High-energy particles

Detector of Ions and Neutral Atoms (DINA)

The main scientific objective of the instrument is to extend the measurements of the precipitating ions to the higher energy range 20 - 500 keV complementing the MEDUSA experiment.

Apart from the main scientific objective, the DINA instrument is supposed to conduct measurements of energetic neutral atoms. Energetic neutral atoms (ENAs) are produced via the exchange of charge between singly - charged magnetospheric ions and atoms of the upper atmosphere / exosphere. ENAs can be found in almost any space environment and are suitable agents to probe remotely ion population of plasmas at a distance, so-called ENA imaging. In magnetospheric physics, general attention has so far concentrated on the ENAs generated within the high altitude ring current, because they are supposed to be used in global magnetospheric imaging from high altitude spacecraft (> 20000 km ).

However, in the auroral region where the ring current / radiation belt particles plunge into the dense upper atmosphere / exosphere, the charge - exchange process is much more effective and ENAs emissions are much more intense. Theoretically, ENAs from low altitudes are emitted from a very thin area near the exobase and the ENA generation region is, essentially, two dimensional.

The ENA camera PIPPI on board the microsatellite Astrid has performed ENA measurements from the 1000 km polar orbit and demonstrated potentials of low altitude ENA imaging. DINA will continue studies of the low altitude ENAs concentrating on measurements close to the generation region. The results from DINA, looking at the ring current from below at low latitudes and close at high latitudes, will undoubtedly help to understand the observations to be performed by IMAGE, the NASA mission to image the ring current from above.

Another interesting topic to be addressed is ENA albedo. The O+ ions precipitating onto the upper atmosphere during major geomagnetic storm transform their energy and momentum into atmospheric heating and escaping fluxes of fast neutral atoms via charge - exchange and elastic scattering. Total neutral flux escaping due to these processes could be significant for the atmosphere evolution for the lifetime of the earth. However, no direct measurements have been performed to prove the correctness of the developed models. The DINA simultaneous measurements of the precipitating and ENA flux would provide the necessary inputs to evaluate the existing models of the mass and energy transport in the ring current - atmosphere interaction.

DINA will also investigate the low altitude equatorial ring current formed by stripped ENAs from the main radiation belt by measuring both the trapped ions and parent ENAs. During geomagnetic storms the ENA flux produced in the low altitude ring current could be sufficient for detection as well although for quit conditions the flux does not exceed 0.3 cm-2s-1sr-1keV-1 for 20 keV. In summary, the DINA scientific objectives are:

  1. Measurements of the ion precipitating flux in the energy range (protons) 20 - 500 keV
  2. Measurements of the ENAs flux from the exobase in the energy range (hydrogen) 20 - 280 keV
  3. Measurements of the outflowing ENA flux (ENA albedo) from the precipitation region in the energy range (hydrogen) 20 - 280 keV
  4. Mass resolving measurement of particles (mainly ions and ENAs with A = 1, 4, >4) in the energy range 100 - 500 keV
  5. Studies of the low altitude ring current

IRF - RYP - SwRI - Luth