Modeling the IRI topside profile using scale heights from ground-based ionosonde measurements

Abstract

Ionograms present a new data resource for an effort to improve the IRI topside profiles. Ground-based ionograms measure the Chapman scale height at the P2 layer peak that is used to construct the topside profile. After a brief review of the topside model extrapolation technique, comparisons are presented between the modeled profiles and height-integrated profiles with incoherent scatter radar and satellite measurements for the mid latitude and equatorial ionosphere. The total electron content TEC, derived from measurements on satellite beacon signals, is compared with the height-integrated profiles ITEC from the ionograms. Good agreement is found with the ISR profiles and with results using the low altitude TOPEX satellite. The TEC values derived from GPS signal analysis are systematically larger than ITEC, the difference being attributed to the plasmasphere. It is suggested to use the scale height HT, routinely measured by a large number of digisondes around the globe, for the construction of a topside electron density profile that could become an option in the IRI model. To quickly establish a large database for HT, it would be useful to take advantage of the autoscaled HT values. A comparison of monthly medians using automatically and manually determined HT values is made. Direct calculation of HT from the bottomside IRI profile defined by B0, B1, D1, NmF2, and hmF2 using the same extrapolation technique suggests an alternate path to an estimate of the topside profile.