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We propose a new method to estimate ion escape from unmagnetized planets that combines observations and models. Assuming that upstream solar wind conditions are known, a computer model of the interaction between the solar wind and the planet is executed for different ionospheric ion production rates. This results in different amounts of mass loading of the solar wind. We then obtain the ion escape rate from the model run that best fits observations of the bow shock location. As an example of the method, we estimate the heavy-ion escape from Mars on 1 March 2015 to be 2×1024 ions s -1 , using a hybrid plasma model and observations by the Mars Atmosphere and Volatile Evolution (MAVEN) and Mars Express (MEX) missions. This method enables studies on how escape depends on different parameters as well as studies on escape rates during extreme solar wind conditions; moreover, the technique is applicable to studies of escape in the early solar system and at exoplanets. [ABSTRACT FROM AUTHOR]

Operation of powerful satellite- and rocket-born sounding radars is often accompanied by a heating/acceleration of the local electrons and ions. On earlier missions, intense fluxes of sounder accelerated particles were detected in Earth's ionosphere when the frequency of the radar transmitter was close to one of the fundamental plasma resonances: harmonic of the electron-cyclotron frequency, plasma or upper-hybrid frequencies. Recently it was found that running a sounder in the ionosphere of the non-magnetized Mars results in the similar effects. Ion and electron sensors of the ASPERA-3 experiment (Analyzer of Space Plasma and Energetic neutral Atoms) onboard the Mars Express spacecraft discovered acceleration of the local ionospheric ions and electrons from thermal threshold energies to 100's of eV during the active sounding phase of the onboard sounder. ESA and NASA missions in development or under study to Jupiter (JUICE- JUpiter ICy moon Explorer in 2022, Europa Clipper in 2023) and to Venus (EnVision in 2032) will also carry powerful sounding radars. In this report we review mechanisms that can cause acceleration of the plasma particles during operations of the proposed sounding radars in the Jovian system and Venusian ionosphere. Using the results of previous studies and characteristics of the proposed sounding radars onboard JUICE, Europa Clipper, and EnVision we define the optimal conditions for observations of sounder accelerated particles, depending on the local conditions, such as plasma density, composition, and intensity of the magnetic field. The EnVision radar operation is expected to results in the most pronounced acceleration of ions and electrons, an effect can be used to improve the local plasma diagnostics. [ABSTRACT FROM AUTHOR]

The deep Solar Cycle (SC) 23 minimum and the modestly active SC 24 maximum have produced generally weaker solar events and heliospheric conditions. Surprisingly, on September 10, 2017 late in the declining phase of SC 24, some of the strongest solar activity erupted from active region (AR) 12673, including an X8.2-class solar flare and a fast coronal mass ejection (CME). Associated with this activity are the solar energetic particles (SEPs), which may be accelerated locally at the flare site or by the moving shock front propagating ahead of the CME. Although AR 12673 was not centrally facing Mars (it was located about 67 degrees east in heliolongitude from the Sun-to-Mars line), the solar events impacted the local space weather environment. To name a few, some of the effects include heating of the upper atmosphere by solar flare emissions, flare-related enhancements of ion and neutral densities, solar energetic particles impacting the atmosphere and surface, bright emissions of a diffuse (global) aurora, deeply penetrating interplanetary magnetic fields over the Martian dayside, and enhanced atmospheric escape rates. In this presentation we will give an overview of the observations at Mars obtained from various Mars missions, including MAVEN, MEX, and MSL. Numerical results from the Wang-Sheeley-Arge (WSA)-Enlil-cone modeling system together with observations at Earth/L1 and STEREO-A will also be presented to provide global heliospheric context of the event period. [ABSTRACT FROM AUTHOR]