scholarly journals Long term variability in solar wind velocity and IMF intensity and the relationship between solar wind parameters & geomagnetic activity

2000 ◽  
Vol 52 (2) ◽  
pp. 121-132 ◽  
Author(s):  
G. K. Rangarajan ◽  
L. M. Barreto
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Geomagnetic Activity ◽  
Solar Wind Velocity ◽  
Solar Wind Parameters ◽  
The Relationship

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.

scholarly journals Average auroral configuration parameterized by geomagnetic activity and solar wind conditions

2010 ◽  
Vol 28 (4) ◽  
pp. 1003-1012 ◽  
Author(s):  
S. E. Milan ◽  
T. A. Evans ◽  
B. Hubert
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Geomagnetic Activity ◽  
Solar Wind Velocity ◽  
Solar Wind Speed ◽  
Auroral Oval ◽  
Similar Amount ◽  
Solar Wind Parameters ◽  
Upstream Solar Wind ◽  
The Imf

Abstract. Average proton and electron auroral images are compiled from three years of observations by the IMAGE spacecraft, binned according to concurrent KP and upstream solar wind conditions measured by the ACE spacecraft. The solar wind parameters include solar wind velocity, density, and pressure, interplanetary magnetic field (IMF) magnitude and orientation, and an estimate of the magnetopause reconnection rate. We use both (a) the overall variation in brightness in the images and (b) the variation in location of the aurorae with respect to the binning parameters to determine which parameters best order the auroral response. We find that the brightness varies by a factor of ~50 with KP, a similar amount with estimated dayside reconnection voltage, ~15 with the IMF, ~3 with solar wind density, ~2 with solar wind velocity, and ~5 with pressure. Clearly, geomagnetic activity as measured by KP and auroral dynamics are closely associated. In terms of the solar wind-magnetosphere coupling that drives auroral dynamics, the IMF is of paramount importance in modulating this, with solar wind speed and density playing a lesser role. Dayside reconnection voltage, derived from the solar wind velocity and IMF magnitude and orientation, orders the data almost as well as KP, though we find a plateau in the auroral response between voltages of 100 and 150 kV. We also discuss changes in configuration and overall size of the average auroral oval with upstream conditions.

Long term periodicity in solar wind velocity during the last three solar cycles

1995 ◽  
Vol 22 (10) ◽  
pp. 1165-1168 ◽  
Author(s):  
P. R. Gazis ◽  
J. D. Richardson ◽  
K. I. Paularena
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Solar Wind Velocity ◽  
Solar Cycles

scholarly journals The coupling between the solar wind and proton fluxes at GEO

2013 ◽  
Vol 31 (10) ◽  
pp. 1631-1636 ◽  
Author(s):  
R. J. Boynton ◽  
S. A. Billings ◽  
O. A. Amariutei ◽  
I. Moiseenko
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Solar Wind Velocity ◽  
Proton Flux ◽  
Dst Index ◽  
Proton Fluxes ◽  
Angle Function ◽  
The Relationship ◽  
Energy Channels ◽  
Imf Clock Angle

Abstract. The relationship between the solar wind and the proton flux at geosynchronous Earth orbit (GEO) is investigated using the error reduction ratio (ERR) analysis. The ERR analysis is able to search for the most appropriate inputs that control the evolution of the system. This approach is a black box method and is able to derive a mathematical model of a system from input-output data. This method is used to analyse eight energy ranges of the proton flux at GEO from 80 keV to 14.5 MeV. The inputs to the algorithm were solar wind velocity, density and pressure; the Dst index; the solar energetic proton (SEP) flux; and a function of the interplanetary magnetic field (IMF) tangential magnitude and clock angle. The results show that for lowest five energy channels (80 to 800 keV) the GEO proton fluxes are controlled by the solar wind velocity with a lag of two to three days. However, above 350 keV, the SEP fluxes, accounts for a significant portion of the GEO proton flux variance. For the highest three energy channels (0.74 to 14.5 MeV), the SEPs account for the majority of the ERR. The results also show an anisotropy of protons with gyrocenters inside GEO and outside GEO, where the protons inside GEO are controlled partly by the Dst index and also an IMF-clock angle function.

scholarly journals Periodic variations of the geomagnetic activity indices Ap and Kp

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.

scholarly journals Long‐Term Variations in Solar Wind Parameters, Magnetopause Location, and Geomagnetic Activity Over the Last Five Solar Cycles

2019 ◽  
Vol 124 (6) ◽  
pp. 4049-4063 ◽  
Author(s):  
A. A. Samsonov ◽  
Y. V. Bogdanova ◽  
G. Branduardi‐Raymont ◽  
J. Safrankova ◽  
Z. Nemecek ◽  
...  
Keyword(s):  
Solar Wind ◽  
Geomagnetic Activity ◽  
Solar Cycles ◽  
Solar Wind Parameters ◽  
Long Term Variations
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