Results 181 to 190 of about 1,198,926 (208)

Observations of Doppler Shifts in a Solar Polar Coronal Hole

The Astrophysical Journal, 1997
Using 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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Coronal holes and the solar wind

2002
Abstract 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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Models for Solar Coronal Holes.

1978
Abstract : 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, 1979
The 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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Acceleration of the High Speed Solar Wind in Coronal Holes

Space Science Reviews, 1999
We 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., McKenzie, J., Sukhorukova, G., Banaszkiewicz, M., Czechowski, A., Ratkiewicz, R.   +5 more
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The effects of coronal holes on the propagation of solar energetic protons

Radiation Measurements, 1999
The 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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Coronal Holes and Solar Mass Loss

1981
During the declining phase of solar activity, and possibly at other phases, solar mass loss occurs in the form of high speed streams in the solar wind. These streams originate in low density, low temperature coronal regions, called “holes.” The physical properties of the wind streams and the holes will be discussed.
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Ion Temperatures as Observed in a Solar Coronal Hole

Space Science Reviews, 1999
From the widths of the extreme ultraviolet (EUV) lines measured by the SUMER instrument on SOHO, it was found previously (Tu et al. 1998) that the average temperature of Ne+7, at heights (relative to h 0) above the southern solar limb from 17″ to 64″, ranges between 1.3 and 5 × 106 K and of Ne+6 between 1 and 4 × 106 K.
Tu, C., Marsch, E., Wilhelm, K.
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Coronal mass ejections: Relationship with solar flares and coronal holes

2002
Abstract The Coronal Mass Ejections (CMEs) observed by the LASCO coronagraph and associated solar activity phenomena whose locations were identified by EIT and solar Hα flare observations during year 2000 indicate that about 40%, 26% and 30% of CMEs were observed when there were coronal holes (CHs) within 1–10, 11–20 and 21–40 degrees, respectively
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Coronal Holes and the High-Speed Solar Wind

Space Science Reviews, 2002
Coronal holes are the lowest density plasma components of the Sun's outer atmosphere, and are associated with rapidly expanding magnetic fields and the acceleration of the high-speed solar wind. Spectroscopic and polarimetric observations of the extended corona, coupled with interplanetary particle and radio sounding measurements going back several ...
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