Titolo della tesi: Planetary environments: exosphere modelling and a new particle detection study
The thesis presents a study of the Mercury and Earth exospheres. For
Mercury, we study and model the source and loss processes of the exosphere
and compare the simulation results with observational data. For the
Earth, we focus on the investigation of interactions between the plasma and
Earth’s exosphere using the Energetic Neutral Atom (ENA) imaging technique,
studying and testing a new ENA detector generation.
We use the 3D Monte Carlo model of the Hermean exosphere from Mura et al.
(2007) to investigate Mercury’s exosphere. In detail, we upgrade the model to
better describe the Micro-Meteoroids Impact Vaporization (MMIV) process
as source of Mercury’s Ca. The in-situ observations of Mercury’s Ca exosphere,
performed during the MESSENGER/NASA mission, exhibited very
high energies, with a scale height consistent with a temperature > 50,000 K,
originated mainly on the dawn-side of the planet. It was suggested that the
originating process is due to MMIV, but previous estimations were not able
to justify the observed intensity and energy. The most likely origin of this
exospheric element may be a combination of different processes involving the
release of atomic and molecular surface particles. We simulate the 3-D spatial
distribution of the Ca-bearing molecule and atomic Ca exospheres generated
through the MMIV process including the meteor stream contribution from
comet 2P/Encke. We show that the morphology and intensity of the Ca
exosphere are consistent with the available MESSENGER observations if we
consider a cloud quenching temperature < 3750 K. The comet contribution
seems to be underestimated and requires further investigations. Our results
can be useful in the exospheric studies and in the interpretation of active
surface release processes, as well as in the exosphere observations planning
for the ESA-JAXA BepiColombo mission that will start its nominal mission
phase in 2026. With the aim to have a complete picture of the solar wind-magnetosphere-exosphere
interactions in the Earth’s environment, we investigate the expected
ENA signals for a possible instrument on board a LEO spacecraft.
We focus on the gas detector, used for the őrst time for ENA applications,
and realize a model to simulate the sensor baseline and its performance.
A prototype of this new generation ENA detector for space instruments has
been tested in Ion-ENA beam facility at the IAPS (Institute for Space Astrophysics and Planetology) in Rome, demonstrating the capability of our setup
to detect ions and ENA particles in a low energy range at low pressure. The
successful demonstration of the feasibility of this innovative instrument for
ENA/Ion detection makes it extremely attractive for a future space mission.