Author name code: jafarzadeh ADS astronomy entries on 2022-09-14 =author:"Jafarzadeh, S." OR =author:"Jafarzadeh, Shahin" ------------------------------------------------------------------------ Title: Propagation of transverse waves in the solar chromosphere probed at different heights with ALMA sub-bands Authors: Guevara Gómez, Juan Camilo; Jafarzadeh, Shahin; Wedemeyer, Sven; Szydlarski, Mikolaj Bibcode: 2022arXiv220812070G Altcode: The Atacama Large Millimeter/sub-millimeter Array (ALMA) has provided us with an excellent diagnostic tool for studies of the dynamics of the Solar chromosphere, albeit through a single receiver band at one time presently. Each ALMA band consists of four sub-bands that are comprised of several spectral channels. To date, however, the spectral domain has been neglected in favour of ensuring optimal imaging, so that time-series observations have been mostly limited to full-band data products, thereby limiting studies to a single chromospheric layer. Here, we report the first observations of a dynamical event (i.e. wave propagation) for which the ALMA Band 3 data (centred at 3\,mm; 100\,GHz) is split into a lower and an upper sideband. In principle, this approach is aimed at mapping slightly different layers in the Solar atmosphere. The side-band data were reduced together with the Solar ALMA Pipeline (SoAP), resulting in time series of brightness-temperature maps for each side-band. Through a phase analysis of a magnetically quiet region, where purely acoustic waves are expected to dominate, the average height difference between the two side-bands is estimated as $73\pm16$~km. Furthermore, we examined the propagation of transverse waves in small-scale bright structures by means of wavelet phase analysis between oscillations at the two atmospheric heights. We find 6\% of the waves to be standing, while 54\% and 46\% of the remaining waves are propagating upwards and downwards, respectively, with absolute propagating speeds on the order of $\approx96$~km/s, resulting in a mean energy flux of $3800$\,W/m$^2$. Title: Investigating of the nature of magnetic oscillations associated with FIP effect Authors: Murabito, Mariarita; Jafarzadeh, Shahin; Van Driel-Gesztelyi, Lidia; Ermolli, Ilaria; Baker, Deborah; Brooks, David; Long, David; Jess, David; Valori, Gherardo; Stangalini, Marco Bibcode: 2022cosp...44.2591M Altcode: Observations of the photosphere, chromosphere, and corona combined with magnetic field modeling of one of the biggest sunspots of the 24 solar cycle, revealed that regions of high FIP bias plasma in the corona were magnetically linked to the locations of the intrinsic magnetic oscillations in the solar chromosphere. In order to characterize the driver of the oscillations, we analyzed the relation between the spatial distribution of the magnetic wave power and the overall field geometry and plasma parameters obtained from the multi-height spectropolarimetric non-local thermodynamic equilibrium (NLTE) inversions. In correspondence with the locations where the magnetic wave energy is observed at chromospheric heights, we found evidence in support of locally excited acoustic waves that, after crossing the equipartition layer located close to the umbra-penumbra boundary at photospheric heights, are converted into magnetic-like waves. These results indicate a direct connection between sunspot chromospheric activity and observable changes in coronal plasma composition, demonstrating the power of high resolution, multi-height studies of the solar atmosphere that will become the gold standard in the era of DKIST. Title: Characterisation of bright chromospheric and oscillating small-scale features observed with ALMA Authors: Guevara Gómez, Juan Camilo; Jafarzadeh, Shahin; Wedemeyer, Sven Bibcode: 2022cosp...44.2549G Altcode: Small-scale chromospheric bright features exhibiting oscillations in brightness temperature, size and horizontal velocity were identified and traced in both solar ALMA observations in Bands 3 ($\sim$3 mm) and 6 ($\sim$1.2 mm) and in a Bifrost simulation resembling the ALMA observation. In total, 492 and 175 features were present in the observations and simulation respectively. Particularly, an anti-correlation between brightness temperature and size is present in the oscillations which might imply that these features are associated with fast-sausage MHD modes. We have performed a wavelet analysis to quantify the periods of oscillation for these three quantities as well as the phase angles between temperature and size. The outcome of a statistical analysis shows that the found periods correspond to high frequency oscillations in photosphere and chromosphere by diagnostics at other wavelengths. We have also estimated the energy carried by these waves and discussed the results from a statistical point of view. Specifically, we compared the outcomes between the the two ALMA frequency bands as they are considered to be formed at distinct heights and used the simulation to discuss the context of the observational results. Title: Quantifying Properties of Photospheric Magnetic Cancellations in the Quiet Sun Internetwork Authors: Ledvina, Vincent E.; Kazachenko, Maria D.; Criscuoli, Serena; Tilipman, Dennis; Ermolli, Ilaria; Falco, Mariachiara; Guglielmino, Salvatore; Jafarzadeh, Shahin; van der Voort, Luc Rouppe; Zuccarello, Francesca Bibcode: 2022ApJ...934...38L Altcode: 2022arXiv220604644L We analyzed spectropolarimetric data from the Swedish 1 m Solar Telescope to investigate the physical properties of small-scale magnetic cancellations in the quiet Sun photosphere. Specifically, we looked at the full Stokes polarization profiles along the Fe I 557.6 nm and of the Fe I 630.1 nm lines measured by the CRisp Imaging SpectroPolarimeter to study the temporal evolution of the line-of-sight magnetic field during 42.5 minutes of quiet Sun evolution. From this magnetogram sequence, we visually identified 38 cancellation events. We then used the Yet Another Feature Tracking Algorithm to characterize the physical properties of these magnetic cancellations. We found on average 1.6 × 1016 Mx of magnetic flux canceled in each event with an average cancellation rate of 3.8 × 1014 Mx s-1. The derived canceled flux is associated with strong downflows, with an average speed of V LOS ≍ 1.1 km s-1. Our results show that the average lifetime of each event is 9.2 minutes with an average of 44.8% of initial magnetic flux being canceled. Our estimates of magnetic fluxes provide a lower limit since studied magnetic cancellation events have magnetic field values that are very close to the instrument noise level. We observed no horizontal magnetic fields at the cancellation sites and therefore cannot conclude whether the events are associated with structures that could cause magnetic reconnection. Title: High frequency waves in chromospheric spicules Authors: Bate, William; Nakariakov, Valery; Jafarzadeh, Shahin; Jess, David; Stangalini, Marco; Grant, Samuel; Keys, Peter; Christian, Damian; Keenan, Francis Bibcode: 2022cosp...44.2548B Altcode: Using high cadence observations from the Hydrogen-alpha Rapid Dynamics camera imaging system on the Dunn Solar Telescope, we present an investigation of the statistical properties of transverse oscillations in spicules captured above the solar limb. At five equally separated atmospheric heights, spanning approximately $4900-7500$~km, we have detected a total of $15{\,}959$ individual wave events, with a mean displacement amplitude of $151\pm 124$~km, a mean period of $54\pm 45$~s, and a mean projected velocity amplitude of $21\pm 13$~km{\,}s$^{-1}$. We find that both the displacement and velocity amplitudes increase with height above the solar limb, ranging from $132\pm 111$~km and $17.7\pm 10.6$~km{\,}s$^{-1}$ at $\approx4900$~km, and $168\pm 125$~km and $26.3\pm 14.1$~km{\,}s$^{-1}$ at $\approx7500$~km, respectively. Following the examination of neighboring oscillations in time and space, we find 45% of the waves to be upwardly propagating, 49% to be downwardly propagating, and 6% to be standing, with mean absolute phase velocities for the propagating waves on the order of $75-150$~km{\,}s$^{-1}$. While the energy flux of the waves propagating downwards does not appear to depend on height, we find the energy flux of the upwardly propagating waves decreases with atmospheric height at a rate of $-13{\,}200\pm6500$~W{\,}m$^{-2}$/Mm. As a result, this decrease in energy flux as the waves propagate upwards may provide significant thermal input into the local plasma. Title: The identification of magnetic perturbations in the solar atmosphere Authors: Stangalini, Marco; Jafarzadeh, Shahin; Baker, Deborah; Jess, David; Murabito, Mariarita; Valori, Gherardo Bibcode: 2022cosp...44.2590S Altcode: Magneto-hydrodynamic (MHD) waves and, in particular, magnetic perturbations associated with specific wave modes are thought to be important mechanisms not only for the heating of the outer layers of the Sun's atmosphere, but also for the elemental abundance anomaly observed in the corona. High resolution spectropolarimetry is nowadays progressively extending to the upper layers of the solar atmosphere, and this provides invaluable insight into MHD wave processes up to chromospheric heights. However, the identification of real magnetic perturbations remains a difficult task due to a number of spurious effects that can mimic the signals associated with them. In this contribution we will show a novel approach to the identification of real magnetic oscillations potentially linked to FIP and discuss proxies to be used in statistical analyses. Title: High-frequency Waves in Chromospheric Spicules Authors: Bate, W.; Jess, D. B.; Nakariakov, V. M.; Grant, S. D. T.; Jafarzadeh, S.; Stangalini, M.; Keys, P. H.; Christian, D. J.; Keenan, F. P. Bibcode: 2022ApJ...930..129B Altcode: 2022arXiv220304997B Using high-cadence observations from the Hydrogen-alpha Rapid Dynamics camera imaging system on the Dunn Solar Telescope, we present an investigation of the statistical properties of transverse oscillations in spicules captured above the solar limb. At five equally separated atmospheric heights, spanning approximately 4900-7500 km, we have detected a total of 15,959 individual wave events, with a mean displacement amplitude of 151 ± 124 km, a mean period of 54 ± 45 s, and a mean projected velocity amplitude of 21 ± 13 km s-1. We find that both the displacement and velocity amplitudes increase with height above the solar limb, ranging from 132 ± 111 km and 17.7 ± 10.6 km s-1 at ≍4900 km, and 168 ± 125 km and 26.3 ± 14.1 km s-1 at ≍7500 km, respectively. Following the examination of neighboring oscillations in time and space, we find 45% of the waves to be upwardly propagating, 49% to be downwardly propagating, and 6% to be standing, with mean absolute phase velocities for the propagating waves on the order of 75-150 km s-1. While the energy flux of the waves propagating downwards does not appear to depend on height, we find the energy flux of the upwardly propagating waves decreases with atmospheric height at a rate of -13,200 ± 6500 W m-2/Mm. As a result, this decrease in energy flux as the waves propagate upwards may provide significant thermal input into the local plasma. Title: Power distribution of oscillations in the atmosphere of a plage region. Joint observations with ALMA, IRIS, and SDO Authors: Narang, Nancy; Chandrashekhar, Kalugodu; Jafarzadeh, Shahin; Fleck, Bernhard; Szydlarski, Mikołaj; Wedemeyer, Sven Bibcode: 2022A&A...661A..95N Altcode: 2022arXiv220211547N Context. Joint observations of the Atacama Large Millimeter/Submillimeter Array (ALMA) with other solar observatories can provide a wealth of opportunities for understanding the coupling between different layers of the solar atmosphere.
Aims: We present a statistical analysis of the power distribution of oscillations in a plage region in active region NOAA AR12651, which was observed jointly with ALMA, the Interface Region Imaging Spectrograph (IRIS), and the Solar Dynamics Observatory (SDO).
Methods: We employ coordinated ALMA Band 6 (1.25 mm) brightness temperature maps, IRIS slit-jaw images in the 2796 Å passband, and observations in six passbands (1600 Å, 304 Å, 131 Å, 171 Å, 193 Å, and 211 Å) from the Atmospheric Imaging Assembly (AIA) on board SDO. We perform Lomb-Scargle transforms to study the distribution of oscillation power by means of dominant period maps and power maps. We study the spatial association of oscillations through the atmosphere, with a focus on the correlation of the power distribution of ALMA oscillations with others.
Results: We do not observe any significant association of ALMA oscillations with IRIS and AIA oscillations. While the global behavior of the dominant ALMA oscillations shows a similarity with that of the transition region and coronal passbands of AIA, the ALMA dominant period maps and power maps do not show any correlation with those from the other passbands. The spatial distribution of dominant periods and power in different period intervals of ALMA oscillations is uncorrelated with those of any other passbands.
Conclusions: We speculate that the non-association of ALMA oscillations with those of IRIS and AIA is due to significant variations in the height of formation of the millimeter continuum observed by ALMA. Additionally, the fact that ALMA directly maps the brightness temperature, in contrast to the intensity observations by IRIS and AIA, can result in the very different intrinsic nature of the ALMA oscillations compared to the IRIS and AIA oscillations. Title: The Solar ALMA Science Archive (SALSA). First release, SALAT, and FITS header standard Authors: Henriques, Vasco M. J.; Jafarzadeh, Shahin; Guevara Gómez, Juan Camilo; Eklund, Henrik; Wedemeyer, Sven; Szydlarski, Mikołaj; Haugan, Stein Vidar H.; Mohan, Atul Bibcode: 2022A&A...659A..31H Altcode: 2021arXiv210902374H In December 2016, the Atacama Large Millimeter/submillimeter Array (ALMA) carried out the first regular observations of the Sun. These early observations and the reduction of the respective data posed a challenge due to the novelty and complexity of observing the Sun with ALMA. The difficulties with producing science-ready, time-resolved imaging products in a format familiar to and usable by solar physicists based on the measurement sets delivered by ALMA had limited the availability of such data to this point. With the development of the Solar ALMA Pipeline, it has now become possible to routinely reduce such data sets. As a result, a growing number of science-ready solar ALMA data sets are now offered in the form of the Solar ALMA Science Archive (SALSA). So far, SALSA contains primarily time series of single-pointing interferometric images at cadences of one or two seconds, accompanied by the respective single-dish full-disc solar images. The data arrays are provided in FITS format. We also present the first version of a standardised header format that accommodates future expansions and fits within the scope of other standards including the ALMA Science Archive itself and SOLARNET. The headers include information designed to aid the reproduction of the imaging products from the raw data. Links to co-observations, if available, with a focus on those of the Interface Region Imaging Spectrograph, are also provided. SALSA is accompanied by the Solar ALMA Library of Auxiliary Tools (SALAT), which contains Interactive Data Language and Python routines for convenient loading and a quick-look analysis of SALSA data.

Movies associated to Figs. 3 and 4 are available at https://www.aanda.org Title: The Importance of Horizontal Poynting Flux in the Solar Photosphere Authors: Silva, Suzana S. A.; Murabito, Mariarita; Jafarzadeh, Shahin; Stangalini, Marco; Verth, Gary; Ballai, Istvan; Fedun, Viktor Bibcode: 2022ApJ...927..146S Altcode: 2022arXiv220301221S The electromagnetic energy flux in the lower atmosphere of the Sun is a key tool to describe the energy balance of the solar atmosphere. Current investigations on energy flux in the solar atmosphere focus primarily on the vertical electromagnetic flux through the photosphere, ignoring the Poynting flux in other directions and its possible contributions to local heating. Based on a realistic Bifrost simulation of a quiet-Sun (coronal hole) atmosphere, we find that the total electromagnetic energy flux in the photosphere occurs mainly parallel to the photosphere, concentrating in small regions along intergranular lanes. Thereby, it was possible to define a proxy for this energy flux based on only variables that can be promptly retrieved from observations, namely, horizontal velocities of the small-scale magnetic elements and their longitudinal magnetic flux. Our proxy accurately describes the actual Poynting flux distribution in the simulations, with the electromagnetic energy flux reaching 1010 erg cm-2 s-1. To validate our findings, we extended the analysis to SUNRISE/IMaX data. First, we show that Bifrost realistically describes photospheric quiet-Sun regions, as the simulation presents similar distributions for line-of-sight magnetic flux and horizontal velocity field. Second, we found very similar horizontal Poynting flux proxy distributions for the simulated photosphere and observational data. Our results also indicate that the horizontal Poynting flux in the observations is considerably larger than the vertical electromagnetic flux from previous observational estimates. Therefore, our analysis confirms that the electromagnetic energy flux in the photosphere is mainly horizontal and is most intense in localized regions along intergranular lanes. Title: Large scale coherent magnetohydrodynamic oscillations in a sunspot Authors: Stangalini, M.; Verth, G.; Fedun, V.; Aldhafeeri, A. A.; Jess, D. B.; Jafarzadeh, S.; Keys, P. H.; Fleck, B.; Terradas, J.; Murabito, M.; Ermolli, I.; Soler, R.; Giorgi, F.; MacBride, C. D. Bibcode: 2022NatCo..13..479S Altcode: Although theoretically predicted, the simultaneous excitation of several resonant modes in sunspots has not been observed. Like any harmonic oscillator, a solar magnetic flux tube can support a variety of resonances, which constitute the natural response of the system to external forcing. Apart from a few single low order eigenmodes in small scale magnetic structures, several simultaneous resonant modes were not found in extremely large sunspots. Here we report the detection of the largest-scale coherent oscillations observed in a sunspot, with a spectrum significantly different from the Sun's global acoustic oscillations, incorporating a superposition of many resonant wave modes. Magnetohydrodynamic numerical modeling agrees with the observations. Our findings not only demonstrate the possible excitation of coherent oscillations over spatial scales as large as 30-40 Mm in extreme magnetic flux regions in the solar atmosphere, but also paves the way for their diagnostic applications in other astrophysical contexts. Title: Investigating the origin of magnetic perturbations associated with the FIP Effect Authors: Murabito, M.; Stangalini, M.; Baker, D.; Valori, G.; Jess, D. B.; Jafarzadeh, S.; Brooks, D. H.; Ermolli, I.; Giorgi, F.; Grant, S. D. T.; Long, D. M.; van Driel-Gesztelyi, L. Bibcode: 2021A&A...656A..87M Altcode: 2021arXiv210811164M Recently, magnetic oscillations were detected in the chromosphere of a large sunspot and found to be linked to the coronal locations where a first ionization potential (FIP) effect was observed. In an attempt to shed light on the possible excitation mechanisms of these localized waves, we further investigate the same data by focusing on the relation between the spatial distribution of the magnetic wave power and the overall field geometry and plasma parameters obtained from multi-height spectropolarimetric non-local thermodynamic equilibrium (NLTE) inversions of IBIS data. We find, in correspondence with the locations where the magnetic wave energy is observed at chromospheric heights, that the magnetic fields have smaller scale heights, meaning faster expansions of the field lines, which ultimately results in stronger vertical density stratification and wave steepening. In addition, the acoustic spectrum of the oscillations at the locations where magnetic perturbations are observed is broader than that observed at other locations, which suggests an additional forcing driver to the p-modes. Analysis of the photospheric oscillations in the sunspot surroundings also reveals a broader spectrum between the two opposite polarities of the active region (the leading spot and the trailing opposite polarity plage), and on the same side where magnetic perturbations are observed in the umbra. We suggest that strong photospheric perturbations between the two polarities are responsible for this broader spectrum of oscillations, with respect to the p-mode spectrum, resulting in locally excited acoustic waves that, after crossing the equipartition layer, located close to the umbra-penumbra boundary at photopheric heights, are converted into magnetic waves and steepen due to the strong density gradient.

Movie associated to Fig. 1 is available at https://www.aanda.org Title: On horizontal Poynting flux in the solar photosphere Authors: Silva, Suzana; Murabito, Mariarita; Jafarzadeh, Shahin; Stangalini, Marco; Verth, Gary; Ballai, Istvan; Fedun, Viktor Bibcode: 2021AGUFMSH44A..03S Altcode: Describing the solar atmospheric energy balance and transport is an essential step to understanding the high temperatures of the upper atmosphere. This work analyses the 3D electromagnetic energy flux in the lower atmosphere by combining Bifrost radiative MHD simulations and Sunrise/IMaX data. Based on a simulated quiet Sun atmosphere, it was found that only a minor fraction of the Poynting flux propagates upwards in the photosphere. Most of the total electromagnetic energy flows parallel to the solar surface, concentrating energy in small regions along the intergranular lanes. The dominance of the horizontal component of the electromagnetic energy flux allows an approximation for the horizontal Poynting flux, which is based solely on the horizontal velocity and the vertical magnetic field. The proxy to the horizontal Poynting flux provides a very similar distribution of the total Poynting flux and can describe the total flux for most of the photosphere with a small relative error, <30%, in regions with an intense concentration of electromagnetic energy. The results of the numerical data analysis were validated by using observational data. First, it was shown that both Bifrost and IMAX/sunrise data presents similar distributions for line-of-sight magnetic field and velocity field, indicating that the simulation realistically describes a quiet Sun region. The horizontal Poynting flux proxy provided very similar distributions for the numerical and observational data, which is considerably larger than previous observational estimates for upwards electromagnetic flux. Thereby, those findings corroborate that the electromagnetic energy flux in the photosphere is mainly parallel to the solar surface and can be properly described by approximated Poynting flux, based only on the horizontal plasma flow and the vertical magnetic field. The results also indicate that small scale intergranular motion may be important to describe the properties of Poynting flux. Therefore, further investigations based on the high-resolution data from DKIST will be important for a valuable description of the energy transport in the lower atmosphere. Title: The Sun at millimeter wavelengths. III. Impact of the spatial resolution on solar ALMA observations Authors: Eklund, Henrik; Wedemeyer, Sven; Szydlarski, Mikołaj; Jafarzadeh, Shahin Bibcode: 2021A&A...656A..68E Altcode: 2021arXiv210913826E Context. Interferometric observations of the Sun with the Atacama Large Millimeter/sub-millimeter Array (ALMA) provide valuable diagnostic tools for studying the small-scale dynamics of the solar atmosphere.
Aims: The aims are to perform estimations of the observability of the small-scale dynamics as a function of spatial resolution for regions with different characteristic magnetic field topology facilitate a more robust analysis of ALMA observations of the Sun.
Methods: A three-dimensional model of the solar atmosphere from the radiation-magnetohydrodynamic code Bifrost was used to produce high-cadence observables at millimeter and submillimeter wavelengths. The synthetic observables for receiver bands 3-10 were degraded to the angular resolution corresponding to ALMA observations with different configurations of the interferometric array from the most compact, C1, to the more extended, C7. The observability of the small-scale dynamics was analyzed in each case. The analysis was thus also performed for receiver bands and resolutions that are not commissioned so far for solar observations as a means for predicting the potential of future capabilities.
Results: The minimum resolution required to study the typical small spatial scales in the solar chromosphere depends on the characteristic properties of the target region. Here, a range from quiet Sun to enhanced network loops is considered. Limited spatial resolution affects the observable signatures of dynamic small-scale brightening events in the form of reduced brightness temperature amplitudes, potentially leaving them undetectable, and even shifts in the times at which the peaks occur of up to tens of seconds. Conversion factors between the observable brightness amplitude and the original amplitude in the fully resolved simulation are provided that can be applied to observational data in principle, but are subject to wavelength-dependent uncertainties. Predictions of the typical appearance at the different combinations of receiver band, array configuration, and properties of the target region are conducted.
Conclusions: The simulation results demonstrate the high scientific potential that ALMA already has with the currently offered capabilities for solar observations. For the study of small-scale dynamic events, however, the spatial resolution is still crucial, and wide array configurations are preferable. In any case, it is essential to take the effects due to limited spatial resolution into account in the analysis of observational data. Finally, the further development of observing capabilities including wider array configurations and advanced imaging procedures yields a high potential for future ALMA observations of the Sun. Title: Penumbral decay observed in active region NOAA 12585 Authors: Murabito, M.; Guglielmino, S. L.; Ermolli, I.; Romano, P.; Jafarzadeh, S.; Rouppe van der Voort, L. H. M. Bibcode: 2021A&A...653A..93M Altcode: 2021arXiv210604936M Context. The physical conditions leading the sunspot penumbra decay are poorly understood so far.
Aims: We investigate the photospheric magnetic and velocity properties of a sunspot penumbra during the decay phase to advance the current knowledge of the conditions leading to this process.
Methods: A penumbral decay was observed with the CRISP instrument at the Swedish 1 m Solar Telescope on 2016 September 4 and 5 in the active region NOAA 12585. During these days, full-Stokes spectropolarimetric scans along the Fe I 630 nm line pair were acquired over more than one hour. We inverted these observations with the VFISV code to obtain the evolution of the magnetic and velocity properties. We complement the study with data from instruments on board the Solar Dynamics Observatory and Hinode space missions.
Results: The studied penumbra disappears progressively in time and space. The magnetic flux evolution seems to be linked to the presence of moving magnetic features (MMFs). Decreasing Stokes V signals are observed. Evershed flows and horizontal fields were detected even after the disappearance of the penumbral sector.
Conclusions: The analyzed penumbral decay seems to result from the interaction between opposite polarity fields in type III MMFs and penumbra, while the presence of overlying canopies regulates the evolution in the different penumbral sectors.

Movies associated with Fig. 6 are available at https://www.aanda.org Title: A novel approach to identify resonant MHD wave modes in solar pores and sunspot umbrae: B − ω analysis Authors: Stangalini, M.; Jess, D. B.; Verth, G.; Fedun, V.; Fleck, B.; Jafarzadeh, S.; Keys, P. H.; Murabito, M.; Calchetti, D.; Aldhafeeri, A. A.; Berrilli, F.; Del Moro, D.; Jefferies, S. M.; Terradas, J.; Soler, R. Bibcode: 2021A&A...649A.169S Altcode: 2021arXiv210311639S The umbral regions of sunspots and pores in the solar photosphere are generally dominated by 3 mHz oscillations, which are due to p-modes penetrating the magnetic region. In these locations, wave power is also significantly reduced with respect to the quiet Sun. However, here we study a pore where not only is the power of the oscillations in the umbra comparable to, or even larger than, that of the quiet Sun, but the main dominant frequency is not 3 mHz as expected, but instead 5 mHz. By combining Doppler velocities and spectropolarimetry and analysing the relationship between magnetic field strength and frequency, the resultant B − ω diagram reveals distinct ridges that are remarkably clear signatures of resonant magneto-hydrodynamic (MHD) oscillations confined within the pore umbra. We demonstrate that these modes, in addition to velocity oscillations, are also accompanied by magnetic oscillations, as predicted from MHD theory. The novel technique of B − ω analysis proposed in this article opens up an exciting new avenue for identifying MHD wave modes in the umbral regions of both pores and sunspots. Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST) Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio, Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart; Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa, Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler, Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun, Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres, Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.; Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini, Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena; Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor; Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael; Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli, Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys, Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.; Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis, Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson, Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.; Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.; Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava, Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas, Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST Instrument Scientists; DKIST Science Working Group; DKIST Critical Science Plan Community Bibcode: 2021SoPh..296...70R Altcode: 2020arXiv200808203R The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute. Title: Analysis of Pseudo-Lyapunov Exponents of Solar Convection Using State-of-the-Art Observations Authors: Viavattene, Giorgio; Murabito, Mariarita; Guglielmino, Salvatore L.; Ermolli, Ilaria; Consolini, Giuseppe; Giorgi, Fabrizio; Jafarzadeh, Shahin Bibcode: 2021Entrp..23..413V Altcode: 2021arXiv210316980V The solar photosphere and the outer layer of the Sun's interior are characterized by convective motions, which display a chaotic and turbulent character. In this work, we evaluated the pseudo-Lyapunov exponents of the overshooting convective motions observed on the Sun's surface by using a method employed in the literature to estimate those exponents, as well as another technique deduced from their definition. We analyzed observations taken with state-of-the-art instruments at ground- and space-based telescopes, and we particularly benefited from the spectro-polarimetric data acquired with the Interferometric Bidimensional Spectrometer, the Crisp Imaging SpectroPolarimeter, and the Helioseismic and Magnetic Imager. Following previous studies in the literature, we computed maps of four quantities which were representative of the physical properties of solar plasma in each observation, and estimated the pseudo-Lyapunov exponents from the residuals between the values of the quantities computed at any point in the map and the mean of values over the whole map. In contrast to previous results reported in the literature, we found that the computed exponents hold negative values, which are typical of a dissipative regime, for all the quantities derived from our observations. The values of the estimated exponents increase with the spatial resolution of the data and are almost unaffected by small concentrations of magnetic field. Finally, we showed that similar results were also achieved by estimating the exponents from residuals between the values at each point in maps derived from observations taken at different times. The latter estimation technique better accounts for the definition of these exponents than the method employed in previous studies. Title: An overall view of temperature oscillations in the solar chromosphere with ALMA Authors: Jafarzadeh, S.; Wedemeyer, S.; Fleck, B.; Stangalini, M.; Jess, D. B.; Morton, R. J.; Szydlarski, M.; Henriques, V. M. J.; Zhu, X.; Wiegelmann, T.; Guevara Gómez, J. C.; Grant, S. D. T.; Chen, B.; Reardon, K.; White, S. M. Bibcode: 2021RSPTA.37900174J Altcode: 2021RSTPA.379..174J; 2020arXiv201001918J By direct measurements of the gas temperature, the Atacama Large Millimeter/submillimeter Array (ALMA) has yielded a new diagnostic tool to study the solar chromosphere. Here, we present an overview of the brightness-temperature fluctuations from several high-quality and high-temporal-resolution (i.e. 1 and 2 s cadence) time series of images obtained during the first 2 years of solar observations with ALMA, in Band 3 and Band 6, centred at around 3 mm (100 GHz) and 1.25 mm (239 GHz), respectively. The various datasets represent solar regions with different levels of magnetic flux. We perform fast Fourier and Lomb-Scargle transforms to measure both the spatial structuring of dominant frequencies and the average global frequency distributions of the oscillations (i.e. averaged over the entire field of view). We find that the observed frequencies significantly vary from one dataset to another, which is discussed in terms of the solar regions captured by the observations (i.e. linked to their underlying magnetic topology). While the presence of enhanced power within the frequency range 3-5 mHz is found for the most magnetically quiescent datasets, lower frequencies dominate when there is significant influence from strong underlying magnetic field concentrations (present inside and/or in the immediate vicinity of the observed field of view). We discuss here a number of reasons which could possibly contribute to the power suppression at around 5.5 mHz in the ALMA observations. However, it remains unclear how other chromospheric diagnostics (with an exception of Hα line-core intensity) are unaffected by similar effects, i.e. they show very pronounced 3-min oscillations dominating the dynamics of the chromosphere, whereas only a very small fraction of all the pixels in the 10 ALMA datasets analysed here show peak power near 5.5 mHz.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: Spectropolarimetric fluctuations in a sunspot chromosphere Authors: Stangalini, M.; Baker, D.; Valori, G.; Jess, D. B.; Jafarzadeh, S.; Murabito, M.; To, A. S. H.; Brooks, D. H.; Ermolli, I.; Giorgi, F.; MacBride, C. D. Bibcode: 2021RSPTA.37900216S Altcode: 2020arXiv200905302S The instrumental advances made in this new era of 4 m class solar telescopes with unmatched spectropolarimetric accuracy and sensitivity will enable the study of chromospheric magnetic fields and their dynamics with unprecedented detail. In this regard, spectropolarimetric diagnostics can provide invaluable insight into magneto-hydrodynamic (MHD) wave processes. MHD waves and, in particular, Alfvénic fluctuations associated with particular wave modes were recently recognized as important mechanisms not only for the heating of the outer layers of the Sun's atmosphere and the acceleration of the solar wind, but also for the elemental abundance anomaly observed in the corona of the Sun and other Sun-like stars (also known as first ionization potential) effect. Here, we take advantage of state-of-the-art and unique spectropolarimetric Interferometric BIdimensional Spectrometer observations to investigate the relation between intensity and circular polarization (CP) fluctuations in a sunspot chromosphere. Our results show a clear link between the intensity and CP fluctuations in a patch which corresponds to a narrow range of magnetic field inclinations. This suggests the presence of Alfvénic perturbations in the sunspot.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: High-frequency oscillations in small chromospheric bright features observed with Atacama Large Millimetre/Submillimetre Array Authors: Guevara Gómez, J. C.; Jafarzadeh, S.; Wedemeyer, S.; Szydlarski, M.; Stangalini, M.; Fleck, B.; Keys, P. H. Bibcode: 2021RSPTA.37900184G Altcode: 2020arXiv200804179G We report detection of oscillations in brightness temperature, size and horizontal velocity of three small bright features in the chromosphere of a plage/enhanced-network region. The observations, which were taken with high temporal resolution (i.e. 2 s cadence) with the Atacama large millimetre/ submillimetre array (ALMA) in Band 3 (centred at 3 mm; 100 GHz), exhibit three small-scale features with oscillatory behaviour with different, but overlapping, distributions of period on the order of, on average, 90 ± 22 s, 110 ± 12 s and 66 ± 23 s, respectively. We find anti-correlations between perturbations in brightness, temperature and size of the three features, which suggest the presence of fast sausage-mode waves in these small structures. In addition, the detection of transverse oscillations (although with a larger uncertainty) may also suggest the presence of Alfvénic oscillations which are likely representative of kink waves. This work demonstrates the diagnostic potential of high-cadence observations with ALMA for detecting high-frequency magnetohydrodynamic waves in the solar chromosphere. Such waves can potentially channel a vast amount of energy into the outer atmosphere of the Sun.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: High-resolution wave dynamics in the lower solar atmosphere Authors: Jess, D. B.; Keys, P. H.; Stangalini, M.; Jafarzadeh, S. Bibcode: 2021RSPTA.37900169J Altcode: 2020arXiv201113940J The magnetic and convective nature of the Sun's photosphere provides a unique platform from which generated waves can be modelled, observed and interpreted across a wide breadth of spatial and temporal scales. As oscillations are generated in-situ or emerge through the photospheric layers, the interplay between the rapidly evolving densities, temperatures and magnetic field strengths provides dynamic evolution of the embedded wave modes as they propagate into the tenuous solar chromosphere. A focused science team was assembled to discuss the current challenges faced in wave studies in the lower solar atmosphere, including those related to spectropolarimetry and radiative transfer in the optically thick regions. Following the Theo Murphy international scientific meeting held at Chicheley Hall during February 2020, the scientific team worked collaboratively to produce 15 independent publications for the current Special Issue, which are introduced here. Implications from the current research efforts are discussed in terms of upcoming next-generation observing and high-performance computing facilities.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: Characterization of shock wave signatures at millimetre wavelengths from Bifrost simulations Authors: Eklund, Henrik; Wedemeyer, Sven; Snow, Ben; Jess, David B.; Jafarzadeh, Shahin; Grant, Samuel D. T.; Carlsson, Mats; Szydlarski, Mikołaj Bibcode: 2021RSPTA.37900185E Altcode: 2020arXiv200805324E Observations at millimetre wavelengths provide a valuable tool to study the small-scale dynamics in the solar chromosphere. We evaluate the physical conditions of the atmosphere in the presence of a propagating shock wave and link that to the observable signatures in mm-wavelength radiation, providing valuable insights into the underlying physics of mm-wavelength observations. A realistic numerical simulation from the three-dimensional radiative magnetohydrodynamic code Bifrost is used to interpret changes in the atmosphere caused by shock wave propagation. High-cadence (1 s) time series of brightness temperature (Tb) maps are calculated with the Advanced Radiative Transfer code at the wavelengths 1.309 mm and 1.204 mm, which represents opposite sides of spectral band 6 of the Atacama Large Millimeter/submillimeter Array (ALMA). An example of shock wave propagation is presented. The brightness temperatures show a strong shock wave signature with large variation in formation height between approximately 0.7 and 1.4 Mm. The results demonstrate that millimetre brightness temperatures efficiently track upwardly propagating shock waves in the middle chromosphere. In addition, we show that the gradient of the brightness temperature between wavelengths within ALMA band 6 can potentially be used as a diagnostics tool in understanding the small-scale dynamics at the sampled layers.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: Magnetoacoustic wave energy dissipation in the atmosphere of solar pores Authors: Gilchrist-Millar, Caitlin A.; Jess, David B.; Grant, Samuel D. T.; Keys, Peter H.; Beck, Christian; Jafarzadeh, Shahin; Riedl, Julia M.; Van Doorsselaere, Tom; Ruiz Cobo, Basilio Bibcode: 2021RSPTA.37900172G Altcode: 2020arXiv200711594G The suitability of solar pores as magnetic wave guides has been a key topic of discussion in recent years. Here, we present observational evidence of propagating magnetohydrodynamic wave activity in a group of five photospheric solar pores. Employing data obtained by the Facility Infrared Spectropolarimeter at the Dunn Solar Telescope, oscillations with periods of the order of 5 min were detected at varying atmospheric heights by examining Si ɪ 10827 Å line bisector velocities. Spectropolarimetric inversions, coupled with the spatially resolved root mean square bisector velocities, allowed the wave energy fluxes to be estimated as a function of atmospheric height for each pore. We find propagating magnetoacoustic sausage mode waves with energy fluxes on the order of 30 kW m-2 at an atmospheric height of 100 km, dropping to approximately 2 kW m-2 at an atmospheric height of around 500 km. The cross-sectional structuring of the energy fluxes reveals the presence of both body- and surface-mode sausage waves. Examination of the energy flux decay with atmospheric height provides an estimate of the damping length, found to have an average value across all five pores of Ld ≈ 268 km, similar to the photospheric density scale height. We find the damping lengths are longer for body mode waves, suggesting that surface mode sausage oscillations are able to more readily dissipate their embedded wave energies. This work verifies the suitability of solar pores to act as efficient conduits when guiding magnetoacoustic wave energy upwards into the outer solar atmosphere.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: Reply to: Signatures of sunspot oscillations and the case for chromospheric resonances Authors: Jess, David B.; Snow, Ben; Fleck, Bernhard; Stangalini, Marco; Jafarzadeh, Shahin Bibcode: 2021NatAs...5....5J Altcode: 2020NatAs.tmp..149J No abstract at ADS Title: Alfvénic Perturbations in a Sunspot Chromosphere Linked to Fractionated Plasma in the Corona Authors: Baker, Deborah; Stangalini, Marco; Valori, Gherardo; Brooks, David H.; To, Andy S. H.; van Driel-Gesztelyi, Lidia; Démoulin, Pascal; Stansby, David; Jess, David B.; Jafarzadeh, Shahin Bibcode: 2021ApJ...907...16B Altcode: 2020arXiv201204308B In this study, we investigate the spatial distribution of highly varying plasma composition around one of the largest sunspots of solar cycle 24. Observations of the photosphere, chromosphere, and corona are brought together with magnetic field modeling of the sunspot in order to probe the conditions that regulate the degree of plasma fractionation within loop populations of differing connectivities. We find that, in the coronal magnetic field above the sunspot umbra, the plasma has photospheric composition. Coronal loops rooted in the penumbra contain fractionated plasma, with the highest levels observed in the loops that connect within the active region. Tracing field lines from regions of fractionated plasma in the corona to locations of Alfvénic fluctuations detected in the chromosphere shows that they are magnetically linked. These results indicate a connection between sunspot chromospheric activity and observable changes in coronal plasma composition. Title: ALMA and IRIS Observations of the Solar Chromosphere. II. Structure and Dynamics of Chromospheric Plages Authors: Chintzoglou, Georgios; De Pontieu, Bart; Martínez-Sykora, Juan; Hansteen, Viggo; de la Cruz Rodríguez, Jaime; Szydlarski, Mikolaj; Jafarzadeh, Shahin; Wedemeyer, Sven; Bastian, Timothy S.; Sainz Dalda, Alberto Bibcode: 2021ApJ...906...83C Altcode: 2020arXiv201205970C We propose and employ a novel empirical method for determining chromospheric plage regions, which seems to better isolate a plage from its surrounding regions than other methods commonly used. We caution that isolating a plage from its immediate surroundings must be done with care in order to successfully mitigate statistical biases that, for instance, can impact quantitative comparisons between different chromospheric observables. Using this methodology, our analysis suggests that λ = 1.25 mm free-free emission in plage regions observed with the Atacama Large Millimeter/submillimeter Array (ALMA)/Band6 may not form in the low chromosphere as previously thought, but rather in the upper chromospheric parts of dynamic plage features (such as spicules and other bright structures), i.e., near geometric heights of transition-region temperatures. We investigate the high degree of similarity between chromospheric plage features observed in ALMA/Band6 (at 1.25 mm wavelengths) and the Interface Region Imaging Spectrograph (IRIS)/Si IV at 1393 Å. We also show that IRIS/Mg II h and k are not as well correlated with ALMA/Band6 as was previously thought, and we discuss discrepancies with previous works. Lastly, we report indications of chromospheric heating due to propagating shocks supported by the ALMA/Band6 observations. Title: ALMA and IRIS Observations of the Solar Chromosphere. I. An On-disk Type II Spicule Authors: Chintzoglou, Georgios; De Pontieu, Bart; Martínez-Sykora, Juan; Hansteen, Viggo; de la Cruz Rodríguez, Jaime; Szydlarski, Mikolaj; Jafarzadeh, Shahin; Wedemeyer, Sven; Bastian, Timothy S.; Sainz Dalda, Alberto Bibcode: 2021ApJ...906...82C Altcode: 2020arXiv200512717C We present observations of the solar chromosphere obtained simultaneously with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Interface Region Imaging Spectrograph. The observatories targeted a chromospheric plage region of which the spatial distribution (split between strongly and weakly magnetized regions) allowed the study of linear-like structures in isolation, free of contamination from background emission. Using these observations in conjunction with a radiative magnetohydrodynamic 2.5D model covering the upper convection zone all the way to the corona that considers nonequilibrium ionization effects, we report the detection of an on-disk chromospheric spicule with ALMA and confirm its multithermal nature. Title: ALMA and IRIS Observations Highlighting the Dynamics and Structure of Chromospheric Plage Authors: Chintzoglou, G.; De Pontieu, B.; Martinez-Sykora, J.; Hansteen, V. H.; de la Cruz Rodriguez, J.; Szydlarski, M.; Jafarzadeh, S.; Wedemeyer, S.; Bastian, T.; Sainz Dalda, A. Bibcode: 2020AGUFMSH0010009C Altcode: We present observations of the solar chromosphere obtained simultaneously with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Interface Region Imaging Spectrograph (IRIS). The observatories targeted a chromospheric plage region of which the spatial distribution (split between strongly and weakly magnetized regions) allowed the study of linear-like structures in isolation, free of contamination from background emission. Using these observations in conjunction with a radiative magnetohydrodynamic 2.5D model covering the upper convection zone all the way to the corona that considers non-equilibrium ionization effects, we report the detection of an on-disk chromospheric spicule with ALMA and confirm its multithermal nature. In addition, we discuss the strikingly high degree of similarity between chromospheric plage features observed in ALMA/Band6 and IRIS/\ion{Si}{4} (also reproduced in our model) suggesting that ALMA/Band6 does not observe in the low chromosphere as previously thought but rather observes the upper chromospheric parts of structures such as spicules and other bright structures above plage at geometric heights near transition region temperatures. We also show that IRIS/\ion{Mg}{2} is not as well correlated with ALMA/Band6 as was previously thought. For these comparisons, we propose and employ a novel empirical method for the determination of plage regions, which seems to better isolate plage from its surrounding regions as compared to other methods commonly used. We caution that isolating plage from its immediate surroundings must be done with care to mitigate statistical bias in quantitative comparisons between different chromospheric observables. Lastly, we report indications for chromospheric heating due to traveling shocks supported by the ALMA/Band6 observations. Title: The Sun at millimeter wavelengths. II. Small-scale dynamic events in ALMA Band 3 Authors: Eklund, Henrik; Wedemeyer, Sven; Szydlarski, Mikolaj; Jafarzadeh, Shahin; Guevara Gómez, Juan Camilo Bibcode: 2020A&A...644A.152E Altcode: 2020arXiv201006400E Context. Solar observations with the Atacama Large Millimeter/sub-millimeter Array (ALMA) facilitate studies of the atmosphere of the Sun at chromospheric heights at high spatial and temporal resolution at millimeter wavelengths.
Aims: ALMA intensity data at millimeter(mm)-wavelengths are used for a first detailed systematic assessment of the occurrence and properties of small-scale dynamical features in the quiet Sun.
Methods: We analyzed ALMA Band 3 data (∼3 mm/100 GHz) with a spatial resolution of ∼1.4-2.1 arcsec and a duration of ∼40 min together with SDO/HMI magnetograms. The temporal evolution of the mm maps is studied to detect pronounced dynamical features, which then are connected to dynamical events via a k-means clustering algorithm. We studied the physical properties of the resulting events and explored whether or not they show properties consistent with propagating shock waves. For this purpose, we calculated observable shock wave signatures at mm wavelengths from one- and three-dimensional model atmospheres.
Results: We detect 552 dynamical events with an excess in brightness temperature (ΔTb) of at least ≥400 K. The events show a large variety in size up to ∼9″, amplitude ΔTb up to ∼1200 K with typical values in the range ∼450-750 K, and lifetime at full width at half maximum of ΔTb of between ∼43 and 360 s, with typical values between ∼55 and 125 s. Furthermore, many of the events show signature properties suggesting that they are likely produced by propagating shock waves.
Conclusions: There are a lot of small-scale dynamic structures detected in the Band 3 data, even though the spatial resolution sets limitations on the size of events that can be detected. The number of dynamic signatures in the ALMA mm data is very low in areas with photospheric footpoints with stronger magnetic fields, which is consistent with the expectation for propagating shock waves. Title: High-resolution observations of the solar photosphere, chromosphere, and transition region. A database of coordinated IRIS and SST observations Authors: Rouppe van der Voort, L. H. M.; De Pontieu, B.; Carlsson, M.; de la Cruz Rodríguez, J.; Bose, S.; Chintzoglou, G.; Drews, A.; Froment, C.; Gošić, M.; Graham, D. R.; Hansteen, V. H.; Henriques, V. M. J.; Jafarzadeh, S.; Joshi, J.; Kleint, L.; Kohutova, P.; Leifsen, T.; Martínez-Sykora, J.; Nóbrega-Siverio, D.; Ortiz, A.; Pereira, T. M. D.; Popovas, A.; Quintero Noda, C.; Sainz Dalda, A.; Scharmer, G. B.; Schmit, D.; Scullion, E.; Skogsrud, H.; Szydlarski, M.; Timmons, R.; Vissers, G. J. M.; Woods, M. M.; Zacharias, P. Bibcode: 2020A&A...641A.146R Altcode: 2020arXiv200514175R NASA's Interface Region Imaging Spectrograph (IRIS) provides high-resolution observations of the solar atmosphere through ultraviolet spectroscopy and imaging. Since the launch of IRIS in June 2013, we have conducted systematic observation campaigns in coordination with the Swedish 1 m Solar Telescope (SST) on La Palma. The SST provides complementary high-resolution observations of the photosphere and chromosphere. The SST observations include spectropolarimetric imaging in photospheric Fe I lines and spectrally resolved imaging in the chromospheric Ca II 8542 Å, Hα, and Ca II K lines. We present a database of co-aligned IRIS and SST datasets that is open for analysis to the scientific community. The database covers a variety of targets including active regions, sunspots, plages, the quiet Sun, and coronal holes. Title: The penumbral solar filaments from the photosphere to the chromosphere Authors: Murabito, M.; Ermolli, I.; Giorgi, F.; Stangalini, M.; Guglielmino, S. L.; Jafarzadeh, S.; Socas-Navarro, H.; Romano, P.; Zuccarello, F. Bibcode: 2020JPhCS1548a2017M Altcode: The magnetic field structure of sunspots above the photosphere remain poorly understood due to limitations in observations and the complexity of these atmospheric layers. In this regard, we studied the large isolated sunspot (70”× 80”) located in the active region NOAA 12546 with spectro-polarimetric measurements acquired along the Fe I 617.3 nm and Ca II 854.2 nm lines with the IBIS/DST instrument, under excellent seeing conditions lasting more than three hours. Using the Non Local Thermodynamic Equilibrium inversion code we inverted both line measurements simultaneously to retrieve the three-dimensional magnetic and thermal structure of the penumbral region from the bottom of the photosphere to the middle chromosphere. The analysis of data acquired at spectral ranges unexplored allow us to show clear evidence of the spine and intra-spine structure of the magnetic field at chromospheric heights. In particular, we found a peak-to-peak variations of the magnetic field strength and inclination of about 200 G and 10° chromospheric heights, respectively, and of about 300 G and 20° in the photosphere. We also investigated the structure of the magnetic field gradient in the penumbra along the vertical and azimuthal directions, confirming previous results reported in the literature from data taken at the spectral region of the He I 1083 nm triplet. Title: The Sun at millimeter wavelengths. I. Introduction to ALMA Band 3 observations Authors: Wedemeyer, Sven; Szydlarski, Mikolaj; Jafarzadeh, Shahin; Eklund, Henrik; Guevara Gomez, Juan Camilo; Bastian, Tim; Fleck, Bernhard; de la Cruz Rodriguez, Jaime; Rodger, Andrew; Carlsson, Mats Bibcode: 2020A&A...635A..71W Altcode: 2020arXiv200102185W Context. The Atacama Large Millimeter/submillimeter Array (ALMA) started regular observations of the Sun in 2016, first offering receiver Band 3 at wavelengths near 3 mm (100 GHz) and Band 6 at wavelengths around 1.25 mm (239 GHz).
Aims: Here we present an initial study of one of the first ALMA Band 3 observations of the Sun. Our aim is to characterise the diagnostic potential of brightness temperatures measured with ALMA on the Sun.
Methods: The observation covers a duration of 48 min at a cadence of 2 s targeting a quiet Sun region at disc-centre. Corresponding time series of brightness temperature maps are constructed with the first version of the Solar ALMA Pipeline and compared to simultaneous observations with the Solar Dynamics Observatory (SDO).
Results: The angular resolution of the observations is set by the synthesised beam, an elliptical Gaussian that is approximately 1.4″ × 2.1″ in size. The ALMA maps exhibit network patches, internetwork regions, and elongated thin features that are connected to large-scale magnetic loops, as confirmed by a comparison with SDO maps. The ALMA Band 3 maps correlate best with the SDO/AIA 171 Å, 131 Å, and 304 Å channels in that they exhibit network features and, although very weak in the ALMA maps, imprints of large-scale loops. A group of compact magnetic loops is very clearly visible in ALMA Band 3. The brightness temperatures in the loop tops reach values of about 8000-9000 K and in extreme moments up to 10 000 K.
Conclusions: ALMA Band 3 interferometric observations from early observing cycles already reveal temperature differences in the solar chromosphere. The weak imprint of magnetic loops and the correlation with the 171, 131, and 304 SDO channels suggests, however, that the radiation mapped in ALMA Band 3 might have contributions from a wider range of atmospheric heights than previously assumed, but the exact formation height of Band 3 needs to be investigated in more detail. The absolute brightness temperature scale as set by total power measurements remains less certain and must be improved in the future. Despite these complications and the limited angular resolution, ALMA Band 3 observations have a large potential for quantitative studies of the small-scale structure and dynamics of the solar chromosphere.

Movies are available at https://www.aanda.org Title: Magnetohydrodynamic Nonlinearities in Sunspot Atmospheres: Chromospheric Detections of Intermediate Shocks Authors: Houston, S. J.; Jess, D. B.; Keppens, R.; Stangalini, M.; Keys, P. H.; Grant, S. D. T.; Jafarzadeh, S.; McFetridge, L. M.; Murabito, M.; Ermolli, I.; Giorgi, F. Bibcode: 2020ApJ...892...49H Altcode: 2020arXiv200212368H The formation of shocks within the solar atmosphere remains one of the few observable signatures of energy dissipation arising from the plethora of magnetohydrodynamic waves generated close to the solar surface. Active region observations offer exceptional views of wave behavior and its impact on the surrounding atmosphere. The stratified plasma gradients present in the lower solar atmosphere allow for the potential formation of many theorized shock phenomena. In this study, using chromospheric Ca II λ8542 line spectropolarimetric data of a large sunspot, we examine fluctuations in the plasma parameters in the aftermath of powerful shock events that demonstrate polarimetric reversals during their evolution. Modern inversion techniques are employed to uncover perturbations in the temperatures, line-of-sight velocities, and vector magnetic fields occurring across a range of optical depths synonymous with the shock formation. Classification of these nonlinear signatures is carried out by comparing the observationally derived slow, fast, and Alfvén shock solutions with the theoretical Rankine-Hugoniot relations. Employing over 200,000 independent measurements, we reveal that the Alfvén (intermediate) shock solution provides the closest match between theory and observations at optical depths of log10τ =-4, consistent with a geometric height at the boundary between the upper photosphere and lower chromosphere. This work uncovers first-time evidence of the manifestation of chromospheric intermediate shocks in sunspot umbrae, providing a new method for the potential thermalization of wave energy in a range of magnetic structures, including pores, magnetic flux ropes, and magnetic bright points. Title: High-resolution spectropolarimetric observations of the temporal evolution of magnetic fields in photospheric bright points Authors: Keys, P. H.; Reid, A.; Mathioudakis, M.; Shelyag, S.; Henriques, V. M. J.; Hewitt, R. L.; Del Moro, D.; Jafarzadeh, S.; Jess, D. B.; Stangalini, M. Bibcode: 2020A&A...633A..60K Altcode: 2019arXiv191108436K Context. Magnetic bright points (MBPs) are dynamic, small-scale magnetic elements often found with field strengths of the order of a kilogauss within intergranular lanes in the photosphere.
Aims: Here we study the evolution of various physical properties inferred from inverting high-resolution full Stokes spectropolarimetry data obtained from ground-based observations of the quiet Sun at disc centre.
Methods: Using automated feature-tracking algorithms, we studied 300 MBPs and analysed their temporal evolution as they evolved to kilogauss field strengths. These properties were inferred using both the NICOLE and SIR Stokes inversion codes. We employ similar techniques to study radiative magnetohydrodynamical simulations for comparison with our observations.
Results: Evidence was found for fast (∼30-100 s) amplification of magnetic field strength (by a factor of 2 on average) in MBPs during their evolution in our observations. Similar evidence for the amplification of fields is seen in our simulated data.
Conclusions: Several reasons for the amplifications were established, namely, strong downflows preceding the amplification (convective collapse), compression due to granular expansion and mergers with neighbouring MBPs. Similar amplification of the fields and interpretations were found in our simulations, as well as amplification due to vorticity. Such a fast amplification will have implications for a wide array of topics related to small-scale fields in the lower atmosphere, particularly with regard to propagating wave phenomena in MBPs. Title: The 3D structure of the penumbra at high resolution from the bottom of the photosphere to the middle chromosphere Authors: Murabito, Mariarita; Ermolli, Ilaria; Giorgi, Fabrizio; Stangalini, Marco; Guglielmino, Salvo L.; Jafarzadeh, Shahin; Socas-Navarro, Hector; Romano, Paolo; Zuccarello, Francesca Bibcode: 2020IAUS..354..448M Altcode: Sunspots are the most prominent feature of the solar magnetism in the photosphere. Although they have been widely investigated in the past, their structure remains poorly understood. Indeed, due to limitations in observations and the complexity of the magnetic field estimation at chromospheric heights, the magnetic field structure of sunspot above the photosphere is still uncertain. Improving the present knowledge of sunspot is important in solar and stellar physics, since spot generation is seen not only on the Sun, but also on other solar-type stars. In this regard, we studied a large, isolated sunspot with spectro-polarimeteric measurements that were acquired at the Fe I 6173 nm and Ca II 8542 nm lines by the spectropolarimeter IBIS/DST under excellent seeing conditions lasting more than three hours. Using the Non-LTE inversion code NICOLE, we inverted both line measurements simultaneously, to retrieve the three-dimensional magnetic and thermal structure of the penumbral region from the bottom of the photosphere to the middle chromosphere. Our analysis of data acquired at spectral ranges unexplored in previous studies shows clear spine and intra-spine structure of the penumbral magnetic field at chromopheric heights. Our investigation of the magnetic field gradient in the penumbra along the vertical and azimuthal directions confirms results reported in the literature from analysis of data taken at the spectral region of the He I 1083 nm triplet. Title: A chromospheric resonance cavity in a sunspot mapped with seismology Authors: Jess, David B.; Snow, Ben; Houston, Scott J.; Botha, Gert J. J.; Fleck, Bernhard; Krishna Prasad, S.; Asensio Ramos, Andrés; Morton, Richard J.; Keys, Peter H.; Jafarzadeh, Shahin; Stangalini, Marco; Grant, Samuel D. T.; Christian, Damian J. Bibcode: 2020NatAs...4..220J Altcode: 2019NatAs...4..220J; 2019NatAs.tmp..502J Sunspots are intense collections of magnetic fields that pierce through the Sun's photosphere, with their signatures extending upwards into the outermost extremities of the solar corona1. Cutting-edge observations and simulations are providing insights into the underlying wave generation2, configuration3,4 and damping5 mechanisms found in sunspot atmospheres. However, the in situ amplification of magnetohydrodynamic waves6, rising from a few hundreds of metres per second in the photosphere to several kilometres per second in the chromosphere7, has, until now, proved difficult to explain. Theory predicts that the enhanced umbral wave power found at chromospheric heights may come from the existence of an acoustic resonator8-10, which is created due to the substantial temperature gradients experienced at photospheric and transition region heights11. Here, we provide strong observational evidence of a resonance cavity existing above a highly magnetic sunspot. Through a combination of spectropolarimetric inversions and comparisons with high-resolution numerical simulations, we provide a new seismological approach to mapping the geometry of the inherent temperature stratifications across the diameter of the underlying sunspot, with the upper boundaries of the chromosphere ranging between 1,300 ± 200 km and 2,300 ± 250 km. Our findings will allow the three-dimensional structure of solar active regions to be conclusively determined from relatively commonplace two-dimensional Fourier power spectra. The techniques presented are also readily suitable for investigating temperature-dependent resonance effects in other areas of astrophysics, including the examination of Earth-ionosphere wave cavities12. Title: Observing the Sun with the Atacama Large Millimeter/submillimeter Array - from continuum to magnetic fields Authors: Wedemeyer, Sven; Szydlarski, Mikolaj; Rodriguez, Jaime de la Cruz; Jafarzadeh, Shahin Bibcode: 2020IAUS..354...24W Altcode: The Atacama Large Millimeter/submillimeter Array offers regular observations of our Sun since 2016. After an extended period of further developing and optimizing the post-processing procedures, first scientific results are now produced. While the first observing cycles mostly provided mosaics and time series of continuum brightness temperature maps with a cadence of 1-2s, additional receiver bands and polarization capabilities will be offered in the future. Currently, polarization capabilities are offered for selected receiver bands but not yet for solar observing. An overview of the recent development, first scientific results and potential of solar magnetic field measurements with ALMA will be presented. Title: The magnetic properties of photospheric magnetic bright points with high-resolution spectropolarimetry Authors: Keys, Peter H.; Reid, Aaron; Mathioudakis, Mihalis; Shelyag, Sergiy; Henriques, Vasco M. J.; Hewitt, Rebecca L.; Del Moro, Dario; Jafarzadeh, Shahin; Jess, David B.; Stangalini, Marco Bibcode: 2019MNRAS.488L..53K Altcode: 2019MNRAS.tmpL..98K; 2019MNRAS.tmpL..95K; 2019arXiv190607687K Magnetic bright points (MBPs) are small-scale magnetic elements ubiquitous across the solar disc, with the prevailing theory suggesting that they form due to the process of convective collapse. Employing a unique full Stokes spectropolarimetric data set of a quiet Sun region close to disc centre obtained with the Swedish Solar Telescope, we look at general trends in the properties of magnetic bright points. In total we track 300 MBPs in the data set and we employ NICOLE inversions to ascertain various parameters for the bright points such as line-of-sight magnetic field strength and line-of-sight velocity, for comparison. We observe a bimodal distribution in terms of maximum magnetic field strength in the bright points with peaks at ∼480 G and ∼1700 G, although we cannot attribute the kilogauss fields in this distribution solely to the process of convective collapse. Analysis of MURAM simulations does not return the same bimodal distribution. However, the simulations provide strong evidence that the emergence of new flux and diffusion of this new flux play a significant role in generating the weak bright point distribution seen in our observations. Title: Height Dependence of the Penumbral Fine-scale Structure in the Inner Solar Atmosphere Authors: Murabito, Mariarita; Ermolli, I.; Giorgi, F.; Stangalini, M.; Guglielmino, S. L.; Jafarzadeh, S.; Socas-Navarro, H.; Romano, P.; Zuccarello, F. Bibcode: 2019ApJ...873..126M Altcode: 2018arXiv181209029M We studied the physical parameters of the penumbra in a large and fully developed sunspot, one of the largest over the last two solar cycles, by using full-Stokes measurements taken at the photospheric Fe I 617.3 nm and chromospheric Ca II 854.2 nm lines with the Interferometric Bidimensional Spectrometer. Inverting measurements with the Non-LTE inversion COde (NICOLE) code, we obtained the three-dimensional structure of the magnetic field in the penumbra from the bottom of the photosphere up to the middle chromosphere. We analyzed the azimuthal and vertical gradient of the magnetic field strength and inclination. Our results provide new insights on the properties of the penumbral magnetic fields in the chromosphere at atmospheric heights unexplored in previous studies. We found signatures of the small-scale spine and intraspine structure of both the magnetic field strength and inclination at all investigated atmospheric heights. In particular, we report typical peak-to-peak variations of the field strength and inclination of ≈300 G and ≈20°, respectively, in the photosphere, and of ≈200 G and ≈10° in the chromosphere. In addition, we estimated the vertical gradient of the magnetic field strength in the studied penumbra: we find a value of ≈0.3 G km-1 between the photosphere and the middle chromosphere. Interestingly, the photospheric magnetic field gradient changes sign from negative in the inner to positive in the outer penumbra. Title: The solar chromosphere at millimetre and ultraviolet wavelengths. I. Radiation temperatures and a detailed comparison Authors: Jafarzadeh, S.; Wedemeyer, S.; Szydlarski, M.; De Pontieu, B.; Rezaei, R.; Carlsson, M. Bibcode: 2019A&A...622A.150J Altcode: 2019arXiv190105763J Solar observations with the Atacama Large Millimeter/submillimeter Array (ALMA) provide us with direct measurements of the brightness temperature in the solar chromosphere. We study the temperature distributions obtained with ALMA Band 6 (in four sub-bands at 1.21, 1.22, 1.29, and 1.3 mm) for various areas at, and in the vicinity of, a sunspot, comprising quasi-quiet and active regions with different amounts of underlying magnetic fields. We compare these temperatures with those obtained at near- and far-ultraviolet (UV) wavelengths (and with the line-core intensities of the optically-thin far-UV spectra), co-observed with the Interface Region Imaging Spectrograph (IRIS) explorer. These include the emission peaks and cores of the Mg II k 279.6 nm and Mg II h 280.4 nm lines as well as the line cores of C II 133.4 nm, O I 135.6 nm, and Si IV 139.4 nm, sampling the mid-to-high chromosphere and the low transition region. Splitting the ALMA sub-bands resulted in an slight increase of spatial resolution in individual temperature maps, thus, resolving smaller-scale structures compared to those produced with the standard averaging routines. We find that the radiation temperatures have different, though somewhat overlapping, distributions in different wavelengths and in the various magnetic regions. Comparison of the ALMA temperatures with those of the UV diagnostics should, however, be interpreted with great caution, the former is formed under the local thermodynamic equilibrium (LTE) conditions, the latter under non-LTE. The mean radiation temperature of the ALMA Band 6 is similar to that extracted from the IRIS C II line in all areas with exception of the sunspot and pores where the C II poses higher radiation temperatures. In all magnetic regions, the Mg II lines associate with the lowest mean radiation temperatures in our sample. These will provide constraints for future numerical models. Title: Propagating Spectropolarimetric Disturbances in a Large Sunspot Authors: Stangalini, M.; Jafarzadeh, S.; Ermolli, I.; Erdélyi, R.; Jess, D. B.; Keys, P. H.; Giorgi, F.; Murabito, M.; Berrilli, F.; Del Moro, D. Bibcode: 2018ApJ...869..110S Altcode: 2018arXiv181012595S We present results derived from the analysis of spectropolarimetric measurements of active region AR12546, which represents one of the largest sunspots to have emerged onto the solar surface over the last 20 years. The region was observed with full-Stokes scans of the Fe I 617.3 nm and Ca II 854.2 nm lines with the Interferometric BIdimensional Spectrometer instrument at the Dunn Solar Telescope over an uncommon, extremely long time interval exceeding three hours. Clear circular polarization (CP) oscillations localized at the umbra-penumbra boundary of the observed region were detected. Furthermore, the multi-height data allowed us to detect the downward propagation of both CP and intensity disturbances at 2.5-3 mHz, which was identified by a phase delay between these two quantities. These results are interpreted as a propagating magnetohydrodynamic surface mode in the observed sunspot. Title: Linear Polarization Features in the Quiet-Sun Photosphere: Structure and Dynamics Authors: Kianfar, S.; Jafarzadeh, S.; Mirtorabi, M. T.; Riethmüller, T. L. Bibcode: 2018SoPh..293..123K Altcode: 2018arXiv180704633K We present detailed characteristics of linear polarization features (LPFs) in the quiet-Sun photosphere from high-resolution observations obtained with SUNRISE/IMaX. We explore differently treated data with various noise levels in linear polarization signals, from which structure and dynamics of the LPFs are studied. Physical properties of the detected LPFs are also obtained from the results of Stokes inversions. The number of LPFs and their sizes and polarization signals are found to be strongly dependent on the noise level and on the spatial resolution. While the linear polarization with a signal-to-noise ratio ≥4.5 covers about 26% of the entire area in the least noisy data in our study (with a noise level of 1.7 ×10−4 in the unit of Stokes I continuum), the detected (spatially resolved) LPFs cover about 10% of the area at any given time, with an occurrence rate on the order of 8 ×10−3s−1 arcsec−2. The LPFs were found to be short lived (in the range of 30 - 300 s), relatively small structures (radii of ≈0.1 - 1.5 arcsec), highly inclined, posing hG fields, and they move with an average horizontal speed of 1.2 km s−1. The LPFs were observed (almost) equally on both upflow and downflow regions, with an intensity contrast always larger than that of the average quiet Sun. Title: Solar Magnetoconvection and Small-Scale Dynamo Authors: Borrero, J. M.; Jafarzadeh, S.; Schüssler, M.; Solanki, S. K. Bibcode: 2018smf..book..275B Altcode: No abstract at ADS Title: Intermittent Reconnection and Plasmoids in UV Bursts in the Low Solar Atmosphere Authors: Rouppe van der Voort, L.; De Pontieu, B.; Scharmer, G. B.; de la Cruz Rodríguez, J.; Martínez-Sykora, J.; Nóbrega-Siverio, D.; Guo, L. J.; Jafarzadeh, S.; Pereira, T. M. D.; Hansteen, V. H.; Carlsson, M.; Vissers, G. Bibcode: 2017ApJ...851L...6R Altcode: 2017arXiv171104581R Magnetic reconnection is thought to drive a wide variety of dynamic phenomena in the solar atmosphere. Yet, the detailed physical mechanisms driving reconnection are difficult to discern in the remote sensing observations that are used to study the solar atmosphere. In this Letter, we exploit the high-resolution instruments Interface Region Imaging Spectrograph and the new CHROMIS Fabry-Pérot instrument at the Swedish 1-m Solar Telescope (SST) to identify the intermittency of magnetic reconnection and its association with the formation of plasmoids in so-called UV bursts in the low solar atmosphere. The Si IV 1403 Å UV burst spectra from the transition region show evidence of highly broadened line profiles with often non-Gaussian and triangular shapes, in addition to signatures of bidirectional flows. Such profiles had previously been linked, in idealized numerical simulations, to magnetic reconnection driven by the plasmoid instability. Simultaneous CHROMIS images in the chromospheric Ca II K 3934 Å line now provide compelling evidence for the presence of plasmoids by revealing highly dynamic and rapidly moving brightenings that are smaller than 0.″2 and that evolve on timescales of the order of seconds. Our interpretation of the observations is supported by detailed comparisons with synthetic observables from advanced numerical simulations of magnetic reconnection and associated plasmoids in the chromosphere. Our results highlight how subarcsecond imaging spectroscopy sensitive to a wide range of temperatures combined with advanced numerical simulations that are realistic enough to compare with observations can directly reveal the small-scale physical processes that drive the wide range of phenomena in the solar atmosphere. Title: Solar Magnetoconvection and Small-Scale Dynamo. Recent Developments in Observation and Simulation Authors: Borrero, J. M.; Jafarzadeh, S.; Schüssler, M.; Solanki, S. K. Bibcode: 2017SSRv..210..275B Altcode: 2015SSRv..tmp..113B; 2015arXiv151104214B A number of observational and theoretical aspects of solar magnetoconvection are considered in this review. We discuss recent developments in our understanding of the small-scale structure of the magnetic field on the solar surface and its interaction with convective flows, which is at the centre of current research. Topics range from plage areas in active regions over the magnetic network shaped by supergranulation to the ubiquituous `turbulent' internetwork fields. On the theoretical side, we focus upon magnetic field generation by small-scale dynamo action. Title: Erratum: Morphological Properties of Slender CaII H Fibrils Observed by sunrise II (ApJS 229, 1, 6) Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.; van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco Suárez, D.; Riethmüller, T. L.; Schmidt, W. Bibcode: 2017ApJS..230...11G Altcode: No abstract at ADS Title: Polarized Kink Waves in Magnetic Elements: Evidence for Chromospheric Helical Waves Authors: Stangalini, M.; Giannattasio, F.; Erdélyi, R.; Jafarzadeh, S.; Consolini, G.; Criscuoli, S.; Ermolli, I.; Guglielmino, S. L.; Zuccarello, F. Bibcode: 2017ApJ...840...19S Altcode: 2017arXiv170402155S In recent years, new high spatial resolution observations of the Sun's atmosphere have revealed the presence of a plethora of small-scale magnetic elements down to the resolution limit of the current cohort of solar telescopes (∼100-120 km on the solar photosphere). These small magnetic field concentrations, due to the granular buffeting, can support and guide several magnetohydrodynamic wave modes that would eventually contribute to the energy budget of the upper layers of the atmosphere. In this work, exploiting the high spatial and temporal resolution chromospheric data acquired with the Swedish 1 m Solar Telescope, and applying the empirical mode decomposition technique to the tracking of the solar magnetic features, we analyze the perturbations of the horizontal velocity vector of a set of chromospheric magnetic elements. We find observational evidence that suggests a phase relation between the two components of the velocity vector itself, resulting in its helical motion. Title: High-frequency Oscillations in Small Magnetic Elements Observed with Sunrise/SuFI Authors: Jafarzadeh, S.; Solanki, S. K.; Stangalini, M.; Steiner, O.; Cameron, R. H.; Danilovic, S. Bibcode: 2017ApJS..229...10J Altcode: 2016arXiv161109302J We characterize waves in small magnetic elements and investigate their propagation in the lower solar atmosphere from observations at high spatial and temporal resolution. We use the wavelet transform to analyze oscillations of both horizontal displacement and intensity in magnetic bright points found in the 300 nm and the Ca II H 396.8 nm passbands of the filter imager on board the Sunrise balloon-borne solar observatory. Phase differences between the oscillations at the two atmospheric layers corresponding to the two passbands reveal upward propagating waves at high frequencies (up to 30 mHz). Weak signatures of standing as well as downward propagating waves are also obtained. Both compressible and incompressible (kink) waves are found in the small-scale magnetic features. The two types of waves have different, though overlapping, period distributions. Two independent estimates give a height difference of approximately 450 ± 100 km between the two atmospheric layers sampled by the employed spectral bands. This value, together with the determined short travel times of the transverse and longitudinal waves provide us with phase speeds of 29 ± 2 km s-1 and 31 ± 2 km s-1, respectively. We speculate that these phase speeds may not reflect the true propagation speeds of the waves. Thus, effects such as the refraction of fast longitudinal waves may contribute to an overestimate of the phase speed. Title: Slender Ca II H Fibrils Mapping Magnetic Fields in the Low Solar Chromosphere Authors: Jafarzadeh, S.; Rutten, R. J.; Solanki, S. K.; Wiegelmann, T.; Riethmüller, T. L.; van Noort, M.; Szydlarski, M.; Blanco Rodríguez, J.; Barthol, P.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Martínez Pillet, V.; Orozco Suárez, D.; Schmidt, W. Bibcode: 2017ApJS..229...11J Altcode: 2016arXiv161003104J A dense forest of slender bright fibrils near a small solar active region is seen in high-quality narrowband Ca II H images from the SuFI instrument onboard the Sunrise balloon-borne solar observatory. The orientation of these slender Ca II H fibrils (SCF) overlaps with the magnetic field configuration in the low solar chromosphere derived by magnetostatic extrapolation of the photospheric field observed with Sunrise/IMaX and SDO/HMI. In addition, many observed SCFs are qualitatively aligned with small-scale loops computed from a novel inversion approach based on best-fit numerical MHD simulation. Such loops are organized in canopy-like arches over quiet areas that differ in height depending on the field strength near their roots. Title: Transverse Oscillations in Slender Ca II H Fibrils Observed with Sunrise/SuFI Authors: Jafarzadeh, S.; Solanki, S. K.; Gafeira, R.; van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco Suárez, D.; Riethmüller, T. L.; Schmidt, W. Bibcode: 2017ApJS..229....9J Altcode: 2016arXiv161007449J 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 Å wide passband covering the line core of Ca II H 3969 Å 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 Alfvénic 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 ≈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. Title: Kinematics of Magnetic Bright Features in the Solar Photosphere Authors: Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Martínez Pillet, V.; Orozco Suárez, D.; Riethmüller, T. L.; Schmidt, W.; van Noort, M. Bibcode: 2017ApJS..229....8J Altcode: 2016arXiv161007634J 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, γ =1.0), travelers with constant speeds over a supergranule (γ =1.9{--}2.0), and decelerating movers in the vicinity of flux emergence and/or within active regions (γ =1.4{--}1.5). The three types of regions host MBFs with mean diffusion coefficients of 130 km2 s-1, 80-90 km2 s-1, and 25-70 km2 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%. Title: Morphological Properties of Slender Ca II H Fibrils Observed by SUNRISE II Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.; van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco Suárez, D.; Riethmüller, T. L.; Schmidt, W. Bibcode: 2017ApJS..229....6G Altcode: 2016arXiv161200319G 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 ≈400 s, and average curvature of 0.002 arcsec-1. The maximum lifetime of the SCFs within our time series of 57 minutes is ≈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. Title: Oscillations on Width and Intensity of Slender Ca II H Fibrils from Sunrise/SuFI Authors: Gafeira, R.; Jafarzadeh, S.; Solanki, S. K.; Lagg, A.; van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco Suárez, D.; Riethmüller, T. L.; Schmidt, W. Bibcode: 2017ApJS..229....7G Altcode: 2017arXiv170102801G 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. Title: Kinematics and Magnetic Properties of a Light Bridge in a Decaying Sunspot Authors: Falco, M.; Borrero, J. M.; Guglielmino, S. L.; Romano, P.; Zuccarello, F.; Criscuoli, S.; Cristaldi, A.; Ermolli, I.; Jafarzadeh, S.; Rouppe van der Voort, L. Bibcode: 2016SoPh..291.1939F Altcode: 2016arXiv160607229F; 2016SoPh..tmp..107F We present the results obtained by analysing high spatial and spectral resolution data of the solar photosphere acquired by the CRisp Imaging SpectroPolarimeter at the Swedish Solar Telescope on 6 August 2011 of a large sunspot with a light bridge (LB) observed in NOAA AR 11263. These data are complemented by simultaneous Hinode Spectropolarimeter (SP) observation in the Fe I 630.15 nm and 630.25 nm lines. The continuum intensity map shows a discontinuity in the radial distribution of the penumbral filaments in correspondence with the LB, which shows a dark lane (≈0.3″ wide and ≈8.0″ long) along its main axis. The available data were inverted with the Stokes Inversion based on Response functions (SIR) code and physical parameters maps were obtained. The line-of-sight (LOS) velocity of the plasma along the LB derived from the Doppler effect shows motions towards and away from the observer up to 0.6 kms−1 that are lower in value than the LOS velocities observed in the neighbouring penumbral filaments. The noteworthy result is that we find motions towards the observer of up to 0.6 kms−1 in the dark lane where the LB is located between two umbral cores, while the LOS velocity motion towards the observer is strongly reduced where the LB is located between an umbral core at one side and penumbral filaments on the other side. Statistically, the LOS velocities correspond to upflows or downflows, and comparing these results with Hinode/SP data, we conclude that the surrounding magnetic field configuration (whether more or less inclined) could have a role in maintaining the conditions for the process of plasma pile-up along the dark lane. The results obtained from our study support and confirm outcomes of recent magneto-hydrodynamic simulations showing upflows along the main axis of an LB. Title: ALMA Observations of the Sun in Cycle 4 and Beyond Authors: Wedemeyer, S.; Fleck, B.; Battaglia, M.; Labrosse, N.; Fleishman, G.; Hudson, H.; Antolin, P.; Alissandrakis, C.; Ayres, T.; Ballester, J.; Bastian, T.; Black, J.; Benz, A.; Brajsa, R.; Carlsson, M.; Costa, J.; DePontieu, B.; Doyle, G.; Gimenez de Castro, G.; Gunár, S.; Harper, G.; Jafarzadeh, S.; Loukitcheva, M.; Nakariakov, V.; Oliver, R.; Schmieder, B.; Selhorst, C.; Shimojo, M.; Simões, P.; Soler, R.; Temmer, M.; Tiwari, S.; Van Doorsselaere, T.; Veronig, A.; White, S.; Yagoubov, P.; Zaqarashvili, T. Bibcode: 2016arXiv160100587W Altcode: This document was created by the Solar Simulations for the Atacama Large Millimeter Observatory Network (SSALMON) in preparation of the first regular observations of the Sun with the Atacama Large Millimeter/submillimeter Array (ALMA), which are anticipated to start in ALMA Cycle 4 in October 2016. The science cases presented here demonstrate that a large number of scientifically highly interesting observations could be made already with the still limited solar observing modes foreseen for Cycle 4 and that ALMA has the potential to make important contributions to answering long-standing scientific questions in solar physics. With the proposal deadline for ALMA Cycle 4 in April 2016 and the Commissioning and Science Verification campaign in December 2015 in sight, several of the SSALMON Expert Teams composed strategic documents in which they outlined potential solar observations that could be feasible given the anticipated technical capabilities in Cycle 4. These documents have been combined and supplemented with an analysis, resulting in recommendations for solar observing with ALMA in Cycle 4. In addition, the detailed science cases also demonstrate the scientific priorities of the solar physics community and which capabilities are wanted for the next observing cycles. The work on this White Paper effort was coordinated in close cooperation with the two international solar ALMA development studies led by T. Bastian (NRAO, USA) and R. Brajsa, (ESO). This document will be further updated until the beginning of Cycle 4 in October 2016. In particular, we plan to adjust the technical capabilities of the solar observing modes once finally decided and to further demonstrate the feasibility and scientific potential of the included science cases by means of numerical simulations of the solar atmosphere and corresponding simulated ALMA observations. Title: Hα Line Profile Asymmetries and the Chromospheric Flare Velocity Field Authors: Kuridze, D.; Mathioudakis, M.; Simões, P. J. A.; Rouppe van der Voort, L.; Carlsson, M.; Jafarzadeh, S.; Allred, J. C.; Kowalski, A. F.; Kennedy, M.; Fletcher, L.; Graham, D.; Keenan, F. P. Bibcode: 2015ApJ...813..125K Altcode: 2015arXiv151001877K The asymmetries observed in the line profiles of solar flares can provide important diagnostics of the properties and dynamics of the flaring atmosphere. In this paper the evolution of the Hα and Ca ii λ8542 lines are studied using high spatial, temporal, and spectral resolution ground-based observations of an M1.1 flare obtained with the Swedish 1 m Solar Telescope. The temporal evolution of the Hα line profiles from the flare kernel shows excess emission in the red wing (red asymmetry) before flare maximum and excess in the blue wing (blue asymmetry) after maximum. However, the Ca ii λ8542 line does not follow the same pattern, showing only a weak red asymmetry during the flare. RADYN simulations are used to synthesize spectral line profiles for the flaring atmosphere, and good agreement is found with the observations. We show that the red asymmetry observed in Hα is not necessarily associated with plasma downflows, and the blue asymmetry may not be related to plasma upflows. Indeed, we conclude that the steep velocity gradients in the flaring chromosphere modify the wavelength of the central reversal in the Hα line profile. The shift in the wavelength of maximum opacity to shorter and longer wavelengths generates the red and blue asymmetries, respectively. Title: Magnetic Upflow Events in the Quiet-Sun Photosphere. I. Observations Authors: Jafarzadeh, S.; Rouppe van der Voort, L.; de la Cruz Rodríguez, J. Bibcode: 2015ApJ...810...54J Altcode: 2015arXiv150707355J Rapid magnetic upflows in the quiet-Sun photosphere were recently uncovered from both Sunrise/IMaX and Hinode/SOT observations. Here, we study magnetic upflow events (MUEs) from high-quality, high- (spatial, temporal, and spectral) resolution, and full Stokes observations in four photospheric magnetically sensitive Fe i lines centered at 5250.21, 6173.34, 6301.51, and 6302.50 Å acquired with the Swedish Solar Telescope (SST)/CRISP. We detect MUEs by subtracting in-line Stokes V signals from those in the far blue wing whose signal-to-noise ratio (S/N) ≥slant 7. We find a larger number of MUEs at any given time (2.0× {10}-2 arcsec-2), larger by one to two orders of magnitude, than previously reported. The MUEs appear to fall into four classes presenting different shapes of Stokes V profiles with (I) asymmetric double lobes, (II) single lobes, (III) double-humped (two same-polarity lobes), and (IV) three lobes (an extra blueshifted bump in addition to double lobes), of which less than half are single-lobed. We also find that MUEs are almost equally distributed in network and internetwork areas and they appear in the interior or at the edge of granules in both regions. Distributions of physical properties, except for horizontal velocity, of the MUEs (namely, Stokes V signal, size, line-of-sight velocity, and lifetime) are almost identical for the different spectral lines in our data. A bisector analysis of our spectrally resolved observations shows that these events host modest upflows and do not show a direct indication of the presence of supersonic upflows reported earlier. Our findings reveal that the numbers, types (classes), and properties determined for MUEs can strongly depend on the detection techniques used and the properties of the employed data, namely, S/Ns, resolutions, and wavelengths. Title: Non-linear propagation of kink waves to the solar chromosphere Authors: Stangalini, M.; Giannattasio, F.; Jafarzadeh, S. Bibcode: 2015A&A...577A..17S Altcode: 2015arXiv150207213S Small-scale magnetic field concentrations (magnetic elements) in the quiet Sun are believed to contribute to the energy budget of the upper layers of the Sun's atmosphere, as they are observed to support a large number of magneto-hydrodynamic modes. In recent years, kink waves in magnetic elements were observed at different heights in the solar atmosphere, from the photosphere to the corona. However, the propagation of these waves has not been fully evaluated. Our aim is to investigate the propagation of kink waves in small magnetic elements in the solar atmosphere. We analysed high-quality, long duration spectropolarimetric data of a photospheric quiet Sun region observed near the disk centre with the spectropolarimeter CRISP at the Swedish Solar Telescope (SST). We complemented these data with simultaneous and co-spatial broadband chromospheric observations of the same region. Our findings reveal a clear upward propagation of kink waves with frequency above 2.6 mHz. Moreover, the signature of a non-linear propagation process is also observed. By comparing photospheric to chromospheric power spectra, no signature of an energy dissipation is found at least at the atmospheric heights at which the data analysed originate. This implies that most of the energy carried by the kink waves (within the frequency range under study < 17 mHz) flows to upper layers in the Sun's atmosphere. Title: Inclinations of small quiet-Sun magnetic features based on a new geometric approach Authors: Jafarzadeh, S.; Solanki, S. K.; Lagg, A.; Bellot Rubio, L. R.; van Noort, M.; Feller, A.; Danilovic, S. Bibcode: 2014A&A...569A.105J Altcode: 2014arXiv1408.2443J Context. High levels of horizontal magnetic flux have been reported in the quiet-Sun internetwork, often based on Stokes profile inversions.
Aims: Here we introduce a new method for deducing the inclination of magnetic elements and use it to test magnetic field inclinations from inversions.
Methods: We determine accurate positions of a set of small, bright magnetic elements in high spatial resolution images sampling different photospheric heights obtained by the Sunrise balloon-borne solar observatory. Together with estimates of the formation heights of the employed spectral bands, these provide us with the inclinations of the magnetic features. We also compute the magnetic inclination angle of the same magnetic features from the inversion of simultaneously recorded Stokes parameters.
Results: Our new, geometric method returns nearly vertical fields (average inclination of around 14° with a relatively narrow distribution having a standard deviation of 6°). In strong contrast to this, the traditionally used inversions give almost horizontal fields (average inclination of 75 ± 8°) for the same small magnetic features, whose linearly polarised Stokes profiles are adversely affected by noise. We show that for such magnetic features inversions overestimate the flux in horizontal magnetic fields by an order of magnitude.
Conclusions: The almost vertical field of bright magnetic features from our geometric method is clearly incompatible with the nearly horizontal magnetic fields obtained from the inversions. This indicates that the amount of magnetic flux in horizontal fields deduced from inversions is overestimated in the presence of weak Stokes signals, in particular if Stokes Q and U are close to or under the noise level. Inversions should be used with great caution when applied to data with no clear Stokes Q and no U signal. By combining the proposed method with inversions we are not just improving the inclination, but also the field strength. This technique allows us to analyse features that are not reliably treated by inversions, thus greatly extending our capability to study the complete magnetic field of the quiet Sun. Title: Migration of Ca II H bright points in the internetwork Authors: Jafarzadeh, S.; Cameron, R. H.; Solanki, S. K.; Pietarila, A.; Feller, A.; Lagg, A.; Gandorfer, A. Bibcode: 2014A&A...563A.101J Altcode: 2014arXiv1401.7522J Context. The migration of magnetic bright point-like features (MBP) in the lower solar atmosphere reflects the dispersal of magnetic flux as well as the horizontal flows of the atmospheric layer they are embedded in.
Aims: We analyse trajectories of the proper motion of intrinsically magnetic, isolated internetwork Ca ii H MBPs (mean lifetime 461 ± 9 s) to obtain their diffusivity behaviour.
Methods: We use seeing-free high spatial and temporal resolution image sequences of quiet-Sun, disc-centre observations obtained in the Ca ii H 3968 Å passband of the Sunrise Filter Imager (SuFI) onboard the Sunrise balloon-borne solar observatory. Small MBPs in the internetwork are automatically tracked. The trajectory of each MBP is then calculated and described by a diffusion index (γ) and a diffusion coefficient (D). We also explore the distribution of the diffusion indices with the help of a Monte Carlo simulation.
Results: We find γ = 1.69 ± 0.08 and D = 257 ± 32 km2 s-1 averaged over all MBPs. Trajectories of most MBPs are classified as super-diffusive, i.e. γ > 1, with the determined γ being the largest obtained so far to our knowledge. A direct correlation between D and timescale (τ) determined from trajectories of all MBPs is also obtained. We discuss a simple scenario to explain the diffusivity of the observed, relatively short-lived MBPs while they migrate within a small area in a supergranule (i.e. an internetwork area). We show that the scatter in the γ values obtained for individual MBPs is due to their limited lifetimes.
Conclusions: The super-diffusive MBPs can be described as random walkers (due to granular evolution and intergranular turbulence) superposed on a large systematic (background) velocity, caused by granular, mesogranular, and supergranular flows. Title: Dynamics of magnetic bright points in the lower solar atmosphere Authors: Jafarzadeh, Shahin Bibcode: 2013PhDT........35J Altcode: In this thesis we have investigated the structure and dynamics of small-scale magnetic bright points (MBPs) in quiet, internetwork regions of the lower solar atmosphere. Such MBPs are associated with small-scale, intense (generally kG) magnetic elements. The internetwork (IN) areas cover the largest fraction of the solar surface and it has been argued that the IN may contain most of the existing unsigned magnetic flux on the surface at any given time. However, the distribution of the magnetic field's properties in the IN regions is still being debated. Thus, only recently has the presence of kG fields in the IN been confirmed of which the studied MBPs are thought to be manifestations. In addition, interaction between intense magnetic features and convective flows on the solar surface (in particular in IN areas) have been proposed to excite waves which can carry energy to the upper solar atmosphere. The properties of these waves and their contribution to the heating of the upper solar atmosphere is still unclear. Moreover, the migration of the small magnetic elements owing to the convective flows/turbulence is not known (due to, e.g., lack of high spatial and temporal resolution observations not affected by seeing). We used high spatial and temporal resolution observations, obtained by the Sunrise balloon-borne solar observatory, to address the above issues. We concentrate on the study of the smallest MBPs visible in the data; whose apparent lack of internal fine-structure facilitates their precise location and tracking in time-series of images. The analyses were performed using an algorithm we developed to identify, locate and track the MBPs as well as to determine their physical properties at any given time. These findings have implications for, e.g., our understanding of the heating mechanisms in the higher layers of the solar atmosphere, estimates of the solar magnetic flux as well as the structure of the convection flows (within a supergranule) advecting small magnetic elements. Title: Structure and dynamics of isolated internetwork Ca II H bright points observed by SUNRISE Authors: Jafarzadeh, S.; Solanki, S. K.; Feller, A.; Lagg, A.; Pietarila, A.; Danilovic, S.; Riethmüller, T. L.; Martínez Pillet, V. Bibcode: 2013A&A...549A.116J Altcode: 2012arXiv1211.4836J
Aims: We aim to improve our picture of the low chromosphere in the quiet-Sun internetwork by investigating the intensity, horizontal velocity, size and lifetime variations of small bright points (BPs; diameter smaller than 0.3 arcsec) observed in the Ca II H 3968 Å passband along with their magnetic field parameters, derived from photospheric magnetograms.
Methods: Several high-quality time series of disc-centre, quiet-Sun observations from the Sunrise balloon-borne solar telescope, with spatial resolution of around 100 km on the solar surface, have been analysed to study the dynamics of BPs observed in the Ca II H passband and their dependence on the photospheric vector magnetogram signal.
Results: Parameters such as horizontal velocity, diameter, intensity and lifetime histograms of the isolated internetwork and magnetic Ca II H BPs were determined. Mean values were found to be 2.2 km s-1, 0.2 arcsec (≈150 km), 1.48 ⟨ ICa ⟩ and 673 s, respectively. Interestingly, the brightness and the horizontal velocity of BPs are anti-correlated. Large excursions (pulses) in horizontal velocity, up to 15 km s-1, are present in the trajectories of most BPs. These could excite kink waves travelling into the chromosphere and possibly the corona, which we estimate to carry an energy flux of 310 W m-2, sufficient to heat the upper layers, although only marginally.
Conclusions: The stable observing conditions of Sunrise and our technique for identifying and tracking BPs have allowed us to determine reliable parameters of these features in the internetwork. Thus we find, e.g., that they are considerably longer lived than previously thought. The large velocities are also reliable, and may excite kink waves. Although these wave are (marginally) energetic enough to heat the quiet corona, we expect a large additional contribution from larger magnetic elements populating the network and partly also the internetwork. Title: First Results from the SUNRISE Mission Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.; Gandorfer, A.; Hirzberger, J.; Jafarzadeh, S.; Lagg, A.; Riethmüller, T. L.; Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; González, M. J. M.; Pillet, V. M.; Khomenko, E.; Yelles Chaouche, L.; Iniesta, J. C. d. T.; Domingo, V.; Palacios, J.; Knölker, M.; González, N. B.; Borrero, J. M.; Berkefeld, T.; Franz, M.; Roth, M.; Schmidt, W.; Steiner, O.; Title, A. M. Bibcode: 2012ASPC..455..143S Altcode: The SUNRISE balloon-borne solar observatory consists of a 1m aperture Gregory telescope, a UV filter imager, an imaging vector polarimeter, an image stabilization system, and further infrastructure. The first science flight of SUNRISE yielded high-quality data that reveal the structure, dynamics, and evolution of solar convection, oscillations, and magnetic fields at a resolution of around 100 km in the quiet Sun. Here we describe very briefly the mission and the first results obtained from the SUNRISE data, which include a number of discoveries. Title: Diffusivity of Isolated Internetwork Ca II H Bright Points Observed by SuFI/SUNRISE Authors: Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Feller, A.; Pietarila, A.; Lagg, A.; Barthol, P.; Berkefeld, T.; Gandorfer, A.; Knoelker, M.; Martinez Pillet, V.; Schmidt, W.; Title, A. Bibcode: 2012decs.confE..99J Altcode: We analyze trajectories of the proper motion of intrinsically magnetic, isolated internetwork Ca II H BPs (with mean lifetime of 461 sec) to obtain their diffusivity behaviors. We use high spatial and temporal resolution image sequences of quiet-Sun, disc-centre observations obtained in the Ca II H 397 nm passband of the Sunrise Filter Imager (SuFI) on board the SUNRISE balloon-borne solar observatory. In order to avoid misidentification, the BPs are semi-manually selected and then automatically tracked. The trajectory of each BP is then calculated and its diffusion index is described by a power law exponent, using which we classify the BPs' trajectories into sub-, normal and super- diffusive. In addition, the corresponding diffusion coefficients (D) based on the observed displacements are consequently computed. We find a strong super-diffusivity at a height sampled by the SuFI/SUNRISE Ca II H passband (i.e. a height corresponding roughly to the temperature minimum). We find that 74% of the identified tiny BPs are super-diffusive, 18% move randomly (i.e. their motion corresponds to normal diffusion) and only 8% belong to the sub-diffusion regime. In addition, we find that 53% of the super-diffusion regime (i.e. 39% of all BPs) have the diffusivity index of 2 which are termed as "Ballistic BPs". Finally, we explore the distribution of diffusion index with the help of a simple simulation. The results suggest that the BPs are random walkers superposed by a systematic (background) velocity in which the magnitude of each component (and hence their ratio) depends on the time and spatial scales. We further discuss a simple sketch to explain the diffusivity of observed BPs while they migrate within a supergranule (i.e. internetwork areas) or close to the network regions. Title: Relation between the Sunrise photospheric magnetic field and the Ca II H bright features Authors: Jafarzadeh, Shahin; Hirzberger, J.; Feller, A.; Lagg, A.; Solanki, S. K.; Pietarila, A.; Danilovic, S.; Riethmueller, T.; Barthol, P.; Berkefeld, T.; Gandorfer, A.; Knülker, M.; Martínez Pillet, V.; Schmidt, W.; Schüssler, M.; Title, A. Bibcode: 2010cosp...38.2856J Altcode: 2010cosp.meet.2856J Recent observations from the Sunrise balloon-borne solar telescope have enabled us to reach an unprecedented high spatial resolution on the solar surface with the near-ultraviolet photo-spheric and chromospheric images as well as the magnetograms. We use these high resolution observations to investigate the structure of the solar upper photosphere and lower chromosphere as well as their temporal evolutions. We study the relation between the inter-granular Ca II 397 nm bright structures in images obtained by the Sunrise Filter Imager (SuFI) and their corresponding photospheric vector magnetic field computed from the Imaging Magnetogram eXperiment (IMaX) observations. The targets under study are in a quiet Sun region and close to disc-centre. Title: Abundance Analysis of Red Horizontal Branch Stars Authors: Jafarzadeh, S.; Lagerholm, C.; Mikolaitis, Š. Bibcode: 2008osa..conf...53J Altcode: During the Observational Stellar Astrophysics research course in Lithuania, we analyzed the spectra of four red horizontal branch stars obtained on the Nordic Optical Telescope and FIES spectrograph. For the analysis we used the program SIU running under IDL. Overall, the metallicity for these stars seems to be higher than what is listed in the literature. We have determined the main atmospheric parameters and abundances of C, N, O and Mg chemical elements. We were only able to get the [O/Fe] abundance for one star because of telluric lines. The abundances were compared with stellar evolutionary models, both for finding the stellar mass and to investigate how well these stars follow theoretical predictions of evolutionary abundance alterations. Title: Photoelectric Observations, Light Curves Analysis and Period Study of the Eclipsing Variable DO Cas Authors: Jafarzadeh, Shahin Bibcode: 2006astro.ph.10647J Altcode: The new B and V photoelectric observations of the beta Lyrae eclipsing binary DO Cas were obtained on 6 nights form December 2000 to January 2001. The observations were made at the Biruni Observatory, Shiraz, Iran and the light curves are analyzed using the Wilson light curve synthesis and differential correction code. So, the relative surface luminosities, new light elements, and new orbital elements have been obtained, and from times of minimum the period is improved. With these and previously published times, the period variation is studied and a constant period is approved, though some authors has mentioned some variations. The solutions of the light curves suggest that DO Cas is a contact binary. Title: Observations and Analysis of the Eclipsing Variable do CAS Authors: Jafarzadeh, Shahin Bibcode: 2003IAUJD..13E..13J Altcode: The new B and V photoelectric observations of the β Lyrae eclipsing binary DO Cas were obtained on 6 nights form December 2000 to January 2001. The observations were made at the Biruni Observatory Shiraz Iran and the light curves are analyzed using the Wilson-Devinny light curve synthesis and differential correction code. So the relative surface luminosities limb darkening coefficient new light elements and new orbital elements have been obtained and from times of minimum the period is improved. The solutions of the light curves suggest that DO Cas is a contact binary.