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Abstract Combined in situ ion measurements and remote sensing of energetic neutral atoms are used to determine the geocoronal Hydrogen density at large (∼10 RE) distances from the Earth. This method for determining the geocoronal density requires global magnetospheric modeling. Observations in the Earth's subsolar magnetosheath from the Magnetospheric Multiscale mission are used to determine the accuracy of using global models to predict the geocoronal density. On average, gas dynamic and magnetohydrodynamic (MHD) models and observations are in reasonable agreement, with differences

At present, the lower ionosphere is the least studied region of the ionosphere. The altitude range and the low concentration of charged particles limit the possibilities of its investigation using radiosondes, balloons, rockets, and satellites. For studies of the lower ionosphere, tweek-atmospherics (tweeks) – ELF–VLF radio waves excited by lightning discharges in the Earth-ionosphere waveguide are used in this work. The authors proposed a method of automatic identification and analysis of tweeks. On the basis of analysis of tweeks recorded in August 2014, the relationship between the regular variations in the height of the ionosphere with the change in the solar zenith angle, which determines the main source of ionization - the radiation of the geocorona at night, was investigated. It is shown that with an increase in the height of the lower boundary of the ionosphere, the rate of tweeks increases, which is associated with a decrease in losses in the ionosphere. The effect of the rise of the lower boundary of the ionosphere during a geomagnetic storm of moderate intensity was detected. Thus, the diagnostic capabilities of the proposed method are demonstrated, which makes it possible to locate thunderstorm foci and to reveal variations in the height of the Earth-ionosphere waveguide along the propagation paths of VLF radio waves excited by lightning discharges from different foci.

Over the past two decades, instruments designed to image plasmas in energetic neutral atom (ENA) emission have flown in space. In contrast to typical satellite-based in situ instruments, ENA imagers provide a global view of the magnetosphere because they remotely measure ion distributions via neutrals that are not tied to the magnetic field. An intrinsic challenge that arises during analysis of magnetospheric ENA images is that the ENA fluxes are integrated along the line-of-sight of the instrument. We propose a method of enhancing ENA emission from a localized region in space, thereby enabling spatially resolved measurements of ENA emission in a remotely obtained ENA image. Here we show that releases of modest volumes (~1.4 m3) of liquid hydrogen in space are sufficient to accomplish the ENA localization.