Publication Date: 2017.
Context. A subclass of broad extreme ultraviolet (EUV) and X-ray jets, called blowout jets, have become a topic of research since they could be the link between standard collimated jets and coronal mass ejections (CMEs). Aims. Our aim is to understand the origin of a series of broad jets, some of which are accompanied by flares and associated with narrow and jet-like CMEs. Methods. We analyze observations of a series of recurrent broad jets observed in AR 10484 on 21?24 October 2003. In particular, one of them occurred simultaneously with an M2.4 flare on 23 October at 02:41 UT (SOLA2003-10-23). Both events were observed by the ARIES Hα Solar Tower-Telescope, TRACE, SOHO, and RHESSI instruments. The flare was very impulsive and followed by a narrow CME. A local force-free model of AR 10484 is the basis to compute its topology. We find bald patches (BPs) at the flare site. This BP topology is present for at least two days before to events. Large-scale field lines, associated with the BPs, represent open loops. This is confirmed by a global potential free source surface (PFSS) model. Following the brightest leading edge of the Hα and EUV jet emission, we can temporarily associate these emissions with a narrow CME. Results. Considering their characteristics, the observed broad jets appear to be of the blowout class. As the most plausible scenario, we propose that magnetic reconnection could occur at the BP separatrices forced by the destabilization of a continuously reformed flux rope underlying them. The reconnection process could bring the cool flux-rope material into the reconnected open field lines driving the series of recurrent blowout jets and accompanying CMEs. Conclusions. Based on a model of the coronal field, we compute the AR 10484 topology at the location where flaring and blowout jets occurred from 21 to 24 October 2003. This topology can consistently explain the origin of these events.
Author affiliation: Chandra, R.. Kumaun University; India
Author affiliation: Mandrini, Cristina Hemilse. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina
Author affiliation: Schmieder, B.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia
Author affiliation: Joshi, B.. Udaipur Solar Observatory; India
Author affiliation: Cristiani, Germán Diego. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina
Author affiliation: Cremades Fernandez, Maria Hebe. Universidad Tecnologica Nacional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Author affiliation: Pariat, E.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia
Author affiliation: Nuevo, Federico Alberto. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina
Author affiliation: Srivastava, A. K.. Indian Institute Of Technology; India
Author affiliation: Uddi, W.. Aryabhatta Research Institute of Observational Sciences; India
Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas
Publication Date: 2009.
Context. Magnetic clouds (MCs) are formed by magnetic flux ropes that are ejected from the Sun as coronal mass ejections. These structures generally have low plasma beta and travel through the interplanetary medium interacting with the surrounding solar wind. Thus, the dynamical evolution of the internal magnetic structure of a MC is a consequence of both the conditions of its environment and of its own dynamical laws, which are mainly dominated by magnetic forces.Aims. With in-situ observations the magnetic field is only measured along the trajectory of the spacecraft across the MC. Therefore, a magnetic model is needed to reconstruct the magnetic configuration of the encountered MC. The main aim of the present work is to extend the widely used cylindrical model to arbitrary cross-section shapes.Methods. The flux rope boundary is parametrized to account for a broad range of shapes. Then, the internal structure of the flux rope is computed by expressing the magnetic field as a series of modes of a linear force-free field.Results. We analyze the magnetic field profile along straight cuts through the flux rope, in order to simulate the spacecraft crossing through a MC. We find that the magnetic field orientation is only weakly affected by the shape of the MC boundary. Therefore, the MC axis can approximately be found by the typical methods previously used (e.g., minimum variance). The boundary shape affects the magnetic field strength most. The measurement of how much the field strength peaks along the crossing provides an estimation of the aspect ratio of the flux-rope cross-section. The asymmetry of the field strength between the front and the back of the MC, after correcting for the time evolution (i.e., its aging during the observation of the MC), provides an estimation of the cross-section global bending. A flat or/and bent cross-section requires a large anisotropy of the total pressure imposed at the MC boundary by the surrounding medium.Conclusions. The new theoretical model developed here relaxes the cylindrical symmetry hypothesis. It is designed to estimate the cross-section shape of the flux rope using the in-situ data of one spacecraft. This allows a more accurate determination of the global quantities, such as magnetic fluxes and helicity. These quantities are especially important for both linking an observed MC to its solar source and for understanding the corresponding evolution. © 2009 ESO.
Author affiliation: Dasso, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Keywords: Interplanetary medium; Sun: coronal mass ejections (CMEs); Sun: magnetic fields; Arbitrary cross section; Boundary shapes; Coronal mass ejection; Cylindrical models; Cylindrical symmetry; Dynamical evolution; Field strengths; Flux ropes; Global quantities; Helicities; In-situ data; In-situ observations; Internal structure; Interplanetary medium; Large anisotropy; Magnetic clouds; Magnetic configuration; Magnetic field orientations; Magnetic field profile; Magnetic field strengths; Magnetic flux ropes; Magnetic models; Minimum variance; Solar source; Sun: coronal mass ejection; Sun: magnetic field; Theoretical models; Time evolutions; Total pressure; Aspect ratio; Astrophysics; Boundary layer flow; Interplanetary spacecraft; Magnetic fields; Magnetic flux; Magnetic structure; Planetary surface analysis; Solar wind; Sun; Semiconductor counters.
Repository: Biblioteca Digital (UBA-FCEN). Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales