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Description of the objective:

In order to better understand the structure of CMEs, we have to explore the following:


  • Self-similar expansion (Cremades and Bothmer, 2004; Gibson and Low, 1998).
  • Cylindrical geometry with the axis of symmetry corresponding to the long axis of a large-scale helical magnetic flux rope that originates in the CME source region (Thernisien et al., 2006).
  •  Interaction with the background velocity and density structures (Odstrcil et al., 2005; Riley et al., 2003; Colaninno et al., 2014).
  •  Aerodynamic drag force and equalization of ICME and solar wind speeds (Gosling and Riley, 1996; Cargill, 2004; Vrsnak et al., 2012; Subramanian et al., 2012).
  •  Relationship between the three-part structure of a CME and the ICME counterparts (magnetic cloud with a flux rope or ‘complex ejecta’ with disordered magnetic fields) (Vourlidas et al., 2013).
  • Bright front evolution to become the sheath of compressed solar wind.
  • Dark cavity corresponds to the flux rope.
  • Presence of an in situ ‘plug’ of cold, dense plasma trailing the flux rope, interpreted as remnant material from the erupting filament (bright core).
  • What is the fate of the erupting filament as the CME propagates?
    • Only a small fraction escapes with the CME?
    • Filament material flows back along magnetic field lines or falls back due to Rayleigh-Taylor instability (Innes et al., 2012; Carlyle et al.,2014; van Driel-Gesztelyi et al., 2014).
    • Filament is present but has lost its expected low-charge state signature because of heating (Skoug et al., 1999; Rakowski et al., 2007)?
  • Relationship between the three-part structure of a CME and shocks in the low corona and in situ.
  • Interaction between CMEs and its effects on SEPs (Gopalswamy et al., 2004; Richardson et al., 2003; Rodriguez-Pacheco et al., 2003).
  • Dynamics in transient coronal holes and recovery phase of the eruption.
  • Improve CME arrival time estimates and predictions of geomagnetic activity.



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Regarding the question about the small fraction of the erupting filament escaping with the CME we must first evaluate the initial total mass (we should remember that a dozen filaments could provide the total mass of the corona) which implies a proper diagnostic of the filaments (including their extensions) before any eruption and/or CME occurrence. EUI He II (FSI 304) and HRI Lalpha (at least) are required + SPICE Lbeta. Of course, the survey of a whole filament requires a large FOV not provided by HRI Lalpha. But the FSI He II could be used to evaluate the overall morphology and the information transferred to Lalpha through the kind of correlation factors developed by Auchère (2005) and follow-ups. The AIA/SDO He II would provide a complementary viewpoint for the morphology, the evaluation of the total mass and also for modelling.


 
  • SPICE
      • Target: Active Regions, Coronal Holes.
      • Observing mode: CME Watch, Composition mapping (with possibility to measure Doppler velocities).
      • Slit size: 4” for CME Watch, 6” for Composition mapping.
      • Exposure time/cadence and number of X positions: 30 s, X=224 for CME Watch, 100 s, X=160 for Composition mapping.
      • Field of View: 15’×11’ for CME Watch, 16’×11’ for Composition mapping.
      • Number of repetitions of the study: 
      • Observation time per day: 1.9 hours per study for CME Watch, 4.4 hours per study for Composition mapping (the total observation time depends on the number of targets).
      • Key SPICE lines to be included: C III 977 Å, O VI 1032 Å, O VI 1037 Å, Ne VIII 770 Å, Mg IX 706 Å, Fe X 1028 Å and Fe XX 721 Å (the last line in case of a flare)– 15 lines (5 profiles+10 intensities) for CME watch;

        Ne VIII 770 Å, Ne VIII 780 Å, Mg IX 706 Å, O II 718 Å, O IV 787 Å, O V 760.4 Å, O V 761 Å, O VI 1032 Å, O VI 1037 Å, Ne VI 999 Å, Ne VI 1010 Å, Mg VIII 772 Å, Mg VIII 782 Å, C III 977 Å, Fe III 1017 Å - 2 profiles and 13 intensities or 4 profiles and 11 intensities (maximum of 15) for Composition mapping.

      • Observing window preference: Close to perihelion is preferred.
      • Other instruments: EUI, PHI, METIS, SWA, EPD, SoloHI.
      • Comments:  The choice of lines, and also the number of intensities and profiles, is flexible, although the sum of the intensities and profiles is constrained to a maximum (e.g 15 for composition mapping). While varying the number of intensities and profiles, within the maximum, has no effect on the duration of the study, it will have an effect on the telemetry.