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31.
P. Démoulin C. H. Mandrini M. G. Rovira J. C. Hénoux M. E. Machado 《Solar physics》1994,150(1-2):221-243
We present a detailed analysis of the magnetic topology of AR 2776 together with Hα UV, X-rays, and radio observations of the November 5, 1980 flares in order to understand the role of the active region large-scale
topology on the flare process. As at present the coronal magnetic field is modeled by an ensemble of sub-photospheric sources
whose positions and intensities are deduced from a least-square fit between the computed and observed longitudinal magnetic
fields. Charges and dipole representations are shown to lead to similar modeling of the magnetic topology provided that the
number of sources is great enough. However, for AR 2776, departure from a potential field has to be taken into account, therefore
a linear force-free field extrapolation is used.
The locations of the four bright off-band Hα kernels in quadrupolar active regions have been studied previously. In this new study the active region is bipolar and shows
a two-ribbon structure. We show that these two ribbons are a consequence of the bipolar photospheric field (the four kernels
of quadrupolar regions merge into two bipolar regions). The two ribbons are found to be located at the intersection of the
separatrices with the chromosphere when the shear, deduced from the fibril direction, is taken into account.
This study supports the hypothesis that magnetic energy is stored in field-aligned currents and released by magnetic reconnection
at the location of the separator, before being transported along field lines to the chromospheric level. It is also possible
that part of the magnetic energy could be stored and released on the separatrices. Our study shows that meeting just one of
two conditions- the presence of intense coronal currents or of a separator in a magnetic field configuration - is not sufficient
for flaring. In order to release the stored energy, the coronal currents need either to be formed along the separatrices or
to be transported towards the separator or separatrices. The location of the observed photospheric current concentrations
on the computed separatrices supports this view.
Member of the Carrera del Investigador Científico, CONICET. 相似文献
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C. H. Mandrini P. Demoulin B. Schmieder E. E. Deluca E. Pariat W. Uddin 《Solar physics》2006,238(2):293-312
A major two-ribbon X17 flare occurred on 28 October 2003, starting at 11:01 UT in active region NOAA 10486. This flare was
accompanied by the eruption of a filament and by one of the fastest halo coronal mass ejections registered during the October–November
2003 strong activity period. We focus on the analysis of magnetic field (SOHO/MDI), chromospheric (NainiTal observatory and
TRACE), and coronal (TRACE) data obtained before and during the 28 October event. By combining our data analysis with a model
of the coronal magnetic field, we concentrate on the study of two events starting before the main flare. One of these events,
evident in TRACE images around one hour prior to the main flare, involves a localized magnetic reconnection process associated
with the presence of a coronal magnetic null point. This event extends as long as the major flare and we conclude that it
is independent from it. A second event, visible in Hα and TRACE images, simultaneous with the previous one, involves a large-scale
quadrupolar reconnection process that contributes to decrease the magnetic field tension in the overlaying field configuration;
this allows the filament to erupt in a way similar to that proposed by the breakout model, but with magnetic reconnection
occurring at Quasi-Separatrix Layers (QSLs) rather than at a magnetic null point.
Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users. 相似文献
34.
G. Cristiani G. Martinez C. H. Mandrini C. G. Giménez De Castro C. W. Da Silva M. G. Rovira P. Kaufmann 《Solar physics》2007,240(2):271-281
Using magnetograms, EUV and Hα images, Owens Valley Solar Array microwave observations, and 212-GHz flux density derived from
the Solar Submillimeter Telescope data, we determine the spatial characteristics of the 1B/M6.9 flare that occurred on November
28, 2001, starting at 16:26 UT in active region (AR) NOAA 9715. This flare is associated with a chromospheric mass ejection
or surge observed at 16:42 UT in the Hα images. We compute the coronal magnetic field under the linear force-free field assumption,
constrained by the photospheric data of the Michelson Doppler Imager and loops observed by the Extreme Ultraviolet Imaging
Telescope. The analysis of the magnetic field connectivity allows us to conclude that magnetic field reconnection between
two different coronal/chromospheric sets of arches was at the origin of the flare and surge, respectively. The optically thick
microwave spectrum at peak time shows a shape compatible with the emission from two different sites. Fitting gyrosynchrotron
emission to the observed spectrum, we derive parameters for each source.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
35.
C. H. Mandrini M. S. Nakwacki G. Attrill L. van Driel-Gesztelyi P. Démoulin S. Dasso H. Elliott 《Solar physics》2007,244(1-2):25-43
Coronal dimmings are often present on both sides of erupting magnetic configurations. It has been suggested that dimmings
mark the location of the footpoints of ejected flux ropes and, thus, their magnetic flux can be used as a proxy for the flux
involved in the ejection. If so, this quantity can be compared to the flux in the associated interplanetary magnetic cloud
to find clues about the origin of the ejected flux rope. In the context of this physical interpretation, we analyze the event,
flare, and coronal mass ejection (CME) that occurred in active region 10486 on 28 October 2003. The CME on this day is associated
with large-scale dimmings, located on either side of the main flaring region. We combine SOHO/Extreme Ultraviolet Imaging
Telescope data and Michelson Doppler Imager magnetic maps to identify and measure the flux in the dimming regions. We model
the associated cloud and compute its magnetic flux using in situ observations from the Magnetometer Instrument and the Solar Wind Electron Proton Alpha Monitor aboard the Advance Composition Explorer. We find that the magnetic fluxes of the dimmings and magnetic cloud are incompatible, in contrast to what has been found
in previous studies. We conclude that, in certain cases, especially in large-scale events and eruptions that occur in regions
that are not isolated from other flux concentrations, the interpretation of dimmings requires a deeper analysis of the global
magnetic configuration, since at least a fraction of the dimmed regions is formed by reconnection between the erupting field
and the surrounding magnetic structures. 相似文献
36.
M.L. Luoni C.H. Mandrini Sergio Dasso L. van Driel-Gesztelyi P. Dmoulin 《Journal of Atmospheric and Solar》2005,67(17-18):1734
On October 14, 1995, a C1.6 long duration event (LDE) started in active region (AR) NOAA 7912 at approximately 5:00 UT and lasted for about 15 h. On October 18, 1995, the Solar Wind Experiment and the Magnetic Field Instrument (MFI) on board the Wind spacecraft registered a magnetic cloud (MC) at 1 AU, which was followed by a strong geomagnetic storm. We identify the solar source of this phenomenon as AR 7912. We use magnetograms obtained by the Imaging Vector Magnetograph at Mees Solar Observatory, as boundary conditions to the linear force-free model of the coronal field, and, we determine the model in which the field lines best fit the loops observed by the Soft X-ray Telescope on board Yohkoh. The computations are done before and after the ejection accompanying the LDE. We deduce the loss of magnetic helicity from AR 7912. We also estimate the magnetic helicity of the MC from in situ observations and force-free models. We find the same sign of magnetic helicity in the MC and in its solar source. Furthermore, the helicity values turn out to be quite similar considering the large errors that could be present. Our results are a first step towards a quantitative confirmation of the link between solar and interplanetary phenomena through the study of magnetic helicity. 相似文献
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Leibacher John Mandrini Cristina H. van Driel-Gesztelyi Lidia Wheatland Michael S. 《Solar physics》2020,295(1):1-20
Solar Physics - Synoptic maps of solar EUV intensities have been constructed for many decades in order to display the distribution of the different EUV emissions across the solar surface, with each... 相似文献
39.
John Leibacher Cristina H. Mandrini Lidia van Driel-Gesztelyi Michael S. Wheatland 《Solar physics》2017,292(1):19
We are pleased to acknowledge, with sincere thanks, the following referees who supported the community by refereeing articles for Solar Physics during 2016. 相似文献
40.
Mariano?PoissonEmail author Pascal?Démoulin Marcelo?López Fuentes Cristina?H.?Mandrini 《Solar physics》2016,291(6):1625-1646
The photospheric spatial distribution of the main magnetic polarities of bipolar active regions (ARs) present during their emergence deformations are known as magnetic tongues. They are attributed to the presence of twist in the toroidal magnetic-flux tubes that form the ARs. The aim of this article is to study the twist of newly emerged ARs from the evolution of magnetic tongues observed in photospheric line-of-sight magnetograms. We apply the procedure described by Poisson et al. (Solar Phys. 290, 727, 2015a) to ARs observed over the full Solar Cycle 23 and the beginning of Cycle 24. Our results show that the hemispherical rule obtained using the tongues as a proxy of the twist has a weak sign dominance (53 % in the southern hemisphere and 58 % in the northern hemisphere). By defining the variation of the tongue angle, we characterize the strength of the magnetic tongues during different phases of the AR emergence. We find that there is a tendency of the tongues to be stronger during the beginning of the emergence and to become weaker as the AR reaches its maximum magnetic flux. We compare this evolution with the emergence of a toroidal flux-rope model with non-uniform twist. The variety of evolution of the tongues in the analyzed ARs can only be reproduced when using a broad range of twist profiles, in particular having a large variety of twist gradients in the direction vertical to the photosphere. Although the analytical model used is a special case, selected to minimize the complexity of the problem, the results obtained set new observational constraints to theoretical models of flux-rope emergence that form bipolar ARs. 相似文献