scholarly journals Seasonal variations in the occurrence of geomagnetic storms

1996 ◽  
Vol 14 (3) ◽  
pp. 286-289 ◽  
Author(s):  
John R. Taylor ◽  
Mark Lester ◽  
Timothy K. Yeoman
Keyword(s):  
Solar Wind ◽  
Seasonal Variations ◽  
Annual Variation ◽  
Geomagnetic Storms ◽  
Magnetic Activity ◽  
Magnetic Storms ◽  
Sudden Commencement ◽  
Sudden Commencements ◽  
Solar Wind Origin

Abstract. Seasonal variations in the onset of magnetic storms are investigated. For the purposes of this study storms have been defined as events in which Dst falls below –50 nT for at least four consecutive hours. The storms have been classified as either storm sudden commencements (SSCs; storms initiated by a sudden commencement) or as storm gradual commencements (SGCs; all other storms). It is found that the semi-annual variation of magnetic activity is reflected in the occurrence statistics of SGC events only, indicative that the solar wind origin is different for SSCs and SGCs. It is suggested that the heliospheric latitude model of seasonal magnetic activity is relatively ineffective in modulating the previously observed seasonal variations in the occurrence of magnetic storms.

scholarly journals Seasonal features of geomagnetic activity: a study on the solar activity dependence

2021 ◽  
Vol 39 (5) ◽  
pp. 929-943
Author(s):  
Adriane Marques de Souza Franco ◽  
Rajkumar Hajra ◽  
Ezequiel Echer ◽  
Mauricio José Alves Bolzan
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
Geomagnetic Activity ◽  
Annual Variation ◽  
Geomagnetic Storms ◽  
Solar Wind Speed ◽  
Solar Cycles ◽  
Annual Variations ◽  
Long Duration ◽  
Activity Dependence

Abstract. Seasonal features of geomagnetic activity and their solar-wind–interplanetary drivers are studied using more than five solar cycles of geomagnetic activity and solar wind observations. This study involves a total of 1296 geomagnetic storms of varying intensity identified using the Dst index from January 1963 to December 2019, a total of 75 863 substorms identified from the SuperMAG AL/SML index from January 1976 to December 2019 and a total of 145 high-intensity long-duration continuous auroral electrojet (AE) activity (HILDCAA) events identified using the AE index from January 1975 to December 2017. The occurrence rates of the substorms and geomagnetic storms, including moderate (-50nT≥Dst>-100nT) and intense (-100nT≥Dst>-250nT) storms, exhibit a significant semi-annual variation (periodicity ∼6 months), while the super storms (Dst≤-250 nT) and HILDCAAs do not exhibit any clear seasonal feature. The geomagnetic activity indices Dst and ap exhibit a semi-annual variation, while AE exhibits an annual variation (periodicity ∼1 year). The annual and semi-annual variations are attributed to the annual variation of the solar wind speed Vsw and the semi-annual variation of the coupling function VBs (where V = Vsw, and Bs is the southward component of the interplanetary magnetic field), respectively. We present a detailed analysis of the annual and semi-annual variations and their dependencies on the solar activity cycles separated as the odd, even, weak and strong solar cycles.

scholarly journals Earth’s geomagnetic response to solar wind changes associated with solar events at low latitude regions at the TRE MAGDAS Station

2021 ◽  
Vol 880 (1) ◽  
pp. 012009
Author(s):  
R Umar ◽  
S N A Syed Zafar ◽  
N H Sabri ◽  
M H Jusoh ◽  
A Yoshikawa ◽  
...  
Keyword(s):  
Solar Wind ◽  
Geomagnetic Storms ◽  
Interplanetary Space ◽  
Coronal Holes ◽  
Magnetic Activity ◽  
Study Results ◽  
Geomagnetic Fields ◽  
Solar Events ◽  
Solar Wind Parameters ◽  
Mass Ejection

Abstract The Sun’s magnetic activity influences disturbances that perturb interplanetary space by producing large fluxes of energetic protons, triggering geomagnetic storms and affecting the ground geomagnetic field. The effect of two solar events, namely Coronal Mass Ejection (CME) and Coronal Holes, on geomagnetic indices (SYM/H), solar wind parameters and ground geomagnetic fields has provided magnetic ground data, which were extracted from the Terengganu (TRE, -4.21° N, 175.91° E) Magnetometer (MAGDAS) station, and investigated in this study. Results show that the physical dynamic mechanism in the Earth’s magnetosphere is triggered by various solar wind parameters associated with CMEs and Coronal hole events during the minimum solar cycle of 24 at low latitudes. It is important to study solar wind-magnetosphere coupling because it has an impact on ground-based technological systems and human activities.

scholarly journals An investigation into the correlation of geomagnetic storms with tropospheric parameters over the South Pole

2003 ◽  
Vol 21 (5) ◽  
pp. 1095-1100 ◽  
Author(s):  
M. M. Lam ◽  
A. S. Rodger
Keyword(s):  
Solar Wind ◽  
Geomagnetic Storm ◽  
Lower Stratosphere ◽  
Geomagnetic Storms ◽  
Cosmic Ray ◽  
Magnetic Activity ◽  
Atmospheric Composition ◽  
South Pole ◽  
The South ◽  
Interplanetary Physics

Abstract. We test the proposal that the Sun’s magnetic activity, communicated via the solar wind, provides a link between solar variability and the Earth’s climate in the Antarctic troposphere. The strength of a geomagnetic storm is one indicator of the state of the solar wind; therefore, we use the dates of 51 moderate to strong winter geomagnetic storms from the period 1961–1990 to conduct a series of superposed epoch analyses of the winter South Pole isobaric height and temperature, at pressures of between 100–500 mbar. Using Student’s t -test to compare the mean value of the pre- and post-storm data sets, we find no evidence to support the hypothesis that there is a statistically-significant correlation between the onset of a geomagnetic storm and changes in the isobaric temperature or height of the troposphere and lower stratosphere over the South Pole during winter months. This concurs with a similar study of the variability of the troposphere and lower stratosphere over the South Pole (Lam and Rodger, 2002) which uses drops in the level of observed galactic cosmic ray intensity, known as Forbush decreases, as a proxy for solar magnetic activity instead of geomagnetic storms.Key words. Interplanetary physics (solar wind plasma; cosmic rays) – Atmospheric composition and structure (pressure, density and temperature)

THE DIURNAL BEHAVIOR OF SUDDEN COMMENCEMENTS OF MAGNETIC STORMS AT AGINCOURT

1956 ◽  
Vol 34 (8) ◽  
pp. 876-883 ◽  
Author(s):  
J. A. Jacobs ◽  
T. Obayashi
Keyword(s):  
Local Time ◽  
Magnetic Storms ◽  
Diurnal Variations ◽  
Sudden Commencement ◽  
Time Effects ◽  
Frequency Distributions ◽  
Initial Rise ◽  
Magnetic Variation ◽  
Sudden Commencements ◽  
Magnetic Vectors

The diurnal variations in the frequencies of sudden commencements of magnetic storms are examined, using the magnetograms from Agincourt for the period from 1946 to 1953 inclusive. The occurrence frequencies of sudden commencements exhibit an apparent diurnal tendency which has its minimum in the morning hours and maximum in the afternoon. The frequency distributions for several groups classified by their amplitudes, however, show different diurnal variations from one another. In order to confirm such local-time effects, a statistical analysis of the shape of sudden commencements has been made, and each sudden commencement classified according to its shape. Results show the following diurnal characteristics. A pronounced augmentation of the sudden commencement impulse occurs in the afternoon hours. In the morning the initial rise of sudden commencements is usually slight and they are frequently inverted in the H-trace, although some of them are quite clear in the D-trace. The local-time variation of the horizontal magnetic vectors at several stages of the initial phase is also estimated statistically. These results suggest that the diurnal control of the magnetic variation must be due to some additional field produced in the earth's upper atmosphere at the time of sudden commencement, tending to modify the primary cause.

scholarly journals A Method for Recognition of Sudden Commencements of Geomagnetic Storms Using Digital Differentiating Filters

2022 ◽  
Vol 12 (1) ◽  
pp. 413
Author(s):  
Victor Getmanov ◽  
Roman Sidorov ◽  
Alexei Gvishiani
Keyword(s):  
Decision Making ◽  
False Recognition ◽  
Geomagnetic Field ◽  
Geomagnetic Storms ◽  
Maximum Amplitude ◽  
Sudden Commencement ◽  
Magnetic Components ◽  
Observatory Data ◽  
Sudden Commencements ◽  
Decision Making Rule

This article describes a method for recognizing sudden commencement events using digital differentiating filters. This method is applied to INTERMAGNET observatory data. Maximum amplitude derivatives for the magnetic components (X, Y, Z) and the total intensity (F) of the geomagnetic field are introduced, and the decision-making rule is formulated. The authors developed a procedure for selecting optimal digital differentiating filters. Estimates of probabilities of correct and false recognition of sudden commencements were obtained. The calculations of the probabilistic characteristics have confirmed the effectiveness of the method.

scholarly journals Seasonal features of geomagnetic activity: evidence for solar activity dependence?

2021 ◽  
Author(s):  
Adriane Marques de Souza Franco ◽  
Rajkumar Hajra ◽  
Ezequiel Echer ◽  
Mauricio José Alves Bolzan
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
Geomagnetic Activity ◽  
Annual Variation ◽  
Geomagnetic Storms ◽  
Solar Wind Speed ◽  
Solar Cycles ◽  
Annual Variations ◽  
Long Duration ◽  
Activity Dependence

Abstract. Seasonal features of geomagnetic activity and their solar wind-interplanetary drivers are studied using more than 5 solar cycles of geomagnetic activity and solar wind observations. This study involves a total of 1239 geomagnetic storms of varying intensity identified using the Dst index from January 1963 to December 2019, a total of 75863 substorms identified from the SML index from January 1976 to December 2019, a total of 145 high-intensity long-duration continuous auroral electrojet (AE) activity (HILDCAA) events identified using the AE index from January 1975 to December 2017. The occurrence rates of the substorms, geomagnetic storms, including moderate (−50 nT ≥ Dst > −100 nT) and intense (−100 nT ≥ Dst > −250 nT), exhibit a significant semi-annual variation (periodicity ~ 6 months), while the super storms (Dst ≤ −250 nT) and HILDCAAs do not exhibit any clear seasonal feature. The geomagnetic activity indices Dst and ap exhibit a semi-annual variation while AE exhibits an annual variation (periodicity ~ 1 year). The annual and semi-annual variations are found to be driven by the annual variation of the solar wind speed Vsw and the semi-annual variation of the coupling function V Bs (where V = Vsw, and Bs is the southward component of the interplanetary magnetic field), respectively. We present a detailed analysis of the annual and semi-annual variations and their dependencies on the solar activity cycles separated as the odd, even, weak and strong solar cycles.

A superposed epoch analysis of geomagnetic storms

1994 ◽  
Vol 12 (7) ◽  
pp. 612-624 ◽  
Author(s):  
J. R. Taylor ◽  
M. Lester ◽  
T. K. Yeoman
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
High Speed ◽  
Geomagnetic Storms ◽  
Solar Wind Speed ◽  
Magnetic Activity ◽  
Wind Pressure ◽  
Superposed Epoch Analysis ◽  
Controlling Parameter ◽  
Epoch Analysis

Abstract. A superposed epoch analysis of geomagnetic storms has been undertaken. The storms are categorised via their intensity (as defined by the Dst index). Storms have also been classified here as either storm sudden commencements (SSCs) or storm gradual commencements (SGCs, that is all storms which did not begin with a sudden commencement). The prevailing solar wind conditions defined by the parameters solar wind speed (vsw), density (ρsw) and pressure (Psw) and the total field and the components of the interplanetary magnetic field (IMF) during the storms in each category have been investigated by a superposed epoch analysis. The southward component of the IMF, appears to be the controlling parameter for the generation of small SGCs (-100 nT< minimum Dst ≤ -50 nT for ≥ 4 h), but for SSCs of the same intensity solar wind pressure is dominant. However, for large SSCs (minimum Dst ≤ -100 nT for ≥ 4 h) the solar wind speed is the controlling parameter. It is also demonstrated that for larger storms magnetic activity is not solely driven by the accumulation of substorm activity, but substantial energy is directly input via the dayside. Furthermore, there is evidence that SSCs are caused by the passage of a coronal mass ejection, whereas SGCs result from the passage of a high speed/ slow speed coronal stream interface. Storms are also grouped by the sign of Bz during the first hour epoch after the onset. The sign of Bz at t = +1 h is the dominant sign of the Bz for ~24 h before the onset. The total energy released during storms for which Bz was initially positive is, however, of the same order as for storms where Bz was initially negative.

The solar causes of major geomagnetic storms

1994 ◽  
Vol 12 (2/3) ◽  
pp. 113-120 ◽  
Author(s):  
S. Bravo ◽  
A. L. Rivera
Keyword(s):  
Solar Wind ◽  
Geomagnetic Storms ◽  
Sudden Commencement ◽  
Interplanetary Scintillation ◽  
Solar Wind Disturbances

Abstract. In this paper we reanalyse the set of ten major geomagnetic storms which occurred between August 1978 and December 1979. We relate them to the characteristics of the solar wind disturbances which caused them and the solar sources of such disturbances as tracked by means of interplanetary scintillation. It seems to us that the shock causing the sudden commencement and the plasma behind it with an important long-lasting Bz south component (Bz.

Disappearing Solar Filaments and Interplanetary Shock Waves

1983 ◽  
Vol 5 (2) ◽  
pp. 202-204 ◽  
Author(s):  
C. S. Wright
Keyword(s):  
Geomagnetic Storms ◽  
Close Association ◽  
Interplanetary Shock ◽  
Sudden Commencement ◽  
The Sun ◽  
Type Ii ◽  
Type Iv ◽  
Magnetohydrodynamic Shock ◽  
Solar Filaments ◽  
Sudden Commencements

The close association between flare events having metric radio type II and type IV bursts and the subsequent occurrence of sudden commencement geomagnetic storms is well known. In such cases it has been amply demonstrated (e.g. Malitson et al. 1973; Cane et al. 1982) that the sudden commencement (SC) is caused by the same magnetohydrodynamic shock which originates near the Sun and which produces the type II burst. Recently, a study of geomagnetic storms thought to be associated with the disappearance of filaments from quiet regions of the Sun (Joselyn and McIntosh 1981) showed that several of these storms began with marked sudden commencements.

Sign in / Sign up

Export Citation Format

Share Document