HOP 0255

abstract of observational proposal

The immediate objective of this proposal is the measurement of magnetic fields in prominences, solar tornados and/or spicules. We propose to exploit the excellent spectro-polarimetric capabilities of THEMIS for measurements of the magnetic field vector in prominences, solar tornadoes and spicules employing the inversions of the He D3 line. These phenomena represent unique examples of the small-scale coupling between magnetic field and plasma in environments with distinct dynamical behaviour. As such they represent key study-cases for deepening of our understanding of the Sun.

Prominences are cool dense regions of plasma lying in a much hotter and rarer coronal environment. They are a key location in the solar corona where we may study the interaction of magnetic fields with plasmas in widely varying circumstances (Labrosse et al 2011, A&A 531, A69; Schmieder et al. 2013, ApJ777, 108).

The immediate objective of this proposal is the dynamics in prominences, solar tornados and/or spicules.

We propose to exploit the excellent spectroscopy capabilities of IRIS for measurements of the velocity vector in prominences, solar tornadoes and spicules.

These phenomena represent unique examples of the formation of cool structures in the hot corona. As such they represent key study-cases for deepening of our understanding of the Sun corona.

Prominences are cool dense regions of plasma lying in a much hotter and rarer coronal environment. They are a key location in the solar corona where we may study the interaction of magnetic fields with plasmas in widely varying circumstances (Labrosse et al 2011, A&A 531, A69; Schmieder, Kucera et al. 2013, ApJ777, 108).
Solar tornadoes are a phenomenon that is so far relatively little understood. They appear as rotating structures in EUV images from SDO/AIA, as well as in some studies by Hinode/EIS (Levens, Labrosse et al 2015, 2016). To fully understand the nature of these events, it is essential to add information to what we can already learn from spectroscopic measurements at different plasma temperatures. We have already worked on some prominences with IRIS (Schmieder, Tian et al 2014). We have shown that the IRIS profiles in Mg II lines is not what was expected from previous modelling (Paletou et al 1993). The profiles of these lines in prominences are not reversed. Heinzel et al 2015 tentatively explain this behaviour with some tests on 2D modelling. They show that Halpha is primordial to correctly interpret Mg II.

We need to have simultaneously Halpha and Mg II spectra.

SOT images could yield transverse motions by linear correlation tracking of the knots. Comparisons between Ca II and Mg II intensities can also help to understand the tornado structures.

If no adequate prominences nor solar tornadoes are present we can use the allocated time to observe ubiquitous spicules protruding from the solar disk.

request to EIS

Study prom_rast_v1 (#310) - runs in 1h13 so at least two runs per day in the morning jointly with THEMIS can be accommodated. This programme should be run in study prom_rast_v1 (#310) – runs in 1h13. Ideally this study should be run twice.

In addition, a number of repeats of the sit-and-stare study #507 HPW023_FULLCCD_V2 to fill the remaining allocated time will be used to fully characterize the plasma in the prominence and its surroundings, compute DEM, etc. These can be inserted between the two rasters described above if practical. The slit position should be at the centre of the raster FOV.

remarks

- Time period of proposed observations, if required.
April 4-8 and 11-15

- Time window
The best timing for joint observations with the MSDP of the Meudon solar tower is ~ 8-11 UT, please use this time window as much as possible.

- Target of interest.
Targets will be off-limb structures, specifically prominences, tornadoes or spicules.

・ List of past HOPs in which the present proposer was the PI, and the publications out of those HOPs.

HOP 4:
Heinzel et al., 2008, The Astrophysical Journal, Volume 686, Issue 2, pp. 1383-1396.
Berger et al., 2008, The Astrophysical Journal, Volume 676, Issue 1, pp. L89-L92.
Berger et al., 2010; The Astrophysical Journal, Volume 716, Issue 2, pp. 1288-1307.
Torok et al., 2009, The Astrophysical Journal, Volume 704, Issue 1, pp. 485-495.
Schmieder et al., 2010, Astronomy and Astrophysics, Volume 514, id.A68, 7
Labrosse et al., 2011, Astronomy & Astrophysics, Volume 531, id.A69, 11

IHOP 255: Schmieder et al 2014, Heinzel et al 2015, Levens et al 2015, Levens et al 2016