Biblio

Found 5 results
Filters: Author is Omura, Y.  [Clear All Filters]
2018
Authors: Nakamura S., Omura Y., and Summers D.
Title: Fine structure of whistler-mode hiss in plasmaspheric plumes observed by the Van Allen Probes
Abstract: We survey 3 years (2013‐2015) of data from the Van Allen Probes related to plasmaspheric plume crossing events. We detect 194 plume crossing events, and we find that 97% of the plumes are accompanied by VLF hiss emissions. The plumes are mainly detected on the duskside or dayside. Careful examination of the hiss spectra reveals that all hiss emissions consist of obvious fine structure. Application of a band pass filter reveals that the fine structure is consistent with the occurrence of discrete wave packets. The hiss data display high coherency. The events are classified by location. Dusk side hiss and night side hiss tend to have extremely high polarization with no chorus at the high‐frequency end of the dynamic spectrum. The dusk side hiss has a distinct upper frequency limit. On th. . .
Date: 10/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025803 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025803
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2016
Authors: Nomura R., Shiokawa K., Omura Y., Ebihara Y., Miyoshi Y, et al.
Title: Pulsating proton aurora caused by rising tone Pc1 waves
Abstract: We found rising tone emissions with a dispersion of ∼1 Hz per several tens of seconds in the dynamic spectrum of a Pc1 geomagnetic pulsation (Pc1) observed on the ground. These Pc1 rising tones were successively observed over ∼30 min from 0250 UT on 14 October 2006 by an induction magnetometer at Athabasca, Canada (54.7°N, 246.7°E, magnetic latitude 61.7°N). Simultaneously, a Time History of Events and Macroscale Interactions during Substorms panchromatic (THEMIS) all-sky camera detected pulsations of an isolated proton aurora with a period of several tens of seconds, ∼10% variations in intensity, and fine structures of 3° in magnetic longitudes. The pulsations of the proton aurora close to the zenith of ATH have one-to-one correspondences with the Pc1 rising tones. This suggests. . .
Date: 02/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2015JA021681 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015JA021681/full
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Authors: Foster J. C., Erickson P. J., Omura Y., Baker D N, Kletzing C A, et al.
Title: Van Allen Probes Observations of Prompt MeV Radiation Belt Electron Acceleration in Non-Linear Interactions with VLF Chorus
Abstract: Prompt recovery of MeV electron populations in the post-storm core of the outer terrestrial radiation belt involves local acceleration of a seed population of energetic electrons in interactions with VLF chorus waves. Electron interactions during the generation of VLF rising tones are strongly non-linear, such that a fraction of the relativistic electrons at resonant energies are trapped by waves, leading to significant non-adiabatic energy exchange. Through detailed examination of VLF chorus and electron fluxes observed by Van Allen Probes, we investigate the efficiency of non-linear processes for acceleration of electrons to MeV energies. We find through subpacket analysis of chorus waveforms that electrons with initial energy 100s keV - 3 MeV can be accelerated by 50 keV - 200 keV in re. . .
Date: 12/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023429 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023429/full
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2015
Authors: Engebretson M. J., Posch J. L., Wygant J R, Kletzing C A, Lessard M. R., et al.
Title: Van Allen probes, NOAA, GOES, and ground observations of an intense EMIC wave event extending over 12 hours in MLT
Abstract: Although most studies of the effects of EMIC waves on Earth's outer radiation belt have focused on events in the afternoon sector in the outer plasmasphere or plume region, strong magnetospheric compressions provide an additional stimulus for EMIC wave generation across a large range of local times and L shells. We present here observations of the effects of a wave event on February 23, 2014 that extended over 8 hours in UT and over 12 hours in local time, stimulated by a gradual 4-hour rise and subsequent sharp increases in solar wind pressure. Large-amplitude linearly polarized hydrogen band EMIC waves (up to 25 nT p-p) appeared for over 4 hours at both Van Allen Probes, from late morning through local noon, when these spacecraft were outside the plasmapause, with densities ~5-20 cm-3. W. . .
Date: 06/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021227 Available at: http://doi.wiley.com/10.1002/2015JA021227
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2014
Authors: Fu H. S., Cao J. B., Zhima Z., Khotyaintsev Y. V., Angelopoulos V, et al.
Title: First observation of rising-tone magnetosonic waves
Abstract: Magnetosonic (MS) waves are linearly polarized emissions confined near the magnetic equator with wave normal angle near 90° and frequency below the lower hybrid frequency. Such waves, also termed equatorial noise, were traditionally known to be “temporally continuous” in their time-frequency spectrogram. Here we show for the first time that MS waves actually have discrete wave elements with rising-tone features in their spectrogram. The frequency sweep rate of MS waves, ~1 Hz/s, is between that of chorus and electromagnetic ion cyclotron (EMIC) waves. For the two events we analyzed, MS waves occur outside the plasmapause and cannot penetrate into the plasmasphere; their power is smaller than that of chorus. We suggest that the rising-tone feature of MS waves is a consequence of nonl. . .
Date: 11/2014 Publisher: Geophysical Research Letters Pages: 7419 - 7426 DOI: 10.1002/grl.v41.2110.1002/2014GL061867 Available at: http://doi.wiley.com/10.1002/grl.v41.21http://doi.wiley.com/10.1002/2014GL061867
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