A1D3.2
From Soteria
Lead Beneficiary: UGOE
Beneficiaries involved: UNIGRAZ
Due Date: Month 16
Contents |
Goal
Development of a 3D model for the structure of CMEs based on the analysis of multi-wavelength space- and ground-based observations. Tests of the model validity through STEREO, SOHO multipoint observations and visualisation of the model for scientific demonstration and public outreach purposes.
Successes
Since launch in October 2006 the scientific instruments of the STEREO mission have provided successfully observations of the Sun and heliosphere in white-light and at EUV-wavelength, amounting to more than 5 TB of data. The in-situ plasma, particle and magnetic field detectors and radio wave antennas complement the scientific payload. With the five imagers of the STEREO/SECCHI telescope suite it has become possible for the first time ever to track solar eruptions from the chromosphere through the corona into the heliosphere up to distances beyond 1 AU. From the inspection of the coronagraph observations of the STEREO A and STEREO B COR 2 instruments we have so far identified about 150 coronal mass ejection events observed by the two spacecraft at separation angles up to 120 degrees to each other. The events observed during this very quiet solar minimum document that CMEs on various scales and energies are an inherent physical process of the Sun's ever changing photospheric fields and coronal structures. The advantage of these events observed at very low solar activity is that they are not obscured by ambient coronal structures and hence reveal an unprecedented signal to noise ratio as well as a unique investigation of their corresponding solar source regions.
Exceptional Discoveries
From the analysis of the STEREO/SECCHI data it has been found that coronal transients occur on various spatial scales. Inside coronal holes the emerging magnetic flux leads to magnetic reconnection processes in which the plasma in the more energetic cases reaches escape velocities and coronal jets are observed heigher up in the outer solar atmosphere by the COR 1 telescopes. Discoveries of the stereoscopic analysis of the events yielded the existence of helical magnetic structures and of micro CMEs, regular CMEs on much smaller spatial scales. The results have been reported in: Nisticò, G., Bothmer, V., Patsourakos, S., Zimbardo, G., Characteristics of EUV Coronal Jets Observed with STEREO/SECCHI, Solar Phys., DOI 10.1007/s11207-009-9424-8, 2009.
In December 2008, for the first time ever a CME has been tracked continously and stereoscopically from the solar chromosphere to the Earth with the STEREO/SECCHI instrument suite. At Earth the CME, which has been followed through interplanetary space by the Heliospheric Imagers of SECCHI, has been measured in-situ with the ACE satellite.
Progress so far
UGOE (Volker Bothmer, Ansgar Reiners)
So far we have identified more than hundred CMEs in the data of the STEREO/SECCHI imagers at separation angles between both S/C of up to 120 degrees. From EUV and SOHO/MDI observations we are identifying the corresponding solar source regions in these events and compare our results with the 3D electron density model for CMEs developed by Thernisien et al. (2009) based on the results of Cremades & Bothmer (2004). The modelling of the magnetic flux ropes in the COR 2 field of view will be extended into the field of view of the Heliospheric Imagers. The scientific analyses in this project are closely carried out together with the Naval Research Laboratory, Washington, DC, USA (A. Thernisien, A. Roillard) and the UK's Rutherford Appleton Laboratory, Didcot, Chilton (Davies, Davis, Harrison) and Imperial College, London (Savani, Forsyth). The results of our study on the 3D structure of CMEs at the Sun and in interplanetary space will be summarised as deliverable D3.2 and in subsequent publications. The work on the 3D visualisation has led to a German proto-type DVD "Die Sonne in 3D" which we will use to develop an English version for the team. Individual national versions can be developed by the different SOTERIA teams on demand. The visualisations are shown at Planetarium Hamburg and at exhibitions dedicated to the IAY 2009.
UNIGRAZ (Manuela Temmer, Astrid Veronig, Olga Flor)
The geometrical triangulation tool (TR) which was developed to derive the de-projected ("true") CME kinematics as well as its direction of propagation was tested on several events. For simple CMEs (non-halo, well observed) the tool works fine and gives results that are comparable to more sophisticated approaches like the forward fitting model by Thernisien et al. 2009. For more complex events the tool is affected by larger errors. A paper was published by Temmer, Preiss, Veronig, 2009 in Solar Physics.
In a next step we will test the directivity results (from TR) and study interplanetary propagation of CMEs observed with the Heliospheric Imager (HI) aboard STEREO (R>30Rs). The study will be performed using COR1 and COR2 observations together with HI1 and HI2 observation of the interplanetary evolution of the CME. For this, a PhD student started developing and working with IDL-routines retrieving and analyzing specific measurement data, and getting skilled in image processing and familiar with the state-of-the-art of CME-theory.
Problem areas
The Ph.D. position at UGOE dedicated to the 3D analysis of CMEs could not be filled with a suitable candidate. In order to perform the work required to fulfill deliverable D3.2 in time a researcher has now been hired as post-doc. We expect no impact on the project goals and schedule.
Suggestions for spin-off, collaboration or improvement
To optimise the outcome of project D3.2 we will intensify collaborations between UGOE and UGRAZ.
