کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1782701 | 1022352 | 2007 | 22 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
An investigation of the field-aligned currents associated with a large-scale ULF wave in the morning sector
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موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
فیزیک زمین (ژئو فیزیک)
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
Previous work by Scoffield, H.C., Yeoman, T.K., Wright, D.M., Milan, S.E., Wright, A.N., Strangeway, R.J. [2005. An investigation of the field aligned currents associated with a large scale ULF wave using data from CUTLASS and FAST. Ann. Geophys. 23, 487-498) investigated a large-scale ULF wave, occurring in the dusk sector (â¼1900 MLT). The wave had a period of â¼800 s (corresponding to 1.2 mHz frequency), an azimuthal wave number of â¼7 and a full-width at half-maximum (FWHM) across the resonance of 350 km. IMAGE ground magnetometer and SuperDARN radar observations of the wave's spatial and temporal characteristics were used to parameterise a simple, two-dimensional field line resonance (FLR) model. The model-calculated field-aligned current (FAC) was compared with FACs derived from the FAST energetic particle spectra and magnetic field measurement. Here the authors use the same method to investigate the FAC structure of a second large-scale ULF wave, with a period of â¼450 s, occurring the dawn sector (â¼0500 MLT) with an opposite sense background region 1-region 2 current system. This wave has a much larger longitudinal scale (mâ¼4.5) and a smaller latitude scale (FWHM=150 km). Unlike the dusk sector wave, which was dominated by upward FAC, FAST observations of the dawn sector wave show an interval of large-scale downward FAC of â¼1.5 μA mâ2. Downgoing magnetospheric electrons with energies of a few keV were observed, which are associated with upward FACs of â¼1 μA mâ2. For both wave studies, downward currents appear to be carried partially by upgoing electrons below the FAST energy detection threshold (5 eV), but also consist of a mixture of hotter downgoing magnetospheric electrons and upgoing ionospheric electrons of energies 30 eV-1 keV. Strong intervals of upward current show that small-scale structuring of scale â¼50 km has been imposed on the current carriers. In general, this study confirms the findings of Scoffield, H.C., Yeoman, T.K., Wright, D.M., Milan, S.E., Wright, A.N., Strangeway, R.J. [2005. An investigation of the FACs associated with a large-scale ULF wave using data from CUTLASS and FAST. Ann. Geophys. 23, 487-498).
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Planetary and Space Science - Volume 55, Issue 6, April 2007, Pages 770-791
Journal: Planetary and Space Science - Volume 55, Issue 6, April 2007, Pages 770-791
نویسندگان
H.C. Scoffield, T.K. Yeoman, D.M. Wright, S.E. Milan, A.N. Wright, R.J. Strangeway,