Forecast of the solar wind velocity and the interplanetary magnetic field radial component polarity at the phase of decay of solar cycle 23

Using data with hourly resolution obtained in near-Earth heliosphere in 1965–2014, we have calculated statistical characteristics of the angles describing the direction of the interplanetary magnetic field (IMF): root-mean-square deviations of azimuthal and elevation angles, asymmetries of their distributions, and coefficient of correlation of the angles. It has been shown that the above characteristics varied in the course of solar cycle, and some of them changed their signs when solar polar magnetic field reversed. The results obtained from the experimental data analysis were compared with a model describing transport of large-scale disturbances of IMF lines by the inhomogeneous solar wind. The comparison has shown that the variations in the angular distribution of IMF in the course of solar cycle probably occur due to the appearance of the large-scale latitudinal gradient of solar wind velocity during solar minima. In addition, the angular distribution of IMF has been found to be substantially affected by the longitudinal velocity gradient in trailing parts of high-speed streams and short-term local-scale variations in velocity gradients.

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Periodic variations of the geomagnetic activity indices Ap and Kp

Journal of University of Shanghai for Science and Technology ◽

10.51201/jusst12634 ◽

2021 ◽

Vol 23 (2) ◽

Author(s):

Pandey A.C. ◽

◽

Sham Singh ◽

Dinesh Kumar Pathak ◽

Archana Shukla ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Solar Cycle ◽

Interplanetary Magnetic Field ◽

Wind Velocity ◽

Geomagnetic Activity ◽

Solar Wind Velocity ◽

Data Sets ◽

Time Intervals ◽

Activity Indices

Yearly averages of geomagnetic activity indices Kp and Ap for the years 1984 to 2018 be compared to the relevant averages of VxBs, where V is the solar wind velocity and Bs is the southward interplanetary magnetic field (IMF) component. The correlation of both quantities is known to be rather good. Comparing the averages of Ap and Kp with V and Bs separately. We found that, during the declining phase of solar cycle, V and during the ascending phase Bs have more influence on Ap and Kp indices. According to this observation the 27 days and semiannual, Ap and Kp variations be analysed discretely for years after and before sunspot minima. The time intervals prior to sunspot minima with a significant 27-day recurrent period of the IMF structure and those intervals after sunspot minima with a significant 28 to28.5 day recurrent phase of the structure be used. The averaged spectra of the two Ap and Kp data sets obviously show a period of 27 days before and a period of 28 to 29 days after sunspot minimum.

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Effect of large-scale inhomogeneity of solar wind velocity on distribution of directions of interplanetary magnetic field vector

Solar-Terrestrial Physics ◽

10.12737/stp-53201905 ◽

2019 ◽

Vol 5 (3) ◽

pp. 42-53

Author(s):

Дмитрий Ерофеев ◽

Dmitry Erofeev

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Angular Distribution ◽

Solar Cycle ◽

Interplanetary Magnetic Field ◽

Wind Velocity ◽

High Speed ◽

Large Scale ◽

Solar Wind Velocity ◽

Statistical Characteristics

Using data with hourly resolution obtained in near-Earth heliosphere in 1965–2014, we have calculated statistical characteristics of the angles describing the direction of the interplanetary magnetic field (IMF): root-mean-square deviations of azimuthal and elevation angles, asymmetries of their distributions, and coefficient of correlation of the angles. It has been shown that the above characteristics varied in the course of solar cycle, and some of them changed their signs when solar polar magnetic field reversed. The results obtained from the experimental data analysis were compared with a model describing transport of large-scale disturbances of IMF lines by the inhomogeneous solar wind. The comparison has shown that the variations in the angular distribution of IMF in the course of solar cycle probably occur due to the appearance of the large-scale latitudinal gradient of solar wind velocity during solar minima. In addition, the angular distribution of IMF has been found to be substantially affected by the longitudinal velocity gradient in trailing parts of high-speed streams and short-term local-scale variations in velocity gradients.

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