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A Simulation Study of Ionization Depletion in the Auroral Ionospheric F-Region Caused by Strong convection electric field

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Wuhan University Journal of Natural Sciences 2001年第3期6卷 680-686页

作者： Cai Hong-tao Ma Shu-ying G. Kirchengast College of Electronic Information Wuhan University Wuhan 430072 China

THe effects of strong convection electric field on the electron density in the auroral ionosphericF-region have been simulated numerically by means of a physical model. It is found that an enhancement of electric field directed west-northward in post-noon or west-southward in pre-noon results in an ionization depletion with its maximum at altitudes 40–50 km higher than that of theF 2 peak. When the enhanced electric field lasts for 45 min and has a maximum about 32 mV/m, the resulted ionization depletions reach their maximum at the time just ～10 min behind the time when the convection electric field and ion temperature enhancements reach their maximum. This is consistent well with EISCAT observations. The magnitudes of the percentage ionization depletions and their recovery time are dependent not only on the intensity of the electric field, but also on the diurnal variation phase of the background electron density.

关键词： auroral ionosphere ionospheric model numerical simulation convection electric field ionization depletion

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Global distributions of storm-time ionospheric currents as seen in geomagnetic field variations

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Advances in Polar Science 2013年第4期24卷 296-314页

作者： Atsuki Shinbori Tomoaki Hori Yoshimasa Tanaka Yukinobu Koyama Takashi Kiku-chi Tsutomu Nagatsuma Research Institute for Sustainable Humanosphere GokashoUjiKyoto 611-0011Japan Solar-Terrestrial Environment Laboratory Nagoya UniversityFurou-choChikusa-kuNagoyaAichi 464-8614Japan National Institute of Polar Research 10-3 Midori-choTachikawaTokyo 190-8518Japan Data Analysis Center for Geomagnetism and Space Magnetism Graduate School of ScienceKyoto UniversityKitashi-rakawa-Oiwake ChoSakyo-kuKyoto 606-8502Japan National Institute of Information and Communications Technology 4-2-1NukuikitamachiKoganeiTokyo 184-0015Japan

To investigate temporal and spatial evolution of global geomagnetic field variations from high-latitude to the equator during geomagnetic storms, we analyzed ground geomagnetic field disturbances from high latitudes to the magnetic equator. The daytime ionospheric equivalent current during the storm main phase showed that twin-vortex ionospheric currents driven by the Region 1 field-aligned currents （R1 FACs） are intensified significantly and expand to the low-latitude region of-30~ magnetic latitude. Centers of the currents were located around 70~ and 65~ in the morning and afternoon, respectively. Corresponding to intensification of the R1 FACs, an enhancement of the eastward/westward equatorial electrojet occurred at the daytime/nighttime dip equator. This signature suggests that the enhanced convection electric field penetrates to both the daytime and nighttime equa- tor. During the recovery phase, the daytime equivalent current showed that two new pairs of twin vortices, which are different from two-cell ionospheric currents driven by the R1 FACs, appear in the polar cap and mid latitude. The former led to enhanced north- ward Bz （NBZ） FACs driven by lobe reconnection tailward of the cusps, owing to the northward interplanetary magnetic field （IMF）. The latter was generated by enhanced Region 2 field-aligned currents （R2 FACs）. Associated with these magnetic field variations in the mid-latitudes and polar cap, the equatorial magnetic field variation showed a strongly negative signature, produced by the westward equatorial electrojet current caused by the dusk-to-dawn electric field.

关键词： solar wind interplanetary magnetic field geomagnetic storm convection electric field field-alignedcurrents equatorial electrojet NBZ FAC system

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