Features of the planetary distribution of ion precipitation at different levels of magnetic activity

Abstract

Observations from DMSP F6 and F7 spacecraft were used to examine the features of the planetary distribution of ion precipitation. Ion characteristics were defined within the boundaries of different types of auroral electron precipitation, which in accordance with the conclusions from (Starkov et al., 2002) were divided into a structured precipitation of an auroral oval (AOP) and zones of diffuse precipitation DAZ and SDP located equatorward and poleward of AOP, respectively. Analogous to electron precipitation, ion precipitation did not demonstrate dependences of the average energy and the average energy flux of precipitating particles on the Dst index value. In the diffuse precipitation zone (DAZ) equatorward of the auroral oval, ion energies clearly peaked in the sector of 1500–1800 MLT. The average energy value grows as magnetic activity increases from ~12 keV at AL =–1000 nT to ~18 keV at AL =–1000 nT. In the region of structured precipitation (AOP), the minimum of the average ion energy is observed in the dawn sector of 0600–0900 MLT. Ion energy fluxes (Fi) are maximal in the nighttime MLT sectors. In the zone of soft diffuse precipitation (SDP) poleward of AOP, the highest ion energy fluxes are observed in the daytime sector, while the nightside Fi values are insignificant. Ion energy fluxes in the SDP zone show an anticorrelation with the average ion energy in the same MLT sector. An ion precipitation model was created which yields a global distribution of both the average ion energies and the ion energy fluxes depending on the magnetic activity expressed by AL and Dst indices. Comparison of this model with the model of electron precipitation shows that the planetary power of ion precipitation at low magnetic activity (|AL| = 100 nT) is ~12% of the electron precipitation power and exponentially decreases to ~4% at |AL| > 1000 nT. The ion precipitation model was used to calculate the plasma pressure at the ionospheric altitudes. The planetary distribution of integral ionospheric conductance depending on the magnetic activity was calculated by using both electron and ion precipitation models.