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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0104

Study of Coronal Hole Dynamics from EIS/Hinode and SUMER/SOHO

plan term


@ @


 name : Srivastava, Dwivedi, Curdt @  e-mail : aks[at]arm.ac.uk

contact person in HINODE team

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

 abstract of observational proposal
This study aims at investigating the dynamics of coronal holes from where the fast solar wind emanates. The acceleration mechanism(s) for the generation of fast solar wind has been one of the outstanding problems in solar physics.Various types of propagating MHD waves are likely candidates for heating the coronal hole plasma, and accelarating the solar wind. Coronal holes are also associated with exotic plume and interplume regions, which may act as a waveguide for the transport of nonthermal energy into the upper corona.

We propose both the 1""-slit raster as well as the sit and stare observations of polar coronal holes. We choose a set of lines which are good to map the density,Doppler velocity, and FWHM in polar coronal holes. The observations of on-disk parts of the polar coronal holes will be useful to probe the local plasma conditions in the solar wind source region.The cool lines of He II, Fe VIII will provide the flow structures in the bottom of on-disk polar coronal holes from where the solar wind accelaration is expected to start. While, the simultaneous observations with Fe (coronal) lines will allow to study its linkage and response in the higher corona. The variation of plasma properties in the plumes and interplumes regions at the same heights will also shed new lights on the exact locations of the concentration of supersonic mataerials, and its possible connection with the MHD modes excited in these waveguide type structures.The Mg VII line pair will be weak in the polar region. However, they can be useful in the dense plume regions, or in the sudden jet like events osccured at the limb.The FeXV line is also reserved to capture any transient activity occurs at the polar limb. Since,the line pairs suitable for the density diagnostics of quiet-Sun's transition region are not much stronger with EIS/Hinode. The SUMER line pairs may play key role to diagnose this region.
The off-limb density and nonthermal velocity variations along 2/3 of the slit height (~1.354 R0) will also be estimated. Few previous studies with SUMER and CDS onboard SOHO, have shown the reduction of nonthermal velocity and Doppler width after ~1.20 R0, and explained them as a signature of the dissipation of Alfven waves. These waves may also have important roles in the acceleration of the fast solar wind. We shall revisit this phenomena under the joint observations of EIS/Hinode, and SUMER/SOHO, which will shed further new lights on the Alfven waves and its exact role in the line-width (or nonthermal velocity) reduction beyond a certain height off-limb (if any).

The 1"" time-series observations will provide the temporal-spatio variations of the plasma properties in the polar coronal holes. We shall be able to find the signature of MHD waves both near the limb as well as on-disk part. We shall study their role in the dynamics of polar coronal holes.

In conclusions, the scan and time-series observations by the 1"" slit will  provide the spatial and temporal variation of plasma parameters respectively in the polar coronal holes. The study of these crucial parameters will enable us to investigate coronal hole dynamics, linking it with possible MHD waves.

 request to SOT

 request to XRT

 request to EIS
Exposure time: 300 s
Slit: 1"" slit
Window width: 56 pixels
Window Height : 512 pixels
Rotation compensation: On
No.of exposure sets: 50, Total duration of Time Series : 15000 s (250 min)
Total duration of study: 4 h 24 min 08 s
Data Rate: 5.9138 KB/s DCPM (Lossless)
Data Volume : 1874.48 KB
Ion Species    Wavelength Default Width (Pixels)
He II        256.32                 56
Ca XVII        192.82                   56
Fe XII        195.12                   56  
Fe XII         186.88                   56
Fe XIII        202.04          56
Fe XIII        203.82                   56
Fe VIII        185.21                   56
Mg VII         278.39                   56    
Mg VII         280.75                   56      
Fe XV        284.16          56"

 other participating instruments

Pointings (Target): On-disk and Off-limb regions at the solar poles. Slit is positioned so that 2/3 pixels of the total slit height (512 pixels) must be off-limb, while the rest of the pixels must be on-disk. The field of view should also capture the plume and interplume structures at the poles. 1. North pole 2. South pole

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