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 Coronal shocks associated with CMEs and flares and their space weather consequences

2008 ◽  
Vol 4 (S257) ◽  
pp. 61-63
Author(s):  
Marina Laskari ◽  
Panagiota Preka-Papadema ◽  
Constantine Caroubalos ◽  
George Pothitakis ◽  
Xenophon Moussas ◽  
...  
Keyword(s):  
Solar Wind ◽  
Geomagnetic Activity ◽  
Space Weather ◽  
Geophysical Data ◽  
Radio Bursts ◽  
Type Ii ◽  
Geomagnetic Indices ◽  
Complex Events ◽  
Solar Wind Parameters ◽  
Solar Energetic Events

AbstractWe study the geoeffectiveness of a sample of complex events; each includes a coronal type II burst, accompanied by a GOES SXR flare and LASCO CME. The radio bursts were recorded by the ARTEMIS-IV radio spectrograph, in the 100-650 MHz range; the GOES SXR flares and SOHO/LASCO CMEs, were obtained from the Solar Geophysical Data (SGD) and the LASCO catalogue respectively. These are compared with changes of solar wind parameters and geomagnetic indices in order to establish a relationship between solar energetic events and their effects on geomagnetic activity.

scholarly journals Possibilities and problems of Solar magnetic field observations for space weather forecast

2017 ◽  
Vol 3 (1) ◽  
pp. 22-33
Author(s):  
Михаил Демидов ◽  
Mikhail Demidov
Keyword(s):  
Solar Wind ◽  
Magnetic Fields ◽  
Space Weather ◽  
Weather Forecast ◽  
Heliospheric Current Sheet ◽  
Calculation Model ◽  
Original Material ◽  
Near Earth Space ◽  
Quantitative Calculation ◽  
Solar Wind Parameters

An essential part of the space weather problem, important in the last decades, is the forecast of near-Earth space parameters, ionospheric and geomagnetic conditions on the basis of observations of various phenomena on the Sun. Of particular importance are measurements of magnetic fields as they determine the spatial structure of outer layers of the solar atmosphere and, to a large extent, solar wind parameters. Due to lack of opportunities to observe magnetic fields directly in the corona, the almost only source of various models for quantitative calculation of heliospheric parameters are daily magnetograms measured in photospheric lines and synoptic maps derived from these magnetograms. It turns out that results of the forecast, in particular of the solar wind velocity in Earth’s orbit and the position of the heliospheric current sheet, greatly depend not only on the chosen calculation model, but also on the original material because magnetograms from different instruments (and often observations in different lines at the same), although being morphologically similar, may differ significantly in a detailed quantitative analysis. A considerable part of this paper focuses on a detailed analysis of this particular aspect of the problem of space weather forecast.

Explicit IMF By-dependence in geomagnetic activity

2020 ◽  
Author(s):  
Lauri Holappa ◽  
Timo Asikainen ◽  
Kalevi Mursula
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Geomagnetic Activity ◽  
Space Weather ◽  
High Latitude ◽  
Coupling Function ◽  
Ionospheric Conductivity ◽  
Future Space ◽  
Southern High Latitude ◽  
The Imf

<p>The interaction of the solar wind with the Earth’s magnetic field produces geomagnetic activity, which is critically dependent on the orientation of the interplanetary magnetic field (IMF). Most solar wind coupling functions quantify this dependence on the IMF orientation with the so-called IMF clock angle in a way, which is symmetric with respect to the sign of the By component. However, recent studies have shown that IMF By is an additional, independent driver of high-latitude geomagnetic activity, leading to higher (weaker) geomagnetic activity in Northern Hemisphere (NH) winter for By > 0 (By < 0). For NH summer the dependence on the By sign is reversed. We quantify the size of this explicit By-effect with respect to the solar wind coupling function, both for northern and southern high-latitude geomagnetic activity. We show that for a given value of solar wind coupling function, geomagnetic activity is about 40% stronger for By > 0 than for By < 0 in NH winter. The physical mechanism of the By-effect is not yet fully understood. Here we show that IMF By modulates the flux of energetic electrons precipitating into the ionosphere which likely modulates the ionospheric conductivity and, thus, geomagnetic activity. Our results highlight the importance of the IMF By-component for space weather and must be taken into account in future space weather modeling.</p>

scholarly journals Possibilities and problems of solar magnetic field observations for space weather forecast

2017 ◽  
Vol 3 (1) ◽  
pp. 26-39 ◽  
Author(s):  
Михаил Демидов ◽  
Mikhail Demidov
Keyword(s):  
Solar Wind ◽  
Magnetic Fields ◽  
Space Weather ◽  
Weather Forecast ◽  
Heliospheric Current Sheet ◽  
Calculation Model ◽  
Original Material ◽  
Near Earth Space ◽  
Quantitative Calculation ◽  
Solar Wind Parameters

An essential part of the space weather problem, important in the last decades, is the forecast of near-Earth space parameters, ionospheric and geomagnetic conditions on the basis of observations of various phenomena on the Sun. Of particular importance are measurements of magnetic fields as they determine the spatial structure of outer layers of the solar atmosphere and, to a large extent, solar wind parameters. Due to lack of opportunities to observe magnetic fields directly in the corona, the almost only source of various models for quantitative calculation of heliospheric parameters are daily magnetograms measured in photospheric lines and synoptic maps derived from these magnetograms. It turns out that results of the forecast, in particular of the solar wind velocity in Earth’s orbit and the position of the heliospheric current sheet, greatly depend not only on the chosen calculation model, but also on the original material because magnetograms from different instruments (and often observations in different lines at the same), although being morphologically similar, may differ significantly in a detailed quantitative analysis. A considerable part of this paper focuses on a detailed analysis of this particular aspect of the problem of space weather forecast.

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 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

Explicit IMF By-dependence in geomagnetic activity

2021 ◽  
Author(s):  
Lauri Holappa ◽  
Timo Asikainen ◽  
Kalevi Mursula
Keyword(s):  
Solar Wind ◽  
Geomagnetic Activity ◽  
Space Weather ◽  
High Latitude ◽  
Coupling Function ◽  
Future Space ◽  
Weather Modeling ◽  
Southern High Latitude ◽  
Imf Clock Angle ◽  
The Imf

<p>The interaction of the solar wind with the Earth’s magnetic field produces geomagnetic activity, which is critically dependent on the orientation of the interplanetary magnetic field (IMF). Most solar wind coupling functions quantify this dependence on the IMF orientation with the so-called IMF clock angle in a way, which is symmetric with respect to the sign of the B<sub>y</sub> component. However, recent studies have shown that IMF B<sub>y</sub> is an additional, independent driver of high-latitude geomagnetic activity, leading to higher (weaker) geomagnetic activity in Northern Hemisphere (NH) winter for B<sub>y</sub> > 0 (B<sub>y</sub> < 0). For NH summer the dependence on the B<sub>y</sub> sign is reversed. We quantify the size of this explicit B<sub>y</sub>-effect with respect to the solar wind coupling function, both for northern and southern high-latitude geomagnetic activity. We show that for a given value of solar wind coupling function, geomagnetic activity is about 40% stronger for B<sub>y</sub> > 0 than for B<sub>y</sub> < 0 in NH winter. We also discuss recent advances in the physical understanding of the B<sub>y</sub>-effect. Our results highlight the importance of the IMF B<sub>y</sub>-component for space weather and must be taken into account in future space weather modeling.</p>

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).

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