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High-speed solar wind streams (HSWS) were identified for solar cycles 22 and 23 (up to 2004). Preliminarily, HSWS were classified
in three groups according to their continuous period of occurrence. In the declining phase of solar cycle 23, 2003 is found
to be anomalous, showing a very large number of HSWS events of long duration (> ten days). We have studied the effect of HSWS
on the cosmic-ray intensity as well as their relationship with geomagnetic disturbance index Ap on yearly, daily, and hourly bases. The yearly average of solar-wind speed was also found to be maximum in 2003. Being within
the declining phase of solar activity, the occurrence of solar flares in 2003 is quite low. In particular during HSWS, no
solar flares have been observed. Associations with cosmic-ray changes do not support the notion that the HSWS are usually
effective in producing significant cosmic-ray decreases. Out of 12 HSWS events observed during the period 2002 (December)
to 2003, four events of significant cosmic-ray decreases at all the stations have been selected for further analysis. The
cosmic-ray intensity has been found to decrease during the first phase of the event (first five days of HSWS) at all three
neutron-monitor stations situated at different latitudes with different cutoff rigidities. The rigidity spectra of observed
decreases in cosmic-ray intensity for these four cases have been found to be significantly different than that of Fds (Forbush
decrease). In two cases the spectra are softer, whereas in the other two they are harder than that of Fds. However, if the
average of all four events is considered together then the spectra of the decrease in cosmic rays during HSWS exactly match
that of Fds. Such a result implies that initially individual events should be considered, instead of combining them together,
as was done earlier. The Ap index is also found to generally increase in the first phase of the event. However, the four events selected on the basis
of cosmic-ray decrease are not always associated with enhanced values of the Ap index. As such, the significance of our study is that further detailed investigations for much longer periods and on an event-by-event
basis is required to understand the effect of coronal-hole-associated HSWS. 相似文献
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Summary Hysteresis curves of Rajmahal Trap basalts in Bihar are drawn and their coercivities obtained. The experimental arrangements and the procedure are described. The initial remanent magnetisation curves of the specimens are also drawn with the help of the same arrangement. Coercive forces of the rock specimens tested range from 70 to 237 oersteds. The values of saturation magnetisation and remanent magnetisation of two typical specimens are also given. 相似文献
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The People's Republic of China has sought, since its inception in 1949, to develop through economic planning at the national level rather than rely on traditional free market mechanisms. This paper examines the changing characteristics of this economic planning over time, including the shifting balance between centralizing and decentralizing policies. The disruptive effects of the “Great Leap Forward” and the Cultural Revolution are also discussed and the general features of the contemporary situation are examined. 相似文献