Hermean sputtering:SERENA/ELENASimulatedobservation

Conf. Planetologia, S.Felice irco06/09/2006Solar windionsSurfaceIon SputteringeV ENAKeV ENAENA features in the solar systemExospheric gasCharge-ExchangeAtomosphericSputteringeV ENANeutral Solar wind

Conf. Planetologia, S.Felice irco06/09/2006

Magnetized bodies (Earth, Mercury, Jupiter, Saturn)Magnetospheric Plasma Circulation Charge exchange! Non-magnetized bodies with atmosphere (Mars, Venus)Solar wind-induced neutral gas escapeCharge exchange & sputtering! Bodies without atmosphere (Mercury, Moon, Asteroids)Solar wind-induced surface erosionSputtering! Solar wind acceleration region & heliospheric border Neutral SW, SW - interstellar gas interaction Charge exchange!PROCESSES INVESTIGATED VIA ENARemote sensing of:Astrid (SAC-B)Cassini IMAGE Doble StarMars ExpressVenus ExpressTWINSChandrayaan !IBEX !BepiColombo !Solar Orbiter !?Kua-Fu ?Laplace (Europa Orbiter) ?MarcoPolo ?Tandem ?

ENVIRONMENTS INVESTIGATED VIA HIGH ENERGY ENA

SOLAR ORBITERSun and corona traced by NSWDcoronal holeSolar Orbiter / SCENARIO Neutral Solar Wind Detector (NSWD)(S. Orsini, M. Hilchenbach, J.K. Hsieh, A.M. Di Lellis, M. Collier, A. Czechovski, I. Dandouras, R. DAmicis, M. Gruntmann, G. Ho, S. Habal, E. Kallio, S. Livi, A. Mura, P. Wurz, et al.) Beyond 3 solar radii, the neutral atoms become more and more decoupled from the plasma of the solar corona. The neutral solar wind constitues an in-situ trace particle population of the solar wind plasma. The expected neutral atom flux is about 103 atoms cm-2 s-1, at 0.21 AU, but it could increase up to 104-105 atoms cm-2 s-1 during Coronal Mass Ejections (CME).

Angular resolution ~ 1Field-of-view = 7Aberration = 9.2(Vsw = 400 km/s, Vorbiter = 65 km/s)Aberration = 4.6(Vsw = 800 km/s and Vorbiter = 65 km/s)

FUTURE APPLICATIONSImaging of the SW Expansion

Pseudo-color map of ENA differential flux as a function of angle from Suns direction (in degrees) for different models. The azimuth angle is along the ecliptic plane and the elevation angle is across the ecliptic plane. Flux is integrated over all energies (upper panel). Bottom panels are for the Solar Orbiter reference frame during the corotation phase (i.e. with the aberration effect included). FAST WINDSLOW WIND IMAGING THE NEUTRAL SOLAR WINDSignal simulation vs 2 different sw models

Ion Sputtering Ei incident particle energy 800 - 1600 eVEb binding energy 1 eVEe Energy of the released particleTe Exospheric temperature TNa 1600Na -800Ion sputtering products depend on: the composition and the chemical structure of the surface; the impinging plasma flux.The basic quantities of interest are: the composition of the ejected particles the space flux distribution and the space density distribution of the sputtered particles Production of ENA from bombardment of a surface by energetic ions

: asteroid or comet nucleus in an evolving population with a lifetime limited to a few million years and an orbit with perihelion distance

CI chondrite - type NEO surface

I-S Directional NA from EuropaC-E ENA from plasma tori interactionC-E ENA from auroral regionsThe Natural Satellites Emissivity in the Jovian System

EUROPADisrupted ice crust in the Conamara region of Jupiter's moon Europa (NASA courtesy)Surface composed mainly by water ice and other components as Na, K, etc... Na and K atmosphere has been observed (Brown and Hill, Nature, 1996; Brown, Icarus, 2001)

Ion flux @ EuropaH+O+S+Ion-sputtering .The emitted flux is proportional to the yield, much higher for higher energies and for heavier ions. (Baragiola et al., NIM B, 2003)

The Natural Satellites Emissivity in the Saturnian Sysytem

Exobase ~ 1500 km altitudeAtmosphere ~ mainly N2Two different incident particles: protons H+ deriving from the solar wind and from Saturns magnetosphere nitrogen ions N+ of the Saturns magnetosphere.(Garnier et al., 2007)TitanAtmospheric SputteringSame process as surface sputtering, but acting on atmospheric particles. Particles may escape directly or after a series of bouncing.At Titan, the atmospheric sputtering is the most efficient escape mechanism (Lammer and Bauer, 1993)

(Shematovich et al. JGR, 2003)H+ N+ANGLEION ENERGYANGLEION ENERGYOur analysis of atmospheric sputtering on Titan, using previous theory and newly data, allow us to be confident in a very high efficiency of the process

Y ~ 110 for H+

Y >10 for N+Our simulationEnergy and pitch angle spectraYields

PROCESSES IN THE HERMEAN ENVIRONMENTGOING TO MERCURY WITH BEPICOLOMBO

ARE ION SPUTTERING AND PSD RELATED TO EACH OTHER?See presentation from a. mura during this conference

New prospect: ENA direct detectionBepiColombo / SERENA - ELENA is a Time-of-Flight Detector, based on the state-of-the art of ultra-sonic oscillating micro-shutters (>100 kHz) and mechanical gratings. Energy range:

Sputtered O imagesimulation, polar viewSputtered signal detection by the SERENA/ELENA unit(simulation)

Nowadays, more and more interest is growing about the capabilities of investigating crucial aspects of the particle regimes present in the solar system by means of ENA detection. These studies range form the properties of the expanding corona, to the escape of matter from the planetary surfaces; from the plasma distributions in the magnetospheres to the interaction between solar and interstellar matter; from the characteristics of escaping fractions of the planetary atmospheres, to the transfer of energy to the internal atmospheric regions.

Such an increase of interest in ENA signal detection is pushing the technological community to produce more and more sophisticated devices, able to accomplish the scientific goals over a wide spectrum of energies and mass species.

S U M M A R Y

MANY THANKSFOR YOUR ATTENTION!

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