Author name code: utz ADS astronomy entries on 2022-09-14 author:"Utz, Dominik" ------------------------------------------------------------------------ Title: The Solar Activity Monitor Network - SAMNet Authors: Erdélyi, Robertus; Korsós, Marianna B.; Huang, Xin; Yang, Yong; Pizzey, Danielle; Wrathmall, Steven A.; Hughes, Ifan G.; Dyer, Martin J.; Dhillon, Vikram S.; Belucz, Bernadett; Brajša, Roman; Chatterjee, Piyali; Cheng, Xuewu; Deng, Yuanyong; Domínguez, Santiago Vargas; Joya, Raúl; Gömöry, Peter; Gyenge, Norbert G.; Hanslmeier, Arnold; Kucera, Ales; Kuridze, David; Li, Faquan; Liu, Zhong; Xu, Long; Mathioudakis, Mihalis; Matthews, Sarah; McAteer, James R. T.; Pevtsov, Alexei A.; Pötzi, Werner; Romano, Paolo; Shen, Jinhua; Temesváry, János; Tlatov, Andrey G.; Triana, Charles; Utz, Dominik; Veronig, Astrid M.; Wang, Yuming; Yan, Yihua; Zaqarashvili, Teimuraz; Zuccarello, Francesca Bibcode: 2022JSWSC..12....2E Altcode: The Solar Activity Magnetic Monitor (SAMM) Network (SAMNet) is a future UK-led international network of ground-based solar telescope stations. SAMNet, at its full capacity, will continuously monitor the Sun's intensity, magnetic, and Doppler velocity fields at multiple heights in the solar atmosphere (from photosphere to upper chromosphere). Each SAMM sentinel will be equipped with a cluster of identical telescopes each with a different magneto-optical filter (MOFs) to take observations in K I, Na D, and Ca I spectral bands. A subset of SAMM stations will have white-light coronagraphs and emission line coronal spectropolarimeters. The objectives of SAMNet are to provide observational data for space weather research and forecast. The goal is to achieve an operationally sufficient lead time of e.g., flare warning of 2-8 h and provide many sought-after continuous synoptic maps (e.g., LoS magnetic and velocity fields, intensity) of the lower solar atmosphere with a spatial resolution limited only by seeing or diffraction limit, and with a cadence of 10 min. The individual SAMM sentinels will be connected to their master HQ hub where data received from all the slave stations will be automatically processed and flare warning issued up to 26 h in advance. Title: Observational evidence for two-component distributions describing solar magnetic bright points Authors: Berrios Saavedra, Gerardine; Utz, Dominik; Vargas Domínguez, Santiago; Campos Rozo, José Iván; González Manrique, Sergio Javier; Gömöry, Peter; Kuckein, Christoph; Balthasar, Horst; Zelina, Peter Bibcode: 2022A&A...657A..79B Altcode: 2021arXiv211012404B Context. High-resolution observations of the solar photosphere reveal the presence of fine structures, in particular the so-called Magnetic Bright Points (MBPs), which are small-scale features associated with strong magnetic field regions of the order of kilogauss (kG). It is especially relevant to study these magnetic elements, which are extensively detected in all moments during the solar cycle, in order to establish their contribution to the behavior of the solar atmosphere, and ultimately a plausible role within the coronal heating problem.
Aims: Characterisation of size and velocity distributions of MBPs in the solar photosphere in two different datasets of quiet Sun images acquired with high-resolution solar instruments i.e. Solar Optical Telescope SOT/Hinode and the High-resolution Fast Imager HiFI/GREGOR, in the G-band (4308 Å).
Methods: In order to detect the MBPs, an automatic segmentation and identification algorithm is used. Next, the identified features were tracked to measure their proper motions. Finally, a statistical analysis of hundreds of MBPs is carried out, generating histograms for areas, diameters and horizontal velocities.
Results: This work establishes that areas and diameters of MBPs display log-normal distributions that are well-fitted by two different components, whereas the velocity vector components follow Gaussians and the vector magnitude a Rayleigh distribution revealing again for all vector elements a two component composition.
Conclusions: The results can be interpreted as due to the presence of two different populations of MBPs in the solar photosphere one likely related to stronger network magnetic flux elements and the other one to weaker intranetwork flux elemens. In particular this work concludes on the effect of the different spatial resolution of GREGOR and Hinode telescopes, affecting detections and average values. Title: The Dark Universe is not invisible Authors: Zioutas, K.; Anastassopoulos, V.; Argiriou, A.; Cantatore, G.; Cetin, S. A.; Gardikiotis, A.; Hoffmann, D. H. H.; Hofmann, S.; Karuza, M.; Kryemadhi, A.; Maroudas, M.; Matteson, E. L.; Ozbozduman, K.; Papaevangelou, T.; Perryman, M.; Semertzidis, Y. K.; Tsagris, I.; Tsagri, M.; Tsiledakis, G.; Utz, D.; Valachovic, E. L. Bibcode: 2021arXiv210811647Z Altcode: Dark matter (DM) comes from long-range gravitational observations, and it is considered as something that does not interact with ordinary matter or emits light. However, also on much smaller scales, a number of unexpected observations of the solar activity and the dynamic Earth atmosphere might arise from DM contradicting the aforementioned DM picture. Because, gravitational (self) focusing effects by the Sun or its planets of streaming DM fit as the interpretation of the otherwise puzzling 11-year solar cycle, the mysterious heating of the solar corona, atmospheric transients, etc. Observationally driven, an external impact by overlooked streaming invisible matter reconciles the investigated mysterious behavior showing otherwise unexpected planetary relationships; this is a signature for gravitational focusing of streaming DM by the solar system bodies. Then, focusing of DM streams could also occur in exoplanetary systems, suggesting for the first time the carrying out of investigations by searching for the associated stellar activity as a function of the exoplanetary orbital phases. Title: Evidence For Two-component Distributions Describing Magnetic Bright Points In The Solar Photosphere Authors: Vargas Domínguez, S.; Berrios Saavedra, G.; Utz, D.; Campos Rozo, J. I.; González Manrique, S.; Gömöry, Peter; Kuckein, Christoph; Balthasar, Horst; Zelina, Peter Bibcode: 2021AAS...23811310V Altcode: High-resolution observations of the Sun reveal the presence of Magnetic Bright Points (MBPs), which are small-scale features associated with strong magnetic field regions, that are found all over the solar photosphere. In this work, we characterize some physical properties and dynamics of MBPs in a quiet Sun region by using time series of images acquired with the High-resolution Fast Imager HiFI/GREGOR and Solar Optical Telescope SOT/Hinode in the G-band (4308 Angstrom). An automated segmentation algorithm is used to identify the MBPs and track their evolution. The results show observational evidence for two-component distributions of areas, diameters and velocities, that can be interpreted as corresponding to different populations of MBPs. Title: Could Switchbacks Originate in the Lower Solar Atmosphere? II. Propagation of Switchbacks in the Solar Corona Authors: Magyar, Norbert; Utz, Dominik; Erdélyi, Robertus; Nakariakov, Valery M. Bibcode: 2021ApJ...914....8M Altcode: 2021arXiv210410126M The magnetic switchbacks observed recently by the Parker Solar Probe have raised the question about their nature and origin. One of the competing theories of their origin is the interchange reconnection in the solar corona. In this scenario, switchbacks are generated at the reconnection site between open and closed magnetic fields, and are either advected by an upflow or propagate as waves into the solar wind. In this paper we test the wave hypothesis, numerically modeling the propagation of a switchback, modeled as an embedded Alfvén wave packet of constant magnetic field magnitude, through the gravitationally stratified solar corona with different degrees of background magnetic field expansion. While switchbacks propagating in a uniform medium with no gravity are relatively stable, as reported previously, we find that gravitational stratification together with the expansion of the magnetic field act in multiple ways to deform the switchbacks. These include WKB effects, which depend on the degree of magnetic field expansion, and also finite-amplitude effects, such as the symmetry breaking between nonlinear advection and the Lorentz force. In a straight or radially expanding magnetic field the propagating switchbacks unfold into waves that cause minimal magnetic field deflections, while a super-radially expanding magnetic field aids in maintaining strong deflections. Other important effects are the mass uplift the propagating switchbacks induce and the reconnection and drainage of plasmoids contained within the switchbacks. In the Appendix, we examine a series of setups with different switchback configurations and parameters, which broaden the scope of our study. Title: Could Switchbacks Originate in the Lower Solar Atmosphere? I. Formation Mechanisms of Switchbacks Authors: Magyar, Norbert; Utz, Dominik; Erdélyi, Robertus; Nakariakov, Valery M. Bibcode: 2021ApJ...911...75M Altcode: 2021arXiv210303726M The recent rediscovery of magnetic field switchbacks or deflections embedded in the solar wind flow by the Parker Solar Probe mission lead to a huge interest in the modeling of the formation mechanisms and origin of these switchbacks. Several scenarios for their generation were put forth, ranging from lower solar atmospheric origins by reconnection, to being a manifestation of turbulence in the solar wind, and so on. Here we study some potential formation mechanisms of magnetic switchbacks in the lower solar atmosphere, using three-dimensional magnetohydrodynamic (MHD) numerical simulations. The model is that of an intense flux tube in an open magnetic field region, aiming to represent a magnetic bright point opening up to an open coronal magnetic field structure, e.g., a coronal hole. The model is driven with different plasma flows in the photosphere, such as a fast up-shooting jet, as well as shearing flows generated by vortex motions or torsional oscillations. In all scenarios considered, we witness the formation of magnetic switchbacks in regions corresponding to chromospheric heights. Therefore, photospheric plasma flows around the foot-points of intense flux tubes appear to be suitable drivers for the formation of magnetic switchbacks in the lower solar atmosphere. Nevertheless, these switchbacks do not appear to be able to enter the coronal heights of the simulation in the present model. In conclusion, based on the presented simulations, switchbacks measured in the solar wind are unlikely to originate from photospheric or chromospheric dynamics. Title: Magnetic Flux Emergence in a Coronal Hole Authors: Palacios, Judith; Utz, Dominik; Hofmeister, Stefan; Krikova, Kilian; Gömöry, Peter; Kuckein, Christoph; Denker, Carsten; Verma, Meetu; González Manrique, Sergio Javier; Campos Rozo, Jose Iván; Koza, Július; Temmer, Manuela; Veronig, Astrid; Diercke, Andrea; Kontogiannis, Ioannis; Cid, Consuelo Bibcode: 2020SoPh..295...64P Altcode: 2020arXiv200611779P A joint campaign of various space-borne and ground-based observatories, comprising the Japanese Hinode mission (Hinode Observing Plan 338, 20 - 30 September 2017), the GREGOR solar telescope, and the Vacuum Tower Telescope (VTT), investigated numerous targets such as pores, sunspots, and coronal holes. In this study, we focus on the coronal hole region target. On 24 September 2017, a very extended non-polar coronal hole developed patches of flux emergence, which contributed to the decrease of the overall area of the coronal hole. These flux emergence patches erode the coronal hole and transform the area into a more quiet-Sun-like area, whereby bipolar magnetic structures play an important role. Conversely, flux cancellation leads to the reduction of opposite-polarity magnetic fields and to an increase in the area of the coronal hole. Title: Revisiting the building blocks of solar magnetic fields by GREGOR Authors: Utz, Dominik; Kuckein, Christoph; Campos Rozo, Jose Iván; González Manrique, Sergio Javier; Balthasar, Horst; Gömöry, Peter; Hernández, Judith Palacios; Denker, Carsten; Verma, Meetu; Kontogiannis, Ioannis; Krikova, Kilian; Hofmeister, Stefan; Diercke, Andrea Bibcode: 2020IAUS..354...38U Altcode: The Sun is our dynamic host star due to its magnetic fields causing plentiful of activity in its atmosphere. From high energetic flares and coronal mass ejections (CMEs) to lower energetic phenomena such as jets and fibrils. Thus, it is of crucial importance to learn about formation and evolution of solar magnetic fields. These fields cover a wide range of spatial and temporal scales, starting on the larger end with active regions harbouring complex sunspots, via isolated pores, down to the smallest yet resolved elements - so-called magnetic bright points (MBPs). Here, we revisit the various manifestations of solar magnetic fields by the largest European solar telescope in operation, the 1.5-meter GREGOR telescope. We show images from the High-resolution Fast Imager (HiFI) and spectropolarimetric data from the GREGOR Infrared Spectrograph (GRIS). Besides, we outline resolved convective features inside the larger structures - so-called light-bridges occurring on large to mid-sized scales. Title: Science Requirement Document (SRD) for the European Solar Telescope (EST) (2nd edition, December 2019) Authors: Schlichenmaier, R.; Bellot Rubio, L. R.; Collados, M.; Erdelyi, R.; Feller, A.; Fletcher, L.; Jurcak, J.; Khomenko, E.; Leenaarts, J.; Matthews, S.; Belluzzi, L.; Carlsson, M.; Dalmasse, K.; Danilovic, S.; Gömöry, P.; Kuckein, C.; Manso Sainz, R.; Martinez Gonzalez, M.; Mathioudakis, M.; Ortiz, A.; Riethmüller, T. L.; Rouppe van der Voort, L.; Simoes, P. J. A.; Trujillo Bueno, J.; Utz, D.; Zuccarello, F. Bibcode: 2019arXiv191208650S Altcode: The European Solar Telescope (EST) is a research infrastructure for solar physics. It is planned to be an on-axis solar telescope with an aperture of 4 m and equipped with an innovative suite of spectro-polarimetric and imaging post-focus instrumentation. The EST project was initiated and is driven by EAST, the European Association for Solar Telescopes. EAST was founded in 2006 as an association of 14 European countries. Today, as of December 2019, EAST consists of 26 European research institutes from 18 European countries. The Preliminary Design Phase of EST was accomplished between 2008 and 2011. During this phase, in 2010, the first version of the EST Science Requirement Document (SRD) was published. After EST became a project on the ESFRI roadmap 2016, the preparatory phase started. The goal of the preparatory phase is to accomplish a final design for the telescope and the legal governance structure of EST. A major milestone on this path is to revisit and update the Science Requirement Document (SRD). The EST Science Advisory Group (SAG) has been constituted by EAST and the Board of the PRE-EST EU project in November 2017 and has been charged with the task of providing with a final statement on the science requirements for EST. Based on the conceptual design, the SRD update takes into account recent technical and scientific developments, to ensure that EST provides significant advancement beyond the current state-of-the-art. The present update of the EST SRD has been developed and discussed during a series of EST SAG meetings. The SRD develops the top-level science objectives of EST into individual science cases. Identifying critical science requirements is one of its main goals. Those requirements will define the capabilities of EST and the post-focus instrument suite. The technical requirements for the final design of EST will be derived from the SRD. Title: Generation of solar spicules and subsequent atmospheric heating Authors: Samanta, Tanmoy; Tian, Hui; Yurchyshyn, Vasyl; Peter, Hardi; Cao, Wenda; Sterling, Alphonse; Erdélyi, Robertus; Ahn, Kwangsu; Feng, Song; Utz, Dominik; Banerjee, Dipankar; Chen, Yajie Bibcode: 2019Sci...366..890S Altcode: 2020arXiv200602571S Spicules are rapidly evolving fine-scale jets of magnetized plasma in the solar chromosphere. It remains unclear how these prevalent jets originate from the solar surface and what role they play in heating the solar atmosphere. Using the Goode Solar Telescope at the Big Bear Solar Observatory, we observed spicules emerging within minutes of the appearance of opposite-polarity magnetic flux around dominant-polarity magnetic field concentrations. Data from the Solar Dynamics Observatory showed subsequent heating of the adjacent corona. The dynamic interaction of magnetic fields (likely due to magnetic reconnection) in the partially ionized lower solar atmosphere appears to generate these spicules and heat the upper solar atmosphere. Title: Photospheric magnetic structure of coronal holes Authors: Hofmeister, Stefan J.; Utz, Dominik; Heinemann, Stephan G.; Veronig, Astrid; Temmer, Manuela Bibcode: 2019A&A...629A..22H Altcode: 2019arXiv190903806H In this study, we investigate in detail the photospheric magnetic structure of 98 coronal holes using line-of-sight magnetograms of SDO/HMI, and for a subset of 42 coronal holes using HINODE/SOT G-band filtergrams. We divided the magnetic field maps into magnetic elements and quiet coronal hole regions by applying a threshold at ±25 G. We find that the number of magnetic bright points in magnetic elements is well correlated with the area of the magnetic elements (cc = 0.83 ± 0.01). Further, the magnetic flux of the individual magnetic elements inside coronal holes is related to their area by a power law with an exponent of 1.261 ± 0.004 (cc = 0.984 ± 0.001). Relating the magnetic elements to the overall structure of coronal holes, we find that on average (69 ± 8)% of the overall unbalanced magnetic flux of the coronal holes arises from long-lived magnetic elements with lifetimes > 40 h. About (22 ± 4)% of the unbalanced magnetic flux arises from a very weak background magnetic field in the quiet coronal hole regions with a mean magnetic field density of about 0.2-1.2 G. This background magnetic field is correlated to the flux of the magnetic elements with lifetimes of > 40 h (cc = 0.88 ± 0.02). The remaining flux arises from magnetic elements with lifetimes < 40 h. By relating the properties of the magnetic elements to the overall properties of the coronal holes, we find that the unbalanced magnetic flux of the coronal holes is completely determined by the total area that the long-lived magnetic elements cover (cc = 0.994 ± 0.001).

Movie associated to Fig. 2 is available at https://www.aanda.org Title: Photospheric plasma and magnetic field dynamics during the formation of solar AR 11190 Authors: Campos Rozo, J. I.; Utz, D.; Vargas Domínguez, S.; Veronig, A.; Van Doorsselaere, T. Bibcode: 2019A&A...622A.168C Altcode: 2019arXiv190102437C Context. The Sun features on its surface typical flow patterns called the granulation, mesogranulation, and supergranulation. These patterns arise due to convective flows transporting energy from the interior of the Sun to its surface. The other well known elements structuring the solar photosphere are magnetic fields arranged from single, isolated, small-scale flux tubes to large and extended regions visible as sunspots and active regions.
Aims: In this paper we will shed light on the interaction between the convective flows in large-scale cells as well as the large-scale magnetic fields in active regions, and investigate in detail the statistical distribution of flow velocities during the evolution and formation of National Oceanic and Atmospheric Administration active region 11190.
Methods: To do so, we employed local correlation tracking methods on data obtained by the Solar Dynamics Observatory in the continuum as well as on processed line-of-sight magnetograms.
Results: We find that the flow fields in an active region can be modelled by a two-component distribution. One component is very stable, follows a Rayleigh distribution, and can be assigned to the background flows, whilst the other component is variable in strength and velocity range and can be attributed to the flux emergence visible both in the continuum maps as well as magnetograms. Generally, the plasma flows, as seen by the distribution of the magnitude of the velocity, follow a Rayleigh distribution even through the time of formation of active regions. However, at certain moments of large-scale fast flux emergence, a second component featuring higher velocities is formed in the velocity magnitudes distribution.
Conclusions: The plasma flows are generally highly correlated to the motion of magnetic elements and vice versa except during the times of fast magnetic flux emergence as observed by rising magnetic elements. At these times, the magnetic fields are found to move faster than the corresponding plasma.

Movie attached to Fig. 1 is available at https://www.aanda.org Title: The photospheric structure of coronal holes: magnetic elements Authors: Hofmeister, Stefan; Utz, Dominik; Heinemann, Stephan; Veronig, Astrid; Temmer, Manuela Bibcode: 2018csc..confE.129H Altcode: Coronal holes attracted recently more attention by the scientific community as they represent the source region for the fast solar wind which is ifself an important ingredient in understanding the space environment and space weather. Nevertheless, our knowledge about the detailed magnetic field structure below coronal holes is quite limited, maybe since such a research would necessarily involve the high atmospheric and photospheric community. In this contribution we would like to bridge this gap and investigate in detail the magnetic field distribution below coronal holes and its relationship to the large-scale coronal hole topology. To do so, we investigate the distribution and properties of photospheric magnetic elements below 106 low and medium latitude coronal holes using SDO/HMI line-of-sight magnetogram data from 2010 to 2016, and relate them to the overall properties of the coronal holes. Since magnetic elements produce clearly visible photospheric structures, they can be well observed and give us valuable insights into the structure of coronal holes. We find that the distribution of the magnetic flux of magnetic elements follows an exponential function. The area and flux of magnetic elements are strongly related to each other by a power law with an exponent of 1.25. The larger magnetic elements are located at the edges of the magnetic network and seem to be the "core" structure of coronal holes. They have lifetimes > 4 days, i.e., longer than the timescale of the supergranulation. Further, they contain up to 50 magnetic bright points as observed by Hinode/SOT in the G-Band, meaning that the large magnetic elements are large clusters of individual magnetic elements. The mean magnetic field density of the overall coronal holes and thus their unbalanced magnetic flux is determined by their percentage coverage with magnetic elements at cc=0.98. Since magnetic elements are the foot points of magnetic funnels and thus the small-scale source regions of high-speed solar wind streams, the dependence of the coverage with magnetic elements on the strength of coronal holes also explains the dependence of the plasma density of high-speed streams near the Sun to the strength of its source coronal hole. The rotation rates of the magnetic elements match the rotation rate of the coronal hole and is surprisingly similar to the differential rotation rate of active regions at low- and medium latitudes, suggesting they are rooted at similar deep layers. This also means that coronal holes do not show an abnormal rotation rate as suggested by various authors. Finally, by projecting the magnetic elements to AIA-171 and 193 filtergrams, we surprisingly find that the magnetic elements are not located in the darkest regions of coronal holes. Therefore, the vertical plasma outflow from magnetic funnels is probably not the primary reason why coronal holes appear as dark patches in EUV images. We conclude that magnetic elements are the basic building blocks of coronal holes which completely determine their magnetic properties. Title: Dynamcis and magnetic properties in coronal holes using high-resolution multi-instrument solar observations Authors: Krikova, K.; Utz, D.; Veronig, A.; Gömöry, P.; Hofmeister, S.; Temmer, M. Bibcode: 2018simi.conf...31K Altcode: Using high-resolution solar observations from the Hinode Instruments SOT/SP, EIS and XRT as well as IRIS from a coronal hole on the 26th of September 2017, we are investigating the dynamics within the coronal hole visible on the specified date. Further satellite data support is given by full disc images from SDO with the AIA and HMI instruments. EIS and IRIS data provide us with crucial information about the plasma and energy flow from the Sun's chromosphere into the corona using the EUV and UV spectra and images. Investigating the magnetic configuration as well as the dynamics and changes within the coronal hole by using the SOT/SP data will give us additional crucial insights about the physical processes leading to the corresponding changes in the higher atmosphere. We compare the Hinode data with AIA and HMI data to get a firm comprehensive picture about the connection from high resolved photospheric fields and its dynamics within the higher layer. Within the timeframe of the analysed EIS dataset two microflare events associated with a solar jet were captured, originating inside the coronal hole under investigation. We believe that it is totally worthwhile to study these features in full detail as not so much attention was paid to high energy processes within coronal holes and their basic relationship to the harboring coronal hole and they show surprisingly high downflows in the Fe XII iron line (up to 140 km/s). In the current proceeding we will outline the state of the art of this investigation and give an overview of the further steps necessary. The mentioned data were obtained during a recent GREGOR campaign with the joint support of IRIS and Hinode (HOP 338). Title: Does the solar granulation change with the activity cycle? Authors: Muller, R.; Hanslmeier, A.; Utz, D.; Ichimoto, K. Bibcode: 2018A&A...616A..87M Altcode: Context. Knowledge of the variation of the solar granulation properties (contrast and scale) with the 11-yr activity cycle is useful for a better understanding of the interaction between magnetic field and convection at global or local scales. A varying granulation may also contribute to irradiance variations and affect the p-mode damping rates and lifetimes.
Aims: HINODE/SOT blue continuum images taken in the frame of the synoptic program at the disk center on a daily basis between November 2006 and February 2016 are used. This period covers the minimum of activity between cycles 23 and 24 and the maximum of cycle 24.
Methods: The sharpness of a significant number of images was reduced because of instrumental aberrations or inaccurate focusing. Only the sharpest images were selected for this investigation.
Results: To be detectable with HINODE/SOT images, the variation of the granulation contrast and of the granulation scale at the disk center should have been larger than 3%. As it is not the case, it is concluded that they varied by less than 3% through the weak cycle 24. Title: Long-term trends of magnetic bright points: The evolution of MBP size Authors: Utz, D.; Van Doorsselaere, T.; Gagelmans, E.; O'Rourke, C.; Vuerinckx, A.; Muller, R.; Veronig, A. Bibcode: 2018simi.conf..179U Altcode: Magnetic Bright Points (MBPs) are small-scale, very strong, solar magnetic field concentrations visible in the lower solar atmosphere. While there is a large and ever-increasing knowledge base and understanding of large-scale solar magnetic fields, i.e., sunspots and active regions, and their involvement in the solar cycle, much less is known about small-scale fields such as MBPs. Thus, we aim on contributing to our understanding of these tiny, but, important solar features by investigating the size distribution and its variation over time.

For this purpose, we obtained the synoptic G-band data set of the Hinode mission which is now since nearly 12 years in space and operational (launched in October 2006). After careful image calibration and selection we analysed the G-band data set with an automated MBP identification algorithm to calculate in a next step the equivalent diameter of the MBPs.

The so gained size distribution follows a Gamma distribution with pronounced changes during the solar activity cycle. The MBP sizes appear to be somewhat smaller during the solar minimum and somewhat more extended during the solar maxima as expressed by the scaleparameter of the Gamma distribution. Title: Modelling the solar photospheric plasma and magnetic field dynamics during the emergence of AR 11190 Authors: Campos Rozo, Jose Ivan; Utz, Dominik; Veronig, Astrig; Vargas Domínguez, Santiago Bibcode: 2018nspm.confE...1C Altcode: The interaction between the plasma and the magnetic field has been studied before by various authors. In this work we will show a detailed study employing two different distributions applied to the flow velocities during the emergence and prior evolution of AR 11190 on 11- April-2011. The velocity fields are computed from intensity as well as LOS magnetograms by using Local Correlation Tracking (LCT) techniques. Horizontal velocities as well as vertical velocities show strong correlation between the emergence of new fast and strong positive magnetic elements, and strong divergences observed from vertical velocities calculated by LCT in continuum data. Although there are several divergence regions within the field of view, just the region of interest shows the emergences of new magnetic field. Title: Modelling the solar photospheric plasma and magnetic field dynamics in the quiet Sun and comparison of these results with the flow fields in an evolving active region Authors: Campos Rozo, Jose Ivan; Utz, Dominik; Veronig, Astrid; Vargas Domínguez, Santiago Bibcode: 2018simi.conf...37C Altcode: In the present work a detailed study of the flow velocities of a quiet solar region is made and then compared with the flow fields during the emergence and prior to the evolution of AR-11190 on 11-April-2010. The velocity fields are computed from intensity as well as LOS magnetograms by using Local Correlation Tracking (LCT) techniques. The magnitudes of the obtained velocity vectors can be modelled by a single and simple Rayleigh distribution in the case of the quiet Sun and by a combination of two different statistical distributions in the case of the active region. Primarily this combination consists of a Rayleigh distribution that models the background velocity magnitudes as well as the general behavior of the combined velocity distribution, plus a weaker additional component that recreates the fast changes within the field of view. We propose two different distributions (implying different physical interpretations) for this second component of our combined fitting model. Generally, we can say that all the distributions show a strong correlation between the plasma motions and the movements of magnetic elements except during time instances when strong and fast magnetic flux elements start to appear within the region of interest. Title: Long time trends of MBP characteristics Authors: Utz, D.; Muller, R.; Van Doorsselaere, T.; Veronig, A.; Gagelmans, E.; O'Rourke, C.; Vuerinckx, A. Bibcode: 2018CEAB...42...13U Altcode: The change of Magnetic Bright Points (MBPs) characteristics over time periods of the solar sunspot cycle is studied. MBPs are small-scale solar magnetic field features reaching well beyond kG magnetic field strength and visible in intergranular lines within the solar photosphere. They are very variable and dynamic on time scales of just a few minutes. Due to their strong magnetic field, which resembles in shape the ideal concept of vertical flux tubes, as well as their dynamic behaviour, they are of special interest for wave triggering and propagation processes. On the other hand these small-scale structures appear brighter on the solar photosphere and thus their long time behaviour in respect of number, size, and intensity is of great importance for the total solar irradiance variability and thus also for climate change studies. In the current contribution we want to have a detailed look on exactly these parameters over the time period from end of 2006 until spring 2017 when unfortunately the Hinode SOT/BFI and NFI CCD cameras failed and thus no more data could be taken by the Hinode spacecrafts BFI instrument. The key findings can be summarized as that the number at the disc centre is variable and correlated to the sunspot cycle but shifted in regards to it. Moreover the size distribution of MBPs varies with the cycle indicating that fundamental magneto-convective properties might change on the 11th-year solar-cycle time-period. Title: Small-scale dynamcis in a coronal-hole related to microflaring events Authors: Krikova, K.; Utz, D.; Veronig, A.; Hofmeister, S.; Temmer, M.; Gömöry, P.; Holzknecht, L. Bibcode: 2018CEAB...42....8K Altcode: Using high-resolution solar imagery and spectroscopy from the Hinode EIS and SDO instruments, we investigate the dynamics within a coronal hole observed on the 26th September 2017. Further data is given by full disc images from SDO with the AIA and HMI instruments. EIS spectra provide us with crucial information about the plasma and energy flows from the Sun's chromosphere into the corona. Within the timeframe of the analysed EIS dataset two microflares associated with a jet-like event were captured, originating inside the coronal hole under investigation. These two microflare events were analysed in the study at hand in detail. Such recurring solar transient events could contribute to the mass and energy input into the solar corona and also to the solar wind. Our analysis shows that microflare temperatures can reach up to 3 MK with a hot component close to the reconnection site. Moreover an enhanced density at the microflare region was found. The obtained EIS ion line ratios suggest a density of up to 2.9 \cdot 10^{10} cm^{-3}. Title: Formation Heights of HINODE SOT/BFI Filters Authors: Kuehner, O.; Utz, D.; Muller, R.; Van Doorsselaere, T.; Magyar, N.; Veronig, A.; Campos Rozo, J. I.; Jelinek, P. Bibcode: 2018CEAB...42....9K Altcode: Small-scale magnetic fields in the solar atmosphere are not static objects with height but expand. Thus, to understand the expansion, one can measure proxy features with various spectral filters forming in different heights. However, this is tricky as, it is well known that the formation height of spectral filters within the solar atmosphere depends on the atmospheric parameters itself. This means that the spectral line formation within small-scale magnetic fields is different compared to the quiet Sun. To investigate the dependency of these formation heights due to different atmospheric parameters we constructed an atmospheric model of the Sun with an embedded flux tube fulfilling magnetostatic conditions. We investigated the behavior of the formation heights of the HINODE SOT/BFI spectral bands (blue, green, red continuum, G-Band, Ca II H) in answer to varying input parameters of our atmospheric model. The currently seen effects are not tremendous. However, this is most likely due to the rather weak magnetic field strength achieved so far in our magnetic flux tube models. Title: Temporal relations between magnetic bright points and the solar sunspot cycle Authors: Utz, Dominik; Muller, Richard; Van Doorsselaere, Tom Bibcode: 2017PASJ...69...98U Altcode: 2017arXiv171001678U The Sun shows a global magnetic field cycle traditionally best visible in the photosphere as a changing sunspot cycle featuring roughly an 11-year period. In addition we know that our host star also harbours small-scale magnetic fields often seen as strong concentrations of magnetic flux reaching kG field strengths. These features are situated in inter-granular lanes, where they show up bright as so-called magnetic bright points (MBPs). In this short paper we wish to analyse an homogenous, nearly 10-year-long synoptic Hinode image data set recorded from 2006 November up to 2016 February in the G-band to inspect the relationship between the number of MBPs at the solar disc centre and the relative sunspot number. Our findings suggest that the number of MBPs at the solar disc centre is indeed correlated to the relative sunspot number, but with the particular feature of showing two different temporal shifts between the decreasing phase of cycle 23 including the minimum and the increasing phase of cycle 24 including the maximum. While the former is shifted by about 22 months, the latter is only shifted by less than 12 months. Moreover, we introduce and discuss an analytical model to predict the number of MBPs at the solar disc centre purely depending on the evolution of the relative sunspot number as well as the temporal change of the relative sunspot number and two background parameters describing a possibly acting surface dynamo as well as the strength of the magnetic field diffusion. Finally, we are able to confirm the plausibility of the temporal shifts by a simplistic random walk model. The main conclusion to be drawn from this work is that the injection of magnetic flux, coming from active regions as represented by sunspots, happens on faster time scales than the removal of small-scale magnetic flux elements later on. Title: P-mode induced convective collapse in vertical expanding magnetic flux tubes? Authors: Utz, D.; van Doorsselaere, T.; Magyar, N.; Bárta, M.; Campos Rozo, J. I. Bibcode: 2017IAUS..327...86U Altcode: Small-scale kG strong magnetic field elements in the solar photosphere are often identified as so-called magnetic bright points (MBPs). In principle these MBPs represent the cross-section of a vertical, strong, magnetic flux tube which is expanding with height in the solar atmosphere. As these magnetic elements represent possible MHD wave guides, a significant interest has been already paid to them from the viewpoint of observations and simulations. In this work we would like to shed more light on a possible scenario for the creation of such strong magnetic field concentrations. The accepted standard scenario involves the convective collapse process. In this ongoing work we will show indications that this convective collapse process may become triggered by sufficiently strong pressure disturbances. However, it is highly unlikely that p-mode waves can be of such a strength. Title: Latitude dependence of the solar granulation during the minimum of activity in 2009 Authors: Muller, R.; Hanslmeier, A.; Utz, D. Bibcode: 2017A&A...598A...6M Altcode: Context. Knowledge of the latitude variation of the solar granulation properties (contrast and scale) is useful to better understand interactions between magnetic field, convection, differential rotation, and meridional circulation in the solar atmosphere.
Aims: We investigated the latitude dependence of the contrast and scale of the solar granulation, with the help of HINODE/SOT blue continuum images taken in the frame of the HOP 79 program, along the central meridian and along the equator on a monthly basis in 2009 during the last solar minimum of activity.
Methods: We selected the sharpest images in latitude and longitude intervals. The selected images in all the N-S and E-W scans taken in 2009 were combined to get statistically reliable results.
Results: The contrast of the solar granulation decreases towards the poles and the scale increases, but not regularly since a perturbation occurs at around 60° where both quantities return close to their values at the disk center.
Conclusions: Such a latitude variation in a period of minimum of activity (2009), is probably not due to magnetic field, neither the quiet magnetic field at the surface, nor the strong magnetic flux tubes associated with active regions, which could be embedded more or less deeply in the convection zone before they reach the surface. The decrease in contrast and increase in scale towards the pole seem to be related to the differential rotation and the perturbation around 60° to the meridional circulation. Title: The Effect of Area Averaging on the Approximated Profile of the H α Spectral Line Authors: Bodnárová, M.; Utz, D.; Rybák, J. Bibcode: 2016ASPC..504...23B Altcode: The Hα line is massively used as a diagnostics of the chromosphere. Often one needs to average the line profile over some area to increase the signal to noise ratio. Thus it is important to understand how derived parameters vary with changing approximations. In this study we investigate the effect of spatial averaging of a selected area on the temporal variations of the width, the intensity and the Dopplershift of the Hα spectral line profile. The approximated profile was deduced from co-temporal observations in five points throughout the Hα line profile obtained by the tunable Lyot filter installed on the Dutch Open Telescope. We found variations of the intensity and the Doppler velocities, which were independent of the size of the area used for the computation of the area averaged Hα spectral line profile. Title: Long-term trends of magnetic bright points. I. Number of magnetic bright points at disc centre Authors: Utz, D.; Muller, R.; Thonhofer, S.; Veronig, A.; Hanslmeier, A.; Bodnárová, M.; Bárta, M.; del Toro Iniesta, J. C. Bibcode: 2016A&A...585A..39U Altcode: 2015arXiv151107767U Context. The Sun shows an activity cycle that is caused by its varying global magnetic field. During a solar cycle, sunspots, I.e. extended regions of strong magnetic fields, occur in activity belts that are slowly migrating from middle to lower latitudes, finally arriving close to the equator during the cycle maximum phase. While this and other facts about the strong extended magnetic fields have been well known for centuries, much less is known about the solar cycle evolution of small-scale magnetic fields. Thus the question arises if similar principles exist for small-scale magnetic fields.
Aims: To address this question, we study magnetic bright points (MBPs) as proxies for such small-scale, kG solar magnetic fields. This study is based on a homogeneous data set that covers a period of eight years. The number of detected MBPs versus time is analysed to find out if there is an activity cycle for these magnetic features too and, if so, how it is related to the sunspot cycle.
Methods: An automated MBP identification algorithm was applied to the synoptic Hinode/SOT G-band data over the period November 2006 to August 2014, I.e. covering the decreasing phase of Cycle 23 and the rise, maximum, and early decrease of Cycle 24. This data set includes, at the moment of investigation, a total of 4162 images, with about 2.9 million single MBP detections.
Results: After a careful preselection and monthly median filtering of the data, the investigation revealed that the number of MBPs close to the equator is coupled to the global solar cycle but shifted in time by about 2.5 yr. Furthermore, the instantaneous number of detected MBPs depends on the hemisphere, with one hemisphere being more prominent, I.e. showing a higher number of MBPs. After the end of Cycle 23 and at the starting point of Cycle 24, the more active hemisphere changed from south to north. Clear peaks in the detected number of MBPs are found at latitudes of about ±7°, in congruence with the positions of the sunspot belts at the end of the solar cycle.
Conclusions: These findings suggest that there is indeed a coupling between the activity of MBPs close to the equator with the global magnetic field. The results also indicate that a significant fraction of the magnetic flux that is visible as MBPs close to the equator originates from the sunspot activity belts. However, even during the minimum of MBP activity, a percentage as large as 60% of the maximum number of detected MBPs has been observed, which may be related to solar surface dynamo action. Title: Fulfilling Magnetostatic Conditions in Numerical Simulations of Expanding Flux Tubes Authors: Utz, D.; Van Doorsselaere, T.; Kühner, O.; Magyar, N.; Calvo Santamaria, I.; Campos Rozo, J. I. Bibcode: 2016CEAB...40....9U Altcode: A long-lasting problem of solar physics is the topic of the heating of the outer atmospheric layers of the Sun. Among the possible heating scenarios are wave driven heating processes. In this scenario disturbances and turbulence in the photosphere of the Sun causes the creation of waves which propagate upwards into the higher atmosphere where these waves are at least partially damped and absorbed, causing heating of the atmosphere. Nowadays it is thought that especially MHD waves play an important role in such heating scenarios. The created MHD waves are guided especially well along strong vertical magnetic field configurations, so-called flux-tubes, into the higher atmosphere. To obtain deeper insights into this fascinating topic, numerical simulations are a useful tool at hand. However, up to now it is still quite common to assume simple non stratified flux tubes which feature in addition weak magnetic field strengths. While this makes the modeling of the solar atmosphere and the magnetic field configuration much easier, the results might be changed drastically by these simplifications. In the current contribution we wish to outline a method of how to construct self-consistent, magneto-static flux tube atmospheres. Title: Parallelization of the SIR code for the investigation of small-scale features in the solar photosphere Authors: Thonhofer, Stefan; Bellot Rubio, Luis R.; Utz, Dominik; Hanslmeier, Arnold; Jurçák, Jan Bibcode: 2015IAUS..305..251T Altcode: 2015arXiv150303710T Magnetic fields are one of the most important drivers of the highly dynamic processes that occur in the lower solar atmosphere. They span a broad range of sizes, from large- and intermediate-scale structures such as sunspots, pores and magnetic knots, down to the smallest magnetic elements observable with current telescopes. On small scales, magnetic flux tubes are often visible as Magnetic Bright Points (MBPs). Apart from simple V/I magnetograms, the most common method to deduce their magnetic properties is the inversion of spectropolarimetric data. Here we employ the SIR code for that purpose. SIR is a well-established tool that can derive not only the magnetic field vector and other atmospheric parameters (e.g., temperature, line-of-sight velocity), but also their stratifications with height, effectively producing 3-dimensional models of the lower solar atmosphere. In order to enhance the runtime performance and the usability of SIR we parallelized the existing code and standardized the input and output formats. This and other improvements make it feasible to invert extensive high-resolution data sets within a reasonable amount of computing time. An evaluation of the speedup of the parallel SIR code shows a substantial improvement in runtime. Title: Magnetic bright point dynamics and evolutions observed by Sunrise/IMaX and other instruments Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot Rubio, L.; Thonhofer, S.; Jurčák, J. Bibcode: 2015hsa8.conf..689U Altcode: In this proceeding we will have a closer look on recent observations and results regarding the dynamics and evolution of so-called magnetic bright points (MBPs). MBPs are manifestations of kG magnetic field strong flux concentrations seen in the solar photosphere. They belong to the class of small-scale solar magnetic features with diameters starting from low values around the current observational resolution limit - about 100 km - up to a few hundred km. They might play an important role in several key research questions like the total solar irradiance variation (TSI variation) as well as the solar atmospheric heating problem. Especially their dynamic behaviour is of interest for the heating problem as they might trigger all kinds of MHD waves which travel up to the higher solar atmospheric layers, where they can get damped leading to a heating of the plasma. Furthermore they might engage in magnetic field reconnection processes leading consequently also to a heating. Due to these reasons, and also for the sake of a better understanding of the physical processes involved on small-scales, detailed investigations on the dynamical behaviour and evolution of such magnetic field proxies like MBPs is in order. In this conference proceeding we wish to give in a first part an overview about the obtained knowledge so far. In a second part we highlight recent results regarding the dynamical evolution of plasma parameters of MBPs such as magnetic field strength, temperature, and line of sight velocity. This proceeding is completed by an outlook on what can and should be done in the near future with available data from recent telescopes. Title: Long time variations of Magnetic Bright Points observed by Hinode/SOT Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot-Rubio, L.; Bodnárová, M.; Muller, R.; Bárta, M.; Thonhofer, S.; Hanslmeier, A. Bibcode: 2015CEAB...39...91U Altcode: Magnetic bright points (MBPs) are manifestations of small-scale solar magnetic flux concentrations, best observable due to their high contrast in molecular bands like the G-band. Moreover, they are among the most interesting magnetic features to be studied in high spatial and temporal resolution in the solar photosphere. Their relevance for solar physics is not only given by their contribution to fundamental solar plasma physics on small scales but in addition due to their involvement in processes like the solar atmospheric heating problem (chromosphere and corona), their influence on granulation and hence the convective energy transport, as well as their contribution to the variations in total solar irradiance caused by their higher relative intensity. In this ongoing study we focus on the long-time evolution of statistical parameters of MBPs over the solar cycle. Are parameters like the mean intensity, average size/diameter, and number of MBPs per unit surface element variable with time? If so, how do these parameters vary and is there a relationship to the solar cycle? In the actual contribution we will discuss preliminary results regarding the variation of the number of MBPs with time. We saw a decrease in the number of MBPs for the first years of observation (2006 until 2011) with two distinct local minima in the years 2009 and 2011. After 2011 the number of MBPs is increasing again along with an increase in general solar activity (as seen by the number of sunspots, flares, and CMEs). Title: The Formation and Disintegration of Magnetic Bright Points Observed by Sunrise/IMaX Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot Rubio, L. R.; Jurčák, J.; Martínez Pillet, V.; Solanki, S. K.; Schmidt, W. Bibcode: 2014ApJ...796...79U Altcode: 2014arXiv1411.3240U The evolution of the physical parameters of magnetic bright points (MBPs) located in the quiet Sun (mainly in the interwork) during their lifetime is studied. First, we concentrate on the detailed description of the magnetic field evolution of three MBPs. This reveals that individual features follow different, generally complex, and rather dynamic scenarios of evolution. Next, we apply statistical methods on roughly 200 observed MBP evolutionary tracks. MBPs are found to be formed by the strengthening of an equipartition field patch, which initially exhibits a moderate downflow. During the evolution, strong downdrafts with an average velocity of 2.4 km s-1 set in. These flows, taken together with the concurrent strengthening of the field, suggest that we are witnessing the occurrence of convective collapses in these features, although only 30% of them reach kG field strengths. This fraction might turn out to be larger when the new 4 m class solar telescopes are operational as observations of MBPs with current state of the art instrumentation could still be suffering from resolution limitations. Finally, when the bright point disappears (although the magnetic field often continues to exist) the magnetic field strength has dropped to the equipartition level and is generally somewhat weaker than at the beginning of the MBP's evolution. Also, only relatively weak downflows are found on average at this stage of the evolution. Only 16% of the features display upflows at the time that the field weakens, or the MBP disappears. This speaks either for a very fast evolving dynamic process at the end of the lifetime, which could not be temporally resolved, or against strong upflows as the cause of the weakening of the field of these magnetic elements, as has been proposed based on simulation results. It is noteworthy that in about 10% of the cases, we observe in the vicinity of the downflows small-scale strong (exceeding 2 km s-1) intergranular upflows related spatially and temporally to these downflows. The paper is complemented by a detailed discussion of aspects regarding the applied methods, the complementary literature, and in depth analysis of parameters like magnetic field strength and velocity distributions. An important difference to magnetic elements and associated bright structures in active region plage is that most of the quiet Sun bright points display significant downflows over a large fraction of their lifetime (i.e., in more than 46% of time instances/measurements they show downflows exceeding 1 km s-1). Title: On Dynamics of G-Band Bright Points Authors: Bodnárová, M.; Utz, D.; Rybák, J. Bibcode: 2014SoPh..289.1543B Altcode: 2013arXiv1312.5464B Various parameters describing the dynamics of G-band bright points (GBPs) were derived from G-band images, acquired by the Dutch Open Telescope (DOT), of a quiet region close to the disk center. Our study is based on four commonly used diagnostics (effective velocity, change in the effective velocity, change in the direction angle, and centrifugal acceleration) and two new ones (rate of motion and time lag between recurrence of GBPs). The results concerning the commonly used parameters are in agreement with previous studies for a comparable spatial and temporal resolution of the used data. The most probable value of the effective velocity is ∼ 0.9 km s−1, whereas we found a deviation of the effective velocity distribution from the expected Rayleigh function for velocities in the range from 2 to 4 km s−1. The change in the effective velocity distribution is consistent with a Gaussian one with FWHM=0.079 km s−2. The distribution of the centrifugal acceleration exhibits a highly exponential nature (a symmetric Gaussian centered at the zero value). To broaden our understanding of the dynamics of GBPs, two new parameters were defined: the real displacement between their appearance and disappearance (rate of motion) and the frequency of their recurrence at the same locations (time lag). For ∼ 45 % of the tracked GBPs, their displacement was found to be small compared to their size (the rate of motion smaller than one). The locations of the tracked GBPs mainly cover the boundaries of supergranules representing the network, and there is no significant difference in the locations of GBPs with small (m<1) and large (m>2) values of the rate of motion. We observed a difference in the overall trend of the obtained distribution for the values of the time lag smaller (slope of the trend line being −0.14) and greater (−0.03) than ∼ 7 min. The time lags mostly lie within the interval of ∼ 2 - 3 min, with those up to ∼ 4 min being more abundant than longer ones. Results for both new parameters indicate that the locations of different dynamical types of GBPs (stable/farther traveling or with short/long lifetimes) are bound to the locations of more stable and long-living magnetic field concentrations. Thus, the disappearance/reappearance of the tracked GBPs cannot be perceived as the disappearance/reappearance of their corresponding magnetic field concentrations. Title: Two-dimensional segmentation of small convective patterns in radiation hydrodynamics simulations Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Veronig, A.; Thonhofer, S.; Grimm-Strele, H.; Kariyappa, R. Bibcode: 2014A&A...563A.107L Altcode: 2015arXiv150500325L Context. Recent results from high-resolution solar granulation observations indicate the existence of a population of small granular cells that are smaller than 600 km in diameter. These small convective cells strongly contribute to the total area of granules and are located in the intergranular lanes, where they form clusters and chains.
Aims: We study high-resolution radiation hydrodynamics simulations of the upper convection zone and photosphere to detect small granular cells, define their spatial alignment, and analyze their physical properties.
Methods: We developed an automated image-segmentation algorithm specifically adapted to high-resolution simulations to identify granules. The resulting segmentation masks were applied to physical quantities, such as intensity and vertical velocity profiles, provided by the simulation. A new clustering algorithm was developed to study the alignment of small granular cells.
Results: Small granules make a distinct contribution to the total area of granules and form clusters of chain-like alignments. The simulation profiles demonstrate a different nature for small granular cells because they exhibit on average lower intensities, lower horizontal velocities, and are located deeper inside of convective layers than regular granules. Their intensity distribution deviates from a normal distribution as known for larger granules, and follows a Weibull distribution. Title: Fractal Dimension Analysis of Solar Granulation- Boxcounting dimension Authors: Hanslmeier, A.; Lemmerer, B.; Utz, D.; Muller, R.; Muthsam, H. Bibcode: 2014CEAB...38...11H Altcode: The fractal dimension of high resolution Hinode solar granulation observations and numerical simulations is studied and the results are compared. These observations are not influenced by atmospheric seeing conditions and therefore allow a more realistic estimate of the fractal dimension than in previous works. Though arriving at similar results for observations and simulation data, non integer fractal dimension <2, some differences in the numerical values occur, and these are discussed. Title: Detection of small convective patterns in observations and simulations Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Veronig, A.; Grimm-Strele, H.; Thonhofer, S.; Piantschitsch, I. Bibcode: 2014CEAB...38...19L Altcode: Recent results from high resolution solar granulation observations indicate the existence of a population of small granular cells on scales below 600 km in diameter, located in the intergranular lanes. We studied a set of Hinode SOT images and high resolution radiation hydrodynamics simulations in order to analyze small granular cells and to study their physical properties. An automated image segmentation algorithm specifically adapted to high resolution simulations for the identification of granules was developed. The algorithm was also used to analyze and compare physical quantities provided by the simulation and the observations. We found that small granules make a distinct contribution to the total area of granules. Both in observations and simulations, small granular cells exhibit on average lower intensities and vertical velocities. Title: Solar Ca II K plage regions as proxies for magnetic fields of solar like stars Authors: Guttenbrunner, S.; Hanslmeier, A.; Utz, D.; Lemmerer, B.; Piantschitsch, I.; Thonhofer, S. Bibcode: 2014CEAB...38...81G Altcode: Solar plage regions can be observed directly, whereas plage regions as well as star-spots on solar like stars, can only be detected via their contribution to spectral irradiances of these stars. Such a spectral irradiance can be modelled by fractions belonging to the quiet star, the plage regions, and the star-spots. The idea is, to measure these fractions as well as the intensity enhancement due to plage regions on our Sun and then use this information to be able to model solar like stars. We verify the close connection between the size of the plage regions and the luminosity of the Sun, given by a correlation coefficient of 0.822. The size of the plage regions varies from 0%, when the Sun is very quiet, up to 2.7% for a more active Sun (a complete solar cycle is not yet analysed and hence our study does not contain an activity maximum). The used data sets are full-disc images taken by the RISE/PSPT instrument during the period from 2005 to 2012, at the MLSO. Title: Two-Fluid 2.5D MHD-Code for Simulations in the Solar Atmosphere Authors: Piantschitsch, I.; Amerstorfer, U.; Thalmann, J.; Utz, D.; Hanslmeier, A.; Bárta, M.; Thonhofer, S.; Lemmerer, B. Bibcode: 2014CEAB...38...59P Altcode: We investigate magnetic reconnection due to the evolution of magnetic flux tubes in the solar chromosphere. We developed a new numerical two-fluid magnetohydrodynamic (MHD) code which will perform a 2.5D simulation of the dynamics from the upper convection zone up to the transition region. Our code is based on the Total Variation Diminishing Lax-Friedrichs scheme and makes use of an alternating-direction implicit method, in order to accommodate the two spatial dimensions. Since we apply a two-fluid model for our simulations, the effects of ion-neutral collisions, ionization/recombination, thermal/resistive diffusivity and collisional/resistive heating are included in the code. As initial conditions for the code we use analytically constructed vertically open magnetic flux tubes within a realistic stratified atmosphere. Initial MHD tests have already shown good agreement with known results of numerical MHD test problems like e.g. the Orszag-Tang vortex test. Title: New insights into the evolution of magnetic bright point plasma parameters Authors: Utz, Dominik; Hanslmeier, Arnold; Bellot Rubio, L. R.; Del Toro Iniesta, Jose Carlos; Jurcak, Jan Bibcode: 2014cosp...40E3448U Altcode: The dynamics within the solar atmosphere are governed by the Suńs magnetic fields. In the recent years the resolution limits were steadily driven up by better and better instruments and telescopes (like Hinode, Sunrise, NST, Gregor, ..) leading to higher resolved data. Therefore the interest in ever smaller magnetic field structures within the solar atmosphere rises. Among the smallest yet identified structures are so-called magnetic bright points (MBPs). These features are thought to be made up of single flux tubes and they have been studied exhaustively in the Fraunhofer G-band since the 70´s of the last century. They are important features not only due to their small scale (about 200 km in diameter) and hence used as proxies for the smallest solar magnetic field physics and processes, but also because they are involved in topics like the chromospheric/coronal heating problem or the total solar irradiance variation. In the current contribution we want to study the evolution of important plasma parameters of MBPs, such as temperature, magnetic field strength and line of sight velocity, to get a deeper understanding of the involved physics and occuring processes. Among the used data will be G-band filtergam data from Hinode/SOT and spectro-polarimetric data from the IMaX instrument onboard the Sunrise mission. Title: New insights into the temporal evolution of MBPs Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot Rubio, L. R.; Jurčak, J.; Thonhofer, S.; Bodnárová, M.; Hanslmeier, A.; Lemmerer, B.; Piantschitsch, I.; Guttenbrunner, S. Bibcode: 2014CEAB...38...73U Altcode: Magnetic bright points (MBPs) are among the most fascinating and interesting manifestations of small-scale solar magnetic fields. In the present work the temporal evolution of MBPs is followed in data sets taken by the Hinode satellite. The analysed data and obtained results confirm a recently presented study done with Sunrise/IMaX data, namely that MBPs are features undergoing fast evolution with magnetic fields starting around the equipartition field strength, then showing strong downflows (between 2 to 4 km/s) causing the magnetic field to amplify into the kG range (700 to 1500 G) before dissolving again. Furthermore the initial field inclinations depend on the initial magnetic field strengths and show an evolution with more vertical angles at some point during the evolution. Title: Parallelization of the SIR code Authors: Thonhofer, S.; Bellot Rubio, L. R.; Utz, D.; Jurčak, J.; Hanslmeier, A.; Piantschitsch, I.; Pauritsch, J.; Lemmerer, B.; Guttenbrunner, S. Bibcode: 2014CEAB...38...31T Altcode: A high-resolution 3-dimensional model of the photospheric magnetic field is essential for the investigation of small-scale solar magnetic phenomena. The SIR code is an advanced Stokes-inversion code that deduces physical quantities, e.g. magnetic field vector, temperature, and LOS velocity, from spectropolarimetric data. We extended this code by the capability of directly using large data sets and inverting the pixels in parallel. Due to this parallelization it is now feasible to apply the code directly on extensive data sets. Besides, we included the possibility to use different initial model atmospheres for the inversion, which enhances the quality of the results. Title: Temporal variations in solar magnetic bright points intensity and plasma parameters Authors: Jurčák, J.; Utz, D.; Bellot Rubio, L. R. Bibcode: 2013JPhCS.440a2032J Altcode: Magnetic bright points are one of the finest magnetic structures observed in the solar atmosphere. They possibly represent single flux tubes in quiet Sun regions. Their formation is described by the convective collapse model, while the decay phase of these structures is not well characterized yet. We attempt to follow the evolution of a few selected examples of MBPs and to study their changes in brightness and also the variations of plasma parameters during their lifetime. We use data from the Hinode satellite and the Sunrise mission. The G-band observations taken with a cadence of 30 seconds by the Hinode Solar Optical Telescope (SOT) show very fast changes of the maximum intensity of these structures. The complementary spectropolarimetric data, which are used to estimate the plasma parameters, were taken with a cadence of approximately two minutes. The variations of plasma parameters cannot be matched one to one to the changes in intensity due to the different temporal resolution. However, the slow changes of intensity with large amplitude are matched with variations of magnetic field strength and line-of-sight (LOS) velocity. The Sunrise/IMaX data have a temporal resolution of 32 seconds and show fast variations in the line wing intensity. These variations are associated with changes in the magnetic field strength and LOS velocity. Title: Variations of Magnetic Bright Point Properties with Longitude and Latitude as Observed by Hinode/SOT G-band Data Authors: Utz, D.; Hanslmeier, A.; Veronig, A.; Kühner, O.; Muller, R.; Jurčák, J.; Lemmerer, B. Bibcode: 2013SoPh..284..363U Altcode: 2012arXiv1212.1310U Small-scale magnetic fields can be observed on the Sun in high-resolution G-band filtergrams as magnetic bright points (MBPs). We study Hinode/Solar Optical Telescope (SOT) longitude and latitude scans of the quiet solar surface taken in the G-band in order to characterise the centre-to-limb dependence of MBP properties (size and intensity). We find that the MBP's sizes increase and their intensities decrease from the solar centre towards the limb. The size distribution can be fitted using a log-normal function. The natural logarithm of the mean (μ parameter) of this function follows a second-order polynomial and the generalised standard deviation (σ parameter) follows a fourth-order polynomial or equally well (within statistical errors) a sine function. The brightness decrease of the features is smaller than one would expect from the normal solar centre-to-limb variation; that is to say, the ratio of a MBP's brightness to the mean intensity of the image increases towards the limb. The centre-to-limb variations of the intensities of the MBPs and the quiet-Sun field can be fitted by a second-order polynomial. The detailed physical process that results in an increase of a MBP's brightness and size from Sun centre to the limb is not yet understood and has to be studied in more detail in the future. Title: Magnetic field strength distribution of magnetic bright points inferred from filtergrams and spectro-polarimetric data Authors: Utz, D.; Jurčák, J.; Hanslmeier, A.; Muller, R.; Veronig, A.; Kühner, O. Bibcode: 2013A&A...554A..65U Altcode: 2013arXiv1304.5508U Context. Small scale magnetic fields can be observed on the Sun in G-band filtergrams as magnetic bright points (MBPs) or identified in spectro-polarimetric measurements due to enhanced signals of Stokes profiles. These magnetic fields and their dynamics play a crucial role in understanding the coronal heating problem and also in surface dynamo models. MBPs can theoretically be described to evolve out of a patch of a solar photospheric magnetic field with values below the equipartition field strength by the so-called convective collapse model. After the collapse, the magnetic field of MBPs reaches a higher stable magnetic field level.
Aims: The magnetic field strength distribution of small scale magnetic fields as seen by MBPs is inferred. Furthermore, we want to test the model of convective collapse and the theoretically predicted stable value of about 1300 G.
Methods: We used four different data sets of high-resolution Hinode/SOT observations that were recorded simultaneously with the broadband filter device (G-band, Ca II-H) and the spectro-polarimeter. To derive the magnetic field strength distribution of these small scale features, the spectropolarimeter (SP) data sets were treated by the Merlin inversion code. The four data sets comprise different solar surface types: active regions (a sunspot group and a region with pores), as well as quiet Sun.
Results: In all four cases the obtained magnetic field strength distribution of MBPs is similar and shows peaks around 1300 G. This agrees well with the theoretical prediction of the convective collapse model. The resulting magnetic field strength distribution can be fitted in each case by a model consisting of log-normal components. The important parameters, such as geometrical mean value and multiplicative standard deviation, are similar in all data sets, so only the relative weighting of the components is different. Title: The Height Evolution of the "True" Coronal Mass Ejection Mass derived from STEREO COR1 and COR2 Observations Authors: Bein, B. M.; Temmer, M.; Vourlidas, A.; Veronig, A. M.; Utz, D. Bibcode: 2013ApJ...768...31B Altcode: 2013arXiv1303.3372B Using combined STEREO-A and STEREO-B EUVI, COR1, and COR2 data, we derive deprojected coronal mass ejection (CME) kinematics and CME "true" mass evolutions for a sample of 25 events that occurred during 2007 December to 2011 April. We develop a fitting function to describe the CME mass evolution with height. The function considers both the effect of the coronagraph occulter, at the beginning of the CME evolution, and an actual mass increase. The latter becomes important at about 10-15 R ⊙ and is assumed to mostly contribute up to 20 R ⊙. The mass increase ranges from 2% to 6% per R ⊙ and is positively correlated to the total CME mass. Due to the combination of COR1 and COR2 mass measurements, we are able to estimate the "true" mass value for very low coronal heights (<3 R ⊙). Based on the deprojected CME kinematics and initial ejected masses, we derive the kinetic energies and propelling forces acting on the CME in the low corona (<3 R ⊙). The derived CME kinetic energies range between 1.0-66 × 1023 J, and the forces range between 2.2-510 × 1014 N. Title: Creating 3-dimensional Models of the Photosphere using the SIR Code Authors: Thonhofer, S.; Utz, D.; Jurčák, J.; Pauritsch, J.; Hanslmeier, A.; Lemmerer, B. Bibcode: 2013CEAB...37..471T Altcode: A high-resolution 3-dimensional model of the photospheric magnetic field is essential for the investigation of magnetic features such as sunspots, pores or smaller elements like single flux tubes seen as magnetic bright points. The SIR code is an advanced inversion code that retrieves physical quantities, e.g. magnetic field, from Stokes profiles. Based on this code, we developed a program for automated inversion of Hinode SOT/SP data and for storing these results in 3-dimensional data cubes in the form of fits files. We obtained models of the temperature, magnetic field strength, magnetic field angles and LOS-velocity in a region of the quiet sun. We will give a first discussion of those parameters in regards of small scale magnetic fields and what we can obtain and learn in the future. Title: A Magnetic Bright Point Case Study Authors: Utz, D.; Jurčák, J.; Bellot-Rubio, L.; del Toro Iniesta, J. C.; Thonhofer, S.; Hanslmeier, A.; Veronig, A.; Muller, R.; Lemmerer, B. Bibcode: 2013CEAB...37..459U Altcode: Due to its magnetic fields our host star - the Sun - becomes the interesting object for research as we know it. The magnetic fields themselves cover different spatial, lifetime and strength scales and reach down from enormous flux concentrations like active sunspot groups to single isolated magnetic flux tubes and even weaker, predominantly inclined intranetwork structures. Flux tubes can be seen in filtergram observations as magnetic bright points (MBPs). They are of interest for research not only due to their sheer existence but due to their important role in atmospheric heating (wave heating as well as reconnection processes), to their role in the understanding of creation and annihilation of magnetic fields as well as to their influence on the total solar irradiance variation. In this study we present a close look onto an evolutionary track of an MBP from its formation to its disintegration. Physical quantities of MBPs like their magnetic field strength and inclination, their line-of-sight velocity, and their temperature at different heights are inferred from the inversion of spectropolarimetric data. Original data are taken from the Sunrise/IMaX instrument and constitute a time series of some 60 min. The presented case resembles the convective collapse model and is in agreement with previous studies. Title: 3D Image Segmentation Applied to Solar RHD Simulations Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Veronig, A.; Grimm-Strele, H.; Thonhofer, S.; Muthsam, H. Bibcode: 2013CEAB...37..477L Altcode: 3D simulation models based on Magneto-hydrodynamics (MHD) and Radiation-hydrodynamics (RHD) equations give insight into the evolution of magnetic fields and convective motions in the solar atmosphere. The analysis of huge amount of data require the development of automated segmentation algorithms. A newly developed 3D segmentation algorithm will be introduced in order to extract and trace convective downflows and is applied to the numerical simulation code ANTARES. The algorithm segments strong downflow velocities resulting in tube-like structures which enables us to analyze the motions with respect to variations of physical parameters over height as well as their evolution with time. Analysis of the segmented structures shows that narrower parts tend to have higher velocities. High temporal variations in the lower model photosphere indicate less stable structures over time in this layer. The mean temperature within the downflow is cooler than in the horizontally averaged simulation box. The analysis of the behavior of vortex flows demonstrates a constant high vorticity within the segment and a linear dependency to the vertical velocity. It appears that vortex flows are strongly present within dominant convective downflows. Title: The Solar Convection over a Solar Cycle Authors: Hanslmeier, A.; Muller, R.; Utz, D. Bibcode: 2012ASPC..463..115H Altcode: We study the variation of granular size and contrast over a solar activity cycle. Two different homogeneous data samples were used, from Pic du Midi and from Hinode. The results do not confirm previous values cited in the literature. From the Hinode data the granulation seems to be constant, the trend found may be of instrumental degradation. We try to explain the result by other observations like the total solar irradiance variation. This variation was small over the past five years and may explain why in the case of Hinode data no significant variations were found. Title: Dependence of Velocity Distributions of Small-Scale Magnetic Fields Derived from Hinode/SOT G-band Filtergrams on the Temporal Resolution of the Used Data Sets Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Veronig, A.; Rybák, J.; Muthsam, H. Bibcode: 2012ASPC..454...55U Altcode: The dynamics of isolated small-scale fields in terms of velocities of magnetic bright points (MBPs) is addressed in this contribution. The empirically determined linear relation between the observed width parameter for the Rayleigh velocity distribution of MBPs versus the temporal cadence of the acquired data is studied by simulations and a simple analytical model. The results of the model and the simulation agree with the found relation for the observations. The conclusion we draw from the model is that there may be no characteristic velocity for MBPs at all. Title: Automated image inversion using SIR compared to MERLIN Code Authors: Thonhofer, S.; Utz, D.; Pauritsch, J.; Hanslmeier, A.; Jurčak, J.; Lemmerer, B.; Kühner, O. Bibcode: 2012CEAB...36...35T Altcode: The SIR code retrieves magnetic and thermodynamic parameters of the solar atmosphere from the Stokes profiles. By means of this tool, the stratification of physical quantities from spectropolarimetric data is obtained and a complete model of the solar photosphere is constructed. Automated SIR inversions of a HINODE data set were performed and the output is compared to results of the MERLIN code, another widespread inversion code in solar physics. Title: Centre to limb intensity variation of magnetic bright points Authors: Utz, D.; Kühner, O.; Hanslmeier, A.; Veronig, A.; Muller, R.; Lemmerer, B.; Pauritsch, J.; Thonhofer, S. Bibcode: 2012CEAB...36...17U Altcode: The solar activity cycle is strongly related and rooted to photospheric magnetic fields. Up to the present, it was mostly or even solely studied by extended fields such as sunspots, sunspot groups or active regions. Interestingly, the domain of magnetic fields on the Sun is not only limited to extended and strong magnetic fields but reaches down to small elements like single flux tubes. These flux elements can be identified in G-band filtergrams as so called magnetic bright points (MBPs). In this study we want to investigate the centre limb variation of the mean MBP intensity for the period of the recent solar minimum up to present (10/2008 - 10/2011). We found that a 4th order polynomial describes the centre limb variation fairly well. Furthermore we established for the symmetrized and normalized centre limb variation (for which the 1st and 3rd order parameter of the polynomial is fixed to zero) a relationship between the 2nd and 4th order fit parameter. Hence it is possible to derive a description with only one free parameter. Finally, we studied the variation with time of this parameter for the period of October 2008 to present, showing a slight increase and a weak correlation to solar activity as given by the relative sunspot number. Title: Segmentation of Data from Simulations and Observations - Evaluation and Outlook Authors: Lemmerer, B.; Utz, D.; Hanslmeier, A.; Kühner, O.; Grimm-Strele, H.; Pauritsch, J.; Thonhofer, S.; Muthsam, H. Bibcode: 2012CEAB...36...29L Altcode: 3D simulation models based on Magneto-hydrodynamics (MHD) and Radiation hydrodynamics (RHD) equations give an insight into the evolution of magnetic field lines and convective motions. A 2D segmentation algorithm was applied to data of the Japanese/US/European space mission Hinode and its solar optical telescope (SOT) as well as on 3D models of the numerical simulation code ANTARES in order to study the solar granulation and evaluate the algorithm. As a next research step, the development of a 3D segmentation algorithm, adapted to the simulation models, is required for the purpose of extracting magnetic and convective phenomena, which furthermore enable an exact tracing of their evolution. Title: Non-Varying Granulation and Photospheric Network During the Extended 2007 - 2009 Solar Minimum Authors: Muller, R.; Utz, D.; Hanslmeier, A. Bibcode: 2011SoPh..274...87M Altcode: We have analysed the wide band images taken by Hinode/SOT, in a blue continuum window and in the G-band, more or less on a daily basis in the frame of the synoptic program, to investigate the variation of the solar granulation and of the photospheric network with the activity cycle. A particular attention has been given to disentangle solar effects from instrumental ones. It appears that a substantial fraction of the images are more or less blurred and/or defocussed. During the analysed period November 2006 - July 2010, the granulation contrast of the sharpest selected images decreased steadily, the granulation scale increased and the number of MBPs decreased (they are the Bright Points of Magnetic origin which form the photospheric network in G-band images). These trends are likely of instrumental origin. Consequently, the granulation and the photospheric network have most probably not changed during the extended solar minimum 2007 - 2009. Title: Impulsive Acceleration of Coronal Mass Ejections. I. Statistics and Coronal Mass Ejection Source Region Characteristics Authors: Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.; Temmer, M.; Muhr, N.; Kienreich, I.; Utz, D.; Vršnak, B. Bibcode: 2011ApJ...738..191B Altcode: 2011arXiv1108.0561B We use high time cadence images acquired by the STEREO EUVI and COR instruments to study the evolution of coronal mass ejections (CMEs) from their initiation through impulsive acceleration to the propagation phase. For a set of 95 CMEs we derived detailed height, velocity, and acceleration profiles and statistically analyzed characteristic CME parameters: peak acceleration, peak velocity, acceleration duration, initiation height, height at peak velocity, height at peak acceleration, and size of the CME source region. The CME peak accelerations we derived range from 20 to 6800 m s-2 and are inversely correlated with the acceleration duration and the height at peak acceleration. Seventy-four percent of the events reach their peak acceleration at heights below 0.5 R sun. CMEs that originate from compact sources low in the corona are more impulsive and reach higher peak accelerations at smaller heights. These findings can be explained by the Lorentz force, which drives the CME accelerations and decreases with height and CME size. Title: Multiwavelength Investigations of Magnetic Bright Points Authors: Kühner, O.; Utz, D.; Hanslmeier, A.; Veronig, A.; Roudier, T.; Muller, R.; Muthsam, H. Bibcode: 2011CEAB...35...29K Altcode: In this contribution we present our results regarding the study of small scale magnetic fields as seen by magnetic bright points (MBPs) in different wavelengths and hence different heights. By the determination of the size distribution of these features we are able to derive the value of the scale height parameter for the photosphere: 107 km ± 18.5 km. For the Fe I line at 630.25 nm we derived a formation height of 225 km. Title: Magnetic energy estimation for small scale magnetic fields Authors: Utz, D.; Hanslmeier, A.; Veronig, A.; Kühner, O.; Muller, R.; Muthsam, H. Bibcode: 2011CEAB...35...19U Altcode: In this paper we derive an estimate of the energy content of small scale magnetic

fields as observed by magnetic bright points (MBPs). For our estimations we use as inputs the size, lifetime, magnetic field strength of MBPs and the average number density of those features in the quiet Sun. Furthermore we introduce an evolutionary model for MBPs. Our results suggest that there is enough magnetic field energy stored in kG fields as seen by MBPs to heat the chromosphere and corona. The actual heating mechanism and process has to be investigated in the future. Title: Dynamika fotosférických jasných bodov v G-páse odvodená použitím dvoch plne automatických algoritmov Title: Dynamika fotosférických jasných bodov v G-páse odvodená použitím dvoch plne automatických algoritmov Title: Dynamics of photospheric bright points in G-band derived from two fully automated algorithms. Authors: Bodnárová, M.; Rybák, J.; Hanslmeier, A.; Utz, D. Bibcode: 2010nspm.conf...25B Altcode: Concentrations of small-scale magnetic field in the solar photosphere can be identified in the G-band of the solar spectrum as bright points. Studying the dynamics of the bright points in the G-band (BPGBs) can also help in addressing many issues related to the problem of the solar corona heating. In this work, we have used a set of 142 specled images in the G-band taken by the Dutch Open Telescope (DOT) on 19 October 2005 to make a comparison of two fully automated algorithms identifying BPGBs: an algorithm developed by Utz et al. (2009, 2010), and an algorithm developed following the work of Berger et al. (1995, 1998). We then followed in time and space motion of the BPGBs identified by both algorithms and constructed the distributions of their lifetimes, sizes and speeds. The results show that both algorithms give very similar results for the BPGB lifetimes and speeds, but their results vary significantly for the sizes of the identified BPGBs. This difference is due to the fact that in the case of the Berger et al. identification algorithm no additional criteria were applied to constrain the allowed BPGB sizes. As a result in further studies of the BPGB dynamics we will prefer to use the Utz algorithm to identify and track BPGBs. Title: Dynamics of isolated magnetic bright points derived from Hinode/SOT G-band observations Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Veronig, A.; Rybák, J.; Muthsam, H. Bibcode: 2010A&A...511A..39U Altcode: 2009arXiv0912.1965U Context. Small-scale magnetic fields in the solar photosphere can be identified in high-resolution magnetograms or in the G-band as magnetic bright points (MBPs). Rapid motions of these fields can cause magneto-hydrodynamical waves and can also lead to nanoflares by magnetic field braiding and twisting. The MBP velocity distribution is a crucial parameter for estimating the amplitudes of those waves and the amount of energy they can contribute to coronal heating.
Aims: The velocity and lifetime distributions of MBPs are derived from solar G-band images of a quiet sun region acquired by the Hinode/SOT instrument with different temporal and spatial sampling rates.
Methods: We developed an automatic segmentation, identification and tracking algorithm to analyse G-Band image sequences to obtain the lifetime and velocity distributions of MBPs. The influence of temporal/spatial sampling rates on these distributions is studied and used to correct the obtained lifetimes and velocity distributions for these digitalisation effects.
Results: After the correction of algorithm effects, we obtained a mean MBP lifetime of (2.50 ± 0.05) min and mean MBP velocities, depending on smoothing processes, in the range of (1-2) km~s-1. Corrected for temporal sampling effects, we obtained for the effective velocity distribution a Rayleigh function with a coefficient of (1.62 ± 0.05) km~s-1. The x- and y-components of the velocity distributions are Gaussians. The lifetime distribution can be fitted by an exponential function. Title: Investigating the Variation of the Solar Granulation with HINODE Synoptic images Authors: Muller, R.; Hanslmeier, A.; Utz, D. Bibcode: 2010CEAB...34...89M Altcode: We have analysed the wide band images taken by HINODE/SOT on a daily basis in the frame of the synoptic program, to investigate the variation of the solar granulation with the activity cycle. A particular attention has been given to disentangle solar from instrumental effects. It appears that a substantial fraction of the images are more or less blurred and/or defocused. The granulation contrast decrease and scale increase of the sharpest images, observed during the period November 2006 - January 2009, is probably not of solar origin. Title: Multiwavelength alignment of Hinode/SOT Data Authors: Kuehner, O.; Utz, D.; Hanslmeier, A.; Veronig, A.; Roudier, T.; Muller, R.; Muthsam, H. Bibcode: 2010CEAB...34...31K Altcode: First results regarding the spatial alignment of observations taken at different wavelengths are presented. An exceptionally long time series (48 hours) of data, obtained by the Solar Optical Telescope (SOT) of the Hinode satellite, has been analysed. Hinode delivers (among other data) high resolution seeing free filtergrams in the magnetic sensitive G-band, blue continuum, chromospheric Ca II H line and Fe I line. For the study of the position and dynamics of small scale fields (MBPs; Magnetic Bright Points) at different wavelengths (at different heights in the photosphere and chromosphere) the alignment of these data at pixel and subpixel level will be essential. Results concerning the height dependence of MBPs will also be of vital importance for questions regarding the coronal heating. Title: G-band to Blue-Continuum Excess as quasi total field strength magnetogram Authors: Utz, D.; Hanslmeier, A.; Veronig, A.; Rybák, J.; Muller, R.; Muthsam, H. Bibcode: 2010CEAB...34...13U Altcode: The dynamics of the solar plasma is driven by strong localized magnetic fields. It is well known that activity like flares and CMEs are related to the dissipation and reconnection of these magnetic fields. These energetic releases influence and make up the so called space weather. It is therefore of vital importance to get a deeper understanding of the magnetic fields of the Sun. To get this insights, it is crucial to obtain information on the magnetic fields with spatial and temporal resolutions as high as possible. In this paper we outline an easy to apply method to obtain quasi total magnetic field strength magnetograms out of two simple filtergrams (blue continuum and G-band). We will present our simple approach and the first results of this method and give finally an outlook what has to be done in the future. Title: Hinode - Synoptic observations of convection dynamics Authors: Hanslmeier, A.; Muller, R.; Utz, D.; Roudier, T. Bibcode: 2010CEAB...34...81H Altcode: The variation of solar convection over the solar activity cycle is still discussed with controversial results. In this paper we study the solar granulation and its variation over the unusual long lasting solar minimum between cycle 23 and 24. Spatially highly resolved Hinode images were segmented and the mean value of the segmented granules as well as their number was found to be practically constant. Title: Magnetic field strength distribution of MBPs infered from Hinode/SOT filtergram and spectro-polarimetric data Authors: Utz, Dominik; Veronig, Astrid; Hanslmeier, Arnold; Muller, Richard; Muthsam, Herbert Bibcode: 2010cosp...38.2944U Altcode: 2010cosp.meet.2944U Small scale magnetic fields can be observed on the Sun in G-band filtergrams as magnetic bright points (MBPs), or by inversions of spectro-polarimetric data. In this study we used three different data sets of Hinode/SOT observations which were recorded simultaneously with the broadband filter device (G-band, Ca II-H) and the spectro-polarimeter. The spectro-polarimetric data were already prepared as magnetograms (level 2 data). For the identification of the MBPs we used an automated identification algorithm. The three data sets comprise active regions (a sunspot group and a small sunspot in the other case) as well as quiet Sun. The obtained magnetic field strength distribution of MBPs is in all three cases similar and shows a peaked maximum at 1250 G, which agrees well with theoretical predictions of the convectice collapse model. Title: Brightness profiles and size distributions of MBPs observed in different heights by HINODE/SOT data Authors: Kühner, Otmar; Veronig, Astrid; Utz, Dominik; Hanslmeier, Arnold; Muthsam, Herbert; Muller, Richard; Roudier, Thierry Bibcode: 2010cosp...38.2948K Altcode: 2010cosp.meet.2948K We study the characteristics of Magnetic Bright Points (MBPs) observed at different wave-lenghts and hence different heights of the photosphere and chromosphere. The data sets were obtained with the Solar Optical Telescope (SOT) of the Hinode satellite. Hinode delivers (among other data) high resolution seeing free filtergrams in the blue continuum, the Fe I line, the magnetic sensitive G-band and the chromospheric Ca II H line. Due to the small scale structure of MBPs it was essential for our study to develop an algorithm for the image co-alignment at subpixel level for the images taken at these four wavelenghts. We studied an exceptionally long time series (48h) and analyzed the brightness profiles and size distributions of MBPs at different heights. The mean size of the features increases with increasing height and shows an exponential behavior. We obtained the scale height parameter of the photosphere to be 110 km. Title: Dynamics of G-band bright points derived using two fully automated algorithms Authors: Bodnárová, M.; Utz, D.; Rybák, J.; Hanslmeier, A. Bibcode: 2010CEAB...34...25B Altcode: Small-scale magnetic field concentrations (∼ 1 kG) in the solar photosphere can be identified in the G-band of the solar spectrum as bright points. Study of the G-band bright points (GBPs) dynamics can help us in solving several questions related also to the coronal heating problem. Here a set of 142 G-band speckled images obtained using the Dutch Open Telescope (DOT) on October 19, 2005 are used to compare identification of the GBPs by two different fully automated identification algorithms: an algorithm developed by Utz et al. (2009a, 2009b) and an algorithm developed according to papers of Berger et al. (1995, 1998). Temporal and spatial tracking of the GBPs identified by both algorithms was performed resulting in distributions of lifetimes, sizes and velocities of the GBPs. The obtained results show that both algorithms give very similar values in the case of lifetime and velocity estimation of the GBPs, but they differ significantly in case of estimation of the GBPs sizes. This difference is caused by the fact that we have applied no additional exclusive criteria on the GBPs identified by the algorithm based on the work of Berger et al. (1995, 1998). Therefore we conclude that in a future study of the GBPs dynamics we will prefer to use the Utz's algorithm to perform identification and tracking of the GBPs in G-band images. Title: The size distribution of magnetic bright points derived from Hinode/SOT observations Authors: Utz, D.; Hanslmeier, A.; Möstl, C.; Muller, R.; Veronig, A.; Muthsam, H. Bibcode: 2009A&A...498..289U Altcode: 2009arXiv0912.2637U Context: Magnetic bright points (MBPs) are small-scale magnetic features in the solar photosphere. They may be a possible source of coronal heating by rapid footpoint motions that cause magnetohydrodynamical waves. The number and size distribution are of vital importance in estimating the small scale-magnetic-field energy.
Aims: The size distribution of MBPs is derived for G-band images acquired by the Hinode/SOT instrument.
Methods: For identification purposes, a new automated segmentation and identification algorithm was developed.
Results: For a sampling of 0.108 arcsec/pixel, we derived a mean diameter of (218 ± 48) km for the MBPs. For the full resolved data set with a sampling of 0.054 arcsec/pixel, the size distribution shifted to a mean diameter of (166 ± 31) km. The determined diameters are consistent with earlier published values. The shift is most probably due to the different spatial sampling.
Conclusions: We conclude that the smallest magnetic elements in the solar photosphere cannot yet be resolved by G-band observations. The influence of discretisation effects (sampling) has also not yet been investigated sufficiently. Title: Discretization Effects on the Size Distribution of Magnetic Bright Points Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Veronig, A.; Muthsam, H.; Möstl, C. Bibcode: 2009CEAB...33...29U Altcode: We developed an automated identification algorithm for magnetic bright points to derive the size distribution of MBPs in a quiet region near solar disc centre. For this purpose two different data sets from the Hinode/SOT mission were used. The first data set had a pixel spatial sampling of 0.108 arcsec/pixel, whereas the second data set had the full achievable spatial sampling of 0.54 arcsec/pixel. We found, that the size distribution shifted from a mean value of 218 km in diameter to a smaller value of about 166 km in diameter when the spatial sampling was higher. Therefore, we suggest that discretization effects play a crucial role for the study of small scale features. How the shift of the two distributions could be explained, and how a deeper insight into the discretization problem could be gained, is discussed. Title: The Size Distribution of Magnetic Bright Points derived from Hinode/SOT Observations Authors: Utz, D.; Hanslmeier, A.; Muller, R.; Astrid, V.; Muthsam, H.; Möstl, Ch. Bibcode: 2008ESPM...12.2.50U Altcode: In our poster we will present our results regarding the size distribution of Magnetic Bright Points (MBPs) in the solar photosphere.

The data sets were obtained through the Solar Optical Telescope (SOT) of the recent Hinode satellite. Hinode was launched in autumn 2006 and delivers (among other data) high resolution seeing free filtergrams in the magnetic sensitive G-Band. We analyzed two different data sets (with different pixel resolutions) near disk center in a network region of the quiet sun. The interesting outcome is that the derived size distribution depends on the used pixel resolution. Discretisation effects and physical implications on the derived size distributions will be discussed.