Results 191 to 200 of about 10,729 (219)

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
openaire   +1 more source

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.
openaire   +1 more source

Investigation of Solar Rotation Using Coronal Holes

Astrophysics, 2015
The rotation of the solar coronal holes was studied. Data from the Kitt Peak Observatory in the line 10830 A He I for 2003—2012 was used for this purpose. The rotation of 434 coronal holes in the latitude interval ±40° was studied. The maximum angular velocity is observed at latitudes ±15°.
D. R. Japaridze, S. R. Bagashvili, B. M. Shergelasvili, B. B. Chargeishvili   +3 more
openaire   +1 more source

Solar cycle dependence of polar coronal holes

Solar Physics, 1993
A study has been made of the polar coronal holes in relation to solar cycle activity. Important results obtained are: (i) the peak of the frequency distribution of coronal hole size shifts towards lower values as the solar cycle advances towards maximum, this being true for both the north and south polar holes, (ii) coronal hole size decreases with the
T. K. Das, T. N. Chatterjee, A. K. Sen
openaire   +1 more source

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
openaire   +1 more source

Observations of the Solar Wind from Coronal Holes

Space Science Reviews, 1994
The solar wind emanating from coronal holes (CH) constitutes a quasi-stationary flow whose properties change only slowly with the evolution of the hole itself. Some of the properties of the wind from coronal holes depend on whether the source is a large polar coronal hole or a small near-equatorial hole.
openaire   +1 more source

Detecting coronal holes for solar activity modeling

2014 48th Asilomar Conference on Signals, Systems and Computers, 2014
Solar image analysis relies on the detection of coronal holes for predicting disruptions to earth's magnetic field. This paper introduces a level-set method for detecting coronal holes based on the processing of extreme ultra-violet images (EUVI) and magnetic images.
Marios S. Pattichis, Venkatesh Jatla, Rachel A. Hock, Carl J. Henney, Charles N. Arge   +4 more
openaire   +1 more source

Polar Coronal Holes During Solar Cycles 22 and 23

Chinese Journal of Astronomy and Astrophysics, 2005
Data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses and synoptic maps from Kitt Peak are used to analyze the polar coronal holes of solar activity cycles 22 and 23 (from 1990 to end of 2003). In the beginning of the declining phase of solar cycles 22 and 23, the north polar coronal holes (PCHs) appear about one year earlier than ...
Zhang, J., Woch, J., Solanki, S.
openaire   +2 more sources

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.
openaire   +1 more source

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
openaire   +1 more source