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- ItemEffects of solar evolution on finite acquisition time of Fabry-Perot interferometers in high resolution solar physics(Les Ulis : EDP Sciences, 2023) Schlichenmaier, R.; Pitters, D.; Borrero, J.M.; Schubert, M.Context. The Visible Tunable Filter (VTF) imaging spectropolarimeter will be operated at the Daniel K. Inouye Solar Telescope (DKIST) in Hawaii. Due to its capability in resolving dynamic fine structure of smaller than 0.05 arcsec, the finite acquisition time of typically 11 s affects the measurement process and potentially causes errors in deduced physical parameters. Aims. We estimate these errors and investigate ways of minimising them. Methods. We mimicked the solar surface using a magnetohydrodynamic simulation with a spatially averaged vertical field strength of 200 G. We simulated the measurement process scanning through successive wavelength points with a temporal cadence of 1 s. We synthesised Fe 1617.3 nm for corresponding snapshots. In addition to the classical composition of the line profile, we introduce a novel method where the intensity in each wavelength point is normalised using the simultaneous continuum intensity, and then multiplied by the temporal mean of the continuum intensity. Milne-Eddington inversions were used to infer the line-of-sight velocity, vlos, and the vertical (longitudinal) component of the magnetic field, Blos. Results. We quantify systematic errors, defining the temporal average of the simulation during the measurement as the truth. We find that with the classical composition of the line profiles, errors exceed the sensitivity for vlos, and in filigree regions also for Blos. The novel method that includes normalisation reduces the measurement errors in all cases. Spatial binning without reducing the acquisition time decreases the measurement error slightly. Conclusions. The evolutionary timescale in inter-granular lanes, in particular in areas with magnetic features (filigree), is shorter than the timescale within granules. Hence, depending on the science objective, fewer accumulations could be used for strong magnetic field in inter-granular lanes and more accumulations could be used for the weak granular magnetic fields. As a key result of this investigation, we suggest including the novel method of normalisation in corresponding data pipelines.
- ItemThe Polarimetric and Helioseismic Imager on Solar Orbiter(Les Ulis : EDP Sciences , 2020) Solanki, S.K.; del Toro Iniesta, J.C.; Woch, J.; Gandorfer, A.; Hirzberger, J.; Alvarez-Herrero, A.; Appourchaux, T.; Martínez Pillet, V.; Pérez-Grande, I.; Sanchis Kilders, E.; Schmidt, W.; Garranzo-García, D.; Laguna, H.; Martín, J.A.; Navarro, R.; Villanueva, J.; Núñez Peral, A.; Royo, M.; Sánchez, A.; Silva-López, M.; Fourmond, J.-J.; Berkefeld, Th.; Ruiz de Galarreta, C.; Bouzit, M.; Hervier, V.; Le Clec'h, J.C.; Szwec, N.; Chaigneau, M.; Buttice, V.; Volkmer, R.; Dominguez-Tagle, C.; Philippon, A.; Baumgartner, J.; Boumier, P.; Le Cocguen, R.; Baranjuk, G.; Bell, A.; Heidecke, F.; Maue, T.; Blanco Rodríguez, J.; Nakai, E.; Scheiffelen, T.; Sigwarth, M.; Soltau, D.; Domingo, V.; Fiethe, B.; Ferreres Sabater, A.; Gasent Blesa, J.L.; Rodríguez Martínez, P.; Osorno Caudel, D.; Bosch, J.; Casas, A.; Carmona, M.; Gómez Cama, J.M.; Herms, A.; Roma, D.; Guan, Y.; Alonso, G.; Gómez-Sanjuan, A.; Piqueras, J.; Torralbo, I.; Lange, T.; Michel, H.; Michalik, H.; Bonet, J.A.; Fahmy, S.; Müller, D.; Zouganelis, I.; Deutsch, W.; Busse, D.; Fernandez-Rico, G.; Grauf, B.; Gizon, L.; Heerlein, K.; Kolleck, M.; Lagg, A.; Meller, R.; Müller, R.; Schühle, U.; Staub, J.; Enge, R.; Albert, K.; Alvarez Copano, M.; Beckmann, U.; Bischoff, J.; Frahm, S.; Germerott, D.; Guerrero, L.; Löptien, B.; Meierdierks, T.; Oberdorfer, D.; Papagiannaki, I.; Ramanath, S.; Bellot Rubio, L.R.; Schou, J.; Werner, S.; Yang, D.; Zerr, A.; Bergmann, M.; Bochmann, J.; Heinrichs, J.; Meyer, S.; Monecke, M.; Müller, M.-F.; Cobos Carracosa, J.P.; Sperling, M.; Álvarez García, D.; Aparicio, B.; Balaguer Jiménez, M.; Girela, F.; Hernández Expósito, D.; Herranz, M.; Labrousse, P.; López Jiménez, A.; Orozco Suárez, D.; Ramos, J.L.; Barandiarán, J.; Vera, I.; Bastide, L.; Campuzano, C.; Cebollero, M.; Dávila, B.; Fernández-Medina, A.; García Parejo, P.This paper describes the Polarimetric and Helioseismic Imager on the Solar Orbiter mission (SO/PHI), the first magnetograph and helioseismology instrument to observe the Sun from outside the Sun-Earth line. It is the key instrument meant to address the top-level science question: How does the solar dynamo work and drive connections between the Sun and the heliosphere? SO/PHI will also play an important role in answering the other top-level science questions of Solar Orbiter, as well as hosting the potential of a rich return in further science. SO/PHI measures the Zeeman effect and the Doppler shift in the FeI 617.3nm spectral line. To this end, the instrument carries out narrow-band imaging spectro-polarimetry using a tunable LiNbO_3 Fabry-Perot etalon, while the polarisation modulation is done with liquid crystal variable retarders (LCVRs). The line and the nearby continuum are sampled at six wavelength points and the data are recorded by a 2kx2k CMOS detector. To save valuable telemetry, the raw data are reduced on board, including being inverted under the assumption of a Milne-Eddington atmosphere, although simpler reduction methods are also available on board. SO/PHI is composed of two telescopes; one, the Full Disc Telescope (FDT), covers the full solar disc at all phases of the orbit, while the other, the High Resolution Telescope (HRT), can resolve structures as small as 200km on the Sun at closest perihelion. The high heat load generated through proximity to the Sun is greatly reduced by the multilayer-coated entrance windows to the two telescopes that allow less than 4% of the total sunlight to enter the instrument, most of it in a narrow wavelength band around the chosen spectral line.
- ItemCombining magneto-hydrostatic constraints with Stokes profiles inversions: III. Uncertainty in the inference of electric currents(Les Ulis : EDP Sciences, 2023) Borrero, J.M.; Pastor Yabar, A.Electric currents play an important role in the energy balance of the plasma in the solar atmosphere. They are also indicative of non-potential magnetic fields and magnetic reconnection. Unfortunately, the direct measuring of electric currents has traditionally been riddled with inaccuracies. Aims. We study how accurately we can infer electric currents under different scenarios. Methods. We carry out increasingly complex inversions of the radiative transfer equation for polarized light applied to Stokes profiles synthesized from radiative three-dimensional magnetohydrodynamic (MHD) simulations. The inversion yields the magnetic field vector. B. from which the electric current density, ./, is derived by applying Ampere's law. Results. We find that the retrieval of the electric current density is only slightly affected by photon noise or spectral resolution. However, the retrieval steadily improves as the Stokes inversion becomes increasingly elaborated. In the least complex case (a Milne- Eddington-like inversion applied to a single spectral region), it is possible to determine the individual components of the electric current density (jx, jy, jz) with an accuracy of cr = 0.90 - l.OOdex, whereas the modulus (|[/
- ItemThe European Solar Telescope(Les Ulis : EDP Sciences, 2022) Quintero Noda, C.; Schlichenmaier, R.; Bellot Rubio, L.R.; Löfdahl, M.G.; Khomenko, E.; Jurčák, J.; Leenaarts, J.; Kuckein, C.; González Manrique, S.J.; Gunár, S.; Nelson, C.J.; Giovannelli, L.; González, F.; González, J.B.; González-Cava, J.M.; González García, M.; Gömöry, P.; Gracia, F.; Grauf, B.; Greco, V.; Grivel, C.; de la Cruz Rodríguez, J.; Guerreiro, N.; Guglielmino, S.L.; Hammerschlag, R.; Hanslmeier, A.; Hansteen, V.; Heinzel, P.; Hernández-Delgado, A.; Hernández Suárez, E.; Hidalgo, S.L.; Hill, F.; Tziotziou, K.; Hizberger, J.; Hofmeister, S.; Jägers, A.; Janett, G.; Jarolim, R.; Jess, D.; Jiménez Mejías, D.; Jolissaint, L.; Kamlah, R.; Kapitán, J.; Tsiropoula, G.; Kašparová, J.; Keller, C.U.; Kentischer, T.; Kiselman, D.; Kleint, L.; Klvana, M.; Kontogiannis, I.; Krishnappa, N.; Kučera, A.; Labrosse, N.; Aulanier, G.; Lagg, A.; Landi Degl’Innocenti, E.; Langlois, M.; Lafon, M.; Laforgue, D.; Le Men, C.; Lepori, B.; Lepreti, F.; Lindberg, B.; Lilje, P.B.; Aboudarham, J.; López Ariste, A.; López Fernández, V.A.; López Jiménez, A.C.; López López, R.; Manso Sainz, R.; Marassi, A.; Marco de la Rosa, J.; Marino, J.; Marrero, J.; Martín, A.; Allegri, D.; Martín Gálvez, A.; Martín Hernando, Y.; Masciadri, E.; Martínez González, M.; Matta-Gómez, A.; Mato, A.; Mathioudakis, M.; Matthews, S.; Mein, P.; Merlos García, F.; Alsina Ballester, E.; Moity, J.; Montilla, I.; Molinaro, M.; Molodij, G.; Montoya, L.M.; Munari, M.; Murabito, M.; Núñez Cagigal, M.; Oliviero, M.; Orozco Suárez, D.; Amans, J.P.; Ortiz, A.; Padilla-Hernández, C.; Paéz Mañá, E.; Paletou, F.; Pancorbo, J.; Pastor Cañedo, A.; Pastor Yabar, A.; Peat, A.W.; Pedichini, F.; Peixinho, N.; Asensio Ramos, A.; Peñate, J.; Pérez de Taoro, A.; Peter, H.; Petrovay, K.; Piazzesi, R.; Pietropaolo, E.; Pleier, O.; Poedts, S.; Pötzi, W.; Podladchikova, T.; Bailén, F.J.; Prieto, G.; Quintero Nehrkorn, J.; Ramelli, R.; Ramos Sapena, Y.; Rasilla, J.L.; Reardon, K.; Rebolo, R.; Regalado Olivares, S.; Reyes García-Talavera, M.; Riethmüller, T.L.; Balaguer, M.; Rimmele, T.; Rodríguez Delgado, H.; Rodríguez González, N.; Rodríguez-Losada, J.A.; Rodríguez Ramos, L.F.; Romano, P.; Roth, M.; Rouppe van der Voort, L.; Rudawy, P.; Ruiz de Galarreta, C.; Baldini, V.; Rybák, J.; Salvade, A.; Sánchez-Capuchino, J.; Sánchez Rodríguez, M.L.; Sangiorgi, M.; Sayède, F.; Scharmer, G.; Scheiffelen, T.; Schmidt, W.; Schmieder, B.; Balthasar, H.; Scirè, C.; Scuderi, S.; Siegel, B.; Sigwarth, M.; Simões, P.J.A.; Snik, F.; Sliepen, G.; Sobotka, M.; Socas-Navarro, H.; Sola La Serna, P.; Barata, T.; Solanki, S. K.; Soler Trujillo, M.; Soltau, D.; Sordini, A.; Sosa Méndez, A.; Stangalini, M.; Steiner, O.; Stenflo, J.O.; Štěpán, J.; Strassmeier, K.G.; Barczynski, K.; Sudar, D.; Suematsu, Y.; Sütterlin, P.; Tallon, M.; Temmer, M.; Tenegi, F.; Tritschler, A.; Trujillo Bueno, J.; Turchi, A.; Utz, D.; Barreto Cabrera, M.; van Harten, G.; van Noort, M.; van Werkhoven, T.; Vansintjan, R.; Vaz Cedillo, J.J.; Vega Reyes, N.; Verma, M.; Veronig, A.M.; Viavattene, G.; Vitas, N.; Baur, A.; Vögler, A.; von der Lühe, O.; Volkmer, R.; Waldmann, T.A.; Walton, D.; Wisniewska, A.; Zeman, J.; Zeuner, F.; Zhang, L.Q.; Zuccarello, F.; Béchet, C.; Collados, M.; Beck, C.; Belío-Asín, M.; Bello-González, N.; Belluzzi, L.; Bentley, R.D.; Berdyugina, S.V.; Berghmans, D.; Berlicki, A.; Berrilli, F.; Berkefeld, T.; Bettonvil, F.; Bianda, M.; Bienes Pérez, J.; Bonaque-González, S.; Brajša, R.; Bommier, V.; Bourdin, P.-A.; Burgos Martín, J.; Calchetti, D.; Calcines, A.; Calvo Tovar, J.; Campbell, R.J.; Carballo-Martín, Y.; Carbone, V.; Carlin, E.S.; Carlsson, M.; Castro López, J.; Cavaller, L.; Cavallini, F.; Cauzzi, G.; Cecconi, M.; Chulani, H.M.; Cirami, R.; Consolini, G.; Coretti, I.; Cosentino, R.; Cózar-Castellano, J.; Dalmasse, K.; Danilovic, S.; De Juan Ovelar, M.; Del Moro, D.; del Pino Alemán, T.; del Toro Iniesta, J. C.; Denker, C.; Dhara, S.K.; Di Marcantonio, P.; Díaz Baso, C.J.; Diercke, A.; Dineva, E.; Díaz-García, J.J.; Doerr, H.-P.; Doyle, G.; Erdelyi, R.; Ermolli, I.; Escobar Rodríguez, A.; Esteban Pozuelo, S.; Faurobert, M.; Felipe, T.; Feller, A.; Feijoo Amoedo, N.; Femenía Castellá, B.; Fernandes, J.; Ferro Rodríguez, I.; Figueroa, I.; Fletcher, L.; Franco Ordovas, A.; Gafeira, R.; Gardenghi, R.; Gelly, B.; Giorgi, F.; Gisler, D.The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operating in visible and near-infrared wavelengths: the Swedish 1m Solar Telescope, the German Vacuum Tower Telescope and GREGOR, the French Télescope Héliographique pour l'Étude du Magnétisme et des Instabilités Solaires, and the Dutch Open Telescope. With its 4.2 m primary mirror and an open configuration, EST will become the most powerful European ground-based facility to study the Sun in the coming decades in the visible and near-infrared bands. EST uses the most innovative technological advances: the first adaptive secondary mirror ever used in a solar telescope, a complex multi-conjugate adaptive optics with deformable mirrors that form part of the optical design in a natural way, a polarimetrically compensated telescope design that eliminates the complex temporal variation and wavelength dependence of the telescope Mueller matrix, and an instrument suite containing several (etalon-based) tunable imaging spectropolarimeters and several integral field unit spectropolarimeters. This publication summarises some fundamental science questions that can be addressed with the telescope, together with a complete description of its major subsystems.
- ItemModels and data analysis tools for the Solar Orbiter mission(Les Ulis : EDP Sciences, 2020) Rouillard, A.P.; Pinto, R.F.; Vourlidas, A.; De Groof, A.; Thompson, W.T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.; Sasso, C.; Spadaro, D.; del Toro Iniesta, J.C.; Ventura, R.; Verbeeck, C.; Vilmer, N.; Warmuth, A.; Walsh, A.P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov, A.N.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.; Strugarek, A.; Brun, A.S.; Alexandre, M.; Berghmans, D.; Raouafi, N.E.; Wiegelmann, T.; Pagano, P.; Arge, C.N.; Nieves-Chinchilla, T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.; Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.; Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.; Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J.M.; Etesi, L.; Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot, V.; Georgoulis, M.K.; Gilbert, H.R.; Giunta, A.; Gomez-Herrero, R.; Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C.J.; Howard, R.A.; Horbury, T.S.; Janvier, M.; Jones, S.T.; Kozarev, K.; Kraaikamp, E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud, B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.; Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C.J.; Papaioannou, A.; Pérez-Suáre, D.; Rodriguez-Pacheco, J.; Parenti, S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J.M.; Riethmüller, T.L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez, L.; Solanki, S.K.; St Cyr, O.C.; Straus, T.; Susino, R.; Teriaca, L.Context. The Solar Orbiter spacecraft will be equipped with a wide range of remote-sensing (RS) and in situ (IS) instruments to record novel and unprecedented measurements of the solar atmosphere and the inner heliosphere. To take full advantage of these new datasets, tools and techniques must be developed to ease multi-instrument and multi-spacecraft studies. In particular the currently inaccessible low solar corona below two solar radii can only be observed remotely. Furthermore techniques must be used to retrieve coronal plasma properties in time and in three dimensional (3D) space. Solar Orbiter will run complex observation campaigns that provide interesting opportunities to maximise the likelihood of linking IS data to their source region near the Sun. Several RS instruments can be directed to specific targets situated on the solar disk just days before data acquisition. To compare IS and RS, data we must improve our understanding of how heliospheric probes magnetically connect to the solar disk. Aims. The aim of the present paper is to briefly review how the current modelling of the Sun and its atmosphere can support Solar Orbiter science. We describe the results of a community-led effort by European Space Agency’s Modelling and Data Analysis Working Group (MADAWG) to develop different models, tools, and techniques deemed necessary to test different theories for the physical processes that may occur in the solar plasma. The focus here is on the large scales and little is described with regards to kinetic processes. To exploit future IS and RS data fully, many techniques have been adapted to model the evolving 3D solar magneto-plasma from the solar interior to the solar wind. A particular focus in the paper is placed on techniques that can estimate how Solar Orbiter will connect magnetically through the complex coronal magnetic fields to various photospheric and coronal features in support of spacecraft operations and future scientific studies. Methods. Recent missions such as STEREO, provided great opportunities for RS, IS, and multi-spacecraft studies. We summarise the achievements and highlight the challenges faced during these investigations, many of which motivated the Solar Orbiter mission. We present the new tools and techniques developed by the MADAWG to support the science operations and the analysis of the data from the many instruments on Solar Orbiter. Results. This article reviews current modelling and tool developments that ease the comparison of model results with RS and IS data made available by current and upcoming missions. It also describes the modelling strategy to support the science operations and subsequent exploitation of Solar Orbiter data in order to maximise the scientific output of the mission. Conclusions. The on-going community effort presented in this paper has provided new models and tools necessary to support mission operations as well as the science exploitation of the Solar Orbiter data. The tools and techniques will no doubt evolve significantly as we refine our procedure and methodology during the first year of operations of this highly promising mission.
- ItemStochastic entropy production in the quite Sun magnetic fields(Oxford : Oxford Univ. Press, 2019) Gorobets, Andriy Y.; Berdyugina, Svetlana V.The second law of thermodynamics imposes an increase of macroscopic entropy with time in an isolated system. Microscopically, however, the entropy production can be negative for a single, microscopic realization of a thermodynamic process. The so-called fluctuation theorems provide exact relations between the stochastic entropy consumption and generation. Here, we analyse pixel-to-pixel fluctuations in time of small-scale magnetic fields (SSMF) in the quiet Sun observed with the SDO/HMI instrument. We demonstrate that entropy generated by SSMF obeys the fluctuation theorems. In particular, the SSMF entropy consumption probability is exactly exponentially smaller than the SSMF entropy generation probability. This may have fundamental implications for the magnetic energy budget of the Sun. © The Author(s) 2018. Published by Oxford University Press on behalf of The Royal Astronomical Society.
- ItemThe Effect of Toroidal Magnetic Fields on Solar Oscillation Frequencies(London : Institute of Physics Publ., 2018) Kiefer, René; Roth, MarkusSolar oscillation frequencies change with the level of magnetic activity. Localizing subsurface magnetic field concentrations in the Sun with helioseismology will help us to understand the solar dynamo. Because the magnetic fields are not considered in standard solar models, adding them to the basic equations of stellar structure changes the eigenfunctions and eigenfrequencies. We use quasi-degenerate perturbation theory to calculate the effect of toroidal magnetic fields on solar oscillation mean multiplet frequencies for six field configurations. In our calculations, we consider both the direct effect of the magnetic field, which describes the coupling of modes, and the indirect effect, which accounts for changes in stellar structure due to the magnetic field. We limit our calculations to self-coupling of modes. We find that the magnetic field affects the multiplet frequencies in a way that depends on the location and the geometry of the field inside the Sun. Comparing our theoretical results with observed shifts, we find that strong tachocline fields cannot be responsible for the observed frequency shifts of p modes over the solar cycle. We also find that part of the surface effect in helioseismic oscillation frequencies might be attributed to magnetic fields in the outer layers of the Sun. The theory presented here is also applicable to models of solar-like stars and their oscillation frequencies.