Observations of large‐amplitude, whistler mode wave ducts in the outer plasmasphere

Koons, H. C.

doi:10.1029/ja094ia11p15393

Cited by 64 publications

(66 citation statements)

References 12 publications

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“…Satellite in situ density measurements, for example by LANL (e.g., Moldwin et al 1995) and CRRES (e.g., , revealed concentrations of irregularities in the plasmapause region, some of which appear to trap and guide whistler-mode waves (Koons 1989). These structures appear to vary widely in cross section, ranging from 50 km upward.…”

Section: Irregular Density Structures In the Outer Plasmaspherementioning

confidence: 99%

Plasmaspheric Density Structures and Dynamics: Properties Observed by the CLUSTER and IMAGE Missions

et al. 2008

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Plasmaspheric density structures have been studied since the discovery of the plasmasphere in the late 1950s. But the advent of the CLUSTER and IMAGE missions in 2000 has added substantially to our knowledge of density structures, thanks to the new 56 F. Darrouzet et al.capabilities of those missions: global imaging with IMAGE and four-point in situ measurements with CLUSTER. The study of plasma sources and losses has given new results on refilling rates and erosion processes. Two-dimensional density images of the plasmasphere have been obtained. The spatial gradient of plasmaspheric density has been computed. The ratios between H + , He + and O + have been deduced from different ion measurements. Plasmaspheric plumes have been studied in detail with new tools, which provide information on their morphology, dynamics and occurrence. Density structures at smaller scales have been revealed with those missions, structures that could not be clearly distinguished before the global images from IMAGE and the four-point measurements by CLUSTER became available. New terms have been given to these structures, like "shoulders", "channels", "fingers" and "crenulations". This paper reviews the most relevant new results about the plasmaspheric plasma obtained since the start of the CLUSTER and IMAGE missions.

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Section: Irregular Density Structures In the Outer Plasmaspherementioning

confidence: 99%

Plasmaspheric Density Structures and Dynamics: Properties Observed by the CLUSTER and IMAGE Missions

et al. 2008

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“…In general, these theoretical studies consider whistler propagation inside channels formed by density enhancement (high‐density ducts or HDDs) or density depletion (low‐density ducts or LDDs) with a density profile that is symmetric about the axis of the channel. Guiding of whistlers in ducts of this type has been observed in the magnetosphere [ Angerami , 1970; Scarf and Chapell , 1973; Carpenter and Anderson , 1992; Koons , 1989; Moullard et al , 1975] and in the ducts created artificially in the laboratory by heating plasma with a circular antenna [ Stenzel , 1976; Kostrov et al , 2000].…”

Section: Introductionmentioning

confidence: 99%

“…Analytical and numerical solutions of the full wave equations have been obtained for ducts with cylindrical and slab geometry and for a wide range of parameters of the plasma, the ambient magnetic field, and the whistler itself. Results from these studies have been successfully used to interpret relevant observations in the magnetosphere [ Angerami , 1970; Scarf and Chapell , 1973; Carpenter and Anderson , 1992; Koons , 1989; Moullard et al , 1975] and in the laboratory experiments.…”

Section: Introductionmentioning

confidence: 99%

Whistler propagation in nonsymmetrical density channels

2007

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[1] We present results from a study of whistler propagation in plasma density channels extended along Earth's geomagnetic field and localized across it. Our study is focused on whistler guiding by channels with a nonsymmetrical density profile across the channel. Such profiles are typical for density inhomogeneities observed on/near the plasmapause formed in the Earth's magnetosphere during strong geomagnetic storms/substorms. Considering these density channels as a combination of high-density and low-density ducts, we analyze leakage of the electromagnetic energy from these ducts depending on various parameters of the system. Our results indicate that a whistler with a frequency less than half of the local electron gyrofrequency can propagate along a nonsymmetrical duct with a homogeneous central part, without any leakage, when the width of the duct is equal to an integral multiple of each of the two internal perpendicular wavelengths. We also show that a homogeneous ducting region is not necessary; a low-frequency whistler can be guided along a region of appropriate density within a monotonic density gradient. This finding makes our results particularly relevant for the interpretation of intense whistler dynamics recorded in a number of satellite observations near/on the plasmapause where strong transverse density gradients are observed.

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“…These works are particularly important in light of the evidence that the plasmapause density profile becomes highly structured in the aftermath of disturbances and during extended recovery periods (e.g. Oya and Ono, 1987;Koons, 1989;Horwitz et al, 1990;Carpenter et al, 1993Carpenter et al, , 2000Moldwin et al, 1995).…”

Section: Examples Of Research On the Pblmentioning

confidence: 99%

The Plasmasphere Boundary Layer

2004

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Abstract.As an inner magnetospheric phenomenon the plasmapause region is of interest for a number of reasons, one being the occurrence there of geophysically important interactions between the plasmas of the hot plasma sheet and of the cool plasmasphere. There is a need for a conceptual framework within which to examine and discuss these interactions and their consequences, and we therefore suggest that the plasmapause region be called the Plasmasphere Boundary Layer, or PBL. Such a term has been slow to emerge because of the complexity and variability of the plasma populations that can exist near the plasmapause and because of the variety of criteria used to identify the plasmapause in experimental data. Furthermore, and quite importantly in our view, a substantial obstacle to the consideration of the plasmapause region as a boundary layer has been the longstanding tendency of textbooks on space physics to limit introductory material on the plasmapause phenomenon to zeroth order descriptions in terms of ideal MHD theory, thus implying that the plasmasphere is relatively well understood. A textbook may introduce the concept of shielding of the inner magnetosphere from perturbing convection electric fields, but attention is not usually paid to the variety of physical processes reported to occur in the PBL, such as heating, instabilities, and fast longitudinal flows, processes which must play roles in plasmasphere dynamics in concert with the flow regimes associated with the major dynamo sources of electric fields. We believe that through the use of the PBL concept in future textbook discussions of the plasmasphere and in scientific communications, much progress can be made on longstanding questions about the physics involved in the formation of the plasmapause and in the cycles of erosion and recovery of the plasmasphere.

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Observations of large‐amplitude, whistler mode wave ducts in the outer plasmasphere

Cited by 64 publications

References 12 publications

Plasmaspheric Density Structures and Dynamics: Properties Observed by the CLUSTER and IMAGE Missions

Plasmaspheric Density Structures and Dynamics: Properties Observed by the CLUSTER and IMAGE Missions

Whistler propagation in nonsymmetrical density channels

The Plasmasphere Boundary Layer

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