Vortragender: Kostas Dialynas

Planetary Group Seminar: The study of the global Heliosheath using Energetic Neutral Atom measurements obtained by the Cassini/INCA imager (K. Dialynas)

  • Datum: 25.11.2015
  • Uhrzeit: 14:00 - 15:00
  • Vortragende(r): Kostas Dialynas
  • University of Athens Department of Physics Section of Astrophysics, Astronomy and Mechanics GREECE
  • Ort: MPS
  • Raum: Auditorium
  • Gastgeber: Urs Mall
Energetic Neutral Atoms (ENAs) result from Charge Exchange (CE) interactions between energetic, singly charged particles and cold neutral gases that co-exist in a plasma environment. Although the Ion and Neutral Camera (INCA), as part of the Magnetospheric Imaging Instrument (MIMI) suite on board Cassini, is designed to perform ENA measurements originating from the vicinity of Saturn (the Cassini s/c is in orbit around Saturn since 2004), imaging of the Heliosphere (in Hydrogen ENAs) lies well within the instrument capabilities. After 11 years of imaging the heliosphere with INCA, the ENA observations together with the Voyager-LECP in-situ measurements (in overlapping energy bands), have already revolutionized our notions about the formation and interactions of the global heliosphere, providing insights on the plasma processes at ~100 AU that were substantially at variance with previous theories and models. Although the question of how the HS responds to the variability of solar wind conditions and in what manner this response is connected to solar activity through the solar cycle has been addressed partly through modeling, the true manifestation of the HS (moreover in a global scale) to the solar activity have not been directly measured to date. Assessing any proposed interpretation of the HS requires the evaluation of the physical properties of the underlying source proton population in the broad context of the solar wind. Our current analysis on yearly averaged all sky ENA maps over the time period 2003-2014, show that ENA intensities decrease during the declining phase of SC23 by ~x3 from 2003 to 2011 but recover through 2014 (SC24). Similarly, V1,2 ion intensities also decrease and then recover through 2014. The similarity of time profiles of remotely sensed ENA and locally measured ions show that (a) ENA originate in the HS, and (b) the global HS responds promptly (within ~1-1.5 years) to outward-propagating solar wind changes throughout the SC. Further, recovery of the HS during SC24 proceeds asymmetrically from south to north in the general direction of the nose, which may be related to the non-symmetric evolution of solar coronal holes during SC recovery. [mehr]
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