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Description of the objective:

Study of density fluctuations in the extended corona as a function of the outflow velocity of the solar wind while evolving in the heliosphere (Telloni et al., 2009).



  • A complete and detailed study of coronal density fluctuations requires a long temporal baseline (more than one day).
  • EUI/FSI 174 would need deep exposures in order to observe up to METIS FoV with good SNR.
  • METIS should observe with the FLUCTS mode for about 1 hour and then turn to MAGTOP (with a cadence of 5-20 minutes). The current SOOP is defined with cycles of 8 hours, but multiple cycles should be planned in order to observe for at least one day. Another possibility would be to observe 8 hours per window for 3 consecutive windows, but this might not meet the minimum observation duration for the lower frequencies.
  • This objective should better be addressed at perihelion for a better METIS SNR for the FLUCTS mode combined to a lower cadence during the rest of the window. 
  • If SPICE participates, we will need to do limb pointing for a certain period of time and then return to disc center for METIS.
  • PSP in quadrature would be an asset for observing the fluctuations in situ.


The SOOP R_FULL_HRES_HCAD_Density-Fluctuations is specifically designed for (and currently only serves) this objective.