Publications (8)9.25 Total impact
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Article: Linking Remote-Sensing and In Situ Observations of Coronal Mass Ejections Using STEREO
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ABSTRACT: The twin STEREO spacecraft have been observing the Sun since 2006. Even though STEREO has only been active during solar minimum conditions so far, an important number of coronal mass ejections (CMEs) and their interplanetary counterparts (ICMEs) have been observed. Many of the ICMEs can be linked back to the corresponding CMEs on the Sun through the combination of remote-sensing and in situ observations. This paper aims to answer the question whether a CME observed by a coronagraph will be detected in situ by a spacecraft in a specific location in the heliosphere. We use a flux-rope-like model fit to the STEREO SECCHI/COR2 data to obtain the direction of CME propagation and its geometrical configuration in three dimensions. Based on model parameters, we then calculate their angular widths and determine whether they should have been detected by STEREO-A, STEREO-B, Wind or ACE. We compare the results with corresponding in situ observations of ICMEs. We find that predictions of ICME detections on the base of COR2 data generally match well the actual in situ observations. KeywordsCoronal mass ejections–CMEs–ICMEs–Interplanetary plasma–Space weather–StereoSolar Physics 05/2012; 270(2):561-573. · 2.78 Impact Factor -
Article: Three-Dimensional Reconstruction of Active Regions
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ABSTRACT: The STEREO mission provides an unprecedented opportunity to reconstruct the 3D configuration of solar features. In this work, we combine SECCHI/EUVI data from both spacecraft by means of a local correlation tracking method. The technique allows an automatic (without user intervention) matching of pixels in both images. This information is then used to triangulate the 3D coordinates of each pixel. We use the method in order to reconstruct and analyze the 3D structure of active regions. In particular, we focus on the extraction of coronal loop heights, observed nearly simultaneously in the 171, 195 and 284Å passbands. We compare the properties of loops in the different wavelengths and extract valuable information regarding their geometry. In particular, we demonstrate that some loops that look co-spatial in the 171Å and 195Å images have in fact different heights and thus occupy different volumes. Our results have important implications for multi-wavelength studies of coronal loops, especially for calculations using filter-ratio techniques.Solar Physics 04/2012; 256(1):41-55. · 2.78 Impact Factor -
Article: Study of a Prominence Eruption using PROBA2/SWAP and STEREO/EUVI Data
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ABSTRACT: Observations of the early rise and propagation phases of solar eruptive prominences can provide clues about the forces acting on them through the behavior of their acceleration with height. We have analyzed such an event, observed on 13 April 2010 by SWAP on PROBA2 and EUVI on STEREO. A feature at the top of the erupting prominence was identified and tracked in images from the three spacecraft. The triangulation technique was used to derive the true direction of propagation of this feature. The reconstructed points were fitted with two mathematical models: i) a power-law polynomial function and ii) a cubic smoothing spline, in order to derive the accelerations. The first model is characterized by five degrees of freedom while the second one is characterized by ten degrees of freedom. The results show that the acceleration increases smoothly and it is continuously increasing with height. We conclude that the prominence is not accelerated immediately by local reconnection but rather is swept away as part of a large-scale relaxation of the coronal magnetic field.03/2012; -
Article: Low polarized emission from the core of coronal mass ejections
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ABSTRACT: In white-light coronagraph images, cool prominence material is sometimes observed as bright patches in the core of coronal mass ejections (CMEs). If, as generally assumed, this emission is caused by Thomson-scattered light from the solar surface, it should be strongly polarised tangentially to the solar limb. However, the observations of a CME made with the SECCHI/STEREO coronagraphs on 31 August 2007 show that the emission from these bright core patches is exceptionally low polarised. We used the polarisation ratio method of Moran and Davila (2004) to localise the barycentre of the CME cloud. By analysing the data from both STEREO spacecraft we could resolve the plane-of-the-sky ambiguity this method usually suffers from. Stereoscopic triangulation was used to independently localise the low-polarisation patch relative to the cloud. We demonstrated for the first time that the bright core material is located close to the centre of the CME cloud. We show that the major part of the CME core emission, more than 85% in our case, is H$\alpha$ radiation and only a small fraction is Thomson-scattered light. Recent calculations also imply that the plasma density in the patch is 8 10$^8$ cm$^{-3}$ or more compared to 2.6 10$^6$ cm$^{-3}$ for the Thomson-scattering CME environment surrounding the core material.05/2011; -
Article: On 3D Reconstruction of Coronal Mass Ejections using SECCHI-COR Data
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ABSTRACT: The data from SECCHI-COR1 and SECCHI-COR2 coronagraphs onboard STEREO mission which was launched in October 2006 provided us with the first-ever stereoscopic images of the Sun's corona. These observations were found to be extremely useful in reconstructing the 3D structure of coronal mass ejections (CMEs). We apply four methods for reconstructing the CMEs: 1) Local correlation tracking (to identify the same feature in COR Ahead and COR Behind images) plus tie-point reconstruction technique; 2) Center of mass of the structures along the line of sight (i.e. along each epipolar lines) plus tie-point reconstruction technique; 3) Polarization ratio technique (see for e.g. Moran and Davila 2004); 4) Forward modelling technique (see Thernisien et al. 2006). The four techniques are applied on three structured CMEs observed by COR1 and COR2 instruments on 15 May 2007, 31 August 2007 and 25 March 2008. A comparison of results obtained from the application of the four reconstruction algorithms is presented and discussed.03/2009; 11:1145. -
Article: Activated T lymphocytes within human solid tumors
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ABSTRACT: The majority of lymphocytes separated from tumor cell suspensions were T cells. Conjugates of T lymphocytes and tumor cells were often seen. Variable numbers of T cells exhibited signs of activation such as the ability to form stable E rosettes and attachment to normal and malignant cells (a phenomenon designated natural attachment: NA). A proportion of T cells activated in vitro by allogeneic stimulation regularly exhibit these properties. The T cell-tumor conjugates in the suspensions may represent the NA phenomenon, but they could also be the product of T cells that adhere on the basis of specific recognition of cell surface antigens.Cancer Immunology and Immunotherapy 06/1979; 6(3):129-133. · 3.70 Impact Factor -
Article: On the 3-D reconstruction of Coronal Mass Ejections using coronagraph data
Annales Geophysicae, v.28, 203-215 (2010). -
Article: On 3D Reconstruction of Coronal Mass Ejections: I. Method Description and Application to SECCHI-COR Data
Solar Phys., v.259, 123-141 (2009).
Top co-authors
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Institutions
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2012
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Solar-Terrestrial Centre of Excellence
Brussels, BRU, Belgium -
University of Bucharest
Bucharest, Bucuresti, Romania
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