A study of quasi-periodic ELF-VLF emissions at three Antarctic stations: evidence for off-equatorial generation?

Morrison, K.; Engebretson, M. J.; Beck, J. R.; Johnson, J. E.; Arnoldy, R. L.; Cahill, L. J.; Carpenter, D. L.; Gallani, M.

doi:10.1007/s005850050043

Cited by 17 publications

(29 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This appears to be roughly consistent with the Cluster spacecraft results (Němec, Santolík, Pickett, et al, ), which also revealed QP emissions occurring at all MLTs, albeit the total number of events included in the analysis was rather low. On the other hand, the results obtained using low‐altitude spacecraft (Hayosh et al, ) and ground‐based measurements (Engebretson et al, ; Morrison et al, ) strongly indicate a preferentially dayside occurrence. This suggests that, although the emissions are generated at all MLTs, they may not be able to propagate down to low altitudes during the nighttime.…”

Section: Discussionmentioning

confidence: 99%

“…Ground‐based and low‐altitude satellite surveys of QP emissions demonstrated that they are primarily daytime phenomenon (Engebretson et al, ; Hayosh et al, ; Morrison et al, ). As for the propagation of the emissions throughout the inner magnetosphere, detailed wave analysis of satellite observations (Němec, Santolík, Pickett, et al, ; Titova et al, ) and multistation ground‐based measurements (Gołkowski & Inan, ) indicate that the emissions propagate unducted, with a possibility of their occasional guiding by the plasmapause boundary when propagating down to low altitudes (Hayosh et al, ).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Quasiperiodic Whistler Mode Emissions Observed by the Van Allen Probes Spacecraft

et al. 2018

View full text Add to dashboard Cite

Quasiperiodic (QP) emissions are whistler mode electromagnetic waves observed in the inner magnetosphere that exhibit a QP time modulation of the wave intensity. We analyze 768 QP events observed during the first 5 years of the operation of the Van Allen Probes spacecraft (September 2012 to October 2017). Multicomponent wave measurements performed in the equatorial region, where the emissions are likely generated, are used to reveal new experimental information about their properties. We show that the events are observed nearly exclusively inside the plasmasphere. Wave frequencies are mostly between about 0.5 and 4 kHz. The events observed at larger radial distances and on the duskside tend to have slightly lower frequencies than the emissions observed elsewhere. The maximum event frequencies are limited by half of the equatorial electron gyrofrequency, suggesting the importance of wave ducting. Modulation periods are typically between about 0.5 and 5 min, and they increase with the in situ measured plasma number density. This increase is consistent with the main mechanisms suggested to explain the origin of the QP modulation. Two-point measurements performed by the Van Allen Probes are used to estimate a typical spatial extent of the emissions to about 1 R E in radial distance and 1.5 hr in magnetic local time. Detailed wave analysis shows that the emissions are right-hand circularly polarized, and they usually come from several different directions simultaneously. They, however, predominantly propagate at rather low wave normal angles and away from the geomagnetic equator.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quasiperiodic Whistler Mode Emissions Observed by the Van Allen Probes Spacecraft

et al. 2018

View full text Add to dashboard Cite

show abstract

“…While according to both ground‐based (Engebretson et al, ; Morrison et al, ; Smith et al, ) and low‐altitude satellite (Hayosh et al, ) surveys the emissions appear to be primarily daytime phenomenon, satellite surveys at larger radial distances (Němec et al, , ) revealed the emissions at principally all local times, with a slight preference for the dusk sector. In the present study, we contrast the occurrence rates of QP emissions as observed by the Van Allen Probes at large radial distances and the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) spacecraft at low radial distances, and we attempt to explain the obtained discrepancies.…”

Section: Introductionmentioning

confidence: 99%

Whistler Mode Quasiperiodic Emissions: Contrasting Van Allen Probes and DEMETER Occurrence Rates

et al. 2020

View full text Add to dashboard Cite

Quasiperiodic emissions are magnetospheric whistler mode waves at frequencies between about 0.5 and 4 kHz which exhibit a nearly periodic time modulation of the wave intensity. We use large data sets of events observed by the Van Allen Probes in the equatorial region at larger radial distances and by the low-altitude DEMETER spacecraft. While Van Allen Probes observe the events at all local times and longitudes, DEMETER observations are limited nearly exclusively to the daytime and significantly less frequent at the longitudes of the South Atlantic Anomaly. Further, while the events observed by Van Allen Probes are smoothly distributed over seasons with only mild maxima in spring/autumn, DEMETER occurrence rate has a single pronounced minimum in July. The apparent inconsistency is explained by considering a nondipolar Earth's magnetic field and significant background wave intensities which in these cases prevent the quasiperiodic events from being identified in DEMETER data.While according to both ground-based (Engebretson et al., 2004;Morrison et al., 1994;Smith et al., 1998) and low-altitude satellite (Hayosh et al., 2014) surveys the emissions appear to be primarily daytime phenomenon, satellite surveys at larger radial distances revealed the emissions at principally all local times, with a slight preference for the dusk sector. In the present study, we contrast the occurrence rates of QP emissions as observed by the Van Allen Probes at large radial distances and the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) spacecraft at low radial distances, and we attempt to explain the obtained discrepancies. The data set is introduced in section 2. The obtained results are presented in section 3. They are discussed and briefly summarized in section 4. We thank the engineers from CNES and scientific laboratories (CBK, IRAP, LPC2E, LPP, and SSD of ESTEC) who largely contributed to the success of the DEMETER mission. DEMETER data are accessible from the https:// sipad-cdpp.cnes.fr website. Van Allen

show abstract

“…The upstream waves propagating into the equatorial magnetosphere as compressional Pc 3±4 waves are considered to modulate the resonance condition, leading to the QP modulation of the whistler (Sato and Fukunishi, 1981;Morrison and Freeman, 1995). A statistical study of the probability of occurrence of QP emissions and their dependence on season and the interplanetary magnetic ®eld proposes that the source of the emissions is located in the``horn'' region of the magnetosphere, away from the equator (Morrison et al, 1994;Alford et al, 1996). The model by Alford et al (1996) is illustrated in Fig.…”

Section: Quasi-periodic Elf-vlf Modulation By Pc 3±4 Wavesmentioning

confidence: 99%

ULF waves: 1997 IAGA division 3 reporter review

Takahashi

1998

Ann Geophysicae

View full text Add to dashboard Cite

Abstract. Highlights of studies of ULF waves from 1995 to early 1997 are presented. The subjects covered include (1) Pc 3±5 waves excited by sources in the solar wind, with emphasis on the role of the magnetospheric cavity in modifying the external source and establishing its own resonances, and the role of the plasmapause in magnetohydrodynamic wave propagation; (2) Pi 2 waves, with emphasis on the plasmaspheric resonances and possible alternative excitation by plasmasheet source waves; (3) the spatial structure of internally excited long-period waves, including a kinetic theory for radially con®ned ring current instability and groundbased multipoint observation of giant pulsations; (4) amplitude-modulated Pc 1±2 waves in the outer magnetosphere (Pc 1±2 bursts) and in the inner magnetosphere (structured Pc 1 waves or pearls); and (5) the source region of the quasi-periodic emissions. Theory and observations are compared, and controversial issues are highlighted. In addition, some future directions are suggested.

show abstract

A study of quasi-periodic ELF-VLF emissions at three Antarctic stations: evidence for off-equatorial generation?

Cited by 17 publications

References 0 publications

Quasiperiodic Whistler Mode Emissions Observed by the Van Allen Probes Spacecraft

Quasiperiodic Whistler Mode Emissions Observed by the Van Allen Probes Spacecraft

Whistler Mode Quasiperiodic Emissions: Contrasting Van Allen Probes and DEMETER Occurrence Rates

ULF waves: 1997 IAGA division 3 reporter review

Contact Info

Product

Resources

About