Consider an instrument that transmits radio waves at different frequencies vertically into the ionosphere and measures the time it takes them to return. Using this technique, one can indirectly measure the electron density as a function of height. Assume a ground-based transmitter emits a vertical signal over a range of 1 to 15 MHz. If the peak electron density is 2×106 electrons/cm3, what range of frequencies will be reflected back to the instrument on the ground? Neglect any absorption effects. Frequencies from MHz to MHz will be reflected back.

Consider an instrument that transmits radio waves at different frequencies vertically into the ionosphere and measures the time it takes them to return. Using this technique, one can indirectly measure the electron density as a function of height. Assume a ground-based transmitter emits a vertical signal over a range of 1 to 15 MHz. If the peak electron density is 2×106 electrons/cm3, what range of frequencies will be reflected back to the instrument on the ground? Neglect any absorption effects. Frequencies from MHz to MHz will be reflected back.