HOP 0047

abstract of observational proposal

Scientific Justification :

AR moss is believed to correspond tothe ~ 1 MK footpoints of hot (>3 MK)
SXR loops and represents a sensitive monitor of coronal heating and conditions. Coronal loop models can run under certain circumstances into trouble when trying to reproduce the moss in that the predicted intensities are much larger than what is observed. Absorption of moss emission by cool and dense spicule plasma is a proposed mechanism for bringing observations and modeling into a better agreement.

Objective :

If absorption is indeed important then it would only affect lines formed below the head of the hydrogen Lyman continuum at 912A which can be absorbed by neutral hydrogen (and probably also below 504 A and 228 A due to absorption by neutral and singly ionized helium respectively) and not lines formed above 912 A. We plan to investigate this possibility by co-temporal and co-spatial EIS
and SUMER moss observations in Fe XII lines at ~ 195 A (EIS) and 1242 A (SUMER).

Moreover, given we will observe lines from the same ion with both EIS and SUMER with the latter also supplying observations in several chromospheric lines which would allow to determine absolute velocities for both instruments.

request to SOT

BFI: G-band, Ca H-line
105x105" FOV, 2x2 summed
NFI: 1. H-alpha -300mA blue wing filtergrams
2. Fe I 6301.5 magnetograms
160x160" FOV, 2x2 summed
SP: Fast Map, 50" scan over the AR, repeat every 30 minutes

Programs 1 & 2 in the NFI can't be run at the same time so we'd run
H-alpha for 2 hours and then switch to the Fe I magnetograms for
another 2 hours. A cadence of 10 - 30 s for the BFI and NFI
filtegrams would be adequate.

request to EIS

Run the following studies :

GAD001_AR_rast: 256x256 arcsec**2 - exposure time 15 s - total
duration ~ 1 hour
JAK_256_AR_STUDY: 256x256 arcsec**2 - exposure time 30 s - total
duration ~ 2 hours
GAD004_AR_slot15_SAS: 40 arcsec slot - total duration ~ 10 min - run 3
times

Using the short exposure raster will prevent potential saturation
in Fe XII in bright moss regions while the long exposure raster
will mostly highlight dimmer loop emissions.
Finally, taking a series of 40" slot images, which should be
spectrally pure in Fe XII, would allow to study the temporal evolution
of the moss observed by EIS & SUMER.

other participating instruments

SUMER:

SUMER observations in the 1240-1260 A range
are requested. Spectral windows centered at the
following lines would be downloaded :

Fe XII (1242.03)
N V (1242.77)
Mg X (2 x 625)
O V (2 x 629)

Moreover. 1-2 windows containing
C I lines (1244.53,1245.94)
close to Fe XII, to supply
wavelength reference for this line,
will be also downloaded.

The 0.3x120 arcsec**2 slit will be used
to cover both moss and coronal parts
of the target AR. The main goal is to
get usable spectra in the not particularly strong Fe XII
line. Therefore, at each slit location 3 30 s exposures
will be taken, to avoid possible saturation in the strong N V
line. We envisage taking ~ 150 steps of the slit, covering
a FOV of 150x120 arcsec**2 in ~ 3.5 hours, which would
cover a typical AR. If the target AR is smaller,
smaller rasters could be build.
After the raster has been built, an additional 30 minutes
of sit-and-stare observations over moss areas
will be taken using the settings of the raster observations.

STEREO/EUVI:

Full FOV high cadence (~ 1 minute) and low compression 304 & 171
images.

remarks

We have been alloctated SUMER time for Nov 08 starting at 05:00 UT and Nov 14 starting at 14:00 UT
(http://www.mps.mpg.de/homes/theissen/scr/planning/mktoptable.cgi?print=no).

TARGET

An AR close to disk center. The AR should show some evidence of hot SXR lines in its core as judged by XRT images. The FOV of the raster images should attempt to contain both polarities of the target AR, while the sit andb stare observations would contain moss regions. Total duration of the proposed study is ~ 4 hours. If a disk AR is not present during the allocated time observe a quiet Sun region near disk center.