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168 results on '"White, Stephen M."'

161. Observations Of The Solar Chromosphere With Alma And Comparison With Theoretical Models

Author

Brajsa, Roman, Sudar, Davor, Skokic, Ivica, Benz, Arnold O., Kuhar, Matej, Kobelski, Adam, Wedemeyer, Sven, White, Stephen M., Ludwig, Hans-G., Temmer, Manuela, Saar, Steven H., and Selhorst, Caius L.

Subjects
Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 14. Life underwater, Astrophysics::Galaxy Astrophysics
Abstract

In this work we use solar observations with the ALMA radio telescope at the wavelength of 1.21 mm. The aim of the analysis is to improve understanding of the solar chromosphere, a dynamic layer in the solar atmosphere between the photosphere and corona. The study has an observational and a modeling part. In the observational part full-disc solar images are analyzed. Based on a modied FAL atmospheric model, radiation models for various observed solar structures are developed. Finally, the observational and modeling results are compared and discussed.

162. The First ALMA Observation of a Solar Plasmoid Ejection from an X-Ray Bright Point

Author

Shimojo, Masumi, Hudson, Hugh S., White, Stephen M., Bastian, Timothy S., and Iwai, Kazumasa

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Eruptive phenomena such as plasmoid ejections or jets are important features of solar activity and have the potential to improve our understanding of the dynamics of the solar atmosphere. Such ejections are often thought to be signatures of the outflows expected in regions of fast magnetic reconnection. The 304 Å EUV line of helium, formed at around 105 K, is found to be a reliable tracer of such phenomena, but the determination of physical parameters from such observations is not straightforward. We have observed a plasmoid ejection from an X-ray bright point simultaneously at millimeter wavelengths with ALMA, at EUV wavelengths with SDO/AIA, and in soft X-rays with Hinode/XRT. This paper reports the physical parameters of the plasmoid obtained by combining the radio, EUV, and X-ray data. As a result, we conclude that the plasmoid can consist either of (approximately) isothermal ~105 K plasma that is optically thin at 100 GHz, or a ~104 K core with a hot envelope. The analysis demonstrates the value of the additional temperature and density constraints that ALMA provides, and future science observations with ALMA will be able to match the spatial resolution of space-borne and other high-resolution telescopes.

163. Observations of the solar chromosphere with ALMA and comparison with theoretical models

Author

Brajsa, Roman, Sudar, Davor, Skokic, Ivica, Benz, Arnold O., Kuhar, Matej, Kobelski, Adam, Wedemeyer, Sven, White, Stephen M., Ludwig, Hans-G., Temmer, Manuela, Saar, Steven H., Selhorst, Caius L., and Scott Wolk

Subjects
14. Life underwater
Abstract

In this work we use solar observations with the ALMA radio telescope at the wavelength of 1.21 mm. The aim of the analysis is to improve understanding of the solar chromosphere, a dynamic layer in the solar atmosphere between the photosphere and corona. The study has an observational and a modeling part. In the observational part full-disc solar images are analyzed. Based on a modied FAL atmospheric model, radiation models for various observed solar structures are developed. Finally, the observational and modeling results are compared and discussed.

166. A RESOLVED RING OF DEBRIS DUST AROUND THE SOLAR ANALOG HD 107146.

Author

Corder, Stuartt, Carpenter, John M., Sargent, Anneila I., Zauderer, B. Ashley, Wright, Melvyn C. H., White, Stephen M., Woody, David P., Teuben, Peter, Scott, Stephen L., Pound, Marc W., Plambeck, Richard L., Lamb, James W., Koda, Jin, Hodges, Mark, Hawkins, David, and Bock, Douglas C. -J.

Published
2009
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167. Books.

Author

White, Stephen M.

Subjects
GUIDE to the Sun (Book)
Abstract

Reviews the book `Guide to the Sun,' by Kenneth J.H. Phillips.

Published
1996

168. Science development study for the Atacama Large Aperture Submillimeter Telescope (AtLAST): Solar and stellar observations.

Author

Wedemeyer S, Barta M, Brajša R, Chai Y, Costa J, Gary D, Gimenez de Castro G, Gunar S, Fleishman G, Hales A, Hudson H, Kirkaune M, Mohan A, Motorina G, Pellizzoni A, Saberi M, Selhorst CL, Simoes PJA, Shimojo M, Skokić I, Sudar D, Menezes F, White SM, Booth M, Klaassen P, Cicone C, Mroczkowski T, Cordiner MA, Di Mascolo L, Johnstone D, van Kampen E, Lee M, Liu D, Maccarone T, Orlowski-Scherer J, Saintonge A, Smith M, and Thelen AE

Abstract

Observations at (sub-)millimeter wavelengths offer a complementary perspective on our Sun and other stars, offering significant insights into both the thermal and magnetic composition of their chromospheres. Despite the fundamental progress in (sub-)millimeter observations of the Sun, some important aspects require diagnostic capabilities that are not offered by existing observatories. In particular, simultaneously observations of the radiation continuum across an extended frequency range would facilitate the mapping of different layers and thus ultimately the 3D structure of the solar atmosphere. Mapping large regions on the Sun or even the whole solar disk at a very high temporal cadence would be crucial for systematically detecting and following the temporal evolution of flares, while synoptic observations, i.e., daily maps, over periods of years would provide an unprecedented view of the solar activity cycle in this wavelength regime. As our Sun is a fundamental reference for studying the atmospheres of active main sequence stars, observing the Sun and other stars with the same instrument would unlock the enormous diagnostic potential for understanding stellar activity and its impact on exoplanets. The Atacama Large Aperture Submillimeter Telescope (AtLAST), a single-dish telescope with 50m aperture proposed to be built in the Atacama desert in Chile, would be able to provide these observational capabilities. Equipped with a large number of detector elements for probing the radiation continuum across a wide frequency range, AtLAST would address a wide range of scientific topics including the thermal structure and heating of the solar chromosphere, flares and prominences, and the solar activity cycle. In this white paper, the key science cases and their technical requirements for AtLAST are discussed., Competing Interests: No competing interests were disclosed., (Copyright: © 2024 Wedemeyer S et al.)

Published
2024
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