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ASPERA-3: Energetic Neutral Atom Imaging
/ en / projekte / venus-express / aspera4 /


Energetic Neutral Atom (ENA) Imaging

Basic Concept

The co-existence of an energetic charged particle population (solar wind, magnetospheric plasma) and a planetary neutral gas leads to interaction, e.g., through charge-exchange:

A+(energetic) + P(cold) => A(energetic) + P+(cold)

In contrast to charged particles, ENAs are no longer influenced by electromagnetic fields and propagate on straight paths from the source to the observer. Directional detection of ENAs yields a global image of the interaction and by complex inversion techniques properties of the source populations can be deduced.

ENA production mechanisms in space plasmas comprise:

  • Charge - exchange reaction with atmospheric / exospheric gases
  • Sputtering of planetary atmospheres
  • Backscattering from the planetary atmospheres (ENA albedo)
  • Sputtering from planetary surfaces
  • Ion neutralization / sputtering on dust particles
  • Recombination (CMI)

ENA Imaging Applications

The > IMAGE mission successfully proved that ENA imaging can provide global views of plasma processes (substorm particle injections, ring current distribution and dynamics) in the Earth's Magnetosphere.

The >MIMI instrument on Cassini provided ENA images of the Jupiter - Io Torus system.

The simulated ASPERA-3 ENA response shows that the solar wind - exosphere interaction processes at Mars can be globally imaged in ENA.

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