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

作     者：Atsuki Shinbori Tomoaki Hori Yoshimasa Tanaka Yukinobu Koyama Takashi Kiku-chi Tsutomu Nagatsuma 

作者机构：Research Institute for Sustainable HumanosphereGokashoUjiKyoto 611-0011Japan Solar-Terrestrial Environment LaboratoryNagoya UniversityFurou-choChikusa-kuNagoyaAichi 464-8614Japan National Institute of Polar Research10-3 Midori-choTachikawaTokyo 190-8518Japan Data Analysis Center for Geomagnetism and Space MagnetismGraduate School of ScienceKyoto UniversityKitashi-rakawa-Oiwake ChoSakyo-kuKyoto 606-8502Japan National Institute of Information and Communications Technology4-2-1NukuikitamachiKoganeiTokyo 184-0015Japan 

出 版 物：《Advances in Polar Science》 (极地科学进展（英文版）)

年 卷 期：2013年第24卷第4期

页      面：296-314页

学科分类：070802[理学-空间物理学] 07[理学] 0708[理学-地球物理学] 

基　　金：supported by the Inter-university Upper atmosphere Global Observation NETwork(IUGONET)project funded by the Ministry of Education,Culture,Sports,Science and Technology(MEXT),Japan,the National Institute of Polar Research through General Collaboration Projects(Grant no.23-14) JSPS KAKENHI(Grant no.11020535) 

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

摘      要：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.