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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>
Danilovic, S.,Solanki, S. K.,Barthol, P.,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Riethmü,ller, T. L.,van Noort, M.,Rodrí,guez, J. Blanco,Del Toro Iniesta, J. C.,Suá,rez, D. Orozco,Schmi American Astronomical Society 2017 The Astrophysical journal, Supplement series Vol.229 No.1
<P>Ellerman Bombs are signatures of magnetic reconnection, which is an important physical process in the solar atmosphere. How and where they occur is a subject of debate. In this paper, we analyze SUNRISE/IMaX data, along with 3D MHD simulations that aim to reproduce the exact scenario proposed for the formation of these features. Although the observed event seems to be more dynamic and violent than the simulated one, simulations clearly confirm the basic scenario for the production of EBs. The simulations also reveal the full complexity of the underlying process. The simulated observations show that the Fe I 525.02 nm line gives no information on the height where reconnection takes place. It can only give clues about the heating in the aftermath of the reconnection. However, the information on the magnetic field vector and velocity at this spatial resolution is extremely valuable because it shows what numerical models miss and how they can be improved.</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>
SUNRISE: INSTRUMENT, MISSION, DATA, AND FIRST RESULTS
Solanki, S. K.,Barthol, P.,Danilovic, S.,Feller, A.,Gandorfer, A.,Hirzberger, J.,Riethmü,ller, T. L.,Schü,ssler, M.,Bonet, J. A.,Pillet, V. Martí,nez,del Toro Iniesta, J. C.,Domingo, V. IOP Publishing 2010 ASTROPHYSICAL JOURNAL LETTERS - Vol.723 No.2
Magneto-static Modeling from Sunrise/IMaX: Application to an Active Region Observed with Sunrise II
Wiegelmann, T.,Neukirch, T.,Nickeler, D. H.,Solanki, S. K.,Barthol, P.,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Riethmü,ller, T. L.,Noort, M. van,Rodrí,guez, J. Blanco,Iniesta, J. C. Del Toro American Astronomical Society 2017 The Astrophysical journal Supplement series Vol.229 No.1
<P>Magneto-static models may overcome some of the issues facing force-free magnetic field extrapolations. So far they have seen limited use and have faced problems when applied to quiet-Sun data. Here we present a first application to an active region. We use solar vector magnetic field measurements gathered by the IMaX polarimeter during the flight of the SUNRISE balloon-borne solar observatory in 2013 June as boundary conditions for a magneto-static model of the higher solar atmosphere above an active region. The IMaX data are embedded in active region vector magnetograms observed with SDO/HMI. This work continues our magneto-static extrapolation approach, which was applied earlier to a quiet-Sun region observed with SUNRISE I. In an active region the signal-to-noise-ratio in the measured Stokes parameters is considerably higher than in the quiet-Sun and consequently the IMaX measurements of the horizontal photospheric magnetic field allow us to specify the free parameters of the model in a special class of linear magneto-static equilibria. The high spatial resolution of IMaX (110-130 km, pixel size 40 km) enables us to model the non-force-free layer between the photosphere and the mid-chromosphere vertically by about 50 grid points. In our approach we can incorporate some aspects of the mixed beta layer of photosphere and chromosphere, e.g., taking a finite Lorentz force into account, which was not possible with lower-resolution photospheric measurements in the past. The linear model does not, however, permit us to model intrinsic nonlinear structures like strongly localized electric currents.</P>
Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields
Chitta, L. P.,Peter, H.,Solanki, S. K.,Barthol, P.,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Riethmü,ller, T. L.,Noort, M. van,Rodrí,guez, J. Blanco,Iniesta, J. C. Del Toro,Suá,rez, D. Or American Astronomical Society 2017 The Astrophysical journal, Supplement series Vol.229 No.1
<P>How and where are coronal loops rooted in the solar lower atmosphere? The details of the magnetic environment and its evolution at the footpoints of coronal loops are crucial to understanding the processes of mass and energy supply to the solar corona. To address the above question, we use high-resolution line-of-sight magnetic field data from the Imaging Magnetograph eXperiment instrument on the SUNRISE balloon-borne observatory and coronal observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory of an emerging active region. We find that the coronal loops are often rooted at the locations with minor small-scale but persistent opposite-polarity magnetic elements very close to the larger dominant polarity. These opposite-polarity small-scale elements continually interact with the dominant polarity underlying the coronal loop through flux cancellation. At these locations we detect small inverse Y-shaped jets in chromospheric Ca II H images obtained from the SUNRISE Filter Imager during the flux cancellation. Our results indicate that magnetic flux cancellation and reconnection at the base of coronal loops due to mixed polarity fields might be a crucial feature for the supply of mass and energy into the corona.</P>