scholarly journals Extremely long baseline interplanetary scintillation measurements of solar wind velocity

2006 ◽  
Vol 111 (A8) ◽  
Author(s):  
A. R. Breen ◽  
R. A. Fallows ◽  
M. M. Bisi ◽  
P. Thomasson ◽  
C. A. Jordan ◽  
...  
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Solar Wind Velocity ◽  
Interplanetary Scintillation ◽  
Long Baseline

scholarly journals EISCAT measurements of solar wind velocity and the associated level of interplanetary scintillation

2002 ◽  
Vol 20 (9) ◽  
pp. 1279-1289 ◽  
Author(s):  
R. A. Fallows ◽  
P. J. S. Williams ◽  
A. R. Breen
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Solar Wind Velocity ◽  
Solar Wind Plasma ◽  
Scintillation Index ◽  
Line Of Sight ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
Interplanetary Physics ◽  
Eiscat Measurements

Abstract. A relative scintillation index can be derived from EISCAT observations of Interplanetary Scintillation (IPS) usually used to study the solar wind velocity. This provides an ideal opportunity to compare reliable measurements of the solar wind velocity derived for a number of points along the line-of-sight with measurements of the overall level of scintillation. By selecting those occasions where either slow- or fast-stream scattering was dominant, it is shown that at distances from the Sun greater than 30 RS , in both cases the scintillation index fell with increasing distance as a simple power law, typically as R-1.7. The level of scintillation for slow-stream scattering is found to be 2.3 times the level for fast-stream scattering.Key words. Interplanetary physics (solar wind plasma)

scholarly journals Physical meaning of the equinoctial effect for semi-annual variation in geomagnetic activity

2009 ◽  
Vol 27 (5) ◽  
pp. 1909-1914 ◽  
Author(s):  
A. Yoshida
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Geomagnetic Activity ◽  
Physical Meaning ◽  
Solar Wind Velocity ◽  
Annual Variation ◽  
Geomagnetic Disturbance ◽  
Data Sets ◽  
Key Factor ◽  
Solar Wind Parameters

Abstract. Physical meaning of the equinoctial effect for semi-annual variation in geomagnetic activity is investigated based on the three-hourly am index and solar wind parameters. When the z component of the interplanetary magnetic field (IMF) in geocentric solar magnetospheric (GSM) coordinates is southward, am indices are well correlated with BsVx2, where Bs is the southward component of the IMF and Vx is the solar wind velocity in the sun-earth direction. The am-BsVx2 relationship, however, depends on the range of Vx2: the am in higher ranges of Vx2 tends to be larger than am in lower ranges of Vx2 for the same value of BsVx2 for both equinoctial and solstitial epochs. Using the data sets of the same Vx2 range, it is shown that distribution of points in the am-BsVx2 diagram at the solstitial epochs overlaps with that at the equinoctial epochs and the average am values in each BsVx2 bin in solstitial epochs are closely consistent with those in equinoctial epochs, if Vx2 for each point at solstices are reduced to Vx2sin2 (Ψ) where Ψ is the geomagnetic colatitude of the sub-solar point. Further, it is shown that monthly averages of the am index in the long period is well correlated with the values of sin2(ψ) for the middle day of each month. These findings indicate that the factor that contributes to the generation of geomagnetic disturbance is not the velocity of the solar wind, but the component of the solar wind velocity perpendicular to the dipole axis of the geomagnetic field. The magnitude of the perpendicular velocity component varies semi-annually even if the solar wind velocity remains constant, which is considered to be the long-missed key factor causing the equinoctial effect.

A New Forecasting Index for Solar Wind Velocity Based on EIT 284 Å Observations

Solar Physics ◽  
2008 ◽  
Vol 250 (1) ◽  
pp. 159-170 ◽  
Author(s):  
Bingxian Luo ◽  
Qiuzhen Zhong ◽  
Siqing Liu ◽  
Jiancun Gong
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Solar Wind Velocity
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