Kilometric continuum detected by Geotail

Hashimoto, K.; Calvert, W.; Matsumoto, Hiroshi

doi:10.1029/1999ja900365

Cited by 39 publications

(65 citation statements)

References 24 publications

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“…[24] Prior to this investigation, many examples of KC events have been found [Hashimoto et al, 1999]. Only a few of these events have been observed in X-rays by the PIXIE instrument since PIXIE was either not yet on orbit or not in a good position to view the X-rays free from serious background.…”

Section: Discussionmentioning

confidence: 99%

“…The components of KC are enhanced at a relatively constant frequency over the same range as auroral kilometric radiation (AKR), which displays predominantly temporal variations in frequency [Calvert, 1981;Farrell and Gurnett, 1985;Farrell et al, 1986]. The earliest reported KC events were observed from the Geotail satellite primarily within $10°of the magnetic equator [Hashimoto et al, 1999]. However, Menietti et al [2003] have reported that KC may be emitted well beyond the 10°latitude range, and Hashimoto et al [2005aHashimoto et al [ , 2005bHashimoto et al [ , 2006 found that the latitude can be ±30°.…”

Section: Introductionmentioning

confidence: 99%

“…Normal continuum extends down to $5 kHz. Since the original investigation of KC [Hashimoto et al, 1999], there have been several studies of this phenomenon [e.g., Green et al, 2002Green et al, , 2004Menietti et al, 2003;Green and Fung, 2005;Hashimoto et al, 2005aHashimoto et al, , 2005bHashimoto et al, , 2006. The components of KC are enhanced at a relatively constant frequency over the same range as auroral kilometric radiation (AKR), which displays predominantly temporal variations in frequency [Calvert, 1981;Farrell and Gurnett, 1985;Farrell et al, 1986].…”

Section: Introductionmentioning

confidence: 99%

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Observed X‐rays associated with kilometric continuum

et al. 2007

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[1] Kilometric continuum (KC) is a recently identified nonthermal magnetospheric radio/plasma wave phenomenon that consists of many narrowband emission lines of nearly constant frequency. The temporal structures of the KC wave intensities measured from the Geotail satellite in near equatorial positions at geocentric distances of 9-30 Earth radii were, on several occasions, similar to the temporal structures of X-rays simultaneously emitted from the atmosphere and mapped in position from the Polar satellite at lower altitudes and at high latitudes. The similarity in behavior of KC waves and X-rays might result from the fact that bremsstrahlung X-rays can be generated in the atmosphere by precipitating electrons produced at high altitudes by incident KC waves. KC waves at low latitudes appear correlated with X-rays at high latitudes. Our study supports the premise that KC waves interacting with high-altitude energetic electrons can lead to the production of X-rays at low altitudes from the resultant precipitation of the electrons. Thus the Polar and Geotail satellites may be used to map the spatial spread of KC, a feat that cannot be currently accomplished with waves observed from a single satellite. In this investigation, it is found that the X-ray emissions extend over a wide range of latitudes and may span a broad longitudinal interval. The energy spectra of X-rays emitted from the Earth at the times of KC events have been examined and found to display a wide variety of intensities and spectral shapes as do the spectra of X-rays associated with auroral kilometric radiation (AKR) events. For most of the high-latitude satellite passes when KC but no AKR was present, the X-ray energy spectra were harder than at times associated with AKR.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Observed X‐rays associated with kilometric continuum

et al. 2007

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“…Continuum radiation is observed over a very broad frequency range from as low as 5 kHz [Gurnett, 1975] to as high as 800 kHz [Hashimoto et al, 1999]. The highest frequency component of the continuum radiation from 100 to 800 kHz has been referred to as 'kilometric' continuum [Hashimoto et al, 1999].…”

Section: Kilometric Continuum Source Regionmentioning

confidence: 99%

An Overview of Results from RPI on IMAGE

Green¹,

Reinisch²

2003

Magnetospheric Imaging — The Image Prime Mission

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Abstract. The Radio Plasma Imager (RPI) on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft was designed as a long-range magnetospheric radio sounder, relaxation sounder, and a passive plasma wave instrument. The RPI is a highly flexible instrument that can be programmed to perform these types of measurements at times when IMAGE is located in key regions of the magnetosphere. RPI is the first radio sounder ever flown to large radial distances into the magnetosphere. The long-range sounder echoes from RPI allow remote sensing of a variety of plasmas structures and boundaries in the magnetosphere. A profile inversion technique for RPI echo traces has been developed and provides a method for determining the density distribution of the plasma from either direct or field-aligned echoes. This technique has enabled the determination of the evolving density structure of the polar cap and the plasmasphere under a variety of geomagnetic conditions. New results from RPI show that the plasmasphere refills in slightly greater than a day at L values of 2.8 and that ion heating is probably playing a major role in the overall density distribution along the field-line. In addition, RPI's plasma resonance observations at large radial distances over the polar cap provided in situ measurements of the plasma density with an accuracy of a few percent. For the first time in the magnetosphere, RPI has also observed the plasma D resonances. RPI's long antennas and its very low noise receivers provide excellent observations in the passive receive-only mode when the instrument measures the thermal plasma noise as well as natural emissions such as the continuum radiation and auroral kilometric radiation (AKR). Recent passive measurements from RPI have been compared extensively with images from the Extreme Ultraviolet (EUV) imager on IMAGE resulting in a number of new discoveries. For instance, these combined observations show that kilometric continuum can be generated at the plasmapause from sources in or very near the magnetic equator, within a bite-out region of the plasmasphere. The process by which plasmaspheric bite-out structures are produced is not completely understood at this time. Finally, RPI has been used to successfully test the feasibility of magnetospheric tomography. During perigee passages of the Wind spacecraft, RPI radio transmissions at one and two frequencies have been observed by the Waves instrument. The received electric field vector was observed to rotate with time due to the changing density of plasma, and thus Faraday rotation was measured. Many future multi-spacecraft missions propose to use Faraday rotation to obtain global density pictures of the magnetosphere.

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“…The free-space electromagnetic waves and electrostatic electron cyclotron harmonic (ESCH) waves can be distinguished by their bandwidths and propagation nature. AKR and kilometric continuum tend to have bandwidths of some 100 kHz and 10-100 kHz, respectively (Hashimoto et al, 1999), which have wider bandwidth than Z-mode waves. ESCH waves have discrete spectra with the bandwidth of less than 1.5 kHz (Shinbori et al, 2004) and narrower than Z-mode waves.…”

Section: Observation and Data Analysismentioning

confidence: 99%

Statistical studies of fast and slow Z-mode plasma waves in and beyond the equatorial plasmasphere based on long-term Akebono observations

et al. 2006

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In order to investigate spatial and temporal variations of fast and slow Z-mode waves frequently observed in the equatorial plasmasphere, statistical studies have been performed by using plasma wave observation data obtained by the Akebono satellite within a period from 1989 to 1995. It has been clarified that fast and slow Z-mode waves are intensified within ±5• of geomagnetic latitudes in an altitude range from 6000 km to the apogee (10500 km) of the satellite without obvious local time dependence. Long-term averaged intensity of fast Z-mode waves has almost the same orders of magnitude as that of slow Z-mode waves. These results indicate that significant part of fast Z-mode waves are not produced by the linear mode conversion process from slow Z-mode waves, but excited by more direct process. Furthermore, the region of intensified fast and slow Z-mode waves has been spread in a wider geomagnetic latitude range of ±10• during geomagnetic storms. These evidences suggest that one of the possible free energy sources is ring current particles injected into the equatorial region of the plasmasphere during geomagnetic storms.

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Kilometric continuum detected by Geotail

Cited by 39 publications

References 24 publications

Observed X‐rays associated with kilometric continuum

Observed X‐rays associated with kilometric continuum

An Overview of Results from RPI on IMAGE

Statistical studies of fast and slow Z-mode plasma waves in and beyond the equatorial plasmasphere based on long-term Akebono observations

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