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A Tale of Two Emergences: Sunrise II Observations of Emergence Sites in a Solar Active Region
Centeno, R.,Rodrí,guez, J. Blanco,Del Toro Iniesta, J. C.,Solanki, S. K.,Barthol, P.,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Riethmü,ller, T. L.,Noort, M. van,Suá,rez, D. Orozco,Berkefe American Astronomical Society 2017 The Astrophysical journal Supplement series Vol.229 No.1
<P>In 2013 June, the two scientific instruments on. board the second SUNRISE mission witnessed, in detail, a small-scale magnetic flux emergence event as part of the birth of an active region. The Imaging Magnetograph Experiment (IMaX) recorded two small (similar to 5 '') emerging flux patches in the polarized filtergrams of a photospheric Fe I spectral line. Meanwhile, the SUNRISE Filter Imager (SuFI) captured the highly dynamic chromospheric response to the magnetic fields pushing their way through the lower solar atmosphere. The serendipitous capture of this event offers a closer look at the inner workings of active region emergence sites. In particular, it reveals in meticulous detail how the rising magnetic fields interact with the granulation as they push through the Sun's surface, dragging photospheric plasma in their upward travel. The plasma that is burdening the rising field slides along the field lines, creating fast downflowing channels at the footpoints. The weight of this material anchors this field to the surface at semi-regular spatial intervals, shaping it in an undulatory fashion. Finally, magnetic reconnection enables the field to release itself from its photospheric anchors, allowing it to continue its voyage up to higher layers. This process releases energy that lights up the arch-filament systems and heats the surrounding chromosphere.</P>
Magnetic field emergence in mesogranular-sized exploding granules observed with sunrise/IMaX data
Palacios, J.,Blanco Rodrí,guez, J.,Vargas Domí,nguez, S.,Domingo, V.,Martí,nez Pillet, V.,Bonet, J. A.,Bellot Rubio, L. R.,Iniesta, J. C. del Toro,Solanki, S. K.,Barthol, P.,Gandorfe EDP Sciences 2012 Astronomy and astrophysics Vol.537 No.-
<P>We report on magnetic field emergences covering significant areas of exploding granules. The balloon-borne mission SUNRISE provided high spatial and temporal resolution images of the solar photosphere. Continuum images, longitudinal and transverse magnetic field maps and Dopplergrams obtained by IMaX onboard SUNRISE are analyzed by local correlation traking (LCT), divergence calculation and time slices, Stokes inversions and numerical simulations are also employed. We characterize two mesogranular-scale exploding granules where~10<SUP>18</SUP> Mx of magnetic flux emerges. The emergence of weak unipolar longitudinal fields (~100 G) start with a single visible magnetic polarity, occupying their respective granules’ top and following the granular splitting. After a while, mixed polarities start appearing, concentrated in downflow lanes. The events last around 20 min. LCT analyses confirm mesogranular scale expansion, displaying a similar pattern for all the physical properties, and divergence centers match between all of them. We found a similar behaviour with the emergence events in a numerical MHD simulation. Granule expansion velocities are around 1 kms<SUP>−1</SUP> while magnetic patches expand at 0.65 kms<SUP>−1</SUP>. One of the analyzed events evidences the emergence of a loop-like structure. Advection of the emerging magnetic flux features is dominated by convective motion resulting from the exploding granule due to the magnetic field frozen in the granular plasma. Intensification of the magnetic field occurs in the intergranular lanes, probably because of being directed by the downflowing plasma.</P>
The Maximum Entropy Limit of Small-scale Magnetic Field Fluctuations in the Quiet Sun
Gorobets, A. Y.,Berdyugina, S. V.,Riethmü,ller, T. L.,Rodrí,guez, J. Blanco,Solanki, S. K.,Barthol, P.,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Noort, M. van,Del Toro Iniesta, J. C.,Suá American Astronomical Society 2017 The Astrophysical journal Supplement series Vol.233 No.1
<P>The observed magnetic field on the solar surface is characterized by a very complex spatial and temporal behavior. Although feature-tracking algorithms have allowed us to deepen our understanding of this behavior, subjectivity plays an important role in the identification and tracking of such features. In this paper, we continue studies of the temporal stochasticity of the magnetic field on the solar surface without relying either on the concept of magnetic features or on subjective assumptions about their identification and interaction. We propose a data analysis method to quantify fluctuations of the line-of-sight magnetic field by means of reducing the temporal field's evolution to the regular Markov process. We build a representative model of fluctuations converging to the unique stationary (equilibrium) distribution in the long time limit with maximum entropy. We obtained different rates of convergence to the equilibrium at fixed noise cutoff for two sets of data. This indicates a strong influence of the data spatial resolution and mixing-polarity fluctuations on the relaxation process. The analysis is applied to observations of magnetic fields of the relatively quiet areas around an active region carried out during the second flight of the SUNRISE/IMAX and quiet Sun areas at the disk center from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory satellite.</P>
Transverse Oscillations in Slender Ca ii H Fibrils Observed with Sunrise/SuFI
Jafarzadeh, S.,Solanki, S. K.,Gafeira, R.,Noort, M. van,Barthol, P.,Rodrí,guez, J. Blanco,Iniesta, J. C. del Toro,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Knö,lker, M.,Suá,rez, D. Orozco American Astronomical Society 2017 The Astrophysical journal, Supplement series Vol.229 No.1
<P>We present observations of transverse oscillations in slender Ca II H fibrils (SCFs) in the lower solar chromosphere. We use a 1 hr long time series of high- (spatial and temporal-) resolution. seeing-free observations in a 1.1 angstrom wide passband covering the line core of Ca II H 3969 angstrom from the second flight of the SUNRISE balloon-borne solar observatory. The entire field of view, spanning the polarity inversion line of an active region close to the solar disk center, is covered with bright, thin, and very dynamic fine structures. Our analysis reveals the prevalence of transverse waves in SCFs with median amplitudes and periods on the order of 2.4 +/- 0.8 km s(-1) and 83 +/- 29 s, respectively (with standard deviations given as uncertainties). We find that the transverse waves often propagate along (parts of) the SCFs with median phase speeds of 9 +/- 14 km s(-1). While the propagation is only in one direction along the axis in some of the SCFs, propagating waves in both directions, as well as standing waves are also observed. The transverse oscillations are likely Alfvenic and are thought to be representative of magnetohydrodynamic kink waves. The wave propagation suggests that the rapid. high-frequency transverse waves,. often produced in the lower photosphere, can penetrate into the chromosphere. with an estimated energy flux of approximate to 15 kW m(-2). Characteristics of these waves differ from those reported for other fibrillar structures, which, however, were observed mainly in the upper solar chromosphere.</P>
Kinematics of Magnetic Bright Features in the Solar Photosphere
Jafarzadeh, S.,Solanki, S. K.,Cameron, R. H.,Barthol, P.,Rodrí,guez, J. Blanco,Iniesta, J. C. del Toro,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Knö,lker, M.,Pillet, V. Martí,nez,Su&aacut American Astronomical Society 2017 The Astrophysical journal Supplement series Vol.229 No.1
<P>Convective flows are known as the prime means of transporting magnetic fields on the solar surface. Thus, small magnetic structures are good tracers of turbulent flows. We study the migration and dispersal of magnetic bright features (MBFs) in intergranular areas observed at high spatial resolution with SUNRISE/IMaX. We describe the flux dispersal of individual MBFs as a diffusion process whose parameters are computed for various areas in the quiet-Sun and the vicinity of active regions from seeing-free data. We find that magnetic concentrations are best described as random walkers close to network areas (diffusion index, gamma = 1.0), travelers with constant speeds over a supergranule (gamma = 1.9-2.0), and decelerating movers in the vicinity of flux emergence and/or within active regions (gamma = 1.4-1.5). The three types of regions host MBFs with mean diffusion coefficients of 130 km(2) s(-1), 80-90 km(2) s(-1), and 25-70 km(2) s(-1), respectively. The MBFs in these three types of regions are found to display a distinct kinematic behavior at a confidence level in excess of 95%.</P>
Spectropolarimetric Evidence for a Siphon Flow along an Emerging Magnetic Flux Tube
Requerey, Iker S.,Cobo, B. Ruiz,Iniesta, J. C. Del Toro,Suá,rez, D. Orozco,Rodrí,guez, J. Blanco,Solanki, S. K.,Barthol, P.,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Riethmü,ller, T. L.,N American Astronomical Society 2017 The Astrophysical journal Supplement series Vol.229 No.1
<P>We study the dynamics and topology of an emerging magnetic flux concentration using high spatial resolution spectropolarimetric data acquired with the Imaging Magnetograph eXperiment on board the SUNRISE balloon-borne solar observatory. We obtain the full vector magnetic field and the line of sight (LOS) velocity through inversions of the Fe I line at 525.02 nm with the SPINOR code. The derived vector magnetic field is used to trace magnetic field lines. Two magnetic flux concentrations with different polarities and LOS velocities are found to be connected by a group of arch-shaped magnetic field lines. The positive polarity footpoint is weaker (1100 G) and displays an upflow, while the negative polarity footpoint is stronger (2200 G) and shows a downflow. This configuration is naturally interpreted as a siphon flow along an arched magnetic flux tube.</P>
Morphological Properties of Slender Ca ${\rm{II}}$ H Fibrils Observed by Sunrise II
Gafeira, R.,Lagg, A.,Solanki, S. K.,Jafarzadeh, S.,Noort, M. van,Barthol, P.,Rodrí,guez, J. Blanco,Iniesta, J. C. del Toro,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Knö,lker, M.,Suá,rez, American Astronomical Society 2017 The Astrophysical journal Supplement series Vol.229 No.1
<P>We use seeing-free high spatial resolution Ca II H data obtained by the SUNRISE observatory to determine properties of slender fibrils in the lower solar chromosphere. In this work we use intensity images taken with the SUFI instrument in the Ca II H line during the second scientific flight of the SUNRISE observatory to identify and track elongated bright structures. After identification, we analyze theses structures to extract their morphological properties. We identify 598 slender Ca II H fibrils (SCFs) with an average width of around 180 km, length between 500 and 4000 km, average lifetime of approximate to 400 s, and average curvature of 0.002 arcsec(-1). The maximum lifetime of the SCFs within our time series of 57 minutes is approximate to 2000 s. We discuss similarities and differences of the SCFs with other small-scale, chromospheric structures such as spicules of type I and II, or Ca II K fibrils.</P>
Oscillations on Width and Intensity of Slender Ca ii H Fibrils from Sunrise/SuFI
Gafeira, R.,Jafarzadeh, S.,Solanki, S. K.,Lagg, A.,van Noort, M.,Barthol, P.,Rodrí,guez, J. Blanco,del Toro Iniesta, J. C.,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Knö,lker, M.,Suá,rez, American Astronomical Society 2017 The Astrophysical journal, Supplement series Vol.229 No.1
<P>We report the detection of oscillations in slender Ca II H fibrils (SCFs) from high-resolution observations acquired with the SUNRISE balloon-borne solar observatory. The SCFs show obvious oscillations in their intensity, but also their width. The oscillatory behaviors are investigated at several positions along the axes of the SCFs. A large majority of fibrils show signs of oscillations in intensity. Their periods and phase speeds are analyzed using a wavelet analysis. The width and intensity perturbations have overlapping distributions of the wave period. The obtained distributions have median values of the period of 32 +/- 17 s and 36 +/- 25 s, respectively. We find that the fluctuations of both parameters propagate in the SCFs with speeds of 11(-11)(+49)+ km s(-1) and 15(-15)(+34) km s(-1), respectively. Furthermore, the width and intensity oscillations have a strong tendency to be either in anti-phase. or, to a smaller extent, in phase. This suggests that the oscillations of both parameters are caused by the same wave mode and that the waves are likely propagating. Taking all the evidence together, the most likely wave mode to explain all measurements and criteria is the fast sausage mode.</P>
A New MHD-assisted Stokes Inversion Technique
Riethmü,ller, T. L.,Solanki, S. K.,Barthol, P.,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Noort, M. van,Rodrí,guez, J. Blanco,Iniesta, J. C. Del Toro,Suá,rez, D. Orozco,Schmidt, W.,Pillet, American Astronomical Society 2017 The Astrophysical journal Supplement series Vol.229 No.1
<P>We present a new method of Stokes inversion of spectropolarimetric data and evaluate it by taking the example of a SUNRISE/IMaX observation. An archive of synthetic Stokes profiles is obtained by the spectral synthesis of stateof- the-art magnetohydrodynamics (MHD) simulations and a realistic degradation to the level of the observed data. The definition of a merit function allows the archive to be searched for the synthetic Stokes profiles that best match the observed profiles. In contrast to traditional Stokes inversion codes, which solve the Unno-Rachkovsky equations for the polarized radiative transfer numerically and fit the Stokes profiles iteratively, the new technique provides the full set of atmospheric parameters. This gives us the ability to start an MHD simulation that takes the inversion result as an initial condition. After a relaxation process of half an hour solar time we obtain physically consistent MHD data sets with a target similar to the observation. The new MHD simulation is used to repeat the method in a second iteration, which further improves the match between observation and simulation, resulting in a factor of 2.2 lower mean chi(2) value. One advantage of the new technique is that it provides the physical parameters on a geometrical height scale. It constitutes a first step toward inversions that give results consistent with the MHD equations.</P>
Moving Magnetic Features Around a Pore
Kaithakkal, A. J.,Riethmü,ller, T. L.,Solanki, S. K.,Lagg, A.,Barthol, P.,Gandorfer, A.,Gizon, L.,Hirzberger, J.,vanNoort, M.,Rodrí,guez, J. Blanco,Iniesta, J. C. Del Toro,Suá,rez, D. American Astronomical Society 2017 The Astrophysical journal, Supplement series Vol.229 No.1
<P>Spectropolarimetric observations from SUNRISE/IMaX, obtained in 2013 June, are used for a statistical analysis to determine the physical properties of moving magnetic features (MMFs) observed near a pore. MMFs of the same and opposite polarity, with respect to the pore, are found to stream from its border at an average speed of 1.3 km s(-1) and 1.2 km s(-1), respectively, with mainly same-polarity MMFs found further away from the pore. MMFs of both polarities are found to harbor rather weak, inclined magnetic fields. Opposite-polarity MMFs are blueshifted, whereas same-polarity MMFs do not show any preference for up-or downflows. Most of the MMFs are found to be of sub-arcsecond size and carry a mean flux of similar to 1.2 x 10(17) Mx.</P>