Results 41 to 50 of about 14,596 (161)

A Community Data Set for Comparing Automated Coronal Hole Detection Schemes

The Astrophysical Journal Supplement Series
Automated detection schemes are nowadays the standard approach for locating coronal holes in extreme-UV images from the Solar Dynamics Observatory (SDO). However, factors such as the noisy nature of solar imagery, instrumental effects, and others make it
Martin A. Reiss, Karin Muglach, Emily Mason, Emma E. Davies, Shibaji Chakraborty, Veronique Delouille, Cooper Downs, Tadhg M. Garton, Jeremy A. Grajeda, Amr Hamada, Stephan G. Heinemann, Stefan Hofmeister, Egor Illarionov, Robert Jarolim, Larisza Krista, Chris Lowder, Erwin Verwichte, Charles N. Arge, Laura E. Boucheron, Claire Foullon, Michael S. Kirk, Alexander Kosovichev, Andrew Leisner, Christian Möstl, James Turtle, Astrid Veronig   +25 more
doaj   +1 more source

Coronal Holes in Global Complexes of Activity

Advances in Astronomy, 2015
We propose a new concept that considers the global complexes of activity as a combination of global and local fields. Traditionally, the complexes of activity have been identified from observations of active regions (ARs). Here, we show that a complex of
Vladimir N. Obridko, Bertha D. Shelting
doaj   +1 more source

What Determines the Brightness of the Magnetically Open Solar Corona?: Insights from Three-dimensional Radiative Magnetohydrodynamic Simulations and Observations

The Astrophysical Journal
We investigate the relationship between solar coronal holes and open-field regions using three-dimensional radiative magnetohydrodynamic simulations combined with remote-sensing observations from the Solar Dynamics Observatory (SDO).
Haruhisa Iijima
doaj   +1 more source

Unipolarity of the Solar Magnetic Field in Equatorial Coronal Holes

The Astrophysical Journal
A study of the unbalanced magnetic polarity distribution of 70 coronal holes was performed. Data from the Helioseismic and Magnetic Imager were used to examine the photospheric line-of-sight magnetic field ( B _LOS ) beneath these coronal holes.
Khagendra Katuwal, R. T. James McAteer
doaj   +1 more source

The spatial relationship between active regions and coronal holes and the occurrence of intense geomagnetic storms throughout the solar activity cycle [PDF]

Annales Geophysicae, 1998
We study the annual frequency of occurrence of intense geomagnetic storms (Dst < –100 nT) throughout the solar activity cycle for the last three cycles and find that it shows different structures.
S. Bravo, J. A. L. Cruz-Abeyro, D. Rojas
doaj   +1 more source

Global Effect of New Active Regions on Coronal Holes and Their Wind Streams

The Astrophysical Journal
Solar wind prediction algorithms and simulations of coronal events often employ photospheric field maps that are assembled over a 27 day solar rotation. This has stimulated efforts to update and better synchronize the maps by applying flux transport and ...
Y.-M. Wang, K. J. Knizhnik, I. Ugarte-Urra, M. J. Weberg   +3 more
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The solar and interplanetary causes of the recent minimum in geomagnetic activity (MGA23): a combination of midlatitude small coronal holes, low IMF B_Z variances, low solar wind speeds and low solar magnetic fields [PDF]

Annales Geophysicae, 2011
Minima in geomagnetic activity (MGA) at Earth at the ends of SC23 and SC22 have been identified. The two MGAs (called MGA23 and MGA22, respectively) were present in 2009 and 1997, delayed from the sunspot number minima in 2008 and 1996 by ~1/2–1 years.
B. T. Tsurutani, B. T. Tsurutani, E. Echer, W. D. Gonzalez   +3 more
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The influence of different coronal hole geometries on simulations of coronal wave -- coronal hole interaction

The geometry of a coronal hole (CH) affects the density profile of the reflected part of an incoming global coronal wave (CW). In this study, we perform for the first time magnetohydrodynamic (MHD) simulations of fast-mode MHD waves interacting with CHs of different geometries, such as circular, elliptic, convex, and concave shapes.
Piantschitsch, I., Terradas, J., Soubrie, E., Heinemann, S. G., Hofmeister, S. J., Soler, R., Temmer, M.   +6 more
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The formation of an equatorial coronal hole [PDF]

Proceedings of the International Astronomical Union, 2009
AbstractThe formation of an equatorial coronal hole (CH) from 2006 January 9 to 12 was simultaneously observed byGOES-12/SXI,SOHO/EIT andSOHO/MDI instruments. The varieties of soft X-ray and EUV brightness, coronal temperature, and total magnetic flux in the CH were examined and compared with that of a quiet-sun (QS) region nearby.
Liheng Yang, Yunchun Jiang, Jun Zhang
openaire   +1 more source

Thermodynamic Evolution of Plumes

The Astrophysical Journal
Plumes are considered to play an important role in the origin of the solar wind. However, an understanding of their thermodynamic evolution is not complete. Here, we perform a detailed study of a plume inside a coronal hole throughout its lifetime, using
Biswanath Malaker, Vishal Upendran, Durgesh Tripathi   +2 more
doaj   +1 more source