Global Pc5 geomagnetic pulsations of March 24, 1991, as observed along the American Sector

Trivedi, N. B.; Arora, B. R.; Padilha, Antônio L.; Costa, J. M. Da; Dutra, S. L. G.; Chamalaun, F. H.; Rigoti, Augustinho

doi:10.1029/97gl00215

Cited by 35 publications

(29 citation statements)

References 14 publications

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“…Such visualization is well supported by the nature of equatorial enhancement that falls off to low values within ±4 dip latitude. Trivedi et al (1997b) found that polarization characteristics of the pulsations across the auroral oval were consistent with the field line resonance model (Southwood, 1974). The occurrence of Pc5 pulsations at low and equatorial latitudes was attributed to the instantaneous transmission of the polar electric field, set up by field line resonance, to the low and equatorial latitudes through the ionosphere.…”

Section: Pc5 Magnetic Pulsations Of 24 March 1991supporting

confidence: 50%

“…Combining the data from the present chain of stations (only those free from anomalous induction effects -documented later) with other mid-and high-latitude stations along American sector, Trivedi et al (1997b) examined the amplitude and polarization parameters of this globally coherent Pc5 event right from the auroral latitude to the equatorial latitudes. The , indicates that, apart from the expected sharp maximum near the auroral oval, the pulsation amplitudes are considerably enhanced in the equatorial belt.…”

Section: Pc5 Magnetic Pulsations Of 24 March 1991mentioning

confidence: 99%

“…3 is that the field variations in the east-west (Y ) component at station BAC are considerably large, although other stations with similar locations in relation to the dip equator do not show this anomalous behaviour. (Trivedi et al, 1997b). Broken curve shows the variation in PSP within the equatorial region when data from stations like BAC, contaminated by the anomalous induction effects, are included.…”

Section: Physical Appraisal Of Induction Effectsmentioning

confidence: 99%

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Appraisal of electromagnetic induction effects on magnetic pulsation studies

et al. 2001

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Abstract. The quantification of wave polarization characteristics of ULF waves from the geomagnetic field variations is done under 'a priori' assumption that fields of internal induced currents are in-phase with the external inducing fields. Such approximation is invalidated in the regions marked by large lateral conductivity variations that perturb the flow pattern of induced currents. The amplitude and phase changes that these perturbations produce, in the resultant fields at the Earth's surface, make determination of polarization and phase of the oscillating external signals problematic. In this paper, with the help of a classical Pc5 magnetic pulsation event of 24 March 1991, recorded by dense network of magnetometers in the equatorial belt of Brazil, we document the nature and extent of the possible influence of anomalous induction effects in the wave polarization of ULF waves. The presence of anomalous induction effects at selected sites lead to an over estimation of the equatorial enhancement at pulsation period and also suggest changes in the azimuth of ULF waves as they propagate through the equatorial electrojet. Through numerical calculations, it is shown that anomalous horizontal fields, that result from induction in the lateral conductivity distribution in the study region, vary in magnitude and phase with the polarization of external source field. Essentially, the induction response is also a function of the period of external inducing source field. It is further shown that when anomalous induction fields corresponding to the magnitude and polarization of the 24 March 1991 pulsation event are eliminated from observed fields, corrected amplitude in the X and Y horizontal components allows for true characterisation of ULF wave parameters.

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Section: Pc5 Magnetic Pulsations Of 24 March 1991supporting

confidence: 50%

Section: Pc5 Magnetic Pulsations Of 24 March 1991mentioning

confidence: 99%

Section: Physical Appraisal Of Induction Effectsmentioning

confidence: 99%

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Appraisal of electromagnetic induction effects on magnetic pulsation studies

et al. 2001

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“…In general, it is still unclear whether the pulsations during strong storms are physically the same as common Pc5 waves. The most intense Pc5 waves, with amplitudes exceeding by an order of magnitude those of common Pc5 pulsations, are observed during the recovery phase of severe magnetic storms (Trivedi et al, 1997;Kleimenova and Kozyreva, 2005). These anomalously strong pulsations are referred to as global Pc5 pulsations (Potapov et al, 2006) because they were observed simultaneously in the morning and evening sectors over a wide range of latitudes.…”

Section: Published By Copernicus Publications On Behalf Of the Europementioning

confidence: 99%

Global Pc5 pulsations during strong magnetic storms: excitation mechanisms and equatorward expansion

et al. 2014

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Abstract. The dynamics of global Pc5 waves during the magnetic storms on 29-31 October 2003 are considered using data from the trans-American and trans-Scandinavian networks of magnetometers in the morning and post-noon magnetic local time (MLT) sectors. We study the latitudinal distribution of Pc5 wave spectral characteristics to determine how deep into the magnetosphere these Pc5 waves can extend at different flanks of the magnetosphere. The wave energy transmission mechanisms are different during 29-30 October and 31 October wave events. Further, we examine whether the self-excited Kelvin-Helmholtz instability is sufficient as an excitation mechanism for the global Pc5 waves. We suggest that on 31 October a magnetospheric magnetohydrodynamic (MHD) waveguide was excited, and the rigid regime of its excitation was triggered by enhancements of the solar wind density. The described features of Pc5 wave activity during recovery phase of strong magnetic storm are to be taken into account during the modeling of the relativistic electron energization by ultra-low-frequency (ULF) waves.Keywords. Magnetospheric physics (MHD waves and instabilities; storms and substorms) -space plasma physics (kinetic and MHD theory)

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“…To date, several studies on the event of 24 March 1991 have been reported in the literature (Cahill and Winckler 1992;Yumoto et al 1992;Fujitani et al 1993;Liu et al 1993;Reddy et al 1994;Trivedi et al 1997;Schott et al 1998). Most of these studies focused on a local investigation of the characteristics and driving causes of the pulsations through an analysis of the data obtained solely from ground stations or from satellites.…”

Section: Introductionmentioning

confidence: 99%

Global Ultra-Low-Frequency Geomagnetic Pulsations Associated with the March 24, 1991 Geomagnetic Storm

Chen

Liu²

2008

Terr. Atmos. Ocean. Sci.

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On 24 March 1991, global ultra-low-frequency (ULF) pulsations (1.1 -3.3 mHz) observed in the magnetosphere as well as on the ground were studied via analyzing magnetic field data obtained from a global network, comprising ground-based observatories and geosynchronous satellites. In the magnetosphere, the compressional and transverse components of the magnetic fields recorded at two satellites, GOES 6 and GOES 7, showed dominant fluctuations when they were in the vicinity of the noon sector, whereas the transverse fluctuations became dominant when they were at the dawn side. Similarly, on the ground, the H and D components had major fluctuations along with an increase in amplitude from low to high geomagnetic latitudes. In addition, the amplitude of the ULF pulsation was enhanced at the dawn and dusk sides. The geomagnetic pulsations propagated anti-sunward and were of counterclockwise and clockwise elliptical polarizations at the dawn and dusk sides respectively. The counterclockwise elliptical polarization reversed to a clockwise elliptical polarization at geomagnetic local noon and linear polarization was observed during the reversal. It appears that the analysis of the global network data not only provided us with a study of the characteristics of the waves in the magnetosphere and on the ground but also provided us with correlations between the geosynchronous and ground observations, which should be essential to the determination of possible mechanisms of this storm-related wave event.

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Global Pc5 geomagnetic pulsations of March 24, 1991, as observed along the American Sector

Cited by 35 publications

References 14 publications

Appraisal of electromagnetic induction effects on magnetic pulsation studies

Appraisal of electromagnetic induction effects on magnetic pulsation studies

Global Pc5 pulsations during strong magnetic storms: excitation mechanisms and equatorward expansion

Global Ultra-Low-Frequency Geomagnetic Pulsations Associated with the March 24, 1991 Geomagnetic Storm

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