Re: An ion beam that will reach the ionisphere.

Are you sure you really NEED to do such a thing? It is a terrible sort of 
need for a young person to have! Tinkering with the Earth's natural systems 
in this sort of way could have bad unforeseen side effects, and at the very 
least would be a dreadful piece of vandalism.

As it turns out, I do not think the sort of thing you are proposing is 
possible anyway. 

Ions are simply atoms or small molecules that are missing an electron. 
Because a negatively charged electron is missing, they have a positive 
electrical charge. (There are negatively charged ions as well, but the 
positively charged ones are the important ones in the ionosphere). Ion 
beams are really useful things, which can be used for a whole lot of 
scientific and engineering purposes. But they will only work in a really 
good vacuum. If you were to try to send an ion beam through the atmosphere, 
all of the ions, which are about the same size as the nitrogen and oxygen 
molecules in the atmosphere, would simply bump into these molecules, bounce 
off them, and finish up moving in all directions and getting thoroughly 
mixed into the air. Trying to get ions from the ground to the ionosphere in 
an ion beam would be a bit like trying to squirt someone swimming near the 
opposite bank of a large lake by holding the nozzle of a hose underwater at 
the near bank.

The other question you ask is about bouncing high frequency waves in the 
ionosphere. The state of the ionosphere is very different at daytime and 
night time. It can also vary enormously with storms on the sun, and that 
sort of thing. And there is not a particularly sharp cut-off; around the 
30 MHz region, the reflection simply gets poorer and poorer as the 
frequency increases. The highest frequency that can be routinely used for 
long-range radio communication (which involves bouncing signals off the 
ionosphere) would correspond with the 13 metre short wave band, which is 
around 23 MHz. VHF television broadcasts (roughly 60-200 MHz) and FM radio 
broadcasts (roughly 90-120 MHz) do not reflect well off the ionosphere.