Relationship between large-scale ionospheric field-aligned currents and electron/ion precipitations: DMSP observations

Abstract:

Auroral field-aligned currents (FACs), which are thought to be highly related to particle precipitations, are an important transport mechanism for energy and momentum between the magnetosphere and ionosphere. In this presentation, we derived FACs from magnetometers onboard the Defense Meteorological Satellite Project (DMSP) satellites. The magnetic latitude versus local time distribution of FACs from DMSP shows comparable dependences with previous findings on the intensity and orientation of interplanetary magnetic field (IMF) By and Bz components, which also confirms the reliability of the DMSP FAC data set. With simultaneous measurements of precipitating particles from DMSP, we further investigate the relation between large-scale FACs and precipitating particle energy flux. Our result shows that precipitation electron and ion fluxes both increase in magnitude and extend to lower latitude for enhanced southward IMF Bz, which is similar to the behavior of FACs. Under weak northward and southward Bz conditions, the location of the R2 current maxima, at both dusk and dawn sides and both hemispheres, are found to be close to the maxima of the particle energy fluxes; while for the same IMF conditions, R1 currents are displaced further to the respective particle flux peaks. Largest displacement (about 3.5⁰) is found between the downward R1 current and ion flux peak at the dawn side. Our results suggest that there exist systematic differences in the peak locations of electron/ion precipitation and large-scale upward/downward FACs, with FAC peaks enclosing the particle energy flux peaks in auroral band at both dusk and dawn sides. Our comparisons also found that particle precipitation at dawn and dusk and in both hemispheres maximizes near the mean R2 current peaks. The particle precipitation maxima closer to the R1 current peaks are lower in magnitude, which is opposite to the known feature that R1 currents are on average stronger than R2 currents.