ASSOCIATION BETWEEN VARIATIONS OF SOLAR WIND PARAMETERS AND GEOMAGNETIC ACTIVITY INDEX Ap IN 2003 - 2005

2011 ◽  
Vol 2 (3) ◽  
pp. 205-210 ◽  
Author(s):  
Igor Savel'evich Fal'kovich ◽  
M. R. Olyak ◽  
Nikolai Nikolaevich Kalinichenko ◽  
I. N. Bubnov
Keyword(s):  
Solar Wind ◽  
Geomagnetic Activity ◽  
Activity Index ◽  
Solar Wind Parameters ◽  
Geomagnetic Activity Index

scholarly journals Comparisons between EUV/IMAGE observations and numerical simulations of the plasmapause formation

2005 ◽  
Vol 23 (7) ◽  
pp. 2635-2646 ◽  
Author(s):  
V. Pierrard ◽  
J. Cabrera
Keyword(s):  
Solar Wind ◽  
Numerical Simulations ◽  
Geomagnetic Activity ◽  
Activity Index ◽  
Quiet Period ◽  
Specific Time ◽  
Period 2 ◽  
Storms And Substorms ◽  
Geomagnetic Activity Index ◽  
Time Sequences

Abstract. Simulations of plasmapause formation described in Pierrard and Lemaire (2004) predict the shape and equatorial distance of the plasmapause as a function of the geomagnetic activity index Kp. The equatorial positions predicted by this model are compared with the observations of EUV/IMAGE during the geomagnetic storm of 24 May 2000, substorm events of 10 June 2001 and 25 June 2000, and also during a prolonged quiet period (2 May 2001) when the plasmasphere was very extended. The formation of structures, like plumes and shoulders observed during periods of high geomagnetic activity, is quite well reproduced by the simulations. These structures are directly related to specific time sequences of Kp variations. The radial distances of the plasmapause are also reproduced, on average, by the model. Keywords. Magnetospheric physics (Plasmasphere; Storms and substorms; Solar wind magnetosphere interactions)

scholarly journals Cometary Brightness Variations and Conditions in Interplanetary Space

1972 ◽  
Vol 45 ◽  
pp. 16-21
Author(s):  
D. A. Andrienko ◽  
A. A. Demenko ◽  
I. M. Demenko ◽  
I. D. Zosimovich
Keyword(s):  
Solar Wind ◽  
Geomagnetic Activity ◽  
Geomagnetic Field ◽  
Interplanetary Space ◽  
Activity Index ◽  
Good Method ◽  
Ecliptic Plane ◽  
Light Curves ◽  
Photometric Observations ◽  
Geomagnetic Activity Index

The study of cometary brightness variations can be a good method for determining conditions in interplanetary space. In this work we compare the light curves of comets with curves showing variations in the geomagnetic field at times when the comets are near the ecliptic plane. We have used photometric observations made of 29 comets between 1881 and 1937. It is shown that an increase in the brightness of a comet is associated with an increase in the geomagnetic activity index and consequently with the influence of the solar corpuscular streams and solar wind.

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 Extremely low geomagnetic activity during the recent deep solar cycle minimum

2011 ◽  
Vol 7 (S286) ◽  
pp. 200-209 ◽  
Author(s):  
E. Echer ◽  
B. T. Tsurutani ◽  
W. D. Gonzalez
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Solar Minimum ◽  
Solar Wind Speed ◽  
Sunspot Cycle ◽  
Cycle Minimum ◽  
Current Minimum ◽  
Solar Wind Parameters ◽  
Xix Century

AbstractThe recent solar minimum (2008-2009) was extreme in several aspects: the sunspot number, Rz, interplanetary magnetic field (IMF) magnitude Bo and solar wind speed Vsw were the lowest during the space era. Furthermore, the variance of the IMF southward Bz component was low. As a consequence of these exceedingly low solar wind parameters, there was a minimum in the energy transfer from solar wind to the magnetosphere, and the geomagnetic activity ap index reached extremely low levels. The minimum in geomagnetic activity was delayed in relation to sunspot cycle minimum. We compare the solar wind and geomagnetic activity observed in this recent minimum with previous solar cycle values during the space era (1964-2010). Moreover, the geomagnetic activity conditions during the current minimum are compared with long term variability during the period of available geomagnetic observations. The extremely low geomagnetic activity observed in this solar minimum was previously recorded only at the end of XIX century and at the beginning of the XX century, and this might be related to the Gleissberg (80-100 years) solar cycle.

On the interplay between solar wind parameters and ULF wave power as a function of geomagnetic activity at high‐ and mid‐latitudes

2021 ◽  
Author(s):  
Stavros Dimitrakoudis ◽  
Ian R. Mann ◽  
Georgios Balasis ◽  
Constantinos Papadimitriou ◽  
Anastasios Anastasiadis ◽  
...  
Keyword(s):  
Solar Wind ◽  
Geomagnetic Activity ◽  
Wave Power ◽  
Ulf Wave ◽  
Solar Wind Parameters

Seasonal and diurnal variations of geomagnetic activity and their role in Space Weather forecast

2001 ◽  
Vol 79 (6) ◽  
pp. 907-920 ◽  
Author(s):  
W Lyatsky ◽  
A M Hamza
Keyword(s):  
Solar Wind ◽  
Seasonal Variation ◽  
Diurnal Variation ◽  
Geomagnetic Activity ◽  
Space Weather ◽  
Weather Forecast ◽  
Diurnal Variations ◽  
Ionospheric Conductivity ◽  
Solar Wind Parameters ◽  
Possible Cause

A possible test for different models explaining the seasonal variation in geomagnetic activity is the diurnal variation. We computed diurnal variations both in the occurrence of large AE (auroral electrojet) indices and in the AO index. (AO is the auroral electrojet index that provides a measure of the equivalent zonal current.) Both methods show a similar diurnal variation in geomagnetic activity with a deep minimum around (3–7) UT (universal time) in winter and a shallower minimum near 5–9 UT in equinoctial months. The observed UT variation is consistent with the results of other scientists, but it is different from that expected from the Russell–McPherron mechanism proposed to explain the seasonal variation. It is suggested that the possible cause for the diurnal and seasonal variations may be variations in nightside ionospheric conductivity. Recent experimental results show an important role for ionospheric conductivity in particle acceleration and geomagnetic disturbance generation. They also show that low ionospheric conductivity is favorable to the generation of auroral and geomagnetic activity. The conductivity in conjugate nightside auroral zones (where substorm generation takes place) is minimum at equinoxes, when both auroral zones are in darkness. The low ionospheric conductivity at equinoxes may be a possible cause for the seasonal variation in the geomagnetic activity with maxima in equinoctial months. The diurnal variation in geomagnetic activity can be produced by the UT variation in the nightside ionospheric conductivity, which in winter and at equinoxes has a maximum around 4–5 UT that may lead to a minimum in geomagnetic activity at this time. We calculated the correlation patterns for the AE index versus solar-wind parameters inside and outside the (2–7) UT sector related to the minimum in geomagnetic activity. The correlation patterns appear different in these two sectors indeed, which is well consistent with the UT variation in geomagnetic activity. It also shows that it is possible to improve significantly the reliability of the Space Weather forecast by taking into account the dependence of geomagnetic activity not only on solar-wind parameters but also on UT and season. Our test shows that a simple account for the dependence of geomagnetic activity on UT can improve the reliability of the Space Weather forecast by at least 50% in the 2–7 UT sector in winter and equinoctial months. PACS No.: 91.25Le

scholarly journals Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr – Part 2: A new reconstruction of the interplanetary magnetic field

2013 ◽  
Vol 31 (11) ◽  
pp. 1979-1992 ◽  
Author(s):  
M. Lockwood ◽  
L. Barnard ◽  
H. Nevanlinna ◽  
M. J. Owens ◽  
R. G. Harrison ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Activity ◽  
Flow Speed ◽  
Range Data ◽  
Solar Wind Flow ◽  
Annual Means ◽  
Solar Wind Parameters ◽  
The Imf

Abstract. We present a new reconstruction of the interplanetary magnetic field (IMF, B) for 1846–2012 with a full analysis of errors, based on the homogeneously constructed IDV(1d) composite of geomagnetic activity presented in Part 1 (Lockwood et al., 2013a). Analysis of the dependence of the commonly used geomagnetic indices on solar wind parameters is presented which helps explain why annual means of interdiurnal range data, such as the new composite, depend only on the IMF with only a very weak influence of the solar wind flow speed. The best results are obtained using a polynomial (rather than a linear) fit of the form B = χ · (IDV(1d) − β)α with best-fit coefficients χ = 3.469, β = 1.393 nT, and α = 0.420. The results are contrasted with the reconstruction of the IMF since 1835 by Svalgaard and Cliver (2010).

Analysis of the Temporal-Spatial Distribution Characteristics of the Geomagnetic Activity Index Vr

2012 ◽  
Vol 55 (2) ◽  
pp. 184-193
Author(s):  
Ya-Hong YUAN ◽  
Dong-Mei YANG ◽  
Hua-Ran CHEN ◽  
Yu-Fei HE ◽  
Chuan-Hua CHEN
Keyword(s):  
Spatial Distribution ◽  
Geomagnetic Activity ◽  
Activity Index ◽  
Distribution Characteristics ◽  
Spatial Distribution Characteristics ◽  
Geomagnetic Activity Index
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