Statistical behavior of the topside electron density as determined from DMSP observations: A probabilistic climatology

The Defense Meteorological Satellite Program (DMSP) has flown spacecraft with ionospheric payloads since 1987. Over this period, DMSP has collected over two hundred million electron density measurements. This paper presents a statistical analysis of the DMSP topside electron density measurements from 1995 to 2005 with additional data from 1992. Nearly 140 million quality-checked data points are binned by solar activity, magnetic latitude, season, and solar zenith angle or magnetic local time. When binned, the data usually obey a three-parameter lognormal distribution. These parameters represent the density floor (the minimum possible density), the median density, and the variability in the densities. In general, the density floor, the median density, and the variability increase with solar activity and peak near the magnetic equator. Away from the equator, these parameters are higher during local summer and for lower solar zenith angles. However, the median density and the variability near the magnetic equator are greater in the dusk sector where the prereversal enhancement pushes F region plasma to higher altitudes. In addition, all three parameters show a marked asymmetry between the northern and southern hemispheres. A probabilistic climatology model is created by modeling these parameters and using the lognormal probability distribution function. This new model provides an occurrence frequency for different densities given the F10.7 solar radio flux, magnetic latitude, day of year, and either solar zenith angle or magnetic local time.