Multistation Observations of Pc1-2 ULF Pulsations in the Vicinity of the Polar Cusp.

Menk, F. W.; Fraser, B. J.; Hansen, H. J.; Newell, P. T.; Meng, C.‐I.; Morris, R. J.

doi:10.5636/jgg.45.1159

Cited by 14 publications

(9 citation statements)

References 62 publications

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“…•.•...a aries are of the greatest current interest. Thus we will place our observations in context principally by comparison with the .recent studies of Menk et al [ 1992Menk et al [ , 1993 and Hansen et al…”

Section: In Both Of These Figures Crosses Represent Observed Polewardmentioning

confidence: 82%

“…Such emissions also often include periodic emissions. Menk et al [1992Menk et al [ , 1993 We used ULF survey plots such as the one in Figure 1, which were routinely produced using data from all stations, to select candidate band-limited pulsations in the appropriate frequency band for HM chorus. In these survey plots power in one component (in this case east/west, or Y) is plotted as a function of universal time using a base 10 logarithmic scale for 10 different frequency bands, whose upper frequency range is shown in the left side of the figure.…”

Section: Event Identification and Sample Eventsmentioning

confidence: 99%

“…Hydromagnetic (HM) chorus emissions are commonly observed at latitudes in and slightly poleward of the auroral zone, indicating their generation region may be in the plasmatrough region in the outer magnetosphere. Other types of emissions, including sustained Pc 1-2 emissions and so-called unstructured noise, are often observed at cusp/cleft latitudes [Bolshakova et al, 1980;Menk et al, 1992Menk et al, , 1993. A recent study by Popecki et al [ 1993] used a full year' s data from South Pole and Siple, Antarctica, and at Sondrestromfjord, Greenland, roughly conjugate to South Pole, to characterize Pc 1-2 pulsation activity; in this paper we use a similarly large data set to characterize HM chorus activity.…”

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confidence: 99%

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Statistical study of hydromagnetic chorus events at very high latitudes

Anderson¹,

Engebretson²,

Arnoldy³

et al. 1995

J. Geophys. Res.

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Hydromagnetic (HM) chorus events are ULF waves with typical frequencies from 0.2 to 0.6 Hz; their frequency‐time spectrum consists of a combination of band‐limited unstructured emissions and discrete elements. These waves are one of a class of short‐period ULF emissions (in the Pc 1 and 2 frequency range) that may be of value in ground‐based identification of the footpoint of magnetospheric boundary regions. As part of an extensive survey of Pc 1 and 2 waves at very high latitudes, we have identified all occurrences of HM chorus in nearly a full year's data from South Pole Station (−74.2° geomagnetic latitude, local noon ∼ 1530 UT) and McMurdo, Antarctica (−80.2° geomagnetic latitude, local noon ∼ 2030 UT) during 1990, and at McMurdo and Sondrestromfjord, Greenland (74.2° geomagnetic latitude, local noon ∼ 1330 UT) during 1988. In agreement with previous studies, these events tend to occur within a few hours of local noon. Earlier studies reported that HM chorus events are typically seen in ground records at auroral zone latitudes and suggested that they originated in the outer dayside magnetosphere. Study of DMSP particle boundary data indicated that the events reported here occurred during conditions of extremely contracted auroral ovals and are thus also consistent with an outer dayside magnetospheric source region. However, the occurrence of HM chorus events in this high‐latitude data set was limited to the months of October through May, with an occurrence peak in February, and no events were found in the months of July through September in either of the years studied. Since both hemispheres are covered, this suggests not a seasonal variation (with late winter minimum) but rather an apparent annual variation. We speculate that such an annual variation in very high latitude occurrence of HM chorus may be related to the MLT‐UT offset of the Earth's geomagnetic and geographic poles, in conjunction with wave propagation cutoffs at the high‐latitude magnetic field minima occurring on dayside magnetic field lines very near the magnetopause.

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Section: In Both Of These Figures Crosses Represent Observed Polewardmentioning

confidence: 82%

Section: Event Identification and Sample Eventsmentioning

confidence: 99%

mentioning

confidence: 99%

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Statistical study of hydromagnetic chorus events at very high latitudes

Anderson¹,

Engebretson²,

Arnoldy³

et al. 1995

J. Geophys. Res.

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“…Our results are also supported by a statistical study of DeLauretis et al (1991), who found that the average daytime background spectra at cusp latitudes (Iqualuit, Canada) exhibit p = −(3.47-3.80) over the Pc3 frequency range. As has been emphasized by Menk et al (1993), these values cannot be explained solely by either the KHI, which predicts p = −5/3 (Kolmogoroff's hydrodynamic turbulence) or p = −3 (ion-acoustic turbulence), or the drift wave insta-bility giving p = −5 (D'Angelo, 1973).…”

Section: Separation Of Signal and Noisementioning

confidence: 99%

Cusp-latitude Pc3 spectra: band-limited and power-law components

et al. 2002

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Abstract. This work attempts to fill a gap in comparative studies of upstream-generated Pc3-4 waves and broad band ULF noise observed at cusp latitudes. We performed a statistical analysis of the spectral properties of three years of cusp-latitude ground magnetometer data, finding that the average daytime Pc3-4 spectra are characterized by two principal components: an upstream-related band-limited enhancement ('signal') and a power-law background ('noise') with S(f ) ∝ f −4 . Based on this information we developed an algorithm allowing for the deconvolution of these two components in the spectral domain. The frequency of the signal enhancement increases linearly with IMF magnitude as f [mHz] 4.4|B IMF |[nT], and its power maximizes around IMF cone angles θ xB 20 and 160 • and at 10:30-11:00 MLT. Both spectral components exhibit similar semiannual variations with equinoctial maxima. The background noise power grows with increasing southward B z and remains nearly constant for northward B z . Its diurnal variation resembles that of Pc5 field-line resonance power, with a maximum near 09:00 MLT. Both the band-limited signal and broad band noise components show power-law growth with solar wind velocity ∝ V 5.71 sw and ∝ V 4.12 sw , respectively. Thus, the effective signal-to-noise ratio increases with increasing V sw . The observations suggest that the noise generation is associated with reconnection processes.

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“…The predominant high‐latitude (L = 6–8) ground ULF signal near local noon is quasi‐structured hydromagnetic chorus/emissions [ Fukunishi et al , 1981; Menk et al , 1993; Anderson et al , 1995]. Since the early 1960s, it has been noted that the ULF waves on the ground near local noon were either turned on or enhanced in association with sudden impulses in the Earth's magnetic field [ Troitskaya , 1961; Heacock and Hessler , 1965; Kokubun and Oguti , 1968; Troitskaya et al , 1968; Hirasawa , 1981].…”

Section: Introductionmentioning

confidence: 99%

Pc 1 waves and associated unstable distributions of magnetospheric protons observed during a solar wind pressure pulse

et al. 2005

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[1] We present observations of Pc 1 waves ($0.6 Hz) that occurred shortly after a strong (>20 nPa) compression of Earth's magnetosphere at 1321 UT, 18 March 2002. Intense Pc 1 waves were observed at several high-latitude ground stations in Antarctica and Greenland from 1321 UT to beyond 1445 UT. Two wave bursts were recorded at the Polar satellite at 1338 and 1343-1344 UT as it passed outbound in the Southern Hemisphere at 1154 local time (SM magnetic latitude of À22°and near L = 7.5) in good magnetic conjunction with the Antarctic. The pressure increase created a significant population of protons between a few hundred eV and several keV, whose fluxes were mostly perpendicular to B. These protons seem to have replaced the quiescent stream of protons (presumably convected from the plasma sheet) that existed before this increase. There was also a nearly two-order-of-magnitude increase in the population of thermal/suprathermal (0.32-410 eV) protons. The generation of ion cyclotron waves is expected to limit the proton temperature anisotropy A, defined as T ? /T k À 1. The ion cyclotron instability driven by the observed hot ion temperature anisotropy is studied using two models, with and without the presence of cold background plasma. Peaks in the calculated instability as a function of time show excellent agreement with the times of the Polar wave bursts, which were measured a few tens of seconds after maxima in the instability calculation. The time delay is consistent with the propagation time to the spacecraft from a source nearer to the equatorial plane. The hot proton population at Polar appears to be driven back to stability by a sudden increase in very field-aligned protons having energies less than the hot perpendicular population, suggesting a different source for the two populations. These observations confirm the importance of both the energization and/or increase in population of protons transverse to B in the several keV range (possibly betatron acceleration as a result of the pressure pulse), and the presence of greatly increased fluxes of lower energy protons (100s of eV to a few keV), predominantly aligned along B, in determining whether the particle population is unstable at a given time.Citation: Arnoldy, R. L., et al. (2005), Pc 1 waves and associated unstable distributions of magnetospheric protons observed during a solar wind pressure pulse,

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Multistation Observations of Pc1-2 ULF Pulsations in the Vicinity of the Polar Cusp.

Cited by 14 publications

References 62 publications

Statistical study of hydromagnetic chorus events at very high latitudes

Statistical study of hydromagnetic chorus events at very high latitudes

Cusp-latitude Pc3 spectra: band-limited and power-law components

Pc 1 waves and associated unstable distributions of magnetospheric protons observed during a solar wind pressure pulse

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