*Title: Velocity fields at the base of polar coronal holes

*Short title: Velocity fields in polar coronal holes

*Authors:

PI: Luca Teriaca      (1) 
    Giannina Poletto  (2)
    Giulia Schettino  (3)
    Shinsuke Imada    (4)
    Alphonse Sterling (5)
    Werner Curdt      (1)    
    
(1) MPS Lindau, Germany
(2) INAF-Arcetri, Italy
(3) University of Florence, Italy
(4) NAOJ, Japan
(5) NASA/MSFC, USA

Contact: teriaca(at)mps.mpg.de

*Participating instruments and observatories:

SOHO/SUMER    (poc Luca Teriaca [teriaca(at)mps.mpg.de])
Hinode/XRT    (poc Alphonse Sterling [alphonse.sterling(at)nasa.gov])
Hinode/EIS    (poc Shinsuke Imada [shinsuke.imada(at)nao.ac.jp])
Hinode/SOT
STEREO/SECCHI
TRACE

*Scientific Justification

Recent analysis of SUMER deep raster scans of the corona
immediately above the limb in polar coronal hole regions
reveals the presence of ubiquitous velocity structures
associated with the brighter coronal regions (plumes) as 
well as with macrospicules (work presented at an ISSI 
workgroup in October 2008). The velocities are of the order 
of few km/s (near the limit of the SUMER velocity resolution) 
but, given the large angle with respect to the line of sight 
(>80 degrees), they are the signature of outward directed 
flows of tens of kilometers per second. As such, they may be 
an important signature of the wind acceleration and could 
help identifying the wind source regions.

However, such raster scans require several hours to cover a 
reasonably large region with adequate signal to noise ratio. 
This way all information about the temporal nature of these 
flows are lost. Are these flows persistent or transient? If 
they are transient, what is the lifetime and their occurrence
rate? Are they associated with the XRT jets that are frequently 
observed in coronal holes? If yes, to what extent?

To answer the above questions, we request observations from SUMER
on SOHO in combination with the XRT and EIS instruments aboard
Hinode. Support from TRACE and STEREO/SECCHI routine observations
would be very valuable.

*Date and Time Information:

Observations to be run during the April 2009 Hinode/SUMER
campaign. A run lasts about five hours. To be run twice.

*Targeting  Requirements:

Target will be the limb of a polar coronal hole.  We will use the SUMER
slit mechanism to have the 4" wide slit off limb and the 1" slit crossing
the slit without changing the pointing. This technique requires the target
coronal hole to be in the Northern polar region.

*Detailed Observing Sequences per Instrument

SUMER: scan few times a 200"x300" region across the limb. 
A special sequence has been designed to observe the limb 
part with the 1" wide slit and the off-limb part with 
4" wide slit. The use of the 4" slit will provide four times 
faster rastering for a given exposure time allowing multiple
rastering of the target region. Total duration about 5 hours.

XRT: Images alternatively in Al/mesh and Al/poly at 30 s cadence.
Every 10 minutes introduce an image in Ti/poly. To cover 5 hours.

EIS: Raster scan of a 240"x400" centered over the north limb
with the 1" wide slit, 30 s exposure and 2" steps (120 spectra),
to cover the required region in 1 h. To be repeated five times.
Lines: He II 256, Fe X 184.5, Fe XI 188.23, Fe XII 195.12, 
Fe XIII 202.4, Fe XV 284, Si VII 275.35.

SOT: Images in Ca II 396.8 nm at 30 s cadence. If telemetry is 
insufficient pass to 60s cadence (or even 90s).

TRACE: images at 17.1 nm every 20 s or 30s. FOV of 350"x350" 
(full resolution).

STEREO/SECCHI: standard observations would be very valuable.