Faraday rotation from API echos

The enhanced echos produced by the API effect can also be used to measure Faraday rotation, i.e., the propagation time difference between the two characteristic modes of radio wave propagation, which is dependent on several plasma parameters, but most importantly electron density. The artificial periodic irregularities are useful here, as they allow us to get strong enhanced backscatter from this region, which would otherwise give such a strong return.

Here is our first Faraday-rotation measurement from API echos. This is still a fairly raw data product, which must be further inverted into an electron density profile.

Faraday rotation measured using enhanced ionospheric backscatter from heating induced artificial periodic irregularities. This allows us to measure small electron densities, which are otherwise difficult to measure. The delay between O and X modes of propagation is given in radians, as a fraction of a radar probing wave cycle.

More post to come, as we have one more week of measurements to go.