Annual report - 2007
Results received during 2007 :
Observations with SOHO (campaigns etc.)
April 23 - 29, 2007, Institut d'Astrophysique Spatiale, MEDOC, Orsay, Paris, France, participation in JOP 178 coordinated campaign between Hinode, SOHO, TRACE and GBO. Planning of the observational targets and coordination of the SOHO: SUMER, CDS; Hinode: SOT and GBO pointing in collaboration with Dr. B. Schmieder and Dr. N. Labrosse
SOHO data analysis
We have analyzed the Lyman spectrum observed by SOHO during JOP 107 on October 15 - 17, 1999. The comparison of the observed spectrum with the synthetic spectrum obtained by 2D prominence fine-structure thread models was published in Schmieder et al. (2007). The approximate orientation of the magnetic field within the prominence/filament fine structures was derived using the morphological analysis of the filament and the comparison of the observed and synthetic spectral lines. The agreement of the results of such two different methods suggests that the synthetic Lyman spectrum can be used for the analysis of the magnetic field orientation.
We have also analyzed the SUMER spectrum obtained on May 25, 2005 during MEDOC campaign No. 15. The observed Lyman-ato Lyman-7 lines were compared with the synthetic Lyman profiles obtained 2D prominence fine-structure thread models. Particular set of the input parameters was found using trial-and-error method and the comparison of the synthetic and observed spectrum shows that such 2D prominence fine-structure thread model can reproduce the observed spectrum much better than 1D models. However, the multi-thread modelling is required in order to improve the agreement between the synthetic and the observed spectrum. The analyses and the comparison of the synthetic and the observed spectrum were published in Gunar et al. (2007)
The properties of the large-scale velocity fields in the solar photosphere (M. Švanda) were studied using data obtained by SOHO/MDI during Dynamics campaigns. During these periods, MDI observed full-disk Dopplergrams in high-cadence of 1 frame/minute. These data are suitable for the calculation of the velocity fields using the local helioseismology and local correlation tracking technique applied to supergranular structures recorded in Dopplergrams. Both techniques show a reasonable match when using the same dataset (Švanda et al. 2007b), which justifies the use of both methods. The local correlation tracking method was applied to all Dynamics campaigns data. The long-term properties clearly reveal the well-known structures of torsional oscillations and the large-scale, mostly poleward meridional flow (Švanda et al. 2008). The periodic analysis did not show any conclusive results, however some signs of periods claimed by other authors to be related to Rossby waves pattern were found. Analysis of the influence of the presence of magnetic field showed an acceleration of the rotation in the area occupied by magnetic field and the relation describing this behaviour was determined (Švanda et al. 2008).
Changes in the topology of the flow field are claimed to influence the topology of the coronal magnetic field and therefore to lead to active phenomena such as flares and CMEs. A case study (Roudier et al. 2008) showed that in the regions beneath the filament, which erupted on October 7th 2004, the increase of the zonal shear in the starting-point area could contribute to destabilisation of the filament. The flow field topology changed significantly in the photosphere under the filament during the filament eruption.
The measured meridional flow is used as a key ingredient of the flux-transport-based solar dynamos. Usually, the flows measured by local helioseismology are used as the input for those models. A careful comparison with the measured flux transport speed (Švanda et al. 2007a) showed that in the activity belt the longitudinally averaged flow derived by local helioseismology is strongly biased by local circulation flows around the active regions. This study suggests that the direct use of time-distance based measurement is not justified.
SOHO data, especially from EIT and SUMER instruments, were used in combination with data from the Yohkoh satellite and, later, from the Hinode satellite for studies aimed at distinquishing between the absorption and so called emissivity blocking by solar prominences. Results have been published by Heinzel et al. (2007) and Anzer et al. (2007).
We made the non-LTE modeling of the filament observed by SOHO/SUMER in the whole series of the hydrogen Lyman lines plus Lyman continuum and by Ondřejov HSFA2 multicamera spectrograph in the Ha line on May, 27, 2005. The observations of the SUMER were unique because the filament was observed in the whole hydrogen Lyman line series including the Lya line for the first time. Lya line was placed on the detector A outside the attenuator, therefore the profiles could be calibrated reliably. Only a part of the detector was working therefore only darker and colder part of the filament was observed - so-called Ha filament. The filament was approximated by the 1D horizontal isobaric slab with the temperature symmetrically decreasing from the prominence-corona transition regions (hereafter PCTR) to the slab interior. The slab was irradiated only from the chromosphere beneath (so-called background irradiation). We used the same methods for fitting of the observed profiles and for estimation of the background irradiation as it was used previously. This work was presented as a poster at the symposium ‘The physics of chromospheric plasmas' which took place in Coimbra, Portugal in 2006 and was then published in the proceedings of the symposium (Schwartz et al., 2007). We obtained similar plasma properties as for other two Ha filaments studied previously - temperatures around 6000 K and 20000 K in the filament interior and in the PCTRs, respectively. PCTRs are geometrically thin and density of the plasma ranges from 10-14 to 10-13 g cm-3. We found that cores of the profiles of the Lyman lines are formed at the top PCTR where temperature is steeply increasing. In the wings of the profiles of the Lyb and higher Lyman lines the filament is transparent. Only the Lya profiles are optically thick also in the near wings. These optically thick parts of the profiles are formed deeper than the core therefore the Lya is suitable for modeling the colder inner part of PCTR where temperature is decreasing more slowly than in a hot part of the PCTR, to temperature of the filament interior where almost whole profile of Ha is formed.
P. Schwartz made a flexible code for data calibration from the spectrograph SOHO/SUMER. He spent one week in May 2007 in the Max-Planck Institut in Lindau, Germany where he discussed his code with the group of scientists who developed the SUMER instrument and SolarSoft procedures for reduction of data from this instrument. After this stay he corrected and finished the code. The code is based on the standard SolarSoft procedures but it is automatically choosing the way and order how the procedures of different corrections are used. It can process also the corrections that are not normally included in SolarSoft, e.g. shift of the no-odd-even structure of the flatfield. This code is suitable for automatic reduction and calibration of the raster observations or large sets of observations as well. The code was already used for calibration of the profiles of hydrogen Lyman lines observed in a prominence on May 25, 2005. The profiles were used for 2D modeling of the prominence threads (Gunár et al., 2007).
P. Heinzel and S. Gunar participated in the first meeting at ISSI (International Space Science Institute) in Bern. This meeting was devoted to space observations of solar prominences, namely using the SOHO and Hinode satellites. P. Heinzel was the leader of spectroscopy group. The collaboration on various publications is in progress.
P. Schwartz and P. Heinzel collaborated with G. Tsiropoula and K. Tziotziou on data analysis from SOHO/CDS. They studied the behaviour of the chromospheric fine structures (mottles), using the wavelet analysis of CDS spactra. Preliminary results were presented during the CESPM meeting in Austria, October 2007 (Tsiropoula et al. 2007).
Two PhD theses were successfully defended at Charles University in Prague (in December, 2007):
S. Gunar - Multi-dimensional radiative transfer in quiescent prominences
M. Švanda - Velocity fields in the solar atmosphere
Both works extensively used the SOHO data.
Theoretical work related to SOHO data
During the visit to Center for Astrophysics (CfA) at Harward (Cambridge, USA), P. Heinzel studied the spectral line formation in solar prominences and chromosphere, in collaboration with G. Avrett. Namely the radiative interaction between the chromosphere and overlying filament was investigated in detail. The lines concerned are mainly the EUV lines as observed with SUMER onboard the SOHO. This work will continue.
U. Anzer and P. Heinzel (Anzer and Heinzel 2007) investigated the magnetic fields in solar prominences and estimated the role of the mass loading on MHS stability. They found that the prominence fine-structure magnetic dips are mostly gravity-induced and thus the magnetic field in prominences is not force-free in most cases.
We have studied the Lyman continuum formation and the dependence of the synthetic Lyman continuum profile on the choice of the 2D fine-structure thread models (Heinzel & Anzer 2001) input parameters. The analyses were published in Gunar et al. (2007a)
The evaluative criteria for image quality have been introduced. There were compared the classical and blind criteria and their utilization in the process of image quality evaluation. Criteria were tested on the synthetic degraded data sets to get the most appropriate ones for the real astronomical images. Experiments with the satellite image data of SOHO mission are discussed regarding to the degradation models with variable noise (Haindl and Simberova 2007).
Hinode - observations and data analysis
SOHO satellite provides no X-ray and optical observations and therefore for many studies the SOHO observations need to be combined with other satellite observations - first with Yohkoh data and, recently, with Hinode data. Such a complex observation is very important and, in fact, necessary for getting answers to many scientific problems and questions. This is why we used the Hinode data in combination with the SOHO observations. Currently we analyze the data obtained during the MEDOC campaign (April 2007). This work is performed within a broad international team.
Solar Orbiter - announcement of opportunity
Solar Orbiter is a very ambitious ESA mission in the field of solar physics. Even when the mission went through a very tough periods and was postponed many times, we expressed our deep interest to participate in the project and that was already stressed in the PECS/SOHO project which could also be understood as our preparation for Czech involvement in a space project from its very beginning. In the past we wrote a supporting letter to ESA.
STIX
The Astronomical Institute ASCR is a member of the STIX instrument consortium and, as soon as the Announcement of Opportunity for Solar Orbiter was issued by ESA, we actively cooperated on the final proposal preparation. Therefore, we participated in the consortium meeting which took place in Zurich, Switzerland, between 1 and 3 October 2007.
J. Kašparová has been involved in the preparation of the STIX proposal as a member of the Czech STIX team based at Astronomical Institute AS CR. If the STIX proposal is accepted (deadline for the proposal submission is January 15, 2008), she will contribute to the data analysis software within the STIX software group. Together with F. Fárník they will be responsible for delivery of low and high power voltage supply and on-board flight software as PIs of the Czech STIX team.
The new PECS proposal related to STIX was submitted, with J. Kašparová being PI.
EUS
The Czech Republic represented by the Astronomical Institute ASCR participates at the international consortium with the intention to prepare a scientific experiment for the ESA's Solar Orbiter mission: Solar Orbiter EUS Spectrometer SPICE (Solar Imagining of the Coronal Environment). The meeting of the working group was held in Orsay, France, December 11-12 2007 in order to write the first science draft for the proposal to NASA SPICE instrument on the Solar Orbiter. The scientific team discused the optical design of the spectrometer, its mechanical and thermal characteristics, observing modes and the scientific goals of the project. The Czech team has specialized in "Sources and acceleration mechanisms of solar energetic particles" and in a special topic: "How the turbulence affects the EUV spectrum", during the preparation of the scientific objectives for the SPICE.
Attached is the summary of expected Czech participation in the Solar Orbiter EUS experiment.
Work presented on international meetings
5th Potsdam Thinkshop „Meridional flow, differential rotation, solar and stellar activity", June 24th to 29th, 2007, AIP, Potsdam, Germany (poster: Švanda, M., Kosovichev, A. G., Zhao, J., Measurement of the meridional flux transport in the solar photosphere. Posters were not published in the special issue of Astronomische Nachrichten).
P. Heinzel has participated in the First Hinode Science Meeting, Dublin (Ireland), September 2007 and presented an oral talk based on new Hinode/SOHO/TRACE coordinated observations obtained during the MEDOC campaign in April 2007 (see 5.1). Full paper is now in preparation for publication in the ApJ journal.
Visits related to PECS project
Visits from AI
M. Svanda - March 12th - April 11th 2007, Stanford University, Palo Alto, USA.
To be able to correctly use the X-ray data from Hinode, we visited the principal investigator of the XRT instrument, Dr.Leon Golub, in the Centrum for Astrophysics in Cambridge, USA, between 29 April and 4 May 2007. Our discussion there on the Hinode X-ray data analysis was extremely important for our following studies. Also, we had an opportunity there to obtain some important observation from the Hinode optical telescope which we also used in our following analysis.
CfA Cambridge (USA) - visit of P. Heinzel, 2 weeks in April-May 2007
Space Research Institute, Athens, Greece, visit of P. Schwartz and P. Heinzel, one week, July 2007
P. Heinzel - ISSI (International Space Science Institut), Bern, 4 - 7 December 2007
E. Dzifčáková - IAS Orsay (MEDOC SOHO Center), France, December 2007
April 23 - 29, 2007, Institut d'Astrophysique Spatiale, MEDOC, Orsay, Paris, France, participation on JOP 178 coordinated campaign between Hinode, SOHO, TRACE and GBO
June 19 - 29, 2007, summer school on radiative transfer and numerical MHD, University of Oslo, Norway
Visits to AI
S. Jejcic - February 2007, one week
U. Anzer - April 2007, two weeks
B. Schmieder - May 2007, 10 days
U. Anzer - October 2007, 10 days
G. Tsiropoula and K. Tziotziou - November 2007, one week
J.-C. Vial - December 2007, 5 days
Activities proposed for 2008
Further deep involvement in the SOHO observations and data analysis.
Observations with Hinode (SOT, XRT, EIS), data analysis.
We will concentrate on the analyses of the observational data obtained during the JOP 178.
In the theoretical field we will concentrate on the development of the models usable of the modeling of both prominence and filament fine structures. Such models requires the 3D geometry and therefore we will work on the development of the 3D radiative transfer code.
Theoretical work on MHD, radiative transfer and spectral diagnostics related to SUMER, CDS, and EIS.
Involvement in the Solar Orbiter Mission, in the STIX and EUS consortia.
Building the Center for Collaboration with ESO and ESA (E2S Center) which will promote the the Czech collaboration with ESO and with ESA in frame of PECS projects and future Czech membership in ESA (ESA collaboration in the fields of astronomy and astrophysics).
The project of large-scale velocity fields in the solar photosphere will continue and will benefit from the data obtained during previous studies. The data series coming from high-cadence campaigns of MDI instrument on-board SOHO are suitable for such kinds of studies.
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