Inner Magnetospheric ULF Waves: The Occurrence and Distribution of Broadband and Discrete Wave Activity

Murphy, K. R.; Inglis, Andrew; Sibeck, D. G.; Watt, Clare E. J.; Rae, I. J.

doi:10.1029/2020ja027887

Cited by 18 publications

(26 citation statements)

References 112 publications

(203 reference statements)

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“…The structure of ULF waves in the Pc5 frequency range play a fundamental role in the dynamic of radiation belts (Mann et al., 2016 ; Ozeke et al., 2018 ; Zong et al., 2017 ), supplying relativistic electrons due to radial diffusion, adiabatic acceleration, drift and drift‐bounce resonance acceleration (Baker et al., 2018 ; Degeling et al., 2008 ; Elkington et al., 2003 , 1999 ; Elkington & Sarris, 2016 ; Mathie & Mann, 2001 ; Ozeke & Mann, 2008 ; Regi et al., 2015 ; Schulz & Lanzerotti, 1974 ; Yeoman & Wright, 2001 ; Zong et al., 2017 ). Especially in the resonant interaction, the distinction between the discrete and broad‐band nature of the waves is fundamental (Murphy et al., 2020 ). Previous studies on this subject were limited by the spectral analysis procedures that often were restricted to the selection of the most relevant peak in the power spectrum, possibly within a set of discrete ULF waves.…”

Section: Discussionmentioning

confidence: 99%

On Differentiating Multiple Types of ULF Magnetospheric Waves in Response to Solar Wind Periodic Density Structures

et al. 2022

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Identifying the nature and source of ultra‐low frequencies (ULF) waves (f ⪅ 4 mHz) at discrete frequencies in the Earth's magnetosphere is a complex task. The challenge comes from the simultaneous occurrence of externally and internally generated waves, and the ability to robustly identify such perturbations. Using a recently developed robust spectral analysis procedure, we study an interval that exhibited in magnetic field measurements at geosynchronous orbit and in‐ground magnetic observatories both internally supported and externally generated ULF waves. The event occurred on 9 November 2002 during the interaction of the magnetosphere with two interplanetary shocks that were followed by a train of 90 min solar wind periodic density structures. Using the Wang‐Sheeley‐Arge model, we mapped the source of this solar wind stream to an active region and a mid‐latitude coronal hole just prior to crossing the Heliospheric current sheet. In both the solar wind density and magnetospheric field fluctuations, we separated broad power increases from enhancements at specific frequencies. For the waves at discrete frequencies, we used the combination of satellite and ground magnetometer observations to identify differences in frequency, polarization, and observed magnetospheric locations. The magnetospheric response was characterized by: (a) forced breathing by periodic solar wind dynamic pressure variations below ≈1 mHz, (b) a combination of directly driven oscillations and wave modes triggered by additional mechanisms (e.g., shock and interplanetary magnetic field discontinuity impact, and substorm activity) between ≈1 and 4 mHz, and (c) largely triggered modes above ≈4 mHz.

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Section: Discussionmentioning

confidence: 99%

On Differentiating Multiple Types of ULF Magnetospheric Waves in Response to Solar Wind Periodic Density Structures

et al. 2022

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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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“…(2017), ULF waves with broadband frequencies can cause radial diffusion of relativistic electrons in a wider energy range than monochromatic waves. Therefore, the classification of ULF waves according to the broadness of their frequency spectra is helpful for us to accurately understand the wave‐particle interaction and energy dynamics of the radiation belts in the terrestrial magnetosphere (Murphy et al., 2020; Sarris, 2014). Recently, Murphy et al.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, Murphy et al. (2020) investigated the occurrence of the broadband and monochromatic ULF waves observed by the GOES‐15 satellite and their dependence on the solar wind condition. Using the AFINO code (Inglis et al., 2015, 2016), they fitted the power spectral density of the magnetic field with three model functions of frequency and automatically chose the most reasonable model among them by Bayesian information criterion (BIC) (Schwarz, 1978).…”

Section: Introductionmentioning

confidence: 99%

“…While the observations of monochromatic/broadband toroidal waves have been reported by both event studies (Matsui et al, 2007;Sarris, 2014;Sarris et al, 2009;Shi et al, 2020;Vellante et al, 2004) and statistical studies (Liu et al, 2009;Murphy et al, 2020;Takahashi et al, 2014;Takahashi, Hartinger et al, 2015), toroidal waves with multi-harmonic discrete frequencies have been mainly investigated in event studies (Engebretson et al, 1986(Engebretson et al, , 1987Takahashi, Denton et al, 2015;Takahashi, Hughes et al, 1984;Takahashi, Waters et al, 2015;Takahashi et al, 2020). The multi-harmonic toroidal waves (MTWs hereinafter) are considered to be standing Alfvén waves with multiple eigenmodes because the wave frequency of MTWs decreases (increases) as the L-value increases (decreases) (e.g., Engebretson et al, 1986).…”

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confidence: 99%

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A Statistical Study of the Solar Wind Dependence of Multi‐Harmonic Toroidal ULF Waves Observed by the Arase Satellite

et al. 2022

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Toroidal standing Alfvén wave is one of the ultra‐low frequency waves that are frequently observed in the terrestrial magnetosphere. They sometimes exhibit multi‐harmonic frequency spectra, indicating wide energy range input in the magnetosphere. However, their energy source has not been fully understood due to the lack of statistical studies. Here we used the data of the Arase satellite observations for ∼3.5 years and conducted a statistical analysis of the solar wind dependence of the occurrence rate, wave power, and frequency of the multi‐harmonic toroidal waves. We automatically detected the multi‐harmonic waves and categorized them into four groups according to the solar wind velocity and the cone angle of the interplanetary magnetic field. We found that the occurrence rate and wave power of the multi‐harmonic waves increase with the solar wind velocity on the flank sides. In the noon sector, the occurrence rate of the multi‐harmonic waves increases with the decrease of the cone angle. The median frequency of the multi‐harmonic waves on the dayside is positively correlated with the upstream wave frequency predicted by the theory of the ion beam instability for a small cone angle. The occurrence rate also increases with the solar wind dynamic pressure fluctuations. Therefore, we suggest that the Kelvin‐Helmholtz instability, the upstream waves, and the dynamic pressure fluctuations are possible sources of the multi‐harmonic waves. This study sheds light on the activity of the multi‐harmonic waves which can affect radiation belt electrons under various solar wind conditions.

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Inner Magnetospheric ULF Waves: The Occurrence and Distribution of Broadband and Discrete Wave Activity

Cited by 18 publications

References 112 publications

On Differentiating Multiple Types of ULF Magnetospheric Waves in Response to Solar Wind Periodic Density Structures

On Differentiating Multiple Types of ULF Magnetospheric Waves in Response to Solar Wind Periodic Density Structures

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

A Statistical Study of the Solar Wind Dependence of Multi‐Harmonic Toroidal ULF Waves Observed by the Arase Satellite

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