North-south asymmetry in global distribution of the solar wind speed during 1985-2013

2015 ◽  
Vol 120 (5) ◽  
pp. 3283-3296 ◽  
Author(s):  
Munetoshi Tokumaru ◽  
Ken'ichi Fujiki ◽  
Tomoya Iju
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Solar Wind Speed ◽  
Global Distribution ◽  
South Asymmetry

North-South Asymmetry of the Polar Solar Wind and Some Characteristics of Solar Magnetic Field

1996 ◽  
Vol 154 ◽  
pp. 165-168
Author(s):  
T.E. Girish ◽  
G. Gopkumar
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Wind Speed ◽  
Solar Magnetic Field ◽  
Solar Wind Speed ◽  
Sunspot Cycle ◽  
Coronal Magnetic Field ◽  
Sunspot Activity ◽  
Dipolar Contribution ◽  
South Asymmetry

AbstractWe have found correlated variations of the yearly averaged north-south asymmetry in the polar solar wind speed (Δsol) and the ratio of the zonal quadrupolar to the zonal dipolar contribution in the inferred coronal magnetic field during the declining phase of sunspot cycle 21. A physically meaningful association between Δsol and some polar solar magnetic field proxies is also observed during the low sunspot activity periods of the above cycle.

Global Distribution of the Solar Wind Speed Reconstructed from Improved Tomographic Analysis of Interplanetary Scintillation Observations between 1985 and 2019

2021 ◽  
Vol 922 (1) ◽  
pp. 73
Author(s):  
Munetoshi Tokumaru ◽  
Ken’ichi Fujiki ◽  
Masayoshi Kojima ◽  
Kazumasa Iwai
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Power Index ◽  
Solar Wind Speed ◽  
Global Distribution ◽  
Interplanetary Scintillation ◽  
Wind Speeds ◽  
In Situ Observations

Abstract Computer-assisted tomography (CAT) for interplanetary scintillation (IPS) observations enables the determination of the global distribution of solar wind speed. We compared solar wind speeds derived from the CAT analysis of IPS observations between 1985 and 2019 with in situ observations conducted by the near-Earth and Ulysses spacecraft. From this comparison, we found that solar wind speeds from the IPS observations for 2009–2019 were systematically higher than the in situ observations, whereas those for the period until 2008 were in good agreement with the in situ observations. Further, we found that the discrepancy between IPS and the in situ observations is improved by changing the power index of the empirical relation between the solar wind speed and density fluctuations. The CAT analysis using an optimal value for the power index determined from the comparison between IPS and in situ observations revealed long-term variations in the solar wind speed distribution over three cycles, leading to a better understanding of the time-varying global heliosphere. We found that polar solar winds become highly anisotropic at the Cycle 24/25 minimum, which is a peculiar aspect of this minimum. The IPS observations showed general agreement with the Parker Solar Probe observations around the perihelion of Orbit 1; this supports the reliability of the CAT analysis. The results of this study suggest that the physical properties of solar wind microturbulence may vary with a long-term decline in the solar activity, which provides important implication on the solar wind acceleration.

Solar cycle dependence of global distribution of solar wind speed

1990 ◽  
Vol 53 (3-4) ◽  
pp. 173-222 ◽  
Author(s):  
Masayoshi Kojima ◽  
Takakiyo Kakinuma
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Wind Speed ◽  
Solar Wind Speed ◽  
Global Distribution ◽  
Cycle Dependence

Coronal density and the solar wind speed at all latitudes

1981 ◽  
Vol 86 (A11) ◽  
pp. 8869 ◽  
Author(s):  
D. G. Sime ◽  
B. J. Rickett
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Solar Wind Speed ◽  
Coronal Density
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