Anomalous electron density events in the quiet summer ionosphere at solar minimum over Millstone Hill

Abstract

Abstract. This study compares the observed behavior of the F region ionosphere over Millstone Hill with calculations from the IZMIRAN model for solar minimum for the geomagnetically quiet period 23±25 June 1986, when anomalously low values of hmp 2`200 km) were observed. We found that these low values of hmp 2 (seen as a G condition on ionograms) exist in the ionosphere due to a decrease of production rates of oxygen ions resulting from low values of atomic oxygen density. Results show that determination of a G condition using incoherent scatter radar data is sensitive both to the true concentration of O relative to the molecular ions, and to the ion composition model assumed in the data reduction process. The increase in the O N 2 loss rate due to vibrationally excited N 2 produces a reduction in xmp 2 of typically 5±10% , but as large as 15% , bringing the model and data into better agreement. The eect of vibrationally excited NO ions on electron densities is negligible.

Thermospheric Parameters during Ionospheric G-Conditions

“…Of course, it would be interesting to compare our retrieved thermospheric parameters to MSISE00 model values as this or MSIS86 thermospheric models were earlier used to describe G-conditions in the F 2 -region [7,9,11]. Such a comparison is given in Table 2 for the days in question.…”

“…This issue was discussed earlier when we mentioned the general decrease of the atomic oxygen abundance in the upper atmosphere during G-condition periods. For this reason, it is not a surprise that neither Pavlov & Buonsanto [9] nor Schlesier & Buonsanto [11] succeeded in trying to describe G-condition N e (h) profiles observed with Millstone Hill ISR using MSIS model.…”

“…An attempt to describe Millstone Hill ISR observations using the IZMIRAN model for quiet 23-25 June 1986 period when G-conditions took place during morning (07:32 LT) hours was undertaken by Pavlov & Buonsanto [9]. It was shown that neutral composition taken from the original MSIS-86 model [10] gives N e (h) profile which has nothing in common with the observed one.…”