Results 151 to 160 of about 600 (183)
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Solar activity and the formation of coronal holes
Advances in Space Research, 2000Abstract We describe the evolution of a complex of active regions belonging to cycle 22 and how its interaction with two new-cycle (23) regions resulted in the formation of several isolated coronal holes, in the development of the large coronal hole extending from the north polar hole observed in late August 1996, and in significant changes in both ...
Karen L. Harvey, Hugh S. Hudson
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Solar structures related to coronal holes
Astronomy Reports, 2007The nature of structures detected recently on the Sun in soft X rays by I.F. Nikulin (Sternberg Astronomical Institute) and called by him “partings” is discussed. It is shown that these structures are sign-reversal lines for the normal component of the curvature vector of the magnetic lines.
M. M. Molodenskiĭ, L. I. Starkova
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Energetics of Solar Coronal Holes
1991We examine the energetics of a solar coronal hole in the framework of magnetohydrodynamics (MHD). Given typical values of the observed parameters, it is estimated that the Poynting flux maintained by the solar rotation and a trailing magnetic field is potentially capable of driving and heating a wind stream in a coronal hole region.
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On the evolutionary aspects of solar coronal holes
2023Coronal holes (CH) are large, long-lived structures commonly observed in the solar corona as regions of reduced emission in EUV and X-ray wavelengths. They feature a characteristic open magnetic field configuration along which ionized electrons and atoms are accelerated into the interplanetary space.
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Models for Solar Coronal Holes.
1978Abstract : This report summarizes several investigations of coronal holes and quiet regions. Temperature-density models for those regions have been derived from EUV observations. It is found that the coronal temperature, density, and temperature gradient are lower in coronal holes than in quiet regions.
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Polar coronal holes and solar cycles
Solar Physics, 1979The relationship between the geomagnetic activity of the three years preceding a sunspot minimum and the peak of the next sunspot maximum confirms the polar origin of the solar wind during one part of the solar cycle. Pointing out that the polar holes have a very small size or disappear at the time of the polar field reversal, we suggest a low latitude
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Coronal holes and the solar wind
2002Abstract Coronal holes are the darkest regions of the ultraviolet and X-ray Sun, both on the disk and above the limb. Coronal holes are associated with rapidly expanding open magnetic fields and the acceleration of the high-speed solar wind. This paper reviews measurements of the plasma properties of coronal holes and how these measurements have been
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Observations of Doppler Shifts in a Solar Polar Coronal Hole
The Astrophysical Journal, 1997Using observations from the Solar Ultraviolet Measurements of Emitted Radiation experiment flown on the Solar and Heliospheric Observatory spacecraft, we have measured Doppler wavelength shifts in the north polar coronal hole in the 1032 and 1038 A emission lines of O VI and the 1036 and 1037 A emission lines of C II relative to chromospheric emission ...
Warren, H., Mariska, J., Wilhelm, K.
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Acceleration of the High Speed Solar Wind in Coronal Holes
Space Science Reviews, 1999We outline a theory for the origin and acceleration of the fast solar wind as a consequence of network microflares releasing a spectrum of high frequency Alfven waves which heat (by cyclotron absorption) the corona close to the Sun. The significant features of our model of the fast wind are that the acceleration is rapid with the sonic point at around ...
Axford, W. +5 more
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The effects of coronal holes on the propagation of solar energetic protons
Radiation Measurements, 1999The accurate prediction of the start of a Solar Energetic Particle Event (SEP) is a high priority for space weather forecasters. The Space Environment Center (SEC) has recorded parameters related to SEPs since 1976, and that list includes a total of 134 events for the period 1976-1997.
J M, Kunches, R D, Zwickl
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