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- Yamauchi, M., et al.
(författare)
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Magnetospheric solitary structure maintained by 3000 km/s ions as a cause of westward moving auroral bulge at 19 MLT
- 2009
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 27:7, s. 2947-2969
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Tidskriftsartikel (refereegranskat)abstract
- In the evening equatorial magnetosphere at about 4 R-E geocentric distance and 19 MLT, the four Cluster spacecraft observed a solitary structure with a width of about 1000 similar to 2000 km in the propagation direction. The solitary structure propagates sunward with about 5 similar to 10 km/s carrying sunward electric field (in the propagation direction) of up to about 10 mV/m (total potential drop of about 5 similar to 10 kV), depletion of magnetic field of about 25%, and a duskward E x B convection up to 50 km/s of He+ rich cold plasma without O+. At the same time, auroral images from the IMAGE satellite together with ground based geomagnetic field data showed a westward (sunward at this location) propagating auroral bulge at the magnetically conjugate ionosphere with the solitary structure. The solitary structure is maintained by flux enhancement of selectively 3000 km/s ions (about 50 keV for H+, 200 keV for He+, and 750 keV for O+). These ions are the main carrier of the diamagnetic current causing the magnetic depletion, whereas the polarization is maintained by different behavior of energetic ions and electrons. Corresponding to aurora, field-aligned accelerated ionospheric plasma of several keV appeared at Cluster from both hemispheres simultaneously. Together with good correspondence in location and propagation velocity between the auroral bulge and the solitary structure, this indicates that the sunward moving auroral bulge is caused by the sunward propagation of the solitary structure which is maintained by energetic ions. The solitary structure might also be the cause of Pi2-like magnetic variation that started simultaneously at Cluster location.
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- Kataoka, R., et al.
(författare)
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High-speed stereoscopy of aurora
- 2016
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 34:1, s. 41-44
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Tidskriftsartikel (refereegranskat)abstract
- We performed 100aEuro-fps stereoscopic imaging of aurora for the first time. Two identical sCMOS cameras equipped with narrow field-of-view lenses (15A degrees by 15A degrees) were directed at magnetic zenith with the north-south base distance of 8.1aEuro-km. Here we show the best example that a rapidly pulsating diffuse patch and a streaming discrete arc were observed at the same time with different parallaxes, and the emission altitudes were estimated as 85-95aEuro-km and > aEuro-100aEuro-km, respectively. The estimated emission altitudes are consistent with those estimated in previous studies, and it is suggested that high-speed stereoscopy is useful to directly measure the emission altitudes of various types of rapidly varying aurora. It is also found that variation of emission altitude is gradual (e.g., 10aEuro-km increase over 5aEuro-s) for pulsating patches and is fast (e.g., 10aEuro-km increase within 0.5aEuro-s) for streaming arcs.
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- Miyoshi, Y., et al.
(författare)
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The energization and radiation in geospace (ERG) project
- 2012
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Ingår i: Dynamics of The Earth's Radiation Belts and Inner Magnetosphere. - : American Geophysical Union (AGU). - 9780875904894 ; , s. 103-116
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Konferensbidrag (refereegranskat)abstract
- The Energization and Radiation in Geospace (ERG) project for solar cycle 24 will explore how relativistic electrons in the radiation belts are generated during space storms. This geospace exploration project consists of three research teams: the ERG satellite observation team, the ground-based network observation team, and the integrated data analysis/simulation team. Satellite observation will provide in situ measurements of features such as the plasma distribution function, electric and magnetic fields, and plasma waves, whereas remote sensing by ground-based observations using, for example, HF radars, magnetometers, optical instruments, and radio wave receivers will provide the global state of the geospace. Various kinds of data will be integrated and compared with numerical simulations for quantitative understanding. Such a synergetic approach is essential for comprehensive understanding of relativistic electron generation/loss processes through crossenergy and cross-regional coupling in which different plasma populations and regions are dynamically coupled with each other. In addition, the ERG satellite will utilize a new and innovative measurement technique for wave-particle interactions that can directly measure the energy exchange process between particles and plasma waves. In this paper, we briefly review some of the profound problems regarding relativistic electron accelerations and losses that will be solved by the ERG project, and we provide an overview of the project.
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