Version: 2009 April 13
|Hinode/EIS/XRT, SOHO/SUMER:||E. Landi (enrico.landi @ nrl.navy.mil)|
|SOHO/UVCS:||M. P. Miralles (mmiralles @ cfa.harvard.edu)|
This is a SOHO/Hinode campaign
scheduled to run on:
April 15 - April 22 UVCS
April 17 , April 21 EIS/SUMER/XRT (HOP 107)
In a recent work, Landi & Cranmer (2009) measured the ion temperatures from the line widths of many ions observed by SUMER in a polar coronal hole. The measurements were done as a function of distance from the limb in the 1.02-1.17 solar radii range. Their study aimed at characterizing the region of acceleration of the fast solar wind by measuring the presence and effectiveness of the ion-cyclotron waves in accelerating the solar wind. They were looking for a relation between ion temperatures and charge-to-mass ratio Z/A as a signature of ion-cyclotron wave action. They found that ion temperatures did depend on the Z/A ratio, but in a different way than predicted by models; at high Z/A values the ion temperature showed an upturn that could be explained by no theoretical model; these results were the same at all heights, meaning that ion cyclotron waves, if present, were active already at 0.02 solar radii from the photosphere. Landi & Cranmer (2009) used a sit'n'stare SUMER full spectrum observation, but many of the lines they used were weak and noisy, so they could only reach up to 1.17 solar radii, and also they could not relate their measurements to either polar plume or inter-plume plasma.
We propose to carry out joint deep exposure SUMER/EIS/UVCS observations of a polar coronal hole in order to measure ion temperatures versus Z/A, improving over Landi & Cranmer 2009 by carrying out measurements
1) for many more ions
2) for a larger height range
3) for a 60"x512" or (if possible) 120"x512" section of a coronal hole
4) linking the results to coronal hole structures on the disk
5) linking the results to UVCS ion temperatures at 1.9 solar radii
Target(s) would be one (or both) polar coronal holes. Plume and interplume lanes preferable near central meridian to maximize height range coverage above the limb and to facilitate feature tracking.
Hinode/EIS will use two different sequences: a long-exposure raster study and an ultra-deep sit'n'stare with full CCD range. Polar coronal holes will be observed with a 1'x8.5' raster with a large number of diagnostic lines. Deep exposures of the entire EIS wavelength range are also planned. The full 512" slit will allow us to study the coronal hole in great detail.
SOHO/SUMER will carry out high signal to noise sit'n'stare observations with 600s or 1200s exposure time, of 15 selected bandpasses that include all relevant coronal ions in the SUMER wavelength range. Type of sequence: Refspec (full SUMER reference spectrum), exposure time 600s or 1200s, slit 1 (4"x300"), detector B. Single pointing position; whether on a plume or on an interplume will be chosen later. If time allows, both in a plume and in an interplume lane.
The SOHO/UVCS sequence will last longer and it will take place at the limb at a height of 1.9 solar radii (or higher). The UVCS slit will cover the P.A. of the polar regions to be observed by EIS & SUMER lower down (plume/interplume region). SOHO/UVCS will observe a set of temperature and outflow diagnostic lines (including O VI and H I Lyman alpha) in the plume/interplume regions in the extended corona.
Hinode/XRT observations in two (or more) filters which ratio is sensitive to low temperature plasma. Cadence is not important, long exposures are preferred to minimize noise.