Characteristics of small-scale magnetic fluctuations over the high-latitude ionosphere

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概要

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• The global amplitude distributions of the small-scale (1<L<35km) or short-time scale (0.12<T<5s) magnetic fluctuations over the high-latitude ionosphere are obtained for various geomagnetic, seasonal and IMF conditions using the MAGSAT data and are compared with the large-scale Birkeland currents. On the dayside, the maximum of the amplitude distribution appears near the poleward edge of the large-scale Birkeland current region-1 or at the latitude poleward of it. The amplitude strongly depends on the ionospheric conductivity and varies about factor three or more even in the same conditions of the geomagnetic activity, suggesting that the fluctuations are generated mainly by small-scale Birkeland currents rather than by Alfven waves. The IMF-By causes the dawn-dusk asymmetry of the amplitude and the IMF-Bz controls the latitudinal distribution of the fluctuations. On the night-side, the amplitude is controlled mainly by the geomagnetic activity, and the active region statistically corresponds to the large scale Birkeland current regions. However, the correlation between the amplitude and the large-scale Birkeland current density is not necessarily good. On both sides, the latitude of the maximum amplitude roughly correspond to that of the large-scale magnetospheric convection reversal, suggesting that the small-scale Birkeland currents originate from the turbulence generated in the strong convection shear regions.

• 国立極地研究所の論文

著者

• Nakagawa Akinari

  Data Analysis Center For Geomagnetism And Spacemagnetism Faculty Of Science Kyoto University

• IYEMORI Toshihiko

  Data Analysis Center for Geomagnetism and Space Magnetism, Garaduate School of Science, Kyoto Univer

• Ikeda Tatsuya

  Data Analysis Center for Geomagnetism and Spacemagnetism, Faculty of Science, Kyoto University

• Iyemori Toshihiko

  DataAnalysis Center for Geomagnetism and Space Magnetism, Kyoto University

• Ikeda Tatsuya

  Data Analysis Center For Geomagnetism And Spacemagnetism Faculty Of Science Kyoto University

• Iyemori T

  Kyoto Univ. Kyoto Jpn

• Iyemori Toshihiko

  Data Analysis Center For Geomagnetism And Space Magnetism Garaduate School Of Science Kyoto Universi

関連論文

• Local time dependence of the dominant frequency of Pi2 pulsations at mid-and low-latitudes
• Characteristics of CNA associated with geomagnetic sudden commencements
• Geomagnetic sudden commencements observed at the Syowa-Iceland conjugate stations
• Characteristics of polarization of geomagnetic sudden commencements observed at Syowa Station
• Structure of large amplitude abrupt magnetic variations observed by the MAGSAT
• Characteristics of small-scale magnetic fluctuations over the high-latitude ionosphere
• Derivation of polar cap AE indices
• Simultaneous observation of geomagnetic sudden commencement above and below the ionosphere
• Characteristics of solar flare effect in the high-latitude ionosphere as observed by the SuperDARN radars
• Local time dependence of the frequency of Pi2 waves simultaneously observed at 5 low-latitude stations
• Local time features of geomagnetic jerks
• Characteristics of the association between an SC and a substorm onset
• Correlations of AKR index with Kp and Dst indices
• Scale-length dependence of the ratio between the magnetic and electric field perturbations in the ionospheric field-aligned current region
• A statistical study of ULF waves observed by MAGSAT at ionospheric altitude

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