Electron energy balance in the F region above Jicamarca

Abstract

Incoherent scatter measurements from Jicamarca, Peru, show that current models and cross sections account quite well for the heating and cooling of F region electrons, in marked contrast to earlier similar studies at low and middle latitudes. The latter showed discrepancies of the order of a factor of 2 between the calculated energy input and loss rates. The equatorial F region ionosphere provides the simplest configuration for such studies because the horizontal magnetic field eliminates vertical photoelectron transport and thermal conduction. We based our estimates of electron heating on photoelectron energy spectra computed from recently developed solar flux models and new absorption and ionization cross sections and included the additional energy source clue to quenching of the 2D metastable state of nitrogen. This extra source is sometimes significant. Electron and ion temperatures and densities measured with the Jicamarca incoherent scatter radar were used to complete the calculations of the heating and cooling rates. We present here data from 2 days, one with low solar activity and one with moderate activity, over the altitude range 220–325 km. The heating/cooling rates ranged from about 500 to 6000 eV cm−3 s−1. Over this entire range the calculated heating and cooling rates differed by 10% or less when the data quality was good.