Equatorial enhancement of Pc5–6 magnetic storm time geomagnetic pulsations

Pathan, B. M.; Клейменова, Н. Г.; Козырева, О. В.; Rao, D. R. K.; Asinkar, R. L.

doi:10.1186/bf03351566

Cited by 13 publications

(5 citation statements)

References 29 publications

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“…Another point that we will emphasize is the equatorial enhancement of the Pi3 pulsation. This has been reported in many phenomena such as for SCs [ Araki , 1977], Pi2 pulsations [ Yanagihara and Shimizu , 1966; Shinohara et al , 1998], Pc3‐4 and Pc5 pulsations [ Sarma and Sastry , 1995; Pathan et al , 1999; Motoba et al , 2002]. It is possible that all of those equatorial enhancements share a common physical mechanism.…”

Section: Introductionmentioning

confidence: 74%

Coupling of perturbations in the solar wind density to global Pi3 pulsations: A case study

et al. 2007

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[1] A typical Pi3 pulsation is examined by magnetic field measurements from multiple satellites and ground stations. Low-latitude ground observations with a wide longitudinal span indicate that the amplitude of the Pi3 pulsation peaks on the dayside and is gradually decreasing toward the nightside. This effect and the fact that the wave phase on the dayside leads that on the nightside, imply that the source of the Pi3 lies on the dayside. Variations in solar wind dynamic pressure observed by the GEOTAIL satellite (just outside of the magnetosphere) are highly correlated with these ground magnetic field variations. We argue in this case that the global Pi3 pulsation is directly driven by impulsive variations in the solar wind dynamic pressure. The Pi3 pulsation observed along the latitudinal magnetometer chain at 0930LT shows significant equatorial enhancement and additional observations along a latitudinal chain at 1630LT show that the phase of the Pi3 pulsation at high latitudes lags behind that at low latitudes. The low-altitude polar orbiting satellite Oersted also observed this pulsation in the dayside inner magnetosphere. The B k (northward) component at Oersted is strictly out of phase with the X component observed at the dip equator below the spacecraft path, which indicates that the Pi3 pulsation at the dip equator is caused by oscillation of an ionospheric current. We propose that the Pi3 pulsations at different latitudes are generated by different mechanisms.

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Section: Introductionmentioning

confidence: 74%

Coupling of perturbations in the solar wind density to global Pi3 pulsations: A case study

et al. 2007

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“…The resonant frequency of a field line is determined by magnetic field line length, the magnetic field intensity, and plasma density distribution along the field line. Pathan et al [1999] suggested that the development of strong magnetic storms can lead to significant large‐scale structural changes of the magnetosphere, and thus the properties of geomagnetic pulsations observed on the ground might be expected to change significantly. Longer field lines or reduced magnetic field intensity would both cause a decrease in eigenfrequency.…”

Section: Discussionmentioning

confidence: 99%

Global Pc5 pulsations observed at unusually low L during the great magnetic storm of 24 March 1991

et al. 2007

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[1] Using CANOPUS, GREENLAND, IMAGE, SAMNET, and 210 MM ground-based magnetometer array data, we examine the global characteristics of ULF waves during the onset day of the great magnetic storm of 24 March 1991. We focus on the main phase in the period of decreasing Dst and investigate the characteristics of discrete frequency Pc5 pulsations. Pc5 pulsations with multiple discrete spectral peaks including a 2.8 mHz pulsation were seen at 0815-0915 UT, and a monochromatic 1.9 mHz wave appeared at 1010-1110 UT. Also, a very monochromatic and large-amplitude 1.7 mHz wave was observed at 1200-1340 UT across a wide range of dayside local times and at unusually low latitudes. We have analyzed the amplitude and phase relationships of waves at these frequencies. The 2.8 mHz, 1.9 mHz, and 1.7 mHz spectral peaks have maximum amplitudes at L = 3.6, L = 4, and L = 4.3, respectively, and exhibit the characteristic features of field line resonances (FLRs). The discrete mHz frequencies are consistent with some of the discrete peaks seen by Samson et al. (1992) and support the hypothesis of the existence of MHD cavity or waveguide modes in the magnetosphere. However, our results show evidence for the penetration of ULF wave power in the Pc5 band to much lower L-values than normal, suggesting a significant reduction of the local Alfvén eigenfrequency continuum as compared to nonstorm times. This may have considerable significance for the interaction between ULF waves and MeV electrons in the outer radiation belt during storms.

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“…Digital dynamic spectra (DDS) for the north-south (X) eastwest (Y) and vertical (Z) components of the recorded data had been constructed for every day for one year period. The X-and Y-components of these DDS have been investigated for undertaking the above diurnal and seasonal statistical study (5)(6)(7)(8) . The stations were situated at very low latitudes in India.…”

Section: Data Analysis and Resultsmentioning

confidence: 99%

“…Abrupt impulsive change (surprising impulses) may also arise and are regularly determined simultaneously everywhere in the world and feature additionally been detected within the magnetosphere. Variation with periods more or less from 0.1s to 10min are grouped collectively and termed as geomagnetic micropulsations (2)(3)(4)(5) .…”

Section: Ultra Low Frequency (Ulfmentioning

confidence: 99%

Interaction of Pc4 ULF waves with solar wind velocity and its dependence on Kp values

Khan¹,

Nafees²,

Singh³

2021

IJST

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Background/Objectives: Magnetic Pulsations recorded on the ground in the earth are produced by processes inside the magnetosphere and solar wind. These processes produce a wide variety of ULF hydromagnetic wave type which can be categorized on the ground as either Pi or Pc pulsations (irregular or continuous). Methods: Distinctive regions of the magnetosphere originate different frequencies of waves. Digital Dynamic Spectra (DDS) for the northsouth (X), east-west (Y) and vertical (Z) components of the recorded data were constructed for every day for 365 days (January 1 to December 31, 2005) in the station order PON, HAN and NAG respectively. Pc4 geomagnetic pulsations are quasi-sinusoidal fluctuations in the earth’s magnetic field in the length range 45-150 seconds. The magnitude of these pulsations ranges from fraction of a Nano Tesla (nT) to several nT. The monthly variation of Pc4 occurrence has a Kp dependence range of 0 to 9-. However, Pc4 occurrence was reported for Kp values, yet the major Pc4 events occurred for rage 5+ <Kp< 8+. The magnitudes of intervals of Pc4 occurrence decreased in the station order PON, HAN and NAG respectively. Analysis of the data for the whole year 2005 provided similar patterns of Pc4 occurrence for Vsw at all the three stations. Although Pc4 ULF wave occurrence become reported for Vsw ranging from 250 to 1000 Km/s, yet the major Pc4 event recorded for a Vsw range of 300-700 Km/sec. Findings: The current study is undertaken for describing the interaction of Pc4 ULF waves with solar wind speed and its dependence on Kp values. The results suggest that the solar wind control Pc4 occurrence through a mechanism in which Pc4 wave energy is convected through the magnetosheath and coupled to the standing oscillations of the magnetospheric field lines. PACS Nos: 94.30.cq; 96.50.Tf Keywords: Geomagnetic micropulsations; MHD waves and instabilities; Solar wind-control of Pc4 pulsation

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Equatorial enhancement of Pc5–6 magnetic storm time geomagnetic pulsations

Cited by 13 publications

References 29 publications

Coupling of perturbations in the solar wind density to global Pi3 pulsations: A case study

Coupling of perturbations in the solar wind density to global Pi3 pulsations: A case study

Global Pc5 pulsations observed at unusually low L during the great magnetic storm of 24 March 1991

Interaction of Pc4 ULF waves with solar wind velocity and its dependence on Kp values

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