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4,235 results on '"Coronal hole"'

104. The Interaction of Solar-System Bodies with the Interplanetary Medium

Author

Encrenaz, Thérèse, Bibring, Jean-Pierre, Blanc, Michel, Barucci, Maria-Antonietta, Roques, Francoise, Zarka, Philippe, Appenzeller, I., editor, Börner, G., editor, Dopita, M. A., editor, Harwit, M., editor, Kippenhahn, R., editor, Lequeux, J., editor, Maeder, A., editor, Trimble, V., editor, Encrenaz, Thérèse, Bibring, Jean-Pierre, Blanc, Michel, Barucci, Maria-Antonietta, Roques, Francoise, and Zarka, Philippe

Published
2004
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112. The Solar Wind

Author

Manoharan, P. K., 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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113. The Solar Corona

Author

Dwivedi, B. N., 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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114. Overview of Solar Physics

Author

Chitre, S. 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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115. Coronal Heating and Reduced MHD

Author

Oughton, Sean, Dmitruk, Pablo, Matthaeus, William H., 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, Löhneysen, H. v., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, Falgarone, Edith, editor, and Passot, Thierry, editor

Published
2003
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118. Phenomenology of Solar Active Regions

Author

Burton, W. B., editor, Kuijpers, J. M. E., editor, Van Den Heuvel, E. P. J., editor, Van Der Laan, H., editor, Appenzeller, I., editor, Bahcall, J. N., editor, Bertola, F., editor, Cassinelli, J. P., editor, Cesarsky, C. J., editor, Engvold, O., editor, McCray, R., editor, Murdin, P. G., editor, Pacini, F., editor, Radhakrishnan, V., editor, Sato, K., editor, Shu, F. H., editor, Somov, B. V., editor, Sunyaev, R. A., editor, Tanaka, Y., editor, Tremaine, S., editor, Weiss, N. O., editor, and Hanslmeier, Arnold

Published
2002
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119. Synthesis of the Four Major Disciplines: Predicting Geomagnetic Storms As A Space Weather Project

Author

Weiss, N. O., Burton, W. B., editor, Kuijpers, J. M. E., editor, Van Den Heuvel, E. P. J., editor, Van Der Laan, H., editor, Appenzeller, I., editor, Bahcall, J. N., editor, Bertola, F., editor, Cassinelli, J. P., editor, Cesarsky, C. J., editor, Engvold, O., editor, McCray, R., editor, Murdin, P. G., editor, Pacini, F., editor, Radhakrishnan, V., editor, Sato, K., editor, Shu, F. H., editor, Somov, B. V., editor, Sunyaev, R. A., editor, Tanaka, Y., editor, Tremaine, S., editor, and Akasofu, Syun-Ichi

Published
2002
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120. Search for the Unknown Quantity in the Solar Wind

Author

Weiss, N. O., Burton, W. B., editor, Kuijpers, J. M. E., editor, Van Den Heuvel, E. P. J., editor, Van Der Laan, H., editor, Appenzeller, I., editor, Bahcall, J. N., editor, Bertola, F., editor, Cassinelli, J. P., editor, Cesarsky, C. J., editor, Engvold, O., editor, McCray, R., editor, Murdin, P. G., editor, Pacini, F., editor, Radhakrishnan, V., editor, Sato, K., editor, Shu, F. H., editor, Somov, B. V., editor, Sunyaev, R. A., editor, Tanaka, Y., editor, Tremaine, S., editor, and Akasofu, Syun-Ichi

Published
2002
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122. Rotation

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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123. On the Relationship between the Magnetic Field of a Low-Latitude Coronal Hole and Its Area

Author

Yu. T. Tsap and Z. S. Akhtemov

Subjects
Physics, Low latitude, Solar phenomena, Correlation coefficient, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Coronal hole, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Magnetic field, Earth's magnetic field, Space and Planetary Science, Physics::Space Physics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Meridian (astronomy), Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics
Abstract

Based on the data obtained with the CHIMERA algorithm, we consider the evolution of a long-lived low-latitude coronal hole during its central meridian passage over the period from February 15, 2012, to October 14, 2012. The correlation coefficient between the photospheric magnetic field strength of the coronal hole and its area in nine Carrington rotations is $$R={-}0.55$$ . It differs noticeably from $$R={-}0.82$$ given in Heinemann et al. The results suggest a significant dependence of the area of coronal holes on the method of determining their boundaries. This can have a noticeable effect both on the prediction of geomagnetic activity and on the understanding of the nature of solar phenomena related to these structures.

Published
2021
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124. Suprathermal ions from coronal holes at 1 au in solar cycles 23 and 24: dependence of ion abundances on solar wind speed

Author

M. A. Zeldovich, Karoly Kecskemety, and Yu. I. Logachev

Subjects
Physics, 010308 nuclear & particles physics, Coronal hole, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Ion, Solar wind, Physics::Plasma Physics, Space and Planetary Science, Physics::Space Physics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics
Abstract

The relative abundances of thermal and suprathermal C, O, and Fe ions are analysed and compared in solar wind streams from near-equatorial coronal holes (CHs) during quiet periods of nearly two solar cycle minima. Ion fluxes with energies of ∼0.04–2 MeV per nucleon are studied using data from the Ultra Low Energy Isotope Spectrometer (ULEIS) instrument aboard the Advanced Composition Explorer (ACE) spacecraft together with thermal ions in the fast and slow (Maxwellian) solar wind using data from the Solar Wind Ion Composition Spectrometer (SWICS) instrument aboard ACE. The analysis was carried out for quiescent periods in 2006–2012 and 2015–2017 when solar wind flows from near-equatorial CHs were detected at 1 au. Near the minimum of SC23, although they displayed large variability, the C/O and Fe/O ratios of suprathermal ions were, on average, near the corresponding relative abundances of the solar wind. During the decreasing solar activity phase of SC24, suprathermal Fe/O ratios matched those of solar wind ions from CHs. In both cycles, the thermal and suprathermal Fe/O ratios exhibited a similar character of dependence on maximum solar wind speed. Our results suggest that the sources of suprathermal ions from CHs in low-solar activity periods are accelerated solar wind thermal ions. The thermal and suprathermal Fe/O ratios were found to be higher in 2015–2017 in comparison to the ratios measured in 2006–2010. This difference can be attributed to that the second quiet period was selected at times when solar activity has not reached its minimum of SC24 yet.

Published
2021
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125. Observations and Interpretation of Rotational Properties of Polar Coronal Holes Based on SDO Data

Author

O. A. Korolkova, I. Zhivanovich, A. Riehokainen, and V. V. Smirnova

Subjects
Physics, 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, media_common.quotation_subject, Coronal hole, Astrophysics, 01 natural sciences, Asymmetry, Interpretation (model theory), Geophysics, Space and Planetary Science, Physics::Space Physics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Polar, Recognition algorithm, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, media_common
Abstract

The rotational effect observed in variations of areas of polar coronal holes with a period of 14 days is analyzed with SDO data by using Coronal Hole Identification with the Multithermal Emission Recognition Algorithm (CHIMERA) algorithm and the algorithm for the identification of solar structures from neural networks. A physical interpretation of the observed rotational effect associated with the asymmetry of coronal holes is proposed.

Published
2020
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144. The heliosphere

Author

Balogh, André, Fisk, Lennard A., Bleeker, Johan A. M., editor, Geiss, Johannes, editor, and Huber, Martin C. E., editor

Published
2001
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145. The solar wind

Author

Neugebauer, Marcia, Von Steiger, Rudolf, Bleeker, Johan A. M., editor, Geiss, Johannes, editor, and Huber, Martin C. E., editor

Published
2001
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146. The solar atmosphere

Author

Solanki, Sami K., Hammer, Reiner, Bleeker, Johan A. M., editor, Geiss, Johannes, editor, and Huber, Martin C. E., editor

Published
2001
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149. Coronal Fine Linear Rays: Are They Fast Streams From Active Regions?

Author

Serge Koutchmy, Philippe Lamy, Christian Viladrich, Boris Filippov, Arthur Nikoghossian, Leon Golub, M. Maksimovic, K. Issautier, N. Meyer-Vernet, M. Moncuquet, F. Pantellini, Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Marseille (LAM), and Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Jets outflows and bipolar flows, Coronal hole, solar magnetism, Astrophysics, 96.60.Vg, Coronal mass ejection, Astrophysics::Solar and Stellar Astrophysics, Eclipse, Physics, solar corona, Astronomy, Particle emission solar wind, 96.60.Hv, Coronal loop, Electric and magnetic fields solar magnetism, Helmet streamer, Corona, Nanoflares, Solar wind, astrophysical jets, solar wind, [SDU]Sciences of the Universe [physics], Physics::Space Physics, 98.58.Fd, 96.60.P
Abstract

International audience; Eclipse observations of the W-L corona show linear rays above active regions at times of solar maximum. We show that these linear rays are also observed in the field-of-view of the C2-LASCO coronagraph, in perfect correspondence with the eclipse results. A selected prominent case taken from the 2001 eclipse observation in Angola is analysed with several different methods, including the use of a synoptic map constructed using SoHO/LASCO C2 images. A clear signature of time variations near the eclipse observation is detected, suggesting that at least some parts of the beam are collimated. These observations strongly suggest high speed streams that apparently ignore the potential large scale coronal magnetic field rooted rather low in the corona. A possible origin is the neutral magnetic points located above the active region. Several mechanisms exist to explain how the plasma is accelerated in these regions to large quasi-relativistic velocities, possibly related to the occurrence of type III radio bursts. We point out a curious analogy with phenomena occurring inside coronal holes.

Published
2022
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150. Geomagnetic storms of cycle 24 and their solar sources.

Author

Watari, Shinichi

Subjects
*MAGNETIC storms, *SOLAR activity, *SOLAR wind, *ELECTRIC fields, *CORONAL mass ejections, *CORONAL holes
Abstract

Solar activity of cycle 24 following the deep minimum between cycle 23 and cycle 24 is the weakest one since cycle 14 (1902-1913). Geomagnetic activity is also low in cycle 24. We show that this low geomagnetic activity is caused by the weak dawn-to-dusk solar wind electric field ( E ) and that the occurrence rate of E > 5 mV/m decreased in the interval from 2013 to 2014. We picked up seventeen geomagnetic storms with the minimum Dst index of less than −100 nT and identified their solar sources in cycle 24 (2009-2015). It is shown that the relatively slow coronal mass ejections contributed to the geomagnetic storms in cycle 24. [ABSTRACT FROM AUTHOR]

Published
2017
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