Correction of the Jicamarca electron-ion temperature ratio problem: Verifying the effect of electron Coulomb collisions on the incoherent scatter spectrum

Ever since the first attempts to fit Jicamarca autocorrelation function (AC F) measurements in the 1970s using a full nonlinear least squares analysis, an apparent electron-ion temperature ratio below unity has been deduced fo r a large portion of the F region data. The cause of this unexpected and ge ophysically unreasonable result has been a mystery until recently, when Sul zer and Gonzalez [1999] (herein SG) explained how electron Coulomb collisio ns can distort, or narrow, the incoherent backscatter spectrum, and that fo r this narrowing to be observable two conditions must be met. First, the ra dar k vector must lie in a small range near perpendicular to the magnetic f ield, and second, the radar wavelength must be sufficiently long. Both of t hese conditions are true at Jicamarca. The accurate calculations from the S G theory are now available in a compact library, which we have incorporated into an incoherent scatter least squares fitting code. Using this code, we have reduced Jicamarca ACF data taken with the Faraday double-pulse mode, and find that the SG theory correctly interprets the ACF data from Jicamarc a, thereby solving the longstanding T-e/T-i ratio problem and thus allowing accurate electron and ion temperature measurements.