Propagation Characteristics of Auroral Hiss Observed by Akebono Satellite.

Kasahara, Yoshiya; Yoshida, Kenichi; Matsuo, Toshio; Kimura, Ikuo; Mukai, T.

doi:10.5636/jgg.47.509

Cited by 14 publications

(12 citation statements)

References 22 publications

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“…They further associated the emission with downgoing low‐energy electrons between 100 eV and several keV. At altitudes of 3000–6000 km Kasahara et al [1995] reported downgoing hiss with wave vectors highly declined from B 0 . Their interpretation of the funnel shaped envelope assumed a line source extended up to radial distances of 2.9 R E .…”

Section: Introductionmentioning

confidence: 93%

“…Auroral hiss is an intense plasma wave emission which frequently occurs in the high‐latitude region of the Earth's magnetosphere [e.g., Gurnett , 1966, Persoon et al , 1988, Kasahara et al , 1995]. Observed by orbiting spacecraft it often appears with a characteristic funnel shaped envelope on time‐frequency spectrograms (the lower‐frequency cutoff first decreases and then increases).…”

Section: Introductionmentioning

confidence: 99%

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Propagation of auroral hiss at high altitudes

Santolı́k

Gurnett

2002

Geophysical Research Letters

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Using multicomponent wave measurements of the Polar spacecraft, we provide direct evidence of the propagation pattern of funnel‐shaped auroral hiss at a radial distance of 5 Earth radii. The waves propagate upward and the Poynting flux is directed toward higher latitudes in the high‐latitude part of the emission and to lower latitudes in the low‐latitude part. The wave vectors are found to be close to the whistler mode resonance angle. Consistent with the theory, the latitudinal component of the wave vector is opposite compared to that of the Poynting flux in the low‐latitude and high‐latitude parts of the funnel‐shaped emission. In the central part of the emission we observe a very broad distribution of the wave energy with respect to the azimuth angle. The waves thus simultaneously come from different directions with different wave vectors. This leads us to the conclusion that hiss is more likely generated in an extended sheet source rather than in a vertical line source or a point source. In this case the observed propagation pattern suggests that the sheet source is oriented roughly in the longitudinal direction, consistent with the region where we can expect presence of upgoing or counterstreaming electron beams.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Propagation of auroral hiss at high altitudes

Santolı́k

Gurnett

2002

Geophysical Research Letters

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“…In some respects, the VLF radiation spectrum is in between the funnel-shaped spectrograms of auroral hiss observed on DE 1 (Gurnett et al, 1983) and the Vshaped spectrograms observed on AKEBONO (Kasahara et al, 1995). The right branch of a``V'' structure may be drawn from $16:00 to 16:23 UT and a left branch from $16:23 to 17:30 UT.…”

Section: Akr Emissions and Associated Phenomenamentioning

confidence: 99%

“…The only way to obtain non-ambiguous estimates of the full propagation characteristic is to perform a wave analysis on the waveforms associated with a minimum of four electromagnetic wave-®eld components: preferably, the three magnetic components and one electric component (Lefeuvre et al, 1981(Lefeuvre et al, , 1986Parrot et al, 1989). This has been done for ELF and VLF waves observed on AKEBONO (Kimura et al, 1990;Kasahara et al, 1995). However, the altitudes are generally too low to be compared with INTERBALL 2.…”

Section: Introductionmentioning

confidence: 99%

Preliminary results from the MEMO multicomponent measurements of waves on-board INTERBALL 2

et al. 1998

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Abstract. The MEMO (MEsure Multicomposante des Ondes) experiment is a part of the INTERBALL 2 wave consortium. It is connected to a total of six electric and nine magnetic independent sensors. It provides waveforms associated with the measurement of two to ®ve components in three frequency bands: ELF (5± 1000 Hz), VLF (1±20 kHz), LF (20±250 kHz). Preliminary analyses of low and high resolution data are presented. The emphasis is put on the estimation of the propagation characteristics of the observed waves.VLF hiss emissions are shown to be mainly whistler mode emissions, but other modes are present. An accurate estimation of the local plasma frequency is proposed when the low L = 0 cuto frequency is identi®ed. AKR emissions observed just above source regions are studied. R-X and L-O modes are found: the ®rst at the lowest frequencies and the second at the highest. Both propagate with wave normal directions weakly oblique or quasi-parallel to the Earth's magnetic ®eld direction. Propagation characteristics are also determined for a (non-drifting) ®ne structure of AKR. There is no fundamental di erence with structurless events. Nightside and dayside bursts of ELF electromagnetic emissions are presented. It is not clear whether the two emissions belong to the``lion roar'' emissions or not.

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“…Results of satellite studies at low altitudes show that auroral hiss propagates in the whistler mode at frequencies below the electron cyclotron frequency or the electron plasma frequency, whichever is smaller. Measurements of the Poynting flux of auroral hiss at altitudes below 5000 km demonstrated that in most cases, waves were propagating downward (Gurnett et al, 1971;Kasahara et al, 1995). At low altitudes, downgoing auroral hiss is considered to be generated below the auroral potential drop by downgoing field-aligned electrons (from 100 eV to above 1 keV) by the Landau resonance (Maggs, 1976;Maggs and Lotko, 1981).…”

Section: Introductionmentioning

confidence: 99%

The relationship between auroral hiss at high altitudes over the polar caps and the substorm dynamics of aurora

et al. 2005

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Abstract. Strong variations of intensity and cutoff frequency of the auroral hiss were observed by INTERBALL-2 and PO-LAR satellites at high altitudes, poleward from the auroral oval. The hiss intensifications are correlated with the auroral activations during substorms and/or pseudo-breakups. The low cutoff frequency of auroral hiss increases with the distance between the aurora and the satellite footprint. Multicomponent wave measurements of the hiss emissions on board the POLAR spacecraft show that the horizontal component of the Poynting flux of auroral hiss changes its direction in good accordance with longitudinal displacements of the bright auroras. The vertical component of the Poynting flux is directed upward from the aurora region, indicating that hiss could be generated by upgoing electron beams. This relationship between hiss and the aurora dynamics means that the upgoing electron beams are closely related to downgoing electron beams which produce the aurora. During the auroral activations the upgoing and downgoing beams move and change their intensities simultaneously.

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Propagation Characteristics of Auroral Hiss Observed by Akebono Satellite.

Cited by 14 publications

References 22 publications

Propagation of auroral hiss at high altitudes

Propagation of auroral hiss at high altitudes

Preliminary results from the MEMO multicomponent measurements of waves on-board INTERBALL 2

The relationship between auroral hiss at high altitudes over the polar caps and the substorm dynamics of aurora

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