scholarly journals On the partial eruption of a bifurcated solar filament structure

2020 ◽  
Vol 500 (1) ◽  
pp. 684-695
Author(s):  
Aabha Monga ◽  
Rahul Sharma ◽  
Jiajia Liu ◽  
Consuelo Cid ◽  
Wahab Uddin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Extreme Ultraviolet ◽  
Free Field ◽  
Small Scale ◽  
Data Sets ◽  
Imaging Data ◽  
Filament Structure ◽  
Filament Channel ◽  
Solar Filament ◽  
Using Data

ABSTRACT The partial eruption of a filament channel with bifurcated substructures is investigated using data sets obtained from both ground-based and space-borne facilities. Small-scale flux reconnection/cancellation events in the region triggered the pile-up of ambient magnetic field, observed as bright extreme ultraviolet (EUV) loops in close proximity to the filament channel. This led to the formation of a V-shaped cusp structure at the site of interaction between the coalesced EUV loops and the filament channel, with the presence of distinct plasmoid structures and associated bidirectional flows. Analysis of imaging data from SDO/AIA further suggests vertical splitting of the filament structure into two substructures. The perturbed upper branch of the filament structure rose up and erupted with the onset of an energetic GOES M1.4 flare at 04:30 ut on 2015 January 28. The estimated twist number and squashing factor obtained from non-linear force free-field extrapolation of the magnetic field data support the vertical split in the filament structure with high twist in the upper substructure. The loss in equilibrium of the upper branch due to torus instability implies that this is a potential triggering mechanism for the observed partial eruption.

scholarly journals A small-scale EUV jet in the quiet Sun region

2012 ◽  
Vol 8 (S294) ◽  
pp. 555-559
Author(s):  
Junchao Hong ◽  
Yunchun Jiang ◽  
Ruisheng Zheng ◽  
Yi Bi
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Reconnection ◽  
Solar Atmosphere ◽  
Extreme Ultraviolet ◽  
Small Scale ◽  
Quiet Sun ◽  
Filament Channel ◽  
Field Lines ◽  
Using Data

AbstractSolar jets are typical proxies of small-scale magnetic reconnection events in the solar atmosphere. In this paper, we observe a small-scale jet in a solar quiet region, using data from SDO/Atmospheric Imaging Assembly (AIA), Helioseismic and Magnetic Imager (HMI), with supplemental data from STEREO/EUVI. From HMI magnetograms and calculated photospheric flows, we find that the jet is related to the interaction between unipolar network fields and emerging internetwork bipoles at the boundary of a supergranular cell. In AIA extreme-ultraviolet images, the jet actually includes two successive plasma ejections along different directions. The first ejection follows a distorted path which guides plasma into a small filament channel nearby. However, the second one shot straight along another direction that is parallel with extrapolated potential magnetic field lines on the local. According to these observations, we advocate that during the jet eruption new emerging magnetic fields are reconnecting at the edge of the supergranular cell with different kinds of ambient fields from low (magnetic canopy) to high (high-reaching loops) to allow the occurrence of successive ejections along different directions.

scholarly journals Eruptions from coronal hole bright points: Observations and non-potential modelling

2020 ◽  
Vol 643 ◽  
pp. A19
Author(s):  
Maria S. Madjarska ◽  
Klaus Galsgaard ◽  
Duncan H. Mackay ◽  
Kostadinka Koleva ◽  
Momchil Dechev
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Coronal Hole ◽  
Extreme Ultraviolet ◽  
Coronal Holes ◽  
Free Field ◽  
Flux Rope ◽  
Small Scale ◽  
X Ray ◽  
Lift Off

Context. We report on the third part of a series of studies on eruptions associated with small-scale loop complexes named coronal bright points (CBPs). Aims. A single case study of a CBP in an equatorial coronal hole with an exceptionally large size is investigated to expand on our understanding of the formation of mini-filaments, their destabilisation, and the origin of the eruption triggering the formation of jet-like features recorded in extreme ultraviolet (EUV) and X-ray emission. We aim to explore the nature of the so-called micro-flares in CBPs associated with jets in coronal holes and mini coronal mass ejections in the quiet Sun. Methods. Co-observations from the Atmospheric Imaging Assembly (AIA) and Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory as well as GONG Hα images are used together with a non-linear force free field (NLFFF) relaxation approach, where the latter is based on a time series of HMI line-of-sight magnetograms. Results. A mini-filament (MF) that formed beneath the CBP arcade about 3−4 h before the eruption is seen in the Hα and EUV AIA images to lift up and erupt triggering the formation of an X-ray jet. No significant photospheric magnetic flux concentration displacement (convergence) is observed and neither is magnetic flux cancellation between the two main magnetic polarities forming the CBP in the time period leading to MF lift-off. The CBP micro-flare is associated with three flare kernels that formed shortly after the MF lift-off. No observational signature is found for magnetic reconnection beneath the erupting MF. The applied NLFFF modelling successfully reproduces both the CBP loop complex as well as the magnetic flux rope that hosts the MF during the build-up to the eruption. Conclusions. The applied NLFFF modelling is able to clearly show that an initial potential field can be evolved into a non-potential magnetic field configuration that contains free magnetic energy in the region that observationally hosts the eruption. The comparison of the magnetic field structure shows that the magnetic NLFFF model contains many of the features that can explain the different observational signatures found in the evolution and eruption of the CBP. In the future, it may eventually indicate the location of destabilisation that results in the eruptions of flux ropes.

scholarly journals Detecting and Characterising Small-Scale Brightenings in Solar Imaging Data

Solar Physics ◽  
2021 ◽  
Vol 296 (9) ◽  
Author(s):  
Llŷr Dafydd Humphries ◽  
Huw Morgan ◽  
David Kuridze
Keyword(s):  
Large Scale ◽  
Extreme Ultraviolet ◽  
Small Scale ◽  
Data Sets ◽  
Imaging Data ◽  
Maximum Brightness ◽  
Quiet Sun ◽  
Band Pass ◽  
Spatio Temporal ◽  
Over Time

AbstractObservations of small-scale brightenings in the low solar atmosphere can provide valuable constraints on possible heating and heat transport mechanisms. We present a method for the detection and analysis of brightenings, and demonstrate its application to time-series imagery of the Interface Region Imaging Spectrograph (IRIS) in the extreme ultraviolet (EUV). The method is based on spatio-temporal band-pass filtering, adaptive thresholding and centroid tracking, and records an event’s spatial position, duration, total brightness and maximum brightness. Spatial area, brightness, and position are also recorded as functions of time throughout the event’s lifetime. Detected brightenings can fragment, or merge, over time – thus the number of distinct regions constituting a brightening event is recorded over time, and the maximum number of regions recorded as $N_{\mathit{frag}}$ N frag , which is a simple measure of an event’s coherence or spatial complexity. A test is made on a synthetic datacube composed of a static background based on IRIS data, Poisson noise and $\approx 10^{4}$ ≈ 10 4 randomly-distributed, moving, small-scale Gaussian brightenings. Maximum brightness, total brightness, area, and duration follow power-law distributions, and the results show the range over which the method can successfully extract information. The test shows that the recorded maximum brightness of an event is a reliable measure for the brightest and most accurately detected events, with an error of 6%. Event area, duration and speed are generally underestimated by around 15% and have an uncertainty of 20–30%. The total brightness is underestimated by 30%, and has an uncertainty of 30%. Applying this detection method to real IRIS quiet-sun data spanning 19 minutes over a $54.40''\times 55.23''$ 54.40 ″ × 55.23 ″ field of view (FOV) yields 2997 detections, 1340 of these detections either remain un-fragmented or fragment to two distinct regions at least once during their lifetime ($N_{\mathit{frag}}\le 2$ N frag ≤ 2 ), equating to an event density of $3.96\times 10^{-4}$ 3.96 × 10 − 4 arcsec−2 s−1. The method will be used for a future large-scale statistical analysis of several quiet-sun (QS) data sets from IRIS, other EUV imagers, and other types of data including H$\alpha $ α and visible photospheric imagery.

scholarly journals Power-law energy distributions of small-scale impulsive events on the active Sun: results from IRIS

2020 ◽  
Vol 499 (1) ◽  
pp. 1385-1394
Author(s):  
Nived Vilangot Nhalil ◽  
Chris J Nelson ◽  
Mihalis Mathioudakis ◽  
J Gerry Doyle ◽  
Gavin Ramsay
Keyword(s):  
Energy Range ◽  
Power Law ◽  
Coronal Heating ◽  
Radiative Energy ◽  
Small Scale ◽  
Data Sets ◽  
Imaging Data ◽  
Power Law Distribution ◽  
Energy Distributions ◽  
Power Law Index

ABSTRACT Numerous studies have analysed inferred power-law distributions between frequency and energy of impulsive events in the outer solar atmosphere in an attempt to understand the predominant energy supply mechanism in the corona. Here, we apply a burst detection algorithm to high-resolution imaging data obtained by the Interface Region Imaging Spectrograph to further investigate the derived power-law index, γ, of bright impulsive events in the transition region. Applying the algorithm with a constant minimum event lifetime (of either 60 s or 110 s) indicated that the target under investigation, such as Plage and Sunspot, has an influence on the observed power-law index. For regions dominated by sunspots, we always find γ < 2; however, for data sets where the target is a plage region, we often find that γ > 2 in the energy range (∼1023, ∼1026) erg. Applying the algorithm with a minimum event lifetime of three time-steps indicated that cadence was another important factor, with the highest cadence data sets returning γ > 2 values. The estimated total radiative power obtained for the observed energy distributions is typically 10–25 per cent of what would be required to sustain the corona indicating that impulsive events in this energy range are not sufficient to solve coronal heating. If we were to extend the power-law distribution down to an energy of 1021 erg, and assume parity between radiative energy release and the deposition of thermal energy, then such bursts could provide 25–50 per cent of the required energy to account for the coronal heating problem.

scholarly journals Flux rope, hyperbolic flux tube, and late extreme ultraviolet phases in a non-eruptive circular-ribbon flare

2017 ◽  
Vol 604 ◽  
pp. A76 ◽  
Author(s):  
Sophie Masson ◽  
Étienne Pariat ◽  
Gherardo Valori ◽  
Na Deng ◽  
Chang Liu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Flux Tube ◽  
Extreme Ultraviolet ◽  
Topological Analysis ◽  
Perfect Match ◽  
Free Field ◽  
Flux Rope ◽  
Null Point ◽  
Second Phase ◽  
Flare Loops

Context. The dynamics of ultraviolet (UV) emissions during solar flares provides constraints on the physical mechanisms involved in the trigger and the evolution of flares. In particular it provides some information on the location of the reconnection sites and the associated magnetic fluxes. In this respect, confined flares are far less understood than eruptive flares generating coronal mass ejections. Aims. We present a detailed study of a confined circular flare dynamics associated with three UV late phases in order to understand more precisely which topological elements are present and how they constrain the dynamics of the flare. Methods. We perform a non-linear force-free field extrapolation of the confined flare observed with the Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA) instruments on board Solar Dynamics Observatory (SDO). From the 3D magnetic field we compute the squashing factor and we analyse its distribution. Conjointly, we analyse the AIA extreme ultraviolet (EUV) light curves and images in order to identify the post-flare loops, and their temporal and thermal evolution. By combining the two analyses we are able to propose a detailed scenario that explains the dynamics of the flare. Results. Our topological analysis shows that in addition to a null-point topology with the fan separatrix, the spine lines and its surrounding quasi-separatix layer (QSL) halo (typical for a circular flare), a flux rope and its hyperbolic flux tube (HFT) are enclosed below the null. By comparing the magnetic field topology and the EUV post-flare loops we obtain an almost perfect match between the footpoints of the separatrices and the EUV 1600 Å ribbons and between the HFT field line footpoints and bright spots observed inside the circular ribbons. We show, for the first time in a confined flare, that magnetic reconnection occurred initially at the HFT below the flux rope. Reconnection at the null point between the flux rope and the overlying field is only initiated in a second phase. In addition, we showed that the EUV late phase observed after the main flare episode is caused by the cooling loops of different length which have all reconnected at the null point during the impulsive phase. Conclusions. Our analysis shows in one example that flux ropes are present in null-point topology not only for eruptive and jet events, but also for confined flares. This allows us to conjecture on the analogies between conditions that govern the generation of jets, confined flares or eruptive flares.

scholarly journals The EUVE Guest Investigator Science Program

1996 ◽  
Vol 152 ◽  
pp. 597-598
Author(s):  
Ken Anderson ◽  
Brett Stroozas
Keyword(s):  
Extreme Ultraviolet ◽  
Research Community ◽  
Information Services ◽  
Data Sets ◽  
Science Program ◽  
Using Data ◽  
And Training

In order to promote research using data from NASA’s Extreme Ultraviolet Explorer (EUVE) satellite, the Center for EUV Astrophysics has implemented a Guest Investigator (GI) Science Program. The purpose of the GI Program is to provide researchers with information, services, and training in the use of public EUVE data sets; in effect, it offers to the research community the technical experience and intricate knowledge of the EUVE data sets resident at CEA. All interested researchers are encouraged to participate as GIs.

scholarly journals On the structure of the magnetic field of sunspots

1968 ◽  
Vol 35 ◽  
pp. 215-229 ◽  
Author(s):  
E. I. Mogilevsky ◽  
L. B. Demkina ◽  
B. A. Ioshpa ◽  
V. N. Obridko
Keyword(s):  
Magnetic Field ◽  
Free Field ◽  
Large Field ◽  
Doppler Velocity ◽  
Small Scale ◽  
High Excitation ◽  
Proposed Model ◽  
Background Magnetic Field ◽  
Definition Of ◽  
The Magnetic Field

The model of the magnetic field of sunspots, taking account of fine structure of magnetic field in solar plasma, is considered. Small-scale subgranules with their own field form magnetic filaments in the external current-free field. The filaments are vertical in the umbra, while in the penumbra they run along the surface with sharp bends. In a number of spot umbra the relation between Doppler velocity and the field is established on polarized spectrograms. The π-component splitting in umbra is interpreted as a result of a weak background magnetic-field existence together with a large field of magnetic filaments. Spectrographic definition of the magnetic field in spot umbra is accomplished on the effect of magnetic-lines intensification and directly on spectrograms of low-excitation (Fe I, Ti I) and high-excitation (Fe II) lines. Magnetic field measured in low-excitation lines exceeds twice the field value obtained in high-excitation lines. This result has been considered in the light of the proposed model of sunspot field.

scholarly journals Three-dimensional magnetic field structure of a flux-emerging region in the solar atmosphere

2019 ◽  
Vol 632 ◽  
pp. A112 ◽  
Author(s):  
Rahul Yadav ◽  
Jaime de la Cruz Rodríguez ◽  
Carlos José Díaz Baso ◽  
Avijeet Prasad ◽  
Tine Libbrecht ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Surface ◽  
Free Field ◽  
Opposite Polarity ◽  
Field Vector ◽  
Small Scale ◽  
Maximum Height ◽  
Horizontal Magnetic Field ◽  
Point Separation ◽  
The Magnetic Field

We analyze high-resolution spectropolarimetric observations of a flux-emerging region (FER) in order to understand its magnetic and kinematic structure. Our spectropolarimetric observations in the He I 10830 Å spectral region of a FER were recorded with GRIS at the 1.5 m aperture GREGOR telescope. A Milne–Eddington-based inversion code was employed to extract the photospheric information of the Si I spectral line, whereas the He I triplet line was analyzed with the Hazel inversion code, which takes into account the joint action of the Hanle and the Zeeman effects. The spectropolarimetric analysis of the Si I line reveals a complex magnetic structure near the vicinity of the FER, where a weak (350–600 G) and horizontal magnetic field was observed. In contrast to the photosphere, the analysis of the He I triplet presents a smooth variation of the magnetic field vector (ranging from 100 to 400 G) and velocities across the FER. Moreover, we find supersonic downflows of ∼40 km s−1 appearing near the foot points of loops connecting two pores of opposite polarity, whereas strong upflows of 22 km s−1 appear near the apex of the loops. At the location of supersonic downflows in the chromosphere, we observed downflows of 3 km s−1 in the photosphere. Furthermore, nonforce-free field extrapolations were performed separately at two layers in order to understand the magnetic field topology of the FER. We determine, using extrapolations from the photosphere and the observed chromospheric magnetic field, that the average formation height of the He I triplet line is ∼2 Mm from the solar surface. The reconstructed loops using photospheric extrapolations along an arch filament system have a maximum height of ∼10.5 Mm from the solar surface with a foot-point separation of ∼19 Mm, whereas the loops reconstructed using chromospheric extrapolations reach around ∼8.4 Mm above the solar surface with a foot-point separation of ∼16 Mm at the chromospheric height. The magnetic topology in the FER suggests the presence of small-scale loops beneath the large loops. Under suitable conditions, due to magnetic reconnection, these loops can trigger various heating events in the vicinity of the FER.

scholarly journals Coronal heating and flaring in QSLs

2010 ◽  
Vol 6 (S273) ◽  
pp. 233-241 ◽  
Author(s):  
Guillaume Aulanier
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Free Field ◽  
Active Regions ◽  
Coronal Heating ◽  
Small Scale ◽  
Flux Tubes ◽  
Solar Instruments ◽  
Field Lines ◽  
New Generation

AbstractQuasi-Separatrix Layers (QSLs) are 3D geometrical objects that define narrow volumes across which magnetic field lines have strong, but finite, gradients of connectivity from one footpoint to another. QSLs extend the concept of separatrices, that are topological objects across which the connectivity is discontinuous. Based on analytical arguments, and on magnetic field extrapolations of the Sun's coronal force-free field above observed active regions, it has long since been conjectured that QSLs are favorable locations for current sheet (CS) formation, as well as for magnetic reconnection, and therefore are good predictors for the locations of magnetic energy release in flares and coronal heating. It is only up to recently that numerical MHD simulations and solar observations, as well as a laboratory experiment, have started to address the validity of these conjectures. When put all together, they suggest that QSL reconnection is involved in the displacement of EUV and SXR brightenings along chromospheric flare ribbons, that it is related with the heating of EUV coronal loops, and that the dissipation of QSL related CS may be the cause of coronal heating in initially homogeneous, braided and turbulent flux tubes, as well as in coronal arcades rooted in the slowly moving and numerous small-scale photospheric flux concentrations, both in active region faculae and in the quiet Sun. The apparent ubiquity of QSL-related CS in the Sun's corona, which will need to be quantified with new generation solar instruments, also suggests that QSLs play an important role in stellar's atmospheres, when their surface radial magnetic fields display complex patterns.

scholarly journals Magnetically coupled atmosphere, fast sausage MHD waves, and forced magnetic field reconnection during the SOL2014-09-10T17:45 flare

2020 ◽  
Vol 643 ◽  
pp. A140
Author(s):  
H. Mészárosová ◽  
P. Gömöry
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
Solar Atmosphere ◽  
Extreme Ultraviolet ◽  
Free Field ◽  
Mhd Waves ◽  
Field Energy ◽  
Plasma Flows ◽  
The Individual ◽  
The Waves

Aims. We study the physical properties and behaviour of the solar atmosphere during the GOES X1.6 solar flare on 2014 September 10. Methods. The steady plasma flows and the fast sausage MHD waves were analysed with the wavelet separation method. The magnetically coupled atmosphere and the forced magnetic field reconnection were studied with the help of the Vertical-Current Approximation Non-linear Force-Free Field code. Results. We studied a mechanism of MHD wave transfer from the photosphere without dissipation or reflection before reaching the corona and a mechanism of the wave energy distribution over the solar corona. We report a common behaviour of (extreme)ultraviolet steady plasma flows (speed of 15.3 → 10.9 km s−1) and fast sausage MHD waves (Alfvén speed of 13.7 → 10.3 km s−1 and characteristic periods of 1587 → 1607 s), propagating in cylindrical plasma waveguides of the individual atmospheric layers (photosphere → corona) observed by SDO/AIA/HMI and IRIS space instruments. A magnetically coupled solar atmosphere by a magnetic field flux tube above a sunspot umbra and a magnetic field reconnection forced by the waves were analysed. The solar seismology with trapped, leakage, and tunnelled modes of the waves, dissipating especially in the solar corona, is discussed with respect to its possible contribution to the outer atmosphere heating. Conclusions. We demonstrate that a dispersive nature of fast sausage MHD waves, which can easily generate the leaky and other modes propagating outside of their waveguide, and magnetic field flux tubes connecting the individual atmospheric layers can distribute the magnetic field energy across the active region. This mechanism can contribute to the coronal energy balance and to our knowledge on how the coronal heating is maintained.

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