XRT: HOP54 and on-disk CH
2007-12-01T05:59:02 to 2007-12-01T15:55:58
Science Goal: DST/IBIS, Hinode/EIS+SOT+XRT, SOHO/MDI and TRACE -Magnetic helicity in active filaments, Multi-point, high cadence EUV (and complementary) observations of the dynamic solar corona
Program: HOP55_and_Disk-CH_3
Target: CH
xcen=0 ycen=0
Instrument: XRT
HOP/JOP: 0
Description:
Daily Note: Weekly meeting SOT: -HOP 35 begins 1 Dec - HOPs 54 and 55. XRT: - XBP EIS: - HOP coverage as above. - support XBP study - On-disk CH obs.
Request to XRT HOP Number 0035: XRT: middle cadence of the images is required using thin Be filter, exposure max of 1 s, cadence of 1 min, no binning and loss-less compression data.
Other Instruments: DST/IBIS SoHO/MDI TRACE
Scientific Objectives: We want to investigate whether the conditions for filament eruption occurrence depends on the shear / twist of the filament magnetic field or on the interaction between the highly sheared core field of the filament and the overlying flux rope. In this context, two main theoretical models have been proposed. The former suggests that the magnetic eruption and the impulsive energy release begins deep in the highly sheared core field of the filament and the overlying flux rope then erupts into interplanetary space (Moore et al., 2001). The latter assumes that a sheared core field pushes through an overlaying restraining filed and that a slow reconnection begins at a neutral point high in corona. After the restraining force of the overlaying field significantly weakens because of the reconnection, the sheared core field explosively erupts into interplanetary space (Antiochos, 1998). We think that the measure of the magnetic helicity or of its flux from the photosphere into the filament axis and the study of the magnetic topology of the active region where the filament eruption occurs, will give us the opportunity to discriminate between these two theoretical models.
Request to XRT HOP Number 0052: At least full disk high cadence (10s) in a single filter (Al poly) over the time period of the SOP.
Other 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. or (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.
Scientific Objectives: 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.
wavelength: Ti_poly cadence: 590.05 min fov: 2107,2107 images: 2 JavaScript Landing Page
