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1,309 results on '"Solar radius"'

1. Solar Radius

Author

Rouan, Daniel, Gargaud, Muriel, editor, Irvine, William M., editor, Amils, Ricardo, editor, Claeys, Philippe, editor, Cleaves, Henderson James, editor, Gerin, Maryvonne, editor, Rouan, Daniel, editor, Spohn, Tilman, editor, Tirard, Stéphane, editor, and Viso, Michel, editor

Published
2023
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7. What Is Coming: Issues Raised from Observation of the Shape of the Sun

Author

Rozelot, J.-P., Beiglböck, Wolf, editor, Ehlers, Jürgen, editor, Hepp, Klaus, editor, Weidenmüller, Hans A., editor, Beig, Robert, editor, Domcke, Wolfgang, editor, Englert, Berthold-Georg, editor, Frisch, Uriel, editor, Hänggi, Peter, editor, Hasinger, Günther, editor, Hillebrandt, Wolfgang, editor, Jaffe, Robert L., editor, Janke, Wolfhard, editor, von Löhneysen, H., editor, Mangano, Michelangelo, editor, Raimond, Jean-Michel, editor, Sornette, Didier, editor, Theisen, Stefan, editor, Weise, W., editor, Zittartz, Johannes, editor, Guinea, Francisco, editor, Vollhardt, Dieter, editor, Rozelot, Jean-Pierre, editor, and Neiner, Coralie, editor

Published
2009
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12. Determining the Moment of Proton Injection in Solar Proton Events According to Their Time Profile

Author

Yu. P. Ochelkov

Subjects
Solar proton, Physics, Proton, Nuclear Theory, Hadron, General Physics and Astronomy, Solar radius, Moment (mathematics), Nuclear physics, Physics::Space Physics, Coronal mass ejection, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Nuclear Experiment, Scaling, Time profile
Abstract

A technique is proposed for determining the moment of 10–100 MeV proton injection in solar proton events with similarity of scale (scaling). It is possible to determine the moment of injection in such events according to their time profile. Using a series of events, it is shown that protons are injected during the propagation of a coronal mass ejection when it reaches a distance of 1–1.5 solar radii.

Published
2021
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18. Measurements of the Sun’s Radius at Calern Observatory

Author

Delmas, Christian, Beig, R., editor, Englert, B. -G., editor, Frisch, U., editor, Hänggi, P., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, v. Löhneysen, H., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, and Rozelot, Jean Pierre, editor

Published
2003
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19. Solar Astrometry with the Astrolabe of Santiago

Author

Noël, Fernando, Beig, R., editor, Englert, B. -G., editor, Frisch, U., editor, Hänggi, P., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, v. Löhneysen, H., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, and Rozelot, Jean Pierre, editor

Published
2003
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20. Solar Interior and Seismology

Author

Antia, H. M., Beig, R., editor, Englert, B. -G., editor, Frisch, U., editor, Hänggi, P., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, v. Löhneysen, H., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, Antia, H. M., editor, Bhatnagar, Arvind, editor, and Ulmschneider, Peter, editor

Published
2003
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22. Characteristics of the Sun

Author

Stix, Michael, Appenzeller, I., editor, Börner, G., editor, Burkert, A., editor, Dopita, M. A., editor, Encrenaz, T., editor, Harwit, M., editor, Kippenhahn, R., editor, Lequeux, J., editor, Maeder, A., editor, Trimble, V., editor, and Stix, Michael

Published
2002
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23. Application of the wavelet phase method of signal study to the analysis of asymmetric barycentric motions of the Sun and changes in processes occurring on the Sun, near-earth space and in the interior of the Earth

Author

Valeriy I. Alekseev

Subjects
Physics, Solar wind, Solar System, Earth's magnetic field, Geographical pole, Planet, Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Solar radius, Astrophysics::Earth and Planetary Astrophysics, Interplanetary magnetic field, Ionosphere, Geodesy
Abstract

A set of studies has been carried out, indicating that solar activity and processes associated with the activity of the Sun: changes in the main magnetic fluxes, areas of polar spots, the number of polar torches at the poles of the Sun; -index of geomagnetic activity and -index of the ratio of plasma pressure to magnetic solar wind (SW), slow and high-speed flows of SW, cosmic ray intensity (CR); average annual values of the interplanetary magnetic field vector and its components; the temperature, density, and flow rate of the SW plasma, the synodic period of the revolution of the Sun as a star, and the radius of the Sun in relative units; the distance of the Earths geographic pole from the conventional international origin, the rate of change of the position of the Earths north magnetic pole, the main ionospheric parameters; the angle of the Earth's axis of rotation and volcanic eruptions; asymmetric movement of the Sun around the solar system of the solar system (in fractions of the solar radius); the distances from the solar systems CM to the Sun in km, the distances from the solar systems CM to the Earth, with high accuracy, are consistent with the movement of the Sun relative to the barycenter. The research is based on the wavelet transformation of the observations listed above variables in various time intervals with the subsequent calculation of their phase-frequency and phase-time characteristics, correlation matrices between characteristics. The studied variables are divided into groups, which include the barycentric movement of the Sun and changes in solar activity. The calculated two correlation matrices of the wavelet characteristics of the group of variables and the graphs of these characteristics in two coordinate systems reflect the consistency of changes in the group. The studies carried out indicate that the thermonuclear reaction occurring in the interior of the Sun, the external manifestation of which is solar activity, is controlled by the movements of the large planets of the Solar System relative to the Sun.

Published
2021
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24. SpaceTime Mission: Clock Test of Relativityat Four Solar Radii

Author

Maleki, Lute, Prestage, John, Beig, R., editor, Ehlers, J., editor, Frisch, U., editor, Hepp, K., editor, Hillebrand, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Kippenhahn, R., editor, Lipowsky, R., editor, Löhneysen, H. v., editor, Ojima, I., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Lämmerzahl, Claus, editor, Everitt, C. W. Francis, editor, and Hehl, Friedrich W., editor

Published
2001
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25. Optical and Thermal Properties of Interplanetary Dust

Author

Levasseur-Regourd, A. Chantal, Mann, Ingrid, Dumont, René, Hanner, Martha S., Appenzeller, I., editor, Görner, G., editor, Harwit, M., editor, Kippenhahn, R., editor, Lequeux, J., editor, Strittmatter, P. A., editor, Trimble, V., editor, Grün, Eberhard, editor, Gustafson, Bo Å. S., editor, Dermott, Stan, editor, and Fechtig, Hugo, editor

Published
2001
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32. Winds Across the Void

Author

Lang, Kenneth R., Appenzeller, I., editor, Börner, G., editor, Harwit, M., editor, Kippenhahn, R., editor, Lequeux, J., editor, Strittmatter, P. A., editor, Trimble, V., editor, and Lang, Kenneth R.

Published
2000
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33. Coronal Mass Ejections

Author

Hundhausen, A., Strong, Keith T., editor, Saba, Julia L. R., editor, Haisch, Bernhard M., editor, and Schmelz, Joan T., editor

Published
1999
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34. Full compressible 3D MHD simulation of solar wind

Author

Takuma Matsumoto

Subjects
Physics, Photosphere, Solar mass, 010504 meteorology & atmospheric sciences, Astronomy and Astrophysics, Solar radius, Solar physics, 01 natural sciences, Corona, Computational physics, Atmosphere, Solar wind, Space and Planetary Science, Physics::Space Physics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Magnetohydrodynamics, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

Identifying the heating mechanisms of the solar corona and the driving mechanisms of solar wind are key challenges in understanding solar physics. A full three-dimensional compressible magnetohydrodynamic (MHD) simulation was conducted to distinguish between the heating mechanisms in the fast solar wind above the open field region. Our simulation describes the evolution of the Alfvénic waves, which includes the compressible effects from the photosphere to the heliospheric distance s of 27 solar radii (R⊙). The hot corona and fast solar wind were reproduced simultaneously due to the dissipation of the Alfvén waves. The inclusion of the transition region and lower atmosphere enabled us to derive the solar mass-loss rate for the first time by performing a full three-dimensional compressible MHD simulation. The Alfvén turbulence was determined to be the dominant heating mechanism in the solar wind acceleration region (s > 1.3 R⊙), as suggested by previous solar wind models. In addition, shock formation and phase mixing are important below the lower transition region (s < 1.03 R⊙) as well.

Published
2020
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35. Solar Cosmic Ray Acceleration at the Front of a Fast Shock in the Lower Solar Corona

Author

E. G. Berezhko and S. N. Taneev

Subjects
Physics, Solid-state physics, Plasma parameters, Astrophysics::High Energy Astrophysical Phenomena, General Physics and Astronomy, Solar radius, Cosmic ray, 01 natural sciences, Charged particle, Spectral line, Shock (mechanics), Acceleration, Physics::Space Physics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Atomic physics, 010306 general physics, Astrophysics::Galaxy Astrophysics
Abstract

Based on the theory of diffusive shock acceleration of charged particles, we have numerically studied the spectra of protons produced by a fast shock with a speed of 5000 km s–1 in the lower solar corona with known solar plasma parameters. We show that protons with energies $$ \gtrsim $$ 105 MeV can be produced at a distance up to 3 $${{R}_{ \odot }}$$ ( $${{R}_{ \odot }}$$ is the solar radius) within 274 s.

Published
2020
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36. Global helium abundance measurements in the solar corona

Author

Lawrence D. Gardner, Jeffrey Newmark, Chloé Guennou, Jean-Christophe Leclec’h, James R. Lemen, Ester Antonucci, A. M. Malvezzi, Nicolas Barbey, Frederic Rouesnel, Jean-Pierre Wuelser, Federico Landini, Lucia Abbo, Giuseppe Massone, Aurélien Canou, Guglielmo Rossi, J. M. Laming, Jean-Pierre Moalic, Frédéric Auchère, Marco Romoli, John L. Kohl, Silvano Fineschi, Maurizio Pancrazzi, Mauro Focardi, John D. Moses, Daniele Telloni, L. Zangrilli, and Dennis Wang

Subjects
Physics, Photosphere, 010504 meteorology & atmospheric sciences, Equator, chemistry.chemical_element, Astronomy and Astrophysics, Solar radius, Astrophysics, 01 natural sciences, Corona, Solar wind, chemistry, Abundance (ecology), Physics::Space Physics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Physics::Atomic Physics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Helium, Heliosphere, 0105 earth and related environmental sciences
Abstract

Solar abundances have been historically assumed to be representative of cosmic abundances. However, our knowledge of the solar abundance of helium, the second most abundant element, relies mainly on models1 and indirect measurements through helioseismic observations2, because actual measurements of helium in the solar atmosphere are very scarce. Helium cannot be directly measured in the photosphere because of its high first ionization potential, and measurements of its abundance in the inner corona have been sporadic3,4. In this Letter, we present simultaneous global images of the helium (out to a heliocentric distance of 3R⊙ (solar radii)) and hydrogen emission in the solar corona during the minimum of solar activity of cycle 23 and directly derive the helium abundance in the streamer region and surrounding corona (out to 2.2R⊙). The morphology of the He+ corona is markedly different from that of the H corona, owing to significant spatial variations in helium abundance. The observations show that the helium abundance is shaped according to and modulated by the structure of the large-scale coronal magnetic field and that helium is almost completely depleted in the equatorial regions during the quiet Sun. This measurement provides a trace back to the coronal source of the anomalously slow solar wind observed in the heliosphere at the Sun–Earth Lagrangian point L1 in 2009, during the exceptionally long-lasting minimum of solar activity cycle 23. Global images of helium and hydrogen emission are used to directly derive the helium abundance out to 2.2R⊙. The helium abundance is shaped by the large-scale coronal magnetic field. Helium is almost completely depleted near the equator in the quiet Sun.

Published
2020
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40. A Guide to the Book

Author

Rozelot, Jean-Pierre, Beig, R., editor, Englert, B. -G., editor, Frisch, U., editor, Hänggi, P., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, v. Löhneysen, H., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, and Rozelot, Jean Pierre, editor

Published
2003
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44. Monitoring the Solar Radius from the Royal Observatory of the Spanish Navy since 1773.

Author

Vaquero, J., Gallego, M., Ruiz-Lorenzo, J., López-Moratalla, T., Carrasco, V., Aparicio, A., González-González, F., and Hernández-García, E.

Subjects
*NUCLEAR size (Physics), *DANJON astrolabes, *STANDARD deviations, *SOLAR cycle, *OBJECT constancy (Psychoanalysis)
Abstract

The solar diameter has been monitored at the Royal Observatory of the Spanish Navy (today the Real Instituto y Observatorio de la Armada: ROA) almost continuously since its creation in 1753 ( i.e. during the past 250 years). After a painstaking effort to collect data in the historical archive of this institution, we present here the data of the solar semidiameter from 1773 to 2006, making up an extensive new database for solar-radius measurements, which can be considered. We have calculated the solar semidiameter from the transit times registered by the observers (except for values of the solar radius from the modern Danjon astrolabe, which were published by ROA). These data were analysed to reveal any significant long-term trends, but no such trends were found. Therefore, the data sample confirms the constancy of the solar diameter during the past 250 years (approximately) within instrumental and methodological limits. Moreover, no relationship between solar radius and the new sunspot-number index has been found from measurements of the ROA. Finally, the mean value for the solar semidiameter (with one standard deviation) calculated from the observations made in the ROA (1773 - 2006), after applying corrections for refraction and diffraction, is equal to $958.87^{\prime\prime}\pm1.77^{\prime\prime}$. [ABSTRACT FROM AUTHOR]

Published
2016
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46. A proposal for a study of the solar wind near the sun by simultaneous observations with SOLAR-A and Kashima 34m antenna

Author

Tokumaru, M., Mori, H., Tanaka, T., Araki, H., editor, Ehlers, J., editor, Hepp, K., editor, Jaffe, R. L., editor, Kippenhahn, R., editor, Ruelle, D., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Beiglböck, W., editor, Uchida, Yutaka, editor, Canfield, Richard C., editor, Watanabe, Tetsuya, editor, and Hiei, Eijiro, editor

Published
1991
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47. Coronal structures and the sunspot cycle

Author

Pasachoff, Jay M., Araki, H., editor, Ehlers, J., editor, Hepp, K., editor, Jaffe, R. L., editor, Kippenhahn, R., editor, Ruelle, D., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Beiglböck, W., editor, Uchida, Yutaka, editor, Canfield, Richard C., editor, Watanabe, Tetsuya, editor, and Hiei, Eijiro, editor

Published
1991
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