Parametrization of Spatial-Energy Distributions of H+ and O+ Ions of the Ring Current on the Main Phase of Magnetic Storms

Abstract

Based on the results of measurements near the equatorial plane a fluxes and energy spectra of H⁺ and O⁺ ions of the magnetosphere’s ring current by the OGO-3, Explorer 45, AMPTE/CCE, and Van Allen Probes (A and B) satellites, a systematic analysis of spatial distributions of the energy density for these ions on the main phase of magnetic storms was carried out. Twelve storms of different strength were considered, with max|Dst| from 64 to 307 nT. The radial profile of the ring current ions energy density is characterized by the maximum (L_m) and by the ratio of the energy densities of the ions and the magnetic field at this maximum (β_m), and at L > L_m this profile is approximated by the function w(L) = w₀ exp(–L/L₀). Quantitative dependences of the parameter L_m on the Dst index and MLT, and also the dependences of the parameters β_m, w₀ and L₀ on the Dst, MLT and L_m, are obtained. These dependences are different for H⁺ and O⁺ ions, as well as for ions of low (E < 60 keV) and higher energies. It has been established that in a narrow inner region of the ring current near its maximum in the nighttime hemisphere of the magnetosphere, the RC asymmetry is much smaller (especially for O⁺ ions) than at L > L_m. It was found that with increasing L, the asymmetry of the ring current by MLT increases significantly, with H⁺ ions concentrated at near 18 MLT, and O⁺ ions at near 24 MLT. It is shown that for O⁺ ions with E ∼ 1–300 keV, β_m ∝ \(L_{m}^{{ - 9}}\); this result shows that a deeper penetration of hot plasma into a geomagnetic trap, during strong storms, requires not only a stronger electric field of convection, but also a significant preliminary accumulation and acceleration of ions (especially O⁺ ions) in the sources of the ring current.