Comparison of the measured and modelled electron densities and temperatures in the ionosphere and plasmasphere during 20-30 January, 1993

We present a comparison of the electron density and temperature behaviour i n the ionosphere and plasmasphere measured by the Millstone Hill incoherent -scatter radar and the instruments on board of the EXOS-D satellite with nu merical model calculations from a time-dependent mathematical model of the Earth's ionosphere and plasmasphere during the geomagnetically quiet and st orm period on 20-30 January, 1993. We have evaluated the value of the addit ional heating rate that should be added to the normal photoelectron heating in the electron energy equation in the daytime plasmasphere region above 5 000 km along the magnetic field line to explain the high electron temperatu re measured by the instruments on board of the EXOS-D satellite within the Millstone Hill magnetic field flux tube in the Northern Hemisphere. The add itional heating brings the measured and modelled electron temperatures into agreement in the plasmasphere and into very large disagreement in the iono sphere if the classical electron heat flux along magnetic field line is use d in the model. A new approach, based on a new effective electron thermal c onductivity coefficient along the magnetic field line, is presented to mode l the electron temperature in the ionosphere and plasmasphere. This new app roach leads to a heat flux which is less than that given by the classical S pitzer-Harm theory. The evaluated additional heating of electrons in the pl asmasphere and the decrease of the thermal conductivity in the topside iono sphere and the greater part of the plasmasphere found for the first time he re allow the model to accurately reproduce the electron temperatures observ ed by the instruments on board the EXOS-D satellite in the plasmasphere and the Millstone Hill incoherent-scatter radar in the ionosphere. The effects of the daytime additional plasmaspheric heating of electrons on the electr on temperature and density are small at the F-region altitudes if the modif ied electron heat flux is used. The deviations from the Boltzmann distribut ion for the first five vibrational levels of N-2(nu) and O-2(nu) were calcu lated. The present study suggests that these deviations are not significant at the first vibrational levels of N-2 and O-2 and the second level of O-2 , and the calculated distributions of N-2(nu) and O-2(nu) are highly non-Bo ltzmann at vibrational levels nu > 2. The resulting effect of N-2(nu > 0) a nd O-2(nu > 0) on NmF2 is the decrease of the calculated daytime NmF2 up to a factor of 1.5. The modelled electron temperature is very sensitive to th e electron density, and this decrease in electron density results in the in crease of the calculated daytime electron temperature up to about 580 K at the F2 peak altitude giving closer agreement between the measured and model led electron temperatures. Both the daytime and night-time densities are no t reproduced by the model without N-2(nu > 0) and O-2(nu > 0), and inclusio n of vibrationally excited N-2 and O-2 brings the model and data into bette r agreement.