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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0106

Velocity fields at the base of polar coronal holes

plan term


@ @


 name : Teriaca, Poletto, Schettino, Imada, Sterling, Curdt @  e-mail : teriaca[at]mps.mpg.de

contact person in HINODE team

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

 abstract of observational proposal
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.

 request to SOT
Target: north polar limb. Duration 5 h. Images in Ca II 396.8 nm at 30 s cadence. If telemetry is insufficient pass to 60s cadence (or even 90s).

 request to XRT
(key instrument) Target: North polar limb. Duration 5 h. Images alternatively in Al/mesh (suggested exposure time: 16 s) and Al/poly (suggested exposure time: 23 s), with one image every 30 s. Every 10 minutes introduce an image in Ti/poly (exposure time of 16 or 23 s). To cover 5 hours.  The XRT CO may adjust exposure times and cadences if required (depending, for example, on whether the CCD will be exposed to active regions).

 request to EIS
EIS study: CHvel_240x400_SUMER (validated and on the database)
Target: north polar limb. Duration 5 h. 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. Lossless compression.

 other participating instruments

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

Target will be the limb of a polar coronal hole. Because of technical requirements in implementing the SUMER observing program, the target need to be the North polar coronal hole.

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