scholarly journals Oscillations observed in umbra, plage, quiet-Sun and the polarity inversion line of active region 11158 using Helioseismic Magnetic Imager/Solar Dynamics Observatory data

2020 ◽  
Vol 379 (2190) ◽  
pp. 20200175 ◽  
Author(s):  
A. A. Norton ◽  
R. B. Stutz ◽  
B. T. Welsch
Keyword(s):  
Active Region ◽  
Wave Mode ◽  
Phase Relations ◽  
Doppler Velocity ◽  
Solar Dynamics Observatory ◽  
Spectra Analysis ◽  
Polarity Inversion ◽  
Quiet Sun ◽  
Polarity Inversion Line ◽  
Magnetic Oscillations

Using data from the Helioseismic Magnetic Imager, we report on the amplitudes and phase relations of oscillations in quiet-Sun, plage, umbra and the polarity inversion line (PIL) of an active region NOAA#11158. We employ Fourier, wavelet and cross-correlation spectra analysis. Waves with 5 min periods are observed in umbra, PIL and plage with common phase values of ϕ ( v , I ) =  π /2, ϕ ( v , B los ) = −( π /2). In addition, ϕ ( I , B los ) =  π in plage are observed. These phase values are consistent with slow standing or fast standing surface sausage wave modes. The line width variations, and their phase relations with intensity and magnetic oscillations, show different values within the plage and PIL regions, which may offer a way to further differentiate wave mode mechanics. Significant Doppler velocity oscillations are present along the PIL, meaning that plasma motion is perpendicular to the magnetic field lines, a signature of Alvènic waves. A time–distance diagram along a section of the PIL shows Eastward propagating Doppler oscillations converting into magnetic oscillations; the propagation speeds range between 2 and 6 km s −1 . Lastly, a 3 min wave is observed in select regions of the umbra in the magnetogram data. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.

scholarly journals Dynamics and connectivity of an extended arch filament system

2019 ◽  
Vol 629 ◽  
pp. A48 ◽  
Author(s):  
A. Diercke ◽  
C. Kuckein ◽  
C. Denker
Keyword(s):  
Near Infrared ◽  
Extreme Ultraviolet ◽  
Solar Dynamics Observatory ◽  
Polarity Inversion ◽  
Quiet Sun ◽  
Filament System ◽  
Time Period ◽  
Context Data ◽  
Polarity Inversion Line ◽  
Solar Dynamics

Aims. In this study, we analyzed a filament system, which expanded between moving magnetic features (MMFs) of a decaying sunspot and opposite flux outside of the active region from the nearby quiet-Sun network. This configuration deviated from a classical arch filament system (AFS), which typically connects two pores in an emerging flux region. Thus, we called this system an extended AFS. We contrasted classical and extended AFSs with an emphasis on the complex magnetic structure of the latter. Furthermore, we examined the physical properties of the extended AFS and described its dynamics and connectivity. Methods. The extended AFS was observed with two instruments at the Dunn Solar Telescope (DST). The Rapid Oscillations in the Solar Atmosphere (ROSA) imager provided images in three different wavelength regions, which covered the dynamics of the extended AFS at different atmospheric heights. The Interferometric Bidimensional Spectropolarimeter (IBIS) provided spectroscopic Hα data and spectropolarimetric data that was obtained in the near-infrared (NIR) Ca IIλ8542 Å line. We derived the corresponding line-of-sight (LOS) velocities and used He IIλ304 Å extreme ultraviolet (EUV) images of the Atmospheric Imaging Assembly (AIA) and LOS magnetograms of the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) as context data. Results. The NIR Ca II Stokes-V maps are not suitable to definitively define a clear polarity inversion line and to classify this chromospheric structure. Nevertheless, this unusual AFS connects the MMFs of a decaying sunspot with the network field. At the southern footpoint, we measured that the flux decreases over time. We find strong downflow velocities at the footpoints of the extended AFS, which increase in a time period of 30 min. The velocities are asymmetric at both footpoints with higher velocities at the southern footpoint. An EUV brigthening appears in one of the arch filaments, which migrates from the northern footpoint toward the southern one. This activation likely influences the increasing redshift at the southern footpoint. Conclusions. The extended AFS exhibits a similar morphology as classical AFSs, for example, threaded filaments of comparable length and width. Major differences concern the connection from MMFs around the sunspot with the flux of the neighboring quiet-Sun network, converging footpoint motions, and longer lifetimes of individual arch filaments of about one hour, while the extended AFS is still very dynamic.

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 The origin of two X-class flares in active region NOAA 12673

2018 ◽  
Vol 612 ◽  
pp. A101 ◽  
Author(s):  
Meetu Verma
Keyword(s):  
Active Region ◽  
Magnetic Polarity ◽  
Horizontal Flow ◽  
Flare Activity ◽  
Active Region Noaa ◽  
Positive Polarity ◽  
Polarity Inversion ◽  
Vector Magnetograms ◽  
Polarity Inversion Line ◽  
Region Noaa

Flare-prolific active region NOAA 12673 produced consecutive X2.2 and X9.3 flares on the 6 September 2017. To scrutinize the morphological, magnetic, and horizontal flow properties associated with these flares, a seven-hour time series was used consisting of continuum images, line-of-sight and vector magnetograms, and 1600 Å UV images. These data were acquired with the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA). The white-light flare emission differed for both flares, while the X2.2 flare displayed localized, confined flare kernels, the X9.3 flare exhibited a two-ribbon structure. In contrast, the excess UV emission exhibited a similar structure for both flares, but with larger areal extent for the X9.3 flare. These two flares represented a scenario in which the first confined flare acted as precursor, setting up the stage for the more extended flare. Difference maps for continuum and magnetograms revealed locations of significant changes, that is, penumbral decay and umbral strengthening. The curved magnetic polarity inversion line in the δ-spot was the fulcrum of most changes. Horizontal proper motions were computed using the differential affine velocity estimator for vector magnetograms (DAVE4VM). Persistent flow features included (1) strong shear flows along the polarity inversion line, where the negative, parasitic polarity tried to bypass the majority, positive-polarity part of the δ-spot in the north, (2) a group of positive-polarity spots, which moved around the δ-spot in the south, moving away from the δ-spot with significant horizontal flow speeds, and (3) intense moat flows partially surrounding the penumbra of several sunspots, which became weaker in regions with penumbral decay. The enhanced flare activity has its origin in the head-on collision of newly emerging flux with an already existing regular, α-spot. Umbral cores of emerging bipoles were incorporated in its penumbra, creating a δ-configuration with an extended polarity inversion line, as the parasitic umbral cores were stretched while circumventing the majority polarity.

scholarly journals A persistent quiet-Sun small-scale tornado

2020 ◽  
Vol 643 ◽  
pp. A166
Author(s):  
K. Tziotziou ◽  
G. Tsiropoula ◽  
I. Kontogiannis
Keyword(s):  
Time Series ◽  
Phase Difference ◽  
Vortex Flow ◽  
Wave Mode ◽  
Doppler Velocity ◽  
Small Scale ◽  
Time Interval ◽  
Difference Analysis ◽  
Quiet Sun ◽  
Wave Modes

Context. Vortex flows can foster a variety of wave modes. A recent oscillatory analysis of a persistent 1.7 h vortex flow with a significant substructure has suggested the existence of various types of waves within it. Aims. We investigate the nature and characteristics of waves within this quiet-Sun vortex flow, over the course of an uninterrupted 48-min observing time interval, in order to better understand its physics and dynamics. Methods. We used a cross-wavelet spectral analysis between pairs of Hα and Ca II 8542 Å intensity time series at different wavelengths and, hence, atmospheric heights, acquired with the CRisp Imaging SpectroPolarimeter at the Swedish Solar Telescope, as well as the derived Hα Doppler velocity and full width at half maximum time series. We constructed halftone frequency-phase difference plots and investigated the existence and propagation characteristics of different wave modes. Results. Our analysis suggests the existence of Alfvénic type waves within the vortex flow that propagate upwards with phase speeds of ∼20–30 km s−1. The dominant wave mode seems to be the fast kink wave mode, however, our analysis also suggests the existence of localised Alfvénic torsional waves, which are related to the dynamics of individual chromospheric swirls that characterise the substructure of the vortex flow. The Hα V–I phase difference analysis seems to imply the existence of a standing wave pattern that is possibly arising from the interference of upwards propagating kink waves with downwards propagating ones that are reflected at the transition region or the corona. Moreover, the results provide further evidence that the central chromospheric swirl drives the dynamics of the vortex flow. Conclusions. This is the first exhaustive phase difference analysis within a vortex flow that explores the nature and dynamics of different wave modes within it. The question, however, of whether, and how, the dissipation of the derived wave modes occurs remains open, and given that such structures are ubiquitous on the solar surface, it’s also important to investigate whether they might ultimately play a significant role in the energy budget of the upper layers of the solar atmosphere.

scholarly journals Photospheric vortex flows close to the polarity inversion line of a fully emerged active region

2019 ◽  
Author(s):  
Jean C. Santos ◽  
Cristiano M. Wrasse
Keyword(s):  
Active Region ◽  
Flow Field ◽  
Critical Points ◽  
Jacobian Matrix ◽  
Line Of Sight ◽  
Geometrical Analysis ◽  
Polarity Inversion ◽  
Average Value ◽  
Polarity Inversion Line ◽  
The One

Abstract. We report on the occurrence of vortexes in flow fields obtained from the evolution of the line-of-sight component of the photospheric magnetic field in a region around the polarity inversion line of a fully emerged active region. Based on a local linear approximation for the flow field, we identify the presence of critical points and classify them according to the eigenvalues of the Jacobian matrix of the linear transformation. Vortexes are associated to the presence of a particular kind of critical point, known as Attracting Focus. Using this method we identified twelve vortexes in the analyzed period and detected the occurrence of other types of critical points, which indicate the complexity of the flow field around the PIL. The detected vortexes show a clockwise preferred sense of rotation with approximately 67 % of the cases. A geometrical analysis of the velocity structures produced an average value of D = 1.63 ± 0.05 for the fractal dimension, which is very close to the one obtained for isotropic homogeneous turbulence (D = 5/3). This suggests that the flow around the polarity inversion line is turbulent in nature.

scholarly journals Magnetic reconnection between an emerging active region and the quiet Sun

2015 ◽  
Vol 11 (S320) ◽  
pp. 185-190
Author(s):  
Bin Zhang ◽  
Jun Zhang ◽  
Shuhong Yang ◽  
Ting Li ◽  
Yuzong Zhang ◽  
...  
Keyword(s):  
Active Region ◽  
Magnetic Reconnection ◽  
Extreme Ultraviolet ◽  
Solar Dynamics Observatory ◽  
Quiet Sun ◽  
Quiet Region ◽  
Released Energy ◽  
Solar Dynamics ◽  
Ultraviolet Observations

AbstractUsing the Solar Dynamics Observatory observations, we study the evolution of an emerging active region (EAR) and its reconnection with the quiet Sun. The EAR continuously interacts with the surrounding quiet region, and dark ribbons at the boundary of the EAR and the quiet Sun are observed. The extreme-ultraviolet observations show that the regions swept by the dark ribbons are brightened and the temperature increases. These results reveal that there exists an uninterrupted magnetic reconnection between the EAR and the quiet region and the released energy heats the corona of the quiet Sun. The dark ribbons are suggested to correspond to the interface of the reconnected fields and the undisturbed ones. The dark ribbon propagates outward, and this phenomenon is considered as a dark wave.

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 Converging photospheric vortex flows close to the polarity inversion line of a fully emerged active region

2019 ◽  
Vol 37 (4) ◽  
pp. 603-612
Author(s):  
Jean C. Santos ◽  
Cristiano M. Wrasse
Keyword(s):  
Active Region ◽  
Flow Field ◽  
Critical Points ◽  
Jacobian Matrix ◽  
Line Of Sight ◽  
Geometrical Analysis ◽  
Polarity Inversion ◽  
Average Value ◽  
Polarity Inversion Line ◽  
The One

Abstract. We report on the occurrence of vortexes in flow fields obtained from the evolution of the line-of-sight component of the photospheric magnetic field in a region around the polarity inversion line (PIL) of a fully emerged active region. Based on a local linear approximation for the flow field, we identify the presence of critical points and classify them according to the eigenvalues of the Jacobian matrix of the linear transformation. Converging vortexes are associated with the presence of a particular kind of critical point, known as the attracting focus. We identified 12 converging vortexes in the analyzed period and detected the occurrence of other types of critical points, which indicate the complexity of the flow field around the PIL. The detected vortexes show a clockwise preferred sense of rotation with approximately 67 % of the cases. A geometrical analysis of the velocity structures produced an average value of D‾=1.63±0.05 for the fractal dimension, which is very close to the one obtained for isotropic homogeneous turbulence (D=5/3). This suggests that the flow around the PIL is turbulent in nature.

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