Geospace exploration project ERG

Miyoshi, Yoshizumi; Shinohara, I.; Takashima, Takeshi; Asamura, Kazushi; Higashio, Nana; Mitani, Takefumi; Kasahara, Satoshi; Yokota, Shoichiro; Kazama, Y.; Wang, Shiang‐Yu; Tam, Sunny Wing-Yee; Ho, P. T. P.; Kasahara, Yoshiya; Kasaba, Yasumasa; Yagitani, Satoshi; Matsuoka, A.; Kojima, Hirotsugu; Katoh, Yutai; Seki, K.

doi:10.1186/s40623-018-0862-0

Cited by 249 publications

(255 citation statements)

References 47 publications

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“…In this study, we use data from the electric field and waves (EFW) instrument (Wygant et al, ) and search coil sensors for the Electric and Magnetic Field Instrument Suite and Integrated Science (Kletzing et al, ) on board the Van Allen Probe‐A. We also use the waveform data from the wave form capture (WFC) of the Plasma Wave Experiment (Kasahara et al, ; Matsuda et al, ) on board the Arase (ERG) satellite (Miyoshi, Hori, et al, ; Miyoshi, Shinohara, et al, ). The Arase satellite has operated the wave burst observations intermittently to obtain the wave form with the sampling frequency of 1,024 Hz.…”

Section: Analysis Of Van Allen Probe and Arase Observationsmentioning

confidence: 99%

EMIC Waves Converted From Equatorial Noise Due to M/Q = 2 Ions in the Plasmasphere: Observations From Van Allen Probes and Arase

Miyoshi

Matsuda

Kurita

et al. 2019

Geophysical Research Letters

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Equatorial noise (EN) emissions are observed inside and outside the plasmapause. EN emissions are referred to as magnetosonic mode waves. Using data from Van Allen Probes and Arase, we found conversion from EN emissions to electromagnetic ion cyclotron (EMIC) waves in the plasmasphere and in the topside ionosphere. A low‐frequency part of EN emissions becomes EMIC waves through branch splitting of EN emissions, and the mode conversion from EN to EMIC waves occurs around the frequency of M/Q = 2 (deuteron and/or alpha particles) cyclotron frequency. These processes result in plasmaspheric EMIC waves. We investigated the ion composition ratio by characteristic frequencies of EN emissions and EMIC waves and obtained ion composition ratios. We found that the maximum composition ratio of M/Q = 2 ions is ~10% below 3,000 km. The quantitative estimation of the ion composition will contribute to improving the plasma model of the deep plasmasphere and the topside ionosphere.

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Section: Analysis Of Van Allen Probe and Arase Observationsmentioning

confidence: 99%

EMIC Waves Converted From Equatorial Noise Due to M/Q = 2 Ions in the Plasmasphere: Observations From Van Allen Probes and Arase

Miyoshi

Matsuda

Kurita

et al. 2019

Geophysical Research Letters

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“…In this study, we report Pc4 ULF waves and proton flux oscillations observed by the Arase satellite (Miyoshi et al, ) and ground magnetometers on 15 April 2017. We estimate the radial gradient of the proton phase space density

1.61em (\frac{\partial f_{H^{+}}}{∂L}, where f_{H^{+}}

is the proton phase space density

1.61em)

from the radial motion of Arase to examine the instability condition.…”

Section: Introductionmentioning

confidence: 74%

“…The Arase satellite, whose main objective is exploration of the outer radiation belt, was launched on 20 December 2016 into an elliptical orbit with the apogee of ∼6 R E and the perigee altitude of

≳

300 km (Miyoshi et al, ). The satellite is spin stabilized ( τ spin ∼8 s, where τ spin is the spin period) and equipped with comprehensive sensors for fields and particles.…”

Section: Instrumentationmentioning

confidence: 99%

Giant Pulsations Excited by a Steep Earthward Gradient of Proton Phase Space Density: Arase Observation

Yamamoto

Nosé

Kasahara

et al. 2018

Geophysical Research Letters

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We present observational evidence of drift resonance between westward propagating odd mode standing ultralow frequency waves and energetic protons. Compressional ∼13 mHz (Pc4 band) waves and proton flux oscillations at >50 keV were detected at ∼03 hr magnetic local time by the Arase satellite on 15 April 2017. The azimuthal wave number (m number) is estimated to be ∼−50 from ground observations, while the theory of drift resonance gives m ∼− 49 for odd mode waves and ∼110‐keV protons, providing evidence that the drift resonance indeed took place in this event. We also found a steep earthward gradient of proton phase space density, which can quantitatively explain the wave excitation. The observed waves show typical features of giant pulsations (Pgs), regarding local time, m number, and flux oscillations. This study, therefore, has great implications to the field line mode structure and excitation mechanism of Pgs.

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“…The hypothesis of pulsating aurora needed confirmation by simultaneous observations with a high‐speed auroral camera, but permanent auroral observation in the region was routinely made at a rate of one frame in a few seconds at best, which is not enough to resolve the 2‐Hz variations. Only at the end of 2016 suitable high‐speed cameras were installed in Northern Europe in association with the Exploration of energization and Radiation in Geospace project (Miyoshi et al, ). In the present paper we study in detail a unique case from 6 November 2016 when the MR detected NED auroral echoes from the region where successful auroral observations were made with the high‐speed camera.…”

Section: Introductionmentioning

confidence: 99%

Ground Echoes Observed by the Meteor Radar and High‐Speed Auroral Observations in the Substorm Growth Phase

et al. 2019

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Multi‐instrument observations by a meteor radar (MR), auroral cameras, ionosondes, and ground magnetometers were made in Northern Europe at auroral latitudes (between 64° and 72° corrected geomagnetic latitude) at 22–24 magnetic local time in the substorm growth phase. The southward drifting growth phase auroral arc was associated with enhanced electron density up to 2⋅1012 m‐3 (corresponding to a plasma frequency, foEs of about 13 MHz) at about 110‐km altitude. Such an enhanced E layer electron density caused bending toward the ground of the MR radio waves transmitted at a frequency, fr, of 36.9 MHz and at low elevation (el. < 25°), such that the radar received ground echoes characterized by a near‐zero Doppler shift. The amplitude of the echoes was modulated at a frequency of a few hertz, and a similar modulation was found in the auroral luminosity at 427.8 nm near the location of the bending of MR radio waves. The modulation was due to irregular (random) fluctuations of auroral precipitation. Although such a few‐hertz variation of the auroral precipitation cannot produce more than 1% modulation of the ionospheric electron density, even such a small modulation can lead to 50% modulation of the MR ground scatter provided foEs ≈ fr sin (el.). The ionosonde and MR data provide evidence that this condition was satisfied in the present case. Due to a high‐frequency (>2 Hz) amplitude modulation of the ground scatter, the MR erroneously accepts such signals as echoes from meteor trails.

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Geospace exploration project ERG

Cited by 249 publications

References 47 publications

EMIC Waves Converted From Equatorial Noise Due to M/Q = 2 Ions in the Plasmasphere: Observations From Van Allen Probes and Arase

EMIC Waves Converted From Equatorial Noise Due to M/Q = 2 Ions in the Plasmasphere: Observations From Van Allen Probes and Arase

Giant Pulsations Excited by a Steep Earthward Gradient of Proton Phase Space Density: Arase Observation

Ground Echoes Observed by the Meteor Radar and High‐Speed Auroral Observations in the Substorm Growth Phase

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