Spectral structure of mid-latitude Pc3-4 geomagnetic pulsations.

Menk, F. W.

doi:10.5636/jgg.40.33

Cited by 20 publications

(4 citation statements)

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“…For example, the assumption that the spectral peaks in a latitudinal distribution correspond to the local resonance wave mode is only valid if the incoming wave source stimulating the field line resonance is broadband and the resonance has a high Q. Kurchashov et al [1987] pointed out that for a low Q, resonance effects will be masked by the source spectrum. The variability and complexity of spectral features in pulsation records [Menk, 1988] suggest the local resonant mode is not always the dominant signal at a particular field site. Considering the effects of ionospheric screening [Hughes and Southwood, 1976] and the existence of other hydromagnetic wave modes originating both outside and inside the magnetosphere [Greenstadt et al, 1983; Yumoto, 1985; Engebretson et al, 1987], the resonant wave mode is likely to be only a minor contributor to the recorded ground spectrum.…”

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confidence: 99%

Low latitude geomagnetic field line resonance: Experiment and modeling

Waters¹,

Menk²,

Fraser³

1994

J. Geophys. Res.

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Geomagnetic field line resonances may be identified in ground magnetometer data by comparing the difference in amplitude and phase of signals recorded at two closely spaced sites or by examining the latitudinal variation in polarization properties across a more extended array. These two methods give comparable results for values of the resonant frequency and width at low latitudes (L < 3). We have also found an upper limit for the damping factor, γ∼0.07 at L=1.8, by applying a damped simple harmonic oscillator model. The field line resonance structure observed in 5 weeks of data showed only one resonant frequency at L=1.8 but up to four harmonies concurrently at L=2.8. An early local morning decrease in eigenfrequency was usually present at L=1.8. This is attributed to dynamic heavy ion mass loading effects in the ionosphere where the plasma density increases around dawn. The observed eigenfrequencies were used to evaluate two plasma density models. Calculations using a combined IRI‐90 and diffusive equilibrium (DE) model gave eigenfrequencies which are considerably smaller than the experimentally observed values at both L=1.8 and L=2.8. Furthermore, the calculated harmonic spacings at L=2.8 do not agree with the experimental values, although the diurnal trends were successfully modeled using the IRI‐DE plasma description. The low‐latitude plasma density model described by Bailey (1983) yields eigenfrequencies which show good agreement with the experimentally observed values at both latitudes.

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confidence: 99%

Low latitude geomagnetic field line resonance: Experiment and modeling

Waters¹,

Menk²,

Fraser³

1994

J. Geophys. Res.

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“…On 22 Feb 2022 there was a weak geomagnetic storm, and on 13 Feb 2022 there was a magnetic storm of medium intensity. The variations shown in the example (falling in the period range Pc3 -Pc4 [40]), during weak and medium magnetic storms, were rarely observed in this form on spectrograms. Observations on URAN-4 of ionospheric scintillations of the radio galaxies 3C 405 and 3C 274, during weak and medium geomagnetic storms, showed that the average periods (in the bands of greatest spectral power) also had values of about 30 seconds and 1 -2 -3 minutes.…”

Section: Interrelation With Geomagnetic Field Variations In the Odess...mentioning

confidence: 73%

About Research Programs at the Radio Telescope "Uran-4" Ira Nasu – Monitoring of Fluxes of Powerful Radio Sources, Study of the Sun's Supercorona, Observations of Solar Eclipse

Sukharev,

Ryabov,

Galanin

et al. 2023

OAP

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During 2020–2023, an initiative series of observation programs was carried out on a radiometer designed and manufactured by V.V. Galanin. Among them are observations of ionospheric scintillations of powerful radio sources Cas A, Cyg A, Vir A, Tau A, Per A, on the URAN-4 radio telescope (IRA NASU) at frequencies of 20 and 25 MHz. The observations were carried out at various states of Solar and geomagnetic activity and allow us to analyze the response of the ionosphere in the region of the Odessa Magnetic Anomaly to disturbing events. It was found that the radio source 3C 84 (Per A) is the least noisy at the location of the URAN-4 antenna and is well suited for studying the ionospheric response during magnetic storms. The recorded scintillation periods of the studied radio sources, on "calm" days, are in the range of 1-2 minutes. During magnetic storms, the periods of scintillations are reduced to 10-30 seconds. The paper considers the features of the response of scintillations of different radio sources to a magnetic storm, since they shine through different spatial regions of the ionosphere. Of particular interest are observations of the radio source Tau A (3C 144), which annually, in June, shines through the Solar Supercorona. Processing scans of such observations of the 3C 144 source shows an increase flux variations with an average "period" of about 5-10 seconds. Observations were also made to record the features of radio background variations during partial Solar eclipse. It is shown that during a Solar eclipse, the level of background radio noise increases significantly. At the same time, the background level on the next day after the eclipse was still quite high. A more detailed analysis of this effect is planned and, if possible, repeated observations.

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“…Pc4 occurrence reported for Vsw starting from 250 to 1000 km/s. But major Pc4 events took place for a Vsw range of 300 -700 km/s (10)(11)(12) .…”

Section: Data Analysis and Resultsmentioning

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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Spectral structure of mid-latitude Pc3-4 geomagnetic pulsations.

Cited by 20 publications

References 54 publications

Low latitude geomagnetic field line resonance: Experiment and modeling

Low latitude geomagnetic field line resonance: Experiment and modeling

About Research Programs at the Radio Telescope "Uran-4" Ira Nasu – Monitoring of Fluxes of Powerful Radio Sources, Study of the Sun's Supercorona, Observations of Solar Eclipse

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

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