Alfven field line resonances at low latitudes (<i>L</i> = 1.5)

Green, A. W.; Worthington, E. William; Baransky, L.; Fedorov, E. N.; Kurneva, N. A.; Pilipenko, V. A.; Shvetzov, D. N.; Bektemirov, A. A.; Philipov, G. V.

doi:10.1029/93ja00644

Cited by 46 publications

(65 citation statements)

References 21 publications

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“…It was found that the occurrence region of Alfven resonance existence spreads at rather low latitudes. The resonant amplification of high-frequency Pc3 band at L = 1.5-1.7 was observed by Hattingh and Sutcliffe (1987), Vellante et al (1989), Waters et al (1991), Yumoto et al (1992), Green et al (1993).…”

Section: Introductionmentioning

confidence: 94%

Gradient and Polarization Methods of Ground-Based Monitoring of Magnetospheric Plasma.

Baransky¹,

Green

Fedorov³

et al. 1995

J. geomagn. geoelec

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The methods of an unambiguous determination of the parameters of the magnetospheric resonator (resonance frequency, its meridional gradient, and width of the resonance) by studying the spatial structure of ULF waves, in the Pc3-4 frequency range, are summarized and reviewed. The methods considered are the gradient technique (synchronous measurements of ULF field at two nearby stations) andthe polarization method (multicomponentobservations atone station). Bothmethods are experimentally tested using the data from an experiment at low latitude (L = 1.5). Taking into account modifications of the structure of the ULF magnetic field due to geoelectric inhomogeneities, both methods demonstrate consistent results and are in a qualitative agreement with theoretical predictions. These methods should provide a useful tool for monitoring resonant frequencies and the distribution of plasma in the magnetosphere.

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Section: Introductionmentioning

confidence: 94%

Gradient and Polarization Methods of Ground-Based Monitoring of Magnetospheric Plasma.

Baransky¹,

Green

Fedorov³

et al. 1995

J. geomagn. geoelec

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“…Therefore Pc2-3s may be generated in the outer plasmasphere as FMS waves, and then they can be coupled/transformed into shear Alfven waves near the plasmapause (Fedorov et al, 1998;Mazur et al, 2001). The two maxima in the CHAMP Pc2-3 occurrence rate and PSD may correspond to two zones of minimal Alfven velocity: the first one is located under the plasmapause and the second one corresponds to low L where the concentration of heavy ions of ionospheric origin is enough to reduce the Alfven velocity (Green et al, 1993).…”

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confidence: 99%

Pc2-3 geomagnetic pulsations on the ground, in the ionosphere, and in the magnetosphere: MM100, CHAMP, and THEMIS observations

Yagova

Heilig²,

Fedorov

2015

Ann. Geophys.

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Abstract. We analyze Pc2-3 pulsations recorded by the CHAMP (CHAllenging Minisatellite Payload) satellite in the F layer of the Earth's ionosphere, on the ground, and in the magnetosphere during quiet geomagnetic conditions. The spectra of Pc2-3 pulsations recorded in the F layer are enriched with frequencies above 50 mHz in comparison to the ground Pc2-3 spectra. These frequencies are higher than the fundamental harmonics of the field line resonances in the magnetosphere. High quality signals with dominant frequencies 70-200 mHz are a regular phenomenon in the F layer and in the magnetosphere. The mean latitude of the maximum Pc2-3 occurrence rate lies at L ≈ 3.5 in the F layer, i.e., inside the plasmasphere. Day-to-day variations of the L value of the CHAMP Pc2-3 occurrence rate maximum follow the plasmapause day-to-day variations. Polarization and amplitude of Pc2-3s in the magnetosphere, in the ionosphere, and on the ground allow us to suggest that they are generated as fast magnetosonic (FMS) waves in the outer magnetosphere and are partly converted into shear Alfven waves near the plasmapause. The observed ground-to-ionosphere amplitude ratio during the night is interpreted as a result of the Alfven wave transmission through the ionosphere. The problem of wave transmission through the ionosphere is solved theoretically by means of a numerical solution of the full-wave equation for the Alfven wave reflection from and transmission through a horizontally stratified ionosphere. The best agreement between the calculated and measured values of the ground-to-ionosphere amplitude ratio is found for k = 5 × 10 −3 km −1 , i.e., the observed ground-to-ionosphere amplitude ratio corresponds to a wave spatial scale which could provide a Doppler shift within a few percent of the apparent frequency of the Pc2-3 pulsations as recorded by a loworbiting spacecraft.

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“…To correct for this effect, we use a procedure which is a generalization of the procedure of Green et al (1993) (applied to the amplitude-ratio and cross-phase methods). That is, we assume that the underground effect changes the amplitude ratio by a constant factor, and changes the cross phase by a constant number, in the vicinity of the FLR frequency at x = x 2 ∼ x 1 .…”

Section: Correction Of the Influence Of The Underground Conductivitymentioning

confidence: 99%

“…These methods utilize the characteristic feature of FLRgenerated ULF waves: Since the amplitude and phase of FLR-generated ULF waves sharply changes across the resonance latitude while the superposed signals are more global and almost the same at the two stations, taking the difference of the data from the two adjacent stations can cancel out the most of the non-FLR signals and extract even weak FLR signals. These methods have been applied to Pc3-4 pulsation data from two ground stations in middle to low latitudes, and the FLR parameters at a point (usually regarded as the midpoint) between the two stations have been successfully obtained (e.g., Baransky et al, 1985Baransky et al, , 1989Kurchashov et al, 1987;Green et al, 1993;Waters et al, 1994;Russell et al, 1999;Chi et al, 2000;Menk et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Hodograph method to estimate the latitudinal profile of the field-line resonance frequency using the data from two ground magnetometers

2013

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The hodograph method enables estimating the latitudinal profile of the field-line resonance (FLR) frequency ( f R ) using the data from two ground magnetometers. This paper provides the full details of this method for the first time, and uses a latitudinal chain of ground magnetometers to examine its validity and usefulness. The hodograph method merges the widely-used amplitude-ratio and cross-phase methods in a sense that the hodograph method uses both the amplitude ratio and the phase difference in a unified manner; further than that, the hodograph method provides f R at any latitude near those of the two ground magnetometers. It is accomplished by (1) making a complex number by using the amplitude ratio (phase difference) as its real (imaginary) part; (2) drawing thus obtained complex numbers (one number for one frequency) in the complex plane to make a hodograph; and (3) fitting to thus obtained hodograph a model satisfying the FLR condition, which is a circle with the assumption that the resonance width is independent of the latitude. To examine the validity and usefulness of the hodograph method, we apply it to a Pc 4 event observed by the Scandinavian BEAR array. We also apply the amplitude-phase gradient method (Pilipenko and Fedorov, 1994;Kawano et al., 2002) to the same event, and compare the results; this is the first article applying the both methods to the same dataset.

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Alfven field line resonances at low latitudes (L = 1.5)

Cited by 46 publications

References 21 publications

Gradient and Polarization Methods of Ground-Based Monitoring of Magnetospheric Plasma.

Gradient and Polarization Methods of Ground-Based Monitoring of Magnetospheric Plasma.

Pc2-3 geomagnetic pulsations on the ground, in the ionosphere, and in the magnetosphere: MM100, CHAMP, and THEMIS observations

Hodograph method to estimate the latitudinal profile of the field-line resonance frequency using the data from two ground magnetometers

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