Observation and analysis of lower hybrid solitary structures as rotating eigenmodes

Pinçon, Jean-Louis; Kintner, P. M.; Schuck, P. W.; Seyler, C. E.

doi:10.1029/97ja00800

Cited by 47 publications

(67 citation statements)

References 33 publications

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“…Similar features have later been observed on several other sounding rockets (e.g. Kintner et al, 1992;Vago et al, 1992;Pinçon et al, 1997;Lynch et al, 1999;Knudsen et al, 1999) and on the Freja satellite (e.g. Eriksson et al, 1994;Pécseli et al, 1996;Dovner et al, 1997;Høymork et al, 2000), all between 700 km and 1800 km altitude.…”

Section: Introductionsupporting

confidence: 57%

Observations of lower hybrid cavities in the inner magnetosphere by the Cluster and Viking satellites

et al. 2004

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Abstract.Observations by the Viking and Cluster satellites at altitudes up to 35 000 km show that Lower Hybrid Cavities (LHCs) are common in the inner magnetosphere. LHCs are density depletions filled with waves in the lower hybrid frequency range. The LHCs have, until recently, only been found at altitudes up to 2000 km. Statistics of the locations and general shape of the LHCs is performed to obtain an overview of some of their properties. In total, we have observed 166 LHCs on Viking during 27 h of data, and 535 LHCs on Cluster during 87 h of data. These LHCs are found at invariant latitudes from the auroral region to the plasmapause. A comparison with lower altitude observations shows that the LHC occurrence frequency does not scale with the flux tube radius, so that the LHCs are moderately rarer at high altitudes. This indicates that the individual LHCs do not reach from the ionosphere to 35 000 km altitude, which gives an upper bound for their length. The width of the LHCs perpendicular to the geomagnetic field at high altitudes is a few times the ion gyroradius, consistent with observations at low altitudes. The estimated depth of the density depletions vary with altitude, being larger at altitudes of 20 000-35 000 km (Cluster, 10-20%), smaller around 1500-13 000 km (Viking and previous Freja results, a few percent) and again larger around 1000 km (previous sounding rocket observations, 10-20%). The LHCs in the inner magnetosphere are situated in regions with background electrostatic hiss in the lower hybrid frequency range, consistent with investigations at low altitudes. Individual LHCs observed at high altitudes are stable at least on time scales of 0.2 s (about the ion gyro period), which is consistent with previous results at lower altitudes, and observations by the four Cluster satellites show that the occurrence of LHCs in a region in space is a stable phenomenon, at least on time scales of an hour.

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Section: Introductionsupporting

confidence: 57%

Observations of lower hybrid cavities in the inner magnetosphere by the Cluster and Viking satellites

et al. 2004

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“…This treatment showed a continuous spectrum of right-hand rotating modes above the ambient lower hybrid frequency f LH and a discrete spectrum of trapped left-hand rotating waves below f LH , that cannot propagate outside the depletion. The results very well describe the properties of LHCs observed on sounding rockets (Pinçon et al, 1997;Bonnell et al, 1998;Schuck et al, 1998) and also of a Cluster satellite observation (Tjulin et al, 2003) for the single event for which data rates allowed such detailed analysis.…”

Section: Introductionsupporting

confidence: 56%

“…LHCs have been observed in the ionosphere by sounding rockets (e.g. Vago et al, 1992;Pinçon et al, 1997;Lynch et al, 1999;Knudsen et al, 1999), and the Freja satellite (e.g. Eriksson et al, 1994;Pécseli et al, 1996;Dovner et al, 1997;Høymork et al, 2000) at altitudes up to about 2000 km.…”

Section: Introductionmentioning

confidence: 99%

Localization of wave fields in lower hybrid cavities

2004

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Abstract. We investigate lower hybrid wave trapping in cylindrically symmetric density depletions in the electrostatic approximation. Our investigation is inspired by previous observations of such trapping by spacecraft in the auroral region at altitudes up to about 2000 km, and the recent discovery of this phenomenon at altitudes above 20 000 km in the inner magnetosphere. No particular shape is assumed for the density depletion, which need not be strictly zero outside some value of the radial coordinate r. Important previously known properties concerning parabolic density depletions extending to finite r are shown to hold also for arbitrary shapes and infinite extent: for a given parallel wave number k z , modes below the ambient lower hybrid frequency f LH are trapped in the density depletion (in the sense that they are evanescent outside the cavity), have a discrete spectrum and rotate in a left-handed sense, while there is a continuous spectrum of freely propagating right-handed rotating modes above f LH . New results are such that even though the density depletion may go to zero slowly with increasing r, and thus be essentially infinite in extent, there is a maximum distance within which a trapped mode with given k z and azimuthal mode number m may propagate. Furthermore, we find that for any monotonic density cavity and given k z , there is a local relation between plasma density gradient and the lowest possible frequency that can be trapped. We combine our theoretical results with spacecraft observations to find an upper bound on k z . Our examples indicate that the length of the cavities is larger than the width by a factor of at least 100.

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“…The sounding rockets, which move slowly and have high telemetry bandwidth, have provided great detail for just a few events (e.g. Pinçon et al, 1997), while Freja, in its nearly three years of operation, yielded a wealth of observations providing occurrence statistics Kjus et al, 1998). It is of great interest to supplement the Freja results from 1500-1750 km altitudes with statistics from the Astrid-2 altitude of 1000 km.…”

Section: Scientific Objectivesmentioning

confidence: 99%

LINDA – the Astrid-2 Langmuir probe instrument

Holback

Jacksén²,

Åhlén

et al. 2001

Ann. Geophys.

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Abstract. The Swedish micro-satellite Astrid-2, designed for studies in magnetosperic physics, was launched into orbit on 10 December 1998 from the Russian cosmodrome Plesetsk. It was injected into a circular orbit at 1000 km and at 83 degrees inclination. The satellite carried, among other instruments, a double Langmuir Probe instrument called LINDA (Langmuir INterferometer and Density instrument for Astrid-2). The scientific goals of this instrument, as well as the technical design and possible modes of operation, are described. LINDA consists of two lightweight deployable boom systems, each carrying a small spherical probe. With these probes, separated by 2.9 meters, and in combination with a high sampling rate, it was possible to discriminate temporal structures (waves) from spatial structures. An onboard memory made it possible to collect data also at times when there was no ground contact. Plasma density and electron temperature data from all magnetic latitudes and for all seasons have been collected.

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Observation and analysis of lower hybrid solitary structures as rotating eigenmodes

Cited by 47 publications

References 33 publications

Observations of lower hybrid cavities in the inner magnetosphere by the Cluster and Viking satellites

Observations of lower hybrid cavities in the inner magnetosphere by the Cluster and Viking satellites

Localization of wave fields in lower hybrid cavities

LINDA – the Astrid-2 Langmuir probe instrument

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