Definition of Terms

Accelerated Planetary Ions
Ionized atoms whose energy has been increased.

Bow Shock
The wave that stands in front of a planet in the solar wind – similar to a bow wave in front of a boat.

Energetic Neutral Atoms
ENAs are atoms with energies greater than the planetary escape velocity. ENAs are produced by a charge-exchange process between singly-charged ions and neutral gases of the exosphere/upper atmosphere. Due to their neutrality, ENAs are decoupled from the electromagnetic fields and propagate straight forward like photons. Directional detection of the ENAs therefore yield a global image of the interaction region.

ENA Albedo
Energetic neutral atoms escaping from a planet.

Energy Specta
The number of ions or electrons per unit of energy (eV), area (cm2), solid angle (steradians) per unit time (sec).

eV
Electron Volt.

Exosphere
The outermost layer of a planetary atmosphere.

In-Situ Plasma
A plasma is an ionized gas, i.e. atoms from which an electron has been removed.

Ionosphere
The ionized atmosphere of a planet.

keV
1000 Electron Volts.

Magnetosphere
The magnetic envelope of a magnetized planet.

Phobos
The larger of the 2 Martian Moons.

Shocked Solar Wind
The solar wind with reduced velocity after it has encountered the bow shock of a planet.

Solar Wind
The flowing, ionized gas from the sun.

Spectrograph
A plasma analyzer which instantaneously measures an energy spectra.

Supersonic Solar Wind
A solar wind that has a velocity greater that Mach 1.