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HINODE Operation Plan (HOP)

accepted on

18-jul-07


 HOP No.

 HOP title

HOP 0033

Off-limb line width measurements

plan term

@ @

proposer

 name : Doyle, O'Shea, Srivastava, Scullion @  e-mail : jgd[at]star.arm.ac.uk

contact person in HINODE team

 name : Culhane @  e-mail : jlc[at]mssl.ucl.ac.uk

 abstract of observational proposal
Using EIS, we wish to measure the variation of line widths at coronal temperatures. Recent CDS/SoHO studies indicate that line widths decrease at high altitudes off-limb in coronal lines, suggesting the damping of upwardly propagating waves and the heating of the corona. EIS will allow us, not only to measure the decrease in line widths, but to accurately measure the related nonthermal velocities, thus allowing us the ability to estimate energy flux densities of the propagating and dissipating waves. The reported decrease in line width above 1150 arcsec coincides with the location where the observed line ratio of Mg X 624/609 indicates a change from a collisionally to a radiatively dominant excitation regime. This has implications for far off-limb electron density measurements, as all density diagnostics calculations uses theoretical line ratios which only take collisional excitation into consideration. The present results suggest that line ratio calculations of electron densities, using solely collision excitation calculations, may be incorrect in regions far off-limb where radiative excitation becomes stronger than collisional excitation (~1150 arcsec). Further investigation into this is required. Data at both poles off-limb and at the equatorial off-limb is required.

 request to SOT
For this study accompanying observations will be needed with SOT observing in
Ca II with a 1 min cadence.


 request to XRT
For this study accompanying observations will be needed XRT with ~ a 1 min cadence.

 request to EIS
arm_width_limb

Target: Off-limb region at the solar poles. Slit to be positioned so that all of the slit is off-limb with the Southern-most portion just touching the limb.
Exposure time: 150s
Slit: 2" slit (use full slit length of 512 pixels, to allow binning along slit of 2-3 later to improve S/N for weaker lines)
Window width: 72 pixels
Rotation compensation: off
No. of exposure sets: 100
Total duration of study: 4h28m
Compression: lossless
Data rate: 12 kBits/s

Ion Species     Wavelength (A)              
Ca XVII         192.82          
Fe XII         195.12        
He II           256.32          
Mg VI           270.40          
Si VII         275.35          
Fe X           184.54          
Fe XII         186.88          
Fe XIII         203.80            
Fe XIII         202.04          
Fe XV           284.16          

 other participating instruments

 remarks
Pointing: 1. Northern region, with end of the slit just touching the solar limb: duration 4h28m  2. Sorthern region, with end of the slit just touching the solar limb: duration 4h28m 3. Western region, with the end of the raster at 100 arcsec, repeat moving the center of the raster to 300 arcsec off-limb, thereby having a raster of 400x512: duration 8h 56m 4. Eestern region, with the end of the raster at 100 arcsec, repeat moving the center of the raster to 300 arcsec off-limb, thereby having a raster of 400x512: duration 8h 56m

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