کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1782508 1022341 2007 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Unusual anisotropic wave trains in cosmic rays
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فیزیک زمین (ژئو فیزیک)
پیش نمایش صفحه اول مقاله
Unusual anisotropic wave trains in cosmic rays
چکیده انگلیسی
Several workers have attempted to find out the possible origin of the “high amplitude wave trains” of enhanced diurnal variation of cosmic rays and to develop a suitable realistic theoretical model that can explain the different harmonics in individual days. The various observed harmonics of the cosmic-ray variation may be understood on a unified basis if the free-space cosmic-ray anisotropy is non-sinusoidal in form. The major objective of this paper is to study the first three harmonics of high-amplitude wave trains of cosmic-ray intensity over the period 1981-1994 for Deep River neutron monitoring station. The main characteristic of these events is that the high-amplitude wave trains show a maximum intensity of diurnal component in a direction earlier than 18:00 h/co-rotational direction. It is noteworthy that the amplitude significantly enhanced and the phase remains in the co-rotational direction during the years close to solar-activity maximum for first harmonic. Significant deviations have been observed in the semi-diurnal amplitude after the onset of solar-activity maximum. This leads us to conclude that the amplitude as well as direction of the first harmonic and the amplitude of second harmonic are correlated with solar-activity cycle during these HAEs. The amplitude and phase of all the three harmonics (diurnal/semi-diurnal/tri-diurnal) are not found to depend on the polarity of Bz component of interplanetary magnetic field for long-term variation. The occurrence of high-amplitude events is dominant for the positive polarity of Bz component of IMF. The occurrence of HAEs is dominant during the period of average solar-wind velocity, but their occurrence during HSSWSs cannot be denied. The possibility of occurrence of these events is more during the periods of co-rotating streams. The occurrence of HAE is dominant when Dst-index remains negative and this point is not reported earlier in the litterature. All the high amplitude events occurred, when geomagnetic activity index, Ap, remains ⩽20.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Planetary and Space Science - Volume 55, Issue 14, November 2007, Pages 2077-2086
نویسندگان
, ,