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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0052

Multi-point, high cadence EUV (and complementary) observations of the dynamic solar corona

plan term


@ @


 name : R. W. Walsh @  e-mail : rwwalsh[at]uclan.ac.uk

contact person in HINODE team

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

 abstract of observational proposal
The aim of this STEREO/SECCHI-led JOP is to use the singular vantage points of the STEREO spacecraft coupled to observations from SOHO, TRACE and Hinode in the Sun-Earth line to produce a unique dataset examining the time-dependent nature of the solar atmosphere.

We know already that this magnetised, plasma environment is highly structured and dynamic. Here we concentrate upon two important aspects:

1. the detection and characterisation of guided wave-modes within active region loops and;
2. the determination of the nature (birth, life, death) of small scale EUV brightenings.

Outlining the significance of these dynamic features is beyond the scope of this short scientific justification. However, concentrating upon the importance of observing simultaneously this dynamic behaviour from several different vantage points, we see that there are some fundamental issues that could be addressed. These include:

(i) for waves:

It should be possible to observe the gsameh propagating wave phenomena at the base of active region loops. Part of the problem with observing these oscillations on the disk from along the Sun-Earth line is that the angle of the emerging loop to the solar surface is unknown. Of course, it can be inferred indirectly from magnetic field extrapolations to a certain degree. Naturally this problem of a single viewing angle has an effect on the accurate calculation of the wave speed. Measuring this propagation speed from different viewpoints, will allow us to obtain a better-constrained value. Also, given that often the change in intensity related to these oscillations can only be <10 percent above the average intensity of the loop, the proper application of an appropriate background subtraction is very important. The different view-points should help to improve/verify the best way of doing this.

(ii) for dynamic brightenings:

We can ask: can we observe the gsame brighteningh from the three vantage points? Are there any discernable differences? If so, what are they? Does the opportunity of tracking the possible evolution of the 3D geometry of a glargeh brightening help us understand their existence in the first place? Can we get obtain a rough estimate of the possible preferred height of these brightening above the limb (or are they ALL very low down in the atmosphere)?

Of course, the above is certainly not an exhaustive list of what could be examined by this proposed unique dataset.

In order to achieve these observations, a short, constrained (2 to 3 hour, approx. 20-30s cadence in a single filter) observing run using SECCHI/EUVI would be undertaken. This will take SECCHI out of its usual synoptic observing mode and possibly suspend all other STEREO observations during this observing period. A short test case at higher cadence (10s) for 10 minutes was undertaken on STEREO-A only in February 2007. Apart from that dataset, no other coordinated high cadence observing programme (and hence data) as suggested here exists.

Thus, when these high cadence SECCHI observations are combined with observations from SOHO, TRACE and Hinode located along the Sun-Earth line, we have the capability to obtain near simultaneous observations of dynamic changes in the solar atmosphere from three lines of sight. EUV imaging in the same filter as SECCHI but from TRACE and SOHO/EIT will be requested along with complementary Hinode/XRT full disk observations. EUV spectroscopy will be undertaken by SOHO/CDS and Hinode/EIS to both increase the wavelength coverage as well as provide plasma diagnostics for the selected targets. Magnetograms from both SOHO/MDI and Hinode/SOT will provide details of the underlying photospheric magnetic field structures.

The obtained time-series observations will be investigated by employing, say, wavelet analysis techniques and/or Bayesian analysed methods across the datasets.

 request to SOT
Full resolution magnetograms at best possible cadence during SOP.

 request to XRT
At least full disk high cadence (10s) in a single filter (Al poly) over the time period of the SOP.

 request to EIS
During the SOP and depending on the target, then
(a) if AR present could plan a run of slot movie observations (eg. COOL_AR_MOVIE, exposure 10s, 40h slot). Some single slit sit and stare observations might also be appropriate (eg. AR_RAPID_SPEC, exposure 20s, 1hslit). Target position would be coordinated with SOHO/CDS and TRACE.

(b) if quiet sun, then suggest suitable version of slot observations on disk centre.

Either side of SOP, a rastered slit (2h say) sequence on the target could be used to help place slot observations in context.

 other participating instruments
STEREO/SECCHI: From both A and B, full disk EUV images in a single filter (195 Angstrom say) with a cadence of at least 20-30s for 2-3 hours. Let us term this the SECCHI Observing Period (or SOP). Note that almost all other observations from STEREO would be suspended during this observing window.

TRACE: Single filter to match SECCHI chosen line (195 Angstrom say) observed continuously with suitable cadence (20-30s say) during SOP. If there is a decent active region, then that would be the given target. Otherwise, quiet sun pointing at disc centre would be requested. Target position would be coordinated with SOHO/CDS and Hinode/EIS.

SOHO/EIT: Full disk images in wavelength to match SECCHI (195 Angstrom say) at best possible cadence during SOP. Shutterless mode would be very welcome but author is aware that this is not undertaken very often. Images should be at full resolution (1024x1024) and if possible, synchronized with SECCHI images during SOP.

SOHO/CDS: Similar to Hinode/EIS in that

(a) if AR target then single slit, sit and stare observations (eg, LOOPS2D_5) somewhere over the active region loops (apex or footpoint)with an EJECT_V3 at beginning and end. Target position would be coordinated with Hinode/EIS and TRACE.
(b) if quiet sun, then suggest multiple repeats of a suitable version of EJECT_V3 on disk centre.

SOHO/MDI: Full disk magnetograms at best possible cadence during SOP. If target region is within high-res fov high-res magnetograms and visible-light filtergrams with best cadence would be desired.

Proposed observing schedule:

1. Wk47 and Wk48 2007:
This is directly after the dedicated SUMER campaign. The JOP-leader realises that the above weeks are a gtroublesomeh period for both SOHO and TRACE!

However, we feel that obtaining a limited number of gtest runsh of the SECCHI high cadence observations before Christmas 2007 would be useful, after which the s/c are 45 degrees apart (and 3D reconstruction errors continue to increase) as well as planning for the Jan SECCHI campaign in January 2008 (see below).

For SOHO: given the keyhole situation, we realise the constraints on EIT, CDS and MDI and that we might not obtain very much. Whatever support you could give would be appreciated.

For TRACE: we realise that during the eclipse season one cannot guarantee the support or quality of the TRACE images. Again, whatever support you can give would be appreciated.

For Hinode: we see that there are other HOPs during those weeks but we hope that the short 2-3 hour windows we request could be supported, especially given the above situation with SOHO and TRACE.

Specific UT times for the SOP to run during these weeks will be confirmed by Simon Plunkett.

Note that RWW will be in GSFC/NRL from 26/11/07 to 03/12/07.

2. There is a SECCHI campaign in January 2008. It is hoped that these high cadence observations will be part of the campaign. With twice the amount of the normal telemetry during those two weeks, one should be able to get higher quality (lower compression) data.

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