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Moreton and EUV Waves Associated with an X1.0 Flare and CME Ejection  

Cristina H. Mandrini   Submitted: 2017-02-13 06:08

A Moreton wave was detected in active region (AR) 12017 on 29 March 2014 with very high cadence with the Hα Solar Telescope for Argentina (HASTA) in association with an X1.0 flare (SOL2014-03-29T17:48). Several other phenomena took place in connection with this event, such as low coronal waves and a coronal mass ejection (CME). We analyze the association between the Moreton wave and the EUV signatures observed with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. These include their low-coronal surface-imprint, and the signatures of the full wave and shock dome propagating outward in the corona. We also study their relation to the white-light CME. We perform a kinematic analysis by tracking the wavefronts in several directions. This analysis reveals a high-directional dependence of accelerations and speeds determined from data at various wavelengths. We speculate that a region of open magnetic field lines northward of our defined radiant point sets favorable conditions for the propagation of a coronal magnetohydrodynamic shock in this direction. The hypothesis that the Moreton wavefront is produced by a coronal shock-wave that pushes the chromosphere downward is supported by the high compression ratio in that region. Furthermore, we propose a 3D geometrical model to explain the observed wavefronts as the chromospheric and low-coronal traces of an expanding and outward-traveling bubble intersecting the Sun. The results of the model are in agreement with the coronal shock-wave being generated by a 3D piston that expands at the speed of the associated rising filament. The piston is attributed to the fast ejection of the filament-CME ensemble, also consistent with the good match between the speed profiles of the low-coronal and white-light shock-waves.

Authors: Carlos Francile, Fernando M. López, Hebe Cremades, Cristina H. Mandrini, María Luisa Luoni, David M. Long
Projects: None

Publication Status: Published Solar Physics
Last Modified: 2017-02-13 12:04
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Parallel Evolution of Quasi-separatrix Layers and Active Region Upflows  

Cristina H. Mandrini   Submitted: 2015-07-08 17:11

Persistent plasma upflows were observed with Hinode's EUV Imaging Spectrometer (EIS) at the edges of active region (AR) 10978 as it crossed the solar disk. We analyze the evolution of the photospheric magnetic and velocity fields of the AR, model its coronal magnetic field, and compute the location of magnetic null-points and quasi-sepratrix layers (QSLs) searching for the origin of EIS upflows. Magnetic reconnection at the computed null points cannot explain all of the observed EIS upflow regions. However, EIS upflows and QSLs are found to evolve in parallel, both temporarily and spatially. Sections of two sets of QSLs, called outer and inner, are found associated to EIS upflow streams having different characteristics. The reconnection process in the outer QSLs is forced by a large-scale photospheric flow pattern which is present in the AR for several days. We propose a scenario in which upflows are observed provided a large enough asymmetry in plasma pressure exists between the pre-reconnection loops and for as long as a photospheric forcing is at work. A similar mechanism operates in the inner QSLs, in this case, it is forced by the emergence and evolution of the bipoles between the two main AR polarities. Our findings provide strong support to the results from previous individual case studies investigating the role of magnetic reconnection at QSLs as the origin of the upflowing plasma. Furthermore, we propose that persistent reconnection along QSLs does not only drive the EIS upflows, but it is also responsible for a continuous metric radio noise-storm observed in AR 10978 along its disk transit by the Nançay Radio Heliograph.

Authors: Mandrini, C. H.; Baker, D.; Démoulin, P.; Cristiani, G. D.; van Driel-Gesztelyi, L.; Vargas Domínguez, S.; Nuevo, F. A.; Vásquez, A. M.; Pick, M.
Projects: None

Publication Status: Accepted Astrophys. J.
Last Modified: 2015-07-10 20:38
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How Can Active Region Plasma Escape into the Solar Wind from below a Closed Helmet Streamer?  

Cristina H. Mandrini   Submitted: 2014-09-25 12:35

Recent studies show that active-region (AR) upflowing plasma, observed by the EUV-Imaging Spectrometer (EIS), onboard Hinode, can gain access to open-fi eld lines and be released into the solar wind (SW) via magnetic interchange reconnection at magnetic null-points in pseudo-streamer configurations. When only one bipolar AR is present on the Sun and it is fully covered by the separatrix of a streamer, such as AR 10978 in December 2007, it seems unlikely that the upflowing AR plasma can find its way into the slow SW. However, signatures of plasma with AR composition have been found at 1 AU by Culhane et al. (2014, Solar Phys. 289, 3799) apparently originating from the West of AR 10978. We present a detailed topology analysis of AR 10978 and the surrounding large-scale corona based on a potential- field source-surface (PFSS) model. Our study shows that it is possible for the AR plasma to get around the streamer separatrix and be released into the SW via magnetic reconnection, occurring in at least two main steps. We analyse data from the Nancay Radioheliograph (NRH) searching for evidence of the chain of magnetic reconnections proposed. We fi nd a noise storm above the AR and several varying sources at 150.9 MHz. Their locations suggest that they could be associated with particles accelerated during the first-step reconnection process and at a null point well outside of the AR. However, we fi nd no evidence of the second-step reconnection in the radio data. Our results demonstrate that even when it appears highly improbable for the AR plasma to reach the SW, indirect channels involving a sequence of reconnections can make it possible.

Authors: C.H. Mandrini, F.A. Nuevo, A.M. Vasquez, P. Demoulin, L. van Driel-Gesztelyi, D. Baker, J.L. Culhane, G.D. Cristiani, M. Pick
Projects: None

Publication Status: In press
Last Modified: 2014-09-25 15:58
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Topological Analysis of Emerging Bipole Clusters Producing Violent Solar Events  

Cristina H. Mandrini   Submitted: 2013-12-26 06:54

During the rising phase of Solar Cycle 24 tremendous activity occurred on the Sun with fast and compact emergence of magnetic flux leading to bursts of flares (C to M and even X-class). We investigate the violent events occurring in the cluster of two active regions (ARs), NOAA numbers 11121 and 11123, observed in November 2010 with instruments onboard the Solar Dynamics Observatory and from Earth. Within one day the total magnetic flux increased by 70% with the emergence of new groups of bipoles in AR 11123. From all the events on 11 November, we study, in particular, the ones starting at around 07:16 UT in GOES soft X-ray data and the brightenings preceding them. A magnetic-field topological analysis indicates the presence of null points, associated separatrices and quasi-separatrix layers (QSLs) where magnetic reconnection is prone to occur. The presence of null points is confirmed by a linear and a non-linear force-free magnetic-field model. Their locations and general characteristics are similar in both modelling approaches, which supports their robustness. However, in order to explain the full extension of the analysed event brightenings, which are not restricted to the photospheric traces of the null separatrices, we compute the locations of QSLs. Based on this more complete topological analysis, we propose a scenario to explain the origin of a low-energy event preceding a filament eruption, which is accompanied by a two-ribbon flare, and a consecutive confined flare in AR 11123. The results of our topology computation can also explain the locations of flare ribbons in two other events, one preceding and one following the ones at 07:16 UT. Finally, this study provides further examples where flare-ribbon locations can be explained when compared to QSLs and only, partially, when using separatrices.

Authors: C.H. Mandrini, B. Schmieder, P. Démoulin, Y. Guo, G. Cristiani
Projects: None

Publication Status: Solar Physics in press
Last Modified: 2013-12-28 04:08
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Companion Event and Precursor of the X17 Flare on 28 October, 2003  

Cristina H. Mandrini   Submitted: 2006-08-31 05:27

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.

Authors: Mandrini, C.H., Demoulin, P., Schmieder, B., DeLuca, E.E., Pariat, E., Uddin, W.
Projects: SoHO-MDI,TRACE

Publication Status: Solar Phys. (in press)
Last Modified: 2006-08-31 10:17
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Interplanetary flux rope ejected from an X-ray bright point  

Cristina H. Mandrini   Submitted: 2005-01-20 16:34

Using multi-instrument and multi-wavelength observations (SOHO/MDI and EIT, TRACE and Yohkoh/SXT), as well as computing the coronal magnetic field of a tiny bipole combined with modelling of WIND {it in situ} data, we provide evidences for the smallest event ever observed which links a sigmoid eruption to an interplanetary magnetic cloud (MC). The tiny bipole, which was observed very close to the solar disc centre, had a factor one hundred less flux than a classical active region (AR). In the corona it had a sigmoidal structure, observed mainly in EUV, and we found a very high level of non-potentiality in the modelled magnetic field, 10 times higher than we have ever found in any AR. From May 11, 1998, and until its disappearance, the sigmoid underwent three intense impulsive events. The largest of these events had extended EUV dimmings and a cusp. The WIND spacecraft detected 4.5 days later one of the smallest MC ever identified (about a factor one hundred times less magnetic flux in the axial component than that of an average MC). The link between this last eruption and the interplanetary magnetic cloud is supported by several pieces of evidence: good timing, same coronal loop and MC orientation, same magnetic field direction and magnetic helicity sign in the coronal loops and in the MC. We further quantify this link by estimating the magnetic flux (measured in the dimming regions and in the MC) and the magnetic helicity (pre- to post-event change in the solar corona and helicity content of the MC). Within the uncertainties, both magnetic fluxes and helicities are in reasonable agreement, which brings further evidences of their link. These observations show that the ejections of tiny magnetic flux ropes are indeed possible and put new constraints on CME models.

Authors: C.H. Mandrini, S. Pohjolainen, S. Dasso, L.M. Green, P. Demoulin, L. van Driel-Gesztelyi, C. Copperwheat and C. Foley
Projects: None

Publication Status: Astronomy and Astrophysics, in press
Last Modified: 2005-01-20 16:34
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Tracing Magnetic Helicity from the Solar Corona to the Interplanetary Space  

Cristina H. Mandrini   Submitted: 2005-01-20 16:24

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 hours. 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 emph{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.

Authors: M.L. Luoni, C.H. Mandrini, S. Dasso, L. van Driel-Gesztelyi and P. Demoulin
Projects: None

Publication Status: JASTP submitted
Last Modified: 2005-01-20 16:24
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Magnetic Helicity Analysis of an InterplanetaryTwisted Flux Tube  

Cristina H. Mandrini   Submitted: 2003-07-07 17:08

We compute the magnetic flux and helicity of an interplanetary flux tube observed by the spacecraft Wind on October 24-25, 1995. We investigate how model-dependent are the results by determining the flux-tube orientation using two different methods (minimum variance and a simultaneous fit), and three different models: a linear force-free field, a uniformly twisted field, and a non force-free field with constant current. We have fitted the set of free parameters for the six cases and have found that the two force-free models fit the data with very similar quality for both methods. Then, both the comparable computed parameters and global quantities, magnetic flux and helicity per unit length, agree to within 10% for the two force-free models. These results imply that the magnetic flux and helicity of the tube are well-determined quantities, nearly independent of the model used, provided that the fit to the data is good enough.

Authors: Dasso, S., Mandrini, C.H., Demoulin, P.
Projects:

Publication Status: JGR (in press)
Last Modified: 2003-07-07 17:12
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How are emerging flux, flares and CMEs related to magneticpolarity imbalance in MDI data?  

Cristina H. Mandrini   Submitted: 2003-04-03 10:55

In order to understand whether major flares or coronal mass ejections (CMEs) can be related to changes in the longitudinal photospheric magnetic field, we study 4 young active regions during seven days of their disc passage. This time period precludes any biases which may be introduced in studies that look at the field evolution during the short-term flare or CME period only. Data from the Michelson Doppler Imager (MDI) with a time cadence of 96 minutes are used. Corrections are made to the data to account for area foreshortening and angle between line of sight and field direction, and also the underestimation of the flux densities. We make a systematic study of the evolution of the longitudinal magnetic field, and analyze flare and CME occurrence in the magnetic evolution. We find that the majority of CMEs and flares occur during or after new flux emergence. The flux in all four active regions is observed to have deviations from polarity balance both on the long-term (solar rotation) and on the short term (few hours). The long-term imbalance is not due to linkage outside the active region; it is primarily related to the east-west distance from central meridian, with the sign of polarity closer to the limb dominating. The sequence of short term imbalances are not closely linked to CMEs and flares and no permanent imbalance remains after them. We propose that both kinds of imbalance are due to the presence of a horizontal field component (parallel to the photospheric surface) in the emerging flux.

Authors: Green, L.M., Demoulin, P., Mandrini, C.H. and van Driel-Gesztelyi, L.
Projects: Soho-MDI

Publication Status: Solar Phys. (in press)
Last Modified: 2003-07-07 17:15
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The role of magnetic bald patches in surges and archfilament systems  

Cristina H. Mandrini   Submitted: 2003-04-03 10:49

The short-lived active region (AR) NOAA 7968 was thoroughly observed all along its disk transit (June 3 to 10, 1996) from space and from the ground. During the early stage of its evolution, flux emerged in between the two main polarities and arch filament systems (AFS) were observed to be linked to this emergence. New bipoles and a related surge were observed on June 9. We have modeled the magnetic configuration of AR 7968 using a magnetohydrostatic approach and we have analyzed its topology on June 6 and June 9 in detail. We have found that some of the AFS and the surge were associated with field lines having dips tangent to the photosphere (the so called ``bald patches'', BPs). Two interacting BP separatrices, defining a separator, have been identified in the configuration where these very different events occurred. The observed evolution of the AFS and the surge is consistent with the expected results of magnetic reconnection occuring in this magnetic topology, which is specific to 3D configurations. Previously BPs have been found to be related to filament feet, small flares and transition region brightenings. Our results are evidence of the importance of BPs in a much wider range of phenomena, and show that current layers can be formed and efficiently dissipated in the chromosphere.

Authors: Mandrini, C.H., Demoulin, P.,Schmieder, B.,Deng, Y.Y. and Rudawy, P.
Projects: Soho-MDI

Publication Status: A&A 391, 317
Last Modified: 2003-07-07 17:17
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Abstracts by Author
Moreton and EUV Waves Associated with an X1.0 Flare and CME Ejection
Parallel Evolution of Quasi-separatrix Layers and Active Region Upflows
How Can Active Region Plasma Escape into the Solar Wind from below a Closed Helmet Streamer?
Topological Analysis of Emerging Bipole Clusters Producing Violent Solar Events
Companion Event and Precursor of the X17 Flare on 28 October, 2003
Interplanetary flux rope ejected from an X-ray bright point
Tracing Magnetic Helicity from the Solar Corona to the Interplanetary Space
Magnetic Helicity Analysis of an InterplanetaryTwisted Flux Tube
How are emerging flux, flares and CMEs related to magneticpolarity imbalance in MDI data?
The role of magnetic bald patches in surges and archfilament systems

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