Very minor ions in the magnetosphere: a hub of the mesospheric, ionospheric, magnetospheric, solar wind, lunar, and meteoroid sciences.

Abstract

This is the summary of findings by ISSI topical team on the molecular and metallic ions in the magnetosphere. Heavy molecular and metallic ions with mass ≥ 27 (Al+, N2+, NO+, O2++, Fe+, Cu+, Ti+, etc) in the magnetosphere provide independent information on the ion sources and entry route to the magnetosphere from traditional four components (H+, He++, He+, O+). There are four ultimate sources of these heavy molecular and metallic ions: the solar wind (high charge-state metallic ions), the ionosphere (mainly molecular ions), the atmospheric metal layers (low charge-state metallic ions and metal-rich molecular ions that ultimately originating from ablation of meteoroids and possibly space debris), and the surface and exosphere go the Moon (low charge-state metallic and molecular ions).  The lunar origin low charge-state metallic ions, if separated from the ionospheric origin, give independent information on the entry route into the magnetosphere for ions of much larger gyroradius than the solar wind ions. The atmospheric-origin molecular ions are essential in understanding energization, ionization altitudes, and upward transport in the ionosphere during various ionospheric and magnetospheric conditions. These ions are also important when considering the evolution of the Earth's atmosphere on the geological timescale.  So far, we cannot dismiss any of four possible sources with the existing data because only a few terrestrial missions have been equipped with instrumentation dedicated to separate these molecular and metallic ions, within only a limited energy range (cold ions of < 50 eV and energetic ions of ~100 keV or more) and a limited mass range (mainly ≤ 40 amu). This is far too limited to make any quantitative discussion on the very heavy ions in the magnetosphere.  Under this circumstance, it is worth to re-examine, using available tools, the existing data from the past and on-going missions, including those not designed for the required mass separation, to search for these ions.   We synthesised these patchy observations and combining all sources with updated models. With such knowledge, we re-examined available data and model that actually provided important indications of the sources of these heavy ions and their amounts that have been overlooked to date.  Finally, we note the possible future contamination of specific masses by ablated space debris (Al, but also Li, Fe, Ni, Cu, Ti, and Ge) in the coming decades.