2024-03-28T18:13:16Z
https://nagoya.repo.nii.ac.jp/oai
oai:nagoya.repo.nii.ac.jp:00022151
2023-01-16T04:09:19Z
879:880:881
North-south asymmetry in global distribution of the solar wind speed during 1985–2013
Tokumaru, Munetoshi
Fujiki, Ken'ichi
Iju, Tomoya
open access
©2015. American Geophysical Union. All Rights Reserved.
Global observations of the solar wind including high-latitude regions
Heliospheric response to long-term change in the solar dynamo activity
Marked north-south asymmetry of the polar solar wind and its origin
Interplanetary scintillation (IPS) observations made between 1985 and 2013 are used to investigate the north-south (N-S) asymmetry in global distribution of the solar wind speed. The IPS observations clearly demonstrate that the global distribution of the solar wind speed systematically changes with the solar activity. This change is found to closely correlate with that in polar magnetic fields of the Sun, while fast wind data at solar minima systematically deviate from this correlation. The IPS observations show that notable N-S asymmetry of polar solar winds occurs at the solar maxima, and small but significant N-S asymmetry exists at the solar minima. The observed asymmetry at the solar maxima is consistent with the time lag in the reversal of polar magnetic fields between north and south hemispheres. We also find that significant N-S asymmetry of the polar fast wind lasts for the period between Cycles 23 and 24 solar maxima, starting from predominance of the fast wind over the north pole and ending with that over the south pole. The N-S asymmetry revealed from IPS observations is found to be generally consistent with Ulysses observations. We compare IPS observations with magnetic field data of the Sun and find that the ratio of the quadrupole to dipole coefficients exhibits a similar time variation to that of the N-S asymmetry revealed from IPS observations. This suggests that higher-order multipole moments play an important role in determining the N-S asymmetry of the solar wind when the dipole moment weakens.
AGU publications
2015-05
eng
journal article
VoR
http://hdl.handle.net/2237/24210
https://nagoya.repo.nii.ac.jp/records/22151
https://doi.org/10.1002/2014JA020765
2169-9380
Journal of Geophysical Research: Space Physics
120
5
3283
3296
https://nagoya.repo.nii.ac.jp/record/22151/files/Tokumaru_et_al-2015-Journal_of_Geophysical_Research_Space_Physics.pdf
application/pdf
3.6 MB
2018-02-21