Ionogram

Abstract: The purpose of this note is to draw attention to certain ionosperic disturbances observed near certain ionospheric disturbances observed near Boulder, Colorado, around the time of the Alaskan earthquake, which occurred at about 0335 UT, March 28, 1964. These ionospheric observation consisted of the spectral analysis of ionospherically propagated radio signals by the method of Watts and Davies [1960]. Observation were made at Boulder on frequencies of 4 and 5 Mc/s, with vertical propagation, and on 10 Mc/s from WWVH in Hawaii, about 5000 km from Boulder. The frequency versus time records are shown in Figure 1. The WWVH 10-Mc/s signal and reflected from the ionosphere by a normal refractive process, whereas, after about 0130 UT, the Boulder 5-Mc/s signal appears to have been scattered by ionospheric irregularities, as can be seen in the ionogram in Figure 2, in which the penetration frequency of the extraordinary wave is less than 5 Mc/s.

Abstract: Empirical models of three dimensional electron density distributions in the ionosphere have been constructed for global as well as regional use. The models differ by their degree of complexity and calculation time and therefore have different uses. All are based on “ionogram parameter” (critical frequencies foE, foF1, foF2 and the F2 region transfer parameter M(3000)F2). The models allow the use of global or regional maps for foF2 and M(3000)F2 and use built-in formulations for foE and foF1. Update (instantaneous mapping / nowcasting) versions exist which take foF2 and M(3000)F2 or F2 region peak height and electron density as input. The ground to F2 layer peak part of the profile is identical for all three models and is based on an Epstein formulation. The “quick calculationr” model NeQuick uses a simple formulation for the topside F layer, which is essentially a semi-Epstein layer with a thickness parameter which increases linearly with height. The “ionospheric model” COSTprof is the model which was adopted by COST 251 in its regional “monthly median” form. Its topside F layer is based on O + -H + diffusive equilibrium with built-in maps for three parameters, namely the oxygen scale height at the F2 peak, its height gradient and the O + -H + transition height. The “ionosphere-plasmasphere” model NeUoG-plas uses a magnetic field aligned “plasmasphere” above COSTprof Typical uses of the models and comparison among them are discussed.