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Propagation / Re: So you think you are are beginning to understand propagation?
« on: December 28, 2021, 1635 UTC »Hey All,Yup - the whistlers are essentially guided along one of the Earth's magnetic field lines, and can bounce back and forth between the hemispheres. It is possible to estimate the integrated electron density along the propagation path by looking at the shape of the whistler in a frequency-time spectrogram of ground-based measurements of these waves. Some researchers at Stanford mapped out the plasmasphere using these kinds of measurements before their work was corroborated by later spaceborne measurements (I want to say back in the 1950s or 1960s, and cannot recall the researchers name!).
FASCINATING INFO !!!
I read along time ago( a bit fuzzy now) about ULF /whistler/ sferics being "conducted" down "tubes" in the magnetosphere and actually getting a measure of natural AMPLIFICATION from incoming solar radiation ,so far , the only known example of NATURAL radio amplification (??).
I also just read /printed a Hardcore Dx Medium Wave Propagation article by KN4LF, good stuff there.
de N1NQC
There are actually a bunch of different instabilities in plasmas that cause waves to grow. Most of the naturally produced plasma waves in the ionosphere and magnetosphere start out as thermal noise that is amplified by these instabilities (whistlers generated by lightning are a notable exception). Some of these plasma waves are electromagnetic, while some are so-called 'electrostatic' waves that have a negligible magnetic component. A couple of decades ago I was in graduate school studying these kinds of waves using instrumentation on spacecraft. I've been fascinated by the ionosphere and magnetosphere for a long time, so it is kind of weird that I am just now getting interested in shortwave!
jason
