scholarly journals Observations of photospheric magnetic structure below a dark filament using the Hinode Spectro-Polarimeter

2019 ◽  
Vol 71 (2) ◽  
Author(s):  
Takaaki Yokoyama ◽  
Yukio Katsukawa ◽  
Masumi Shimojo
Keyword(s):  
Magnetic Structure ◽  
Flux Rope ◽  
Transverse Field ◽  
Optical Telescope ◽  
Polarity Inversion ◽  
Normal Orientation ◽  
Normal Polarity ◽  
East Limb ◽  
Polarity Inversion Line ◽  
Dark Filament

Abstract The structure of the photospheric vector magnetic field below a dark filament on the Sun is studied using the observations of the Spectro-Polarimeter attached to the Solar Optical Telescope onboard Hinode. Special attention is paid to discriminating between two suggested models, a flux rope or a bent arcade. “Inverse polarity” orientation is possible below the filament in a flux rope, whereas “normal polarity” can appear in both models. We study a filament in the active region NOAA 10930, which appeared on the solar disk during 2006 December. The transverse field perpendicular to the line of sight has a direction almost parallel to the filament spine with a shear angle of 30°, the orientation of which includes the 180° ambiguity. To know whether it is in the normal orientation or in the inverse one, the center-to-limb variation is used for the solution under the assumption that the filament does not drastically change its magnetic structure during the passage. When the filament is near the east limb, we found that the line-of-site magnetic component below the filament is positive, while it is negative near the west limb.This change of sign indicates that the horizontal photospheric field perpendicular to the polarity inversion line beneath the filament has an “inverse-polarity”, which indicates a flux-rope structure of the filament supporting field.

scholarly journals Evolution of Plasma Composition in an Eruptive Flux Rope

2022 ◽  
Vol 924 (1) ◽  
pp. 17
Author(s):  
D. Baker ◽  
L. M. Green ◽  
D. H. Brooks ◽  
P. Démoulin ◽  
L. van Driel-Gesztelyi ◽  
...  
Keyword(s):  
Magnetic Energy ◽  
Flux Rope ◽  
Plasma Composition ◽  
Imaging Spectrometer ◽  
Polarity Inversion ◽  
Magnetic Flux Ropes ◽  
Flux Ropes ◽  
Free Magnetic Energy ◽  
Polarity Inversion Line ◽  
Euv Imaging

Abstract Magnetic flux ropes are bundles of twisted magnetic field enveloping a central axis. They harbor free magnetic energy and can be progenitors of coronal mass ejections (CMEs). However, identifying flux ropes on the Sun can be challenging. One of the key coronal observables that has been shown to indicate the presence of a flux rope is a peculiar bright coronal structure called a sigmoid. In this work, we show Hinode EUV Imaging Spectrometer observations of sigmoidal active region (AR) 10977. We analyze the coronal plasma composition in the AR and its evolution as a sigmoid (flux rope) forms and erupts as a CME. Plasma with photospheric composition was observed in coronal loops close to the main polarity inversion line during episodes of significant flux cancellation, suggestive of the injection of photospheric plasma into these loops driven by photospheric flux cancellation. Concurrently, the increasingly sheared core field contained plasma with coronal composition. As flux cancellation decreased and a sigmoid/flux rope formed, the plasma evolved to an intermediate composition in between photospheric and typical AR coronal compositions. Finally, the flux rope contained predominantly photospheric plasma during and after a failed eruption preceding the CME. Hence, plasma composition observations of AR 10977 strongly support models of flux rope formation by photospheric flux cancellation forcing magnetic reconnection first at the photospheric level then at the coronal level.

scholarly journals New data-driven method of simulating coronal mass ejections

2019 ◽  
Vol 626 ◽  
pp. A91 ◽  
Author(s):  
Cheng’ao Liu ◽  
Tao Chen ◽  
Xinhua Zhao
Keyword(s):  
Magnetic Field ◽  
Coronal Mass Ejections ◽  
Three Dimensional ◽  
Flux Rope ◽  
Mhd Equations ◽  
Data Driven ◽  
Flux Emergence ◽  
Polarity Inversion ◽  
Polarity Inversion Line ◽  
The Magnetic Field

Context. Coronal mass ejections (CMEs) are large eruptions of plasma and magnetic field from the Sun’s corona. Understanding the evolution of the CME is important to evaluate its impact on space weather. Using numerical simulation, we are able to reproduce the occurrence and evolution process of the CME. Aims. The aim of this paper is to provide a new data-driven method to mimic the coronal mass ejections. By using this method, we can investigate the phsical mechanisms of the flux rope formation and the cause of the CME eruption near the real background. Methods. Starting from a potential magnetic field extrapolation, we have solved a full set of magnetohydrodynamic (MHD) equations by using the conservation element and solution element (CESE) numerical method. The bottom boundary is driven by the vector magnetograms obtained from SDO/HMI and vector velocity maps derived from DAVE4VM method. Results. We present a three-dimensional numerical MHD data-driven model for the simulation of the CME that occurred on 2015 June 22 in the active region NOAA 12371. The numerical results show two elbow-shaped loops formed above the polarity inversion line (PIL), which is similar to the tether-cutting picture previously proposed. The temporal evolutions of magnetic flux show that the sunspots underwent cancellation and flux emergence. The signature of velocity field derived from the tracked magnetograms indicates the persistent shear and converging motions along the PIL. The simulation shows that two elbow-shaped loops were reconnected and formed an inverse S-shaped sigmoid, suggesting the occurrence of the tether-cutting reconnection, which was supported by observations of the Atmospheric Imaging Assembly (AIA) telescope. Analysis of the decline rate of the magnetic field indicates that the flux rope reached a region where the torus instability was triggered. Conclusions. We conclude that the eruption of this CME was caused by multiple factors, such as photosphere motions, reconnection, and torus instability. Moreover, our simulation successfully reproduced the three-component structures of typical CMEs.

scholarly journals FIP bias in a sigmoidal active region

2013 ◽  
Vol 8 (S300) ◽  
pp. 222-226
Author(s):  
D. Baker ◽  
D. H. Brooks ◽  
P. Démoulin ◽  
Lidia van Driel-Gesztelyi ◽  
L. M. Green ◽  
...  
Keyword(s):  
Active Region ◽  
Ionization Potential ◽  
Coronal Hole ◽  
Flux Rope ◽  
Field Of View ◽  
Large Field ◽  
Polarity Inversion ◽  
Spatially Resolved ◽  
Polarity Inversion Line ◽  
First Ionization Potential

AbstractWe investigate first ionization potential (FIP) bias levels in an anemone active region (AR) - coronal hole (CH) complex using an abundance map derived from Hinode/EIS spectra. The detailed, spatially resolved abundance map has a large field of view covering 359″ × 485″. Plasma with high FIP bias, or coronal abundances, is concentrated at the footpoints of the AR loops whereas the surrounding CH has a low FIP bias, ~1, i.e. photospheric abundances. A channel of low FIP bias is located along the AR's main polarity inversion line containing a filament where ongoing flux cancellation is observed, indicating a bald patch magnetic topology characteristic of a sigmoid/flux rope configuration.

scholarly journals Rapid changes of sunspot structure associated with solar eruptions

2010 ◽  
Vol 6 (S273) ◽  
pp. 15-20
Author(s):  
Haimin Wang ◽  
Chang Liu
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Transverse Field ◽  
Line Of Sight ◽  
Polarity Inversion ◽  
Rapid Changes ◽  
Solar Eruptions ◽  
Polarity Inversion Line ◽  
Coronal Field

AbstractIn this paper we summarize the studies of flare-related changes of photospheric magnetic fields. When vector magnetograms are available, we always find an increase of transverse field at the polarity inversion line (PIL). We also discuss 1 minute cadence line-of-sight MDI magnetogram observations, which usually show prominent changes of magnetic flux contained in the flaring δ spot region. The observed limb-ward flux increases while disk-ward flux decreases rapidly and irreversibly after flares. These observations provides evidences, either direct or indirect, for the theory and prediction of Hudson, Fisher & Welsch (2008) that the photospheric magnetic fields would respond to coronal field restructuring and turn to a more horizontal state near the PIL after eruptions. From the white-light observations, we find that at flaring PIL, the structure becomes darker after an eruption, while the peripheral penumbrae decay. Using high-resolution Hinode data, we find evidence that only dark fibrils in the “uncombed” penumbral structure disappear while the bright grains evolve to G-band bright points after flares.

scholarly journals Observations of flux rope formation prior to coronal mass ejections

2013 ◽  
Vol 8 (S300) ◽  
pp. 209-214 ◽  
Author(s):  
Lucie M. Green ◽  
Bernhard Kliem
Keyword(s):  
Magnetic Flux ◽  
Magnetic Structure ◽  
Solar Atmosphere ◽  
Coronal Mass Ejections ◽  
Flux Rope ◽  
Active Regions ◽  
Magnetic Configuration ◽  
Magnetic Flux Rope ◽  
Source Regions ◽  
Flux Ropes

AbstractUnderstanding the magnetic configuration of the source regions of coronal mass ejections (CMEs) is vital in order to determine the trigger and driver of these events. Observations of four CME productive active regions are presented here, which indicate that the pre-eruption magnetic configuration is that of a magnetic flux rope. The flux ropes are formed in the solar atmosphere by the process known as flux cancellation and are stable for several hours before the eruption. The observations also indicate that the magnetic structure that erupts is not the entire flux rope as initially formed, raising the question of whether the flux rope is able to undergo a partial eruption or whether it undergoes a transition in specific flux rope configuration shortly before the CME.

scholarly journals Vector Magnetic Fields at the Base of Filaments and the Filament Environment

1998 ◽  
Vol 167 ◽  
pp. 98-101 ◽  
Author(s):  
Jingxiu Wang ◽  
Wei Li
Keyword(s):  
Magnetic Fields ◽  
Magnetic Structure ◽  
Field Gradient ◽  
Neutral Line ◽  
Transverse Field ◽  
Line Of Sight ◽  
Horizontal Gradient ◽  
Major Fraction ◽  
Flux System ◽  
Magnetic Neutral Line

AbstractBased on an analysis of three active filaments in AR 6891, we find that vector magnetic fields at the base of filaments and the filament environment is characterized by the following: (1) The transverse field is parallel along the magnetic neutral line for most of the filaments. The average transverse field beneath the filaments is more than 400 G. (2) The horizontal gradient of the line-of-sight field crossing the neutral line is, more or less, constant along the major fraction of a filament, but very steep at the two ends. The average gradient is 0.06 G/km. (3) For each of the filaments there is a squeezing magnetic structure which represents an intrusion of a satellite bipole into the main flux system. The neutral line for a squeezing magnetic structure has a large curvature, a strong sheared transverse field of more than 1 KG, and a steep field gradient of approximate 0.3 G/km. (4) The transverse field and field gradient are clearly enhanced before the filament eruption.

scholarly journals Evolution of Stokes V area asymmetry related to a quiet Sun cancellation observed with GRIS/IFU

2020 ◽  
Vol 634 ◽  
pp. A131
Author(s):  
A. J. Kaithakkal ◽  
J. M. Borrero ◽  
C. E. Fischer ◽  
C. Dominguez-Tagle ◽  
M. Collados
Keyword(s):  
Magnetic Flux ◽  
Opposite Polarity ◽  
Disk Center ◽  
Significant Rise ◽  
Polarity Inversion ◽  
Quiet Sun ◽  
Additional Information ◽  
Line Core ◽  
Polarity Inversion Line ◽  
Field Unit

A quiet Sun magnetic flux cancellation event at the disk center was recorded using the Integral Field Unit (IFU) mounted on the GREGOR Infrared Spectrograph (GRIS). The GRIS instrument sampled the event in the photospheric Si I 10827 Å spectral line. The cancellation was preceded by a significant rise in line core intensity and excitation temperature, which is inferred from Stokes inversions under local thermodynamic equilibrium (LTE). The opposite polarity features seem to undergo reconnection above the photosphere. We also found that the border pixels neighboring the polarity inversion line of one of the polarities exhibit a systematic variation of area asymmetry. Area asymmetry peaks right after the line core intensity enhancement and gradually declines thereafter. Analyzing Stokes profiles recorded from either side of the polarity inversion line could therefore potentially provide additional information on the reconnection process related to magnetic flux cancellation. Further analysis without assuming LTE will be required to fully characterize this event.

scholarly journals Where Do Solar Filaments Form?

2013 ◽  
Vol 8 (S300) ◽  
pp. 445-446 ◽  
Author(s):  
Duncan H Mackay ◽  
Victor Gaizauskas ◽  
Anthony R. Yeates
Keyword(s):  
Magnetic Flux ◽  
Large Scale ◽  
Polarity Inversion ◽  
Solar Filaments ◽  
Polarity Inversion Line

AbstractIn the present study, we consider where large, stable solar filaments form relative to underlying magnetic polarities. We find that 92% of all large stable filaments form in magnetic configurations involving the interaction of two or more bipoles. Only 7% form above the Polarity Inversion Line (PIL) of a single bipole. This indicates that a key element in the formation of large-scale stable filaments is the convergence of magnetic flux, resulting in either flux cancellation or coronal reconnection.

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