Diurnal UT Variation of Low Latitude Geomagnetic Storms Using Six Indices

Balan, N.; Ram, S. Tulasi; Varghese, Manu; Zhao, Lingxin; Zou, Xing; Zhang, Qinghe

doi:10.1029/2020ja028854

Cited by 10 publications

(7 citation statements)

References 49 publications

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“…This implies there is some net inter-hemispheric current flow as well as between dawn and dusk. It also implicates the UT variations in the ring current (that connects to the R2 FACs) that have reported in large ring current storms by Balan et al (2021). An anticorrelation is seen for the converse combination (Northern dusk R1 and Southern dawn R1; Figure 17F) but is not as strong.…”

Section: Universal Time Variations In Field-aligned Currents and Ring...supporting

confidence: 75%

“…In the century since Bartels' original deduction, a very large number of papers have discussed UT variations in the magnetosphere which, given that many magnetospheric processes take place in limited magnetic local time regions (in particular, substorm phenomena take place in the sector around local midnight), gives potential longitudinal variations in space weather and also means that the effects of a given disturbance in interplanetary space depend upon its time of arrival at Earth. UT variations have been reported in geomagnetic indices in a great many studies (Waldo-Lewis and McIntosh, 1953;McIntosh, 1959;Nicholson and Wulf, 1961;Davis and Sugiura, 1966;Berthelier, 1976;Aoki, 1977;Mayaud, 1978;Russell, 1989;Berthelier, 1990;Saroso et al, 1993;Takalo et al, 1995;de La Sayette and Berthelier, 1996;Siscoe and Crooker, 1996;Hajkowicz, 1998;Ahn et al, 2000;Cliver et al, 2000;Lyatsky et al, 2001;O'Brien and McPherron, 2002;Ahn and Moon, 2003;Karinen and Mursula, 2005;Wang and Lühr, 2007;Yakovchouk et al, 2012;Chu et al, 2015;Lockwood et al, 2020a;Lockwood et al, 2020b;Lockwood et al, 2020c;Balan et al, 2021;Lockwood et al, 2021;Wang et al, 2021). A problem for all these studies is that if the longitudinal distribution of magnetometer stations employed is not even, then a spurious UT variation is introduced into the geomagnetic data (Mayaud, 1978;Mayaud, 1980;Takalo and Mursula, 2001;Lockwood et al, 2019b).…”

Section: Introductionmentioning

confidence: 99%

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Universal Time variations in the magnetosphere

Lockwood¹,

McWilliams²,

Milan³

2023

Front. Astron. Space Sci.

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We study the dependencies of Earth’s magnetosphere on Universal Time, UT. These are introduced because Earth’s magnetic axis is not aligned with the rotational axis and complicated because it is eccentric, which makes the offset of the magnetic and rotation poles considerably greater in the Southern hemisphere and the longitudinal separation of the magnetic poles less than 180°: hence consequent UT variations in the two hemispheres are not in equal in amplitude nor in exact antiphase and do not cancel, as they would for a geocentric dipole. We use long series of a variety of geomagnetic data to demonstrate the inductive effect of motions of the polar caps in a “geocentric-solar” frame, which is phase-locked to the Russell-McPherron (R-M) effect on solar-wind magnetosphere coupling. This makes the response of the magnetosphere-ionosphere system different for the two polarities of the Y-component of the Interplanetary Magnetic Field in the GSEQ reference frame, explaining the difference in response to the March and September equinox peaks in solar wind forcing. The sunward/antisunward pole-motion effect is detected directly in satellite transpolar voltage data and is shown to have a greater effect on the geomagnetic data than the full dipole tilt effect which generates the equinoctial pattern, the potential origins of which are discussed in terms of the dipole tilt effect on ionospheric conductivities and the stability of the near-Earth tail. Persistent UT variations in Region-1 and Region-2 field-aligned currents and in partial ring current indices are presented: their explanation is an important challenge for numerical modelling of the magnetosphere-ionosphere-thermosphere system which we need to quantify the relative contributions of the various mechanisms and to give understanding of the effect of arrival time on the response of the system to large, geoeffective disturbances in interplanetary space.Plain language summary: The effect on terrestrial space weather of Earth’s magnetic axis not being aligned with the rotational axis is investigated. It is complex because not only do these two axes not align in direction (the “dipole tilt”), the magnetic axis does not pass through the centre of the Earth, which sets a requirement for an “eccentric” model of the field and not the commonly-used “geocentric” one. For many years, it has been known that the dipole tilt gives a peak in geomagnetic activity at the equinoxes (the semi-annual variation) through the “Russell-McPherron” (R-M) effect. However, although the variation with Universal Time is consistent with the R-M effect for the September equinox, it is not for the March equinox. We here solve this long-standing puzzle by investigating the effects of the motions of the two poles in a frame fixed with respect to both the Earth and the Sun for an eccentric dipole model. But solving one puzzle generates many others. We present observations of the Universal Time variations that these mechanisms combine to generate, which set an important challenge to the numerical modelling of the near-Earth space environment.

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Section: Universal Time Variations In Field-aligned Currents and Ring...supporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Universal Time variations in the magnetosphere

Lockwood¹,

McWilliams²,

Milan³

2023

Front. Astron. Space Sci.

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“…Here we discuss the largest GIC events in 4 seasons. Figure 3 shows the GIC (3a) data at September equinox (29-30 October 2003) when the largest GICmax (57.05A) and largest number (11) of GICmax > 25A occurred in the 21 years of this study (Table 1). This case is associated with the rst of a super double geomagnetic storm (SymHMin − 391 nT, Kpmax 9 and AEmax 4056 nT; 3b-3c), fastest solar wind velocity (2242 km/s; 3d) (e.g., Skoug et al 2004) and largest negative V×Bz (-97.23x10 3 km/s nT; 3f) in 21 years with -Bz up to -45.05 nT (3e).…”

Section: Largest Gic In Seasonsmentioning

confidence: 85%

Relationship of the largest GIC during geomagnetic storms with solar wind-IMF parameters

Balan

Zou

et al. 2022

Preprint

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The association of GIC (geomagnetically induced current) with various solar and geophysical conditions has been known. However, what determines the time of occurrence and amplitude of the largest GIC during geomagnetic storms, which during extreme storms can cause sudden damage of vulnerable utility systems, is not yet known. We address this important question by analyzing the GIC data measured in Finland for 21 years (1999–2019) during 106 geomagnetic activities (DstMin ≤-50 nT) at low, mid and high latitudes and the corresponding solar wind velocity V, dynamic pressure P, north-south component of interplanetary magnetic field (IMF Bz), and the products V×Bz and P×Bz. The results show for the first time that the largest GIC (≥ 10 A) occurs at the time of the largest -(V×Bz) in all seasons and solar activity levels with its time determined by the time of the largest -Bz and magnitude determined by both V and -Bz, except in one case. The two power outages happened in the 21-year period (06 November 2001 and 30 October 2003) also occurred at the UT time of the largest GICmax. The correlation of largest GICmax is also highest (0.92) with the largest -(V×Bz) at September equinox. The results highlight the importance of the single station GIC measurements and possibility of improving the forecasting of the rate of change of the local horizontal geomagnetic field (dH/dt) directly related to GIC.

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“…The storms are more frequent and more intense at equinoxes than in solstices (e.g., Svalgaard, 2011; Newell et al., 2001; Balan, Tulasiram, et al., 2017; Lockwood, McWilliams, et al., 2020; Lockwood, Owens, et al., 2020; Franco et al., 2021). The occurrence time of the storm peak intensity (maximum negative value of Dst during main phase (MP) of the storm) exhibits a quasi‐semidiurnal type variation at low latitudes (e.g., Ahn et al., 2002; Balan et al., 2021). The seasonal and diurnal UT variations are understood in terms of equinoctial hypothesis (Bartels, 1932) and Russell‐McPherron effect (Russell & McPherron, 1973).…”

Section: Introductionmentioning

confidence: 99%

Double Superposed Epoch Analysis of Geomagnetic Storms and Corresponding Solar Wind and IMF in Solar Cycles 23 and 24

et al. 2023

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The large (fluctuating) electric currents flowing at different regions in the magnetosphere and ionosphere during space weather events produce large fluctuations in the geomagnetic field lasting from several hours to several days in all latitudes (e.g., Akasofu, 1981;Gonzalez et al., 1994;Svalgaard, 1977). The field fluctuations at low latitudes are produced mainly by the enhanced low latitude magnetospheric ring current; they undergo 3-phase variations and are referred as geomagnetic storms. At high latitudes, the field fluctuations are produced mainly by the enhanced high latitude ionospheric auroral electrojet current; they undergo irregular variations and are referred as storm-time substorms or activities. At mid latitudes, the field fluctuations are the combined effect of the poleward extension of the low latitude fluctuations and equatorward extension of the high latitude fluctuations; they undergo 2-phase variations and are referred also as geomagnetic storms (e.g.

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Diurnal UT Variation of Low Latitude Geomagnetic Storms Using Six Indices

Abstract: Large disturbances in the geomagnetic field lasting from several hours to several days are known as geomagnetic storms. The storms are characterized by enhanced magnetospheric and ionospheric current systems (e.g.

Cited by 10 publications

References 49 publications

Universal Time variations in the magnetosphere

Universal Time variations in the magnetosphere

Relationship of the largest GIC during geomagnetic storms with solar wind-IMF parameters

Double Superposed Epoch Analysis of Geomagnetic Storms and Corresponding Solar Wind and IMF in Solar Cycles 23 and 24

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