yoshiakk

• Noda, C. Quintero; Kato, Yoshiaki; Katsukawa, Y.; Oba, T.; Rodriguez, Jaime de la Cruz & Carlsson, Mats [Show all 13 contributors for this article] (2017). Chromospheric polarimetry through multiline observations of the 850-nm spectral region – II. A magnetic flux tube scenario. Monthly notices of the Royal Astronomical Society. ISSN 0035-8711. 472(1), p. 727–737. doi: 10.1093/mnras/stx2022. Full text in Research Archive Show summary

  Future solar missions and ground-based telescopes aim to understand the magnetism of the solar chromosphere. We performed a supporting study in Quintero Noda et al. focused on the infrared Ca ii 8542 Å line and we concluded that it is one of the best candidates because it is sensitive to a large range of atmospheric heights, from the photosphere to the middle chromosphere. However, we believe that it is worth trying to improve the results produced by this line observing additional spectral lines. In that regard, we examined the neighbourhood solar spectrum looking for spectral lines which could increase the sensitivity to the atmospheric parameters. Interestingly, we discovered several photospheric lines which greatly improve the photospheric sensitivity to the magnetic field vector. Moreover, they are located close to a second chromospheric line which also belongs to the Ca ii infrared triplet, i.e. the Ca ii 8498 Å line, and enhances the sensitivity to the atmospheric parameters at chromospheric layers. We conclude that the lines in the vicinity of the Ca ii 8542 Å line not only increase its sensitivity to the atmospheric parameters at all layers, but also they constitute an excellent spectral window for chromospheric polarimetry. © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

• Kato, Yoshiaki & Wedemeyer, Sven (2017). Vortex flows in the solar chromosphere: I. Automatic detection method. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 601. doi: 10.1051/0004-6361/201630082. Full text in Research Archive Show summary

  Solar “magnetic tornadoes” are produced by rotating magnetic field structures that extend from the upper convection zone and the photosphere to the corona of the Sun. Recent studies show that these kinds of rotating features are an integral part of atmospheric dynamics and occur on a large range of spatial scales. A systematic statistical study of magnetic tornadoes is a necessary next step towards understanding their formation and their role in mass and energy transport in the solar atmosphere. For this purpose, we develop a new automatic detection method for chromospheric swirls, meaning the observable signature of solar tornadoes or, more generally, chromospheric vortex flows and rotating motions. Unlike existing studies that rely on visual inspections, our new method combines a line integral convolution (LIC) imaging technique and a scalar quantity that represents a vortex flow on a two-dimensional plane. We have tested two detection algorithms, based on the enhanced vorticity and vorticity strength quantities, by applying them to three-dimensional numerical simulations of the solar atmosphere with CO5BOLD. We conclude that the vorticity strength method is superior compared to the enhanced vorticity method in all aspects. Applying the method to a numerical simulation of the solar atmosphere reveals very abundant small-scale, short-lived chromospheric vortex flows that have not been found previously by visual inspection. © ESO, 2017

• Kato, Yoshiaki; Steiner, Oskar; Hansteen, Viggo; Gudiksen, Boris Vilhelm; Wedemeyer, Sven & Carlsson, Mats (2016). Chromospheric and Coronal Wave Generation in a Magnetic Flux Sheath. The Astrophysical Journal (ApJ). ISSN 0004-637X. 827(1). doi: 10.3847/0004-637X/827/1/7. Full text in Research Archive
• Wedemeyer, Sven; Bastian, T.; Brajsa, R.; Hudson, H.; Fleishman, G. & Loukitcheva, M. [Show all 38 contributors for this article] (2016). Solar Science with the Atacama Large Millimeter/Submillimeter Array—A New View of Our Sun. Space Science Reviews. ISSN 0038-6308. 200(1), p. 1–73. doi: 10.1007/s11214-015-0229-9. Full text in Research Archive
• Wedemeyer, Sven; Bastian, Timothy; Brajša, Roman; Barta, Miroslav; Hudson, Hugh & Fleishman, Gregory [Show all 29 contributors for this article] (2015). SSALMON - The Solar Simulations for the Atacama Large Millimeter Observatory Network. Advances in Space Research. ISSN 0273-1177. 56(12), p. 2679–2692. doi: 10.1016/j.asr.2015.05.027. Full text in Research Archive

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• Kato, Yoshiaki; Steiner, Oskar; Hansteen, Viggo; Carlsson, Mats & Gudiksen, Boris Vilhelm (2014). Chromospheric and Corona Wave Generation in Flux Tubes. Full text in Research Archive
• Kato, Yoshiaki; Pontieu, Bart Walter De; Martinez-Sykora, J.; Hansteen, Viggo; Pereira, Tiago Mendes Domingos & Leenaarts, Jorritt [Show all 7 contributors for this article] (2014). Measuring energy flux of magneto-acoustic wave in the magnetic elements by using IRIS. Full text in Research Archive Show summary

  NASA's Interface Region Imaging Spectrograph (IRIS) has opened a new window to explore the chromospheric/coronal waves that potentially energize the solar atmosphere. By using an imaging spectrograph covering the Si IV and Mg II h&k lines as well as a slit-jaw imager centered at Si IV and Mg II k onboard IRIS, we can determine the nature of propagating magneto-acoustic waves just below and in the transition region. In this study, we compute the vertically emergent intensity of the Si IV and Mg II h&k lines from a time series of snapshots of a magnetic element in a two-dimensional Radiative MHD simulation from the Bifrost code. We investigate the synthetic line profiles to detect the slow magneto-acoustic body wave (slow mode) which becomes a slow shock at the lower chromosphere in the magnetic element. We find that the Doppler shift of the line core gives the velocity amplitude of the longitudinal magneto-acoustic body wave. The contribution function of the line core indicates that the formation of Mg II h&k lines is associated with the propagating shocks and therefore the time evolution of the line core intensity represents the propagating shocks projected on the optical surface. We will report on measurement of the energy flux of slow modes in the magnetic elements by using IRIS observations.

• Kato, Yoshiaki (2014). Theory, Modelling, and Observation of MHD Waves in the Flux Tube. Full text in Research Archive

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