An ionosonde sends radio pulses vertically into the F2 layer

PHYSICS · Multi-part · Fermi University Physics · Plasma Physics · Waves in plasmas · Waves in plasmas

Plasma Physics, Ch Cold magnetised plasma waves: the dielectric tensor, cutoffs, resonances and the CMA diagram

Problem

An ionosonde sends radio pulses vertically into the F2 layer. Its peak electron density corresponds to an ordinary-mode critical frequency foF2=10.0 MHzfoF2 = 10.0\,\mathrm{MHz} (the frequency at which P=0P=0 at the density peak), and the local electron gyrofrequency there is fce=1.2 MHzf_{ce}=1.2\,\mathrm{MHz}. ((a)) State which of the two cold-plasma modes, O or X, stops being reflected (is no longer cut off) at the lower sweep frequency, and give the physical reason. ((b)) Using the R-wave cutoff formula fR=12[fce+(fce2+4 foF22)1/2]f_R = \tfrac12\left[f_{ce}+\left(f_{ce}^2+4\,foF2^2\right)^{1/2}\right], calculate the extraordinary-mode critical frequency fxF2fxF2 and the difference fxF2−foF2fxF2-foF2.

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