ineffective in bending HF waves back to earth. Not good for long distance skip. This is one of the reasons frequencies up to 7 Mhz during daylight hours has a very short skip. Something to keep in mind when needing the short skip for emergency communications.

 

The ionosphere has other layers that will be presented in a future article.

 

73,
Ralph WD0EJA