Fil: Mandrini, Cristina Hemilse. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Astronomia y Fisica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomia y Fisica del Espacio; Argentina

https://www.lesia.obspm.fr/perso/pascal-demoulin/07/mandrini07-dimmings.pdf

Are CME-Related Dimmings Always a Simple Signature of Interplanetary Magnetic Cloud Footpoints?

Magnetic clouds (MCs), and more generally, interplanetary coronal mass ejections (ICMEs), are believed to be the interplanetary counterparts of CMEs. The link has usually been shown by taking into account the CME launch position on the Sun, the expected time delay and by comparing the orientation of the coronal and interplanetary magnetic field. Making such a link more quantitative is challenging since it requires a relation between very different kinds of magnetic field measurements: (i) photospheric magnetic maps, which are observed from a distant vantage point (remote sensing) and (ii) in-situ measurements of MCs, which provide precise, directly measured, magnetic field data merely from one-dimensional linear samples. The association between events in these different domains can be made using adequate coronal and MC models. Then, global quantities like magnetic fluxes and helicity can be derived and compared. This review paper describes all the general trends found in the above association criteria. A special focus is given for the cases which do not follow the earlier derived mean laws since interesting physics is usually involved.

/pdf/a-review-of-the-quantitative-links-between-cmes-and-magnetic-4w39fuxk6z.pdf

A review of the quantitative links between CMEs and magnetic clouds

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.

/pdf/companion-event-and-precursor-of-the-x17-flare-on-28-october-8c7e37iiv2.pdf

Companion event and precursor of the x17 flare on 28 october 2003

We studied the behavior of magnetic field, horizontal motion and helicity in a fast emerging flux region NOAA 10488 which eventually forms a δ spot. It is found that the rotation of photospheric footpoints forms in the earlier stage of magnetic flux emergence and the relative shear motion of different magnetic flux systems appears later in this active region (AR). Therefore the emerging process of the AR can be separated into two phases: rotation and shear. We have computed the magnetic helicity injected into the corona using the local correlation tracking (LCT) technique. Furthermore we determined the vertical component of current helicity density and the vertical component of induction electric fields Ez = (V× B)z in the photosphere. Particularly we have presented the comparison of the injection rate of magnetic helicity and the variation of the current helicity density. The main results are as follows: (1) The strong shear motion (SSM) between the new emerging flux system and the old one brings more magnetic helicity into the corona than the twisting motions. (2) After the maturity of the main bipolar spots, their twist decreases and the SSM becomes dominant and the major contributor of magnetic non-potentiality in the solar atmosphere in this AR. (3) The positions of the maxima of Ez (about 0.1 ∼ 0.2 V cm−1) shift from the twisting areas to the areas showing SSMs as the AR evolved from the rotation phase to the shear one, but no obvious correlation is found between the kernels of Hα flare and Ez for the M1.6 flare in this AR. (4) The coronal helicity inferred from the horizontal motion of this AR amounts to −6 × 1043 Mx2. It is comparable with the coronal helicity of ARs producing flares with coronal mass ejections (CMEs) or helicity carried away by magnetic clouds (MCs) reported in previous studies (Nindos, Zhang, and Zhang, 2003; Nindos and Andrews, 2004). In addition, the formation of the δ configuration in this AR belongs to the third formation type indicated by Zirin and Liggett (1987), i.e., collision of opposite polarities from different dipoles, and can be naturally explained by the SSM.

The Magnetic Field, Horizontal Motion and Helicity in a Fast Emerging Flux Region which Eventually forms a Delta Spot

The Transition Region and Coronal Explorer (TRACE) satellite, launched 2 April 1998, is a NASA Small Explorer (SMEX) that images the solar photosphere, transition region and corona with unprecedented spatial resolution and temporal continuity. To provide continuous coverage of solar phenomena, TRACE is located in a sun-synchronous polar orbit. The ∼700 Mbytes of data which are collected daily are made available for unrestricted use within a few days of observation. The instrument features a 30-cm Cassegrain telescope with a field of view of 8.5×.5 arc min and a spatial resolution of 1 arc sec (0.5 arc sec pixels). TRACE contains multilayer optics and a lumogen-coated CCD detector to record three EUV wavelengths and several UV wavelengths. It observes plasmas at selected temperatures from 6000 K to 10 MK with a typical temporal resolution of less than 1 min.

The Transition Region and Coronal Explorer

We analyze the magnetic configurations of three super active regions, NOAA 10484, 10486 and 10488, observed by the Huairou Multi-Channel Solar Tele- scope (MCST) from 2003 October 18 to November 4. Many energetic phenomena, such as flares (including a X-28 flare) and coronal mass ejections (CMEs), occurred during this period. We think that strong shear and fast emergence of magnetic flux are the main causes of these events. The question is also of great interest why these dramatic eruptions occurred so close together in the descending phase of the solar cycle.

http://iopscience.iop.org/article/10.1088/1009-9271/3/6/491/pdf

Three Super Active Regions in the Descending Phase of Solar Cycle 23

On July 14, 2000, a powerful solar flare(X5.7/3B) associated with a violent halo CME launched in active region NOAA 9077 near the solar disk center. By using the time sequence of the solar photospheric vector magnetograms and H β chromspheric magnetograms, and H β filtergrams from Huairou Solar Observing Station(HSOS), we explored the causes of the flares eruption. We found that the occurrence of reversed polarity strucures (RPSs) in vector magnetic fields were closely related to the eruption of X5.7/3B flare and surge, and they should be the key ingredient to the high flare-productivity of sunspot group, especially, number and extent of the occurrences of the RPS in a active region could determine the solar event level.

Wei Li

Papers

Three Super Active Regions in the Descending Phase of Solar Cycle 23

Reversed polarity structures and powerful X5.7/3B flare on July 14, 2000