Latitudinal density dependence of magnetic field lines inferred from Polar plasma wave data

Goldstein, J.; Denton, R. E.; Hudson, M. K.; Miftakhova, E. G.; Young, S. L.; Menietti, J. D.; Gallagher, D. L.

doi:10.1029/2000ja000068

Cited by 66 publications

(128 citation statements)

References 25 publications

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“…To make analytic progress, but take into account the presence of the heavy ions, we included the mass density component by number as observed for O + , as well as He + and He ++ , assuming the remaining ion population was made up of protons to match quasi-neutrality with the electron number density. During this time the Cluster satellites also crossed close to the equator, such that the mass density can be assumed to be a good approximation to that at the equatorial plane -an assumption consistent with the results of Goldstein et al (2001), who showed using Polar data that there is in general only a weak dependence of electron density along the field line close to the equatorial plane. Finally, the magnetic field strength observed by Cluster was mapped from the observed dipole magnetic latitude to the dipole equator using a dipole model and combined with the derived mass density to provide a proxy for the equatorial Alfvén speed required to compute the FLR frequency in the Allan and Knox model.…”

Section: Discussionsupporting

confidence: 70%

Multi-satellite study of the excitation of Pc3 and Pc4-5 ULF waves and their penetration across the plasmapause during the 2003 Halloween superstorm

et al. 2015

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Abstract. We use multi-satellite and ground-based magnetic data to investigate the concurrent characteristics of Pc3 (22-100 mHz) and Pc4-5 (1-22 mHz) ultra-low-frequency (ULF) waves on the 31 October 2003 during the Halloween magnetic superstorm. ULF waves are seen in the Earth's magnetosphere, topside ionosphere, and Earth's surface, enabling an examination of their propagation characteristics. We employ a time-frequency analysis technique and examine data from when the Cluster and CHAMP spacecraft were in good local time (LT) conjunction near the dayside noon-midnight meridian. We find clear evidence of the excitation of both Pc3 and Pc4-5 waves, but more significantly we find a clear separation in the L shell of occurrence of the Pc4-5 and Pc3 waves in the equatorial inner magnetosphere, separated by the density gradients at the plasmapause boundary layer. A key finding of the wavelet spectral analysis of data collected from the Geotail, Cluster, and CHAMP spacecraft and the CARISMA and GIMA magnetometer networks was a remarkably clear transition of the waves' frequency into dominance in a higher-frequency regime within the Pc3 range. Analysis of the local field line resonance frequency suggests that the separation of the Pc4-5 and Pc3 emissions across the plasmapause is consistent with the structure of the inhomogeneous field line resonance Alfvén continuum. The Pc4-5 waves are consistent with direct excitation by the solar wind in the plasma trough, as well as Pc3 wave absorption in the plasmasphere following excitation by upstream waves originating at the bow shock in the local noon sector. However, despite good solar wind coverage, our study was not able to unambiguously identify a clear explanation for the sharp universal time (UT) onset of the discrete frequency and largeamplitude Pc3 wave power.

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Section: Discussionsupporting

confidence: 70%

Multi-satellite study of the excitation of Pc3 and Pc4-5 ULF waves and their penetration across the plasmapause during the 2003 Halloween superstorm

et al. 2015

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“…However, it is evident from previous observational studies that the density variation obey different power laws in different magnetospheric regions. For example, inside the plasma trough m = 3 (Carpenter and Smith 1964), outside the plasmasphere m = 4 (Carpenter and Smith 1964), inside the plasmasphere m = 3.38 (Newbury et al 1989), m = 0 at low latitudes close to equatorial plane (Gallagher et al 2000), and at the equatorial plane m = 1 (Goldstein et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Toroidal quarter waves in the Earth’s magnetosphere: theoretical studies

Bulusu

Sinha

Vichare

2014

Astrophys Space Sci

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An analytic model has been developed for toroidal quarter wave (QW) oscillations in the Earth's magnetosphere using idealistic and highly asymmetric ionospheric boundary condition. The background magnetic field is dipolar and plasma density distribution is governed by a power law 1/r m where r is the geocentric distance of any point along the field line and m is the density index. The solution thus obtained has been compared with the numerical solutions. Earlier workers had developed the analytic model for trivial 1/r 6 (m = 6) type of plasma density distribution along the field line for which the period of the fundamental is twice that of corresponding half wave (i.e. toroidal oscillation in the symmetric ionospheric boundary). The present analytic model does reproduce this feature. In addition, it is seen that this ratio decreases for lower values of m. Moreover, for a particular value of m, this ratio shows a decreasing trend with increased harmonic number. The spatial characteristics of QW obtained from present analytic model are in excellent agreement with those computed numerically, thereby validating the model. The departure of frequency computed analytically from that obtained numerically is significant only for the fundamental and this departure reduces sharply with the increased harmonic number. It should be noted that there is no such departure for 1/r 6 type of plasma density distribution and spatial structures as well as frequency computed from the present analytic model match perfectly with those computed numerically.

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“…The distribution of the plasma density along field lines is assumed to follow the power law ρ(s)=ρ eq (LR E /r) α , where α=2 is typical for the vicinity of the plasmapause (e.g. Goldstein et al, 2001). From the modeled electron density distribution n eq (Carpenter and Anderson, 1992) we receive the plasma mass density ρ eq =n eq m corr m p , where m p is the proton mass.…”

Section: Poloidal Alfvén Resonatormentioning

confidence: 99%

Spatio-temporal structure of a poloidal Alfvén wave detected by Cluster adjacent to the dayside plasmapause

et al. 2008

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Abstract.A case study of a poloidal ULF pulsation near the dayside plasmapause is presented based on Cluster observations of magnetic and electric fields. The pulsation is detected close to the magnetic equatorial plane at L shells L=[4.4, 4.6] and oscillates with a frequency of f =23 mHz. Investigating the wave energy flux reveals the standing wave nature of the observed pulsation. An estimation of the azimuthal wave number exposes a narrow azimuthal structure of the wave field with m≈160. Spatial and temporal characteristics of the pulsation are analyzed in detail by representing data in a field line related coordinate system and a rangetime-intensity representation. This allows an estimation of both the spatial extension of the wave field in the radial direction and its temporal decay rate. The analysis furthermore indicates that the same field lines are excited to a standing wave oscillation twice. Furthermore an accurate identification of a phase jump of the wave field across L shells is possible. Comparing the radial localization of the detected wave with theoretically expected field line eigenfrequencies reveals that the wave field is confined in the Alfvén resonator at the outer edge of the plasmapause.

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Latitudinal density dependence of magnetic field lines inferred from Polar plasma wave data

Cited by 66 publications

References 25 publications

Multi-satellite study of the excitation of Pc3 and Pc4-5 ULF waves and their penetration across the plasmapause during the 2003 Halloween superstorm

Multi-satellite study of the excitation of Pc3 and Pc4-5 ULF waves and their penetration across the plasmapause during the 2003 Halloween superstorm

Toroidal quarter waves in the Earth’s magnetosphere: theoretical studies

Spatio-temporal structure of a poloidal Alfvén wave detected by Cluster adjacent to the dayside plasmapause

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