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Here we report an in-depth reanalysis of an article by Vats et al. (Astrophys. J. 548, L87, 2001) that was based on measurements of differential rotation with altitude as a function of observing frequencies (as lower and higher frequencies indicate higher and lower heights, respectively) in the solar corona. The radial differential rotation of the solar corona is estimated from daily measurements of the disc-integrated solar radio flux at 11 frequencies: 275, 405, 670, 810, 925, 1080, 1215, 1350, 1620, 1755, and 2800 MHz. We use the same data as were used in Vats et al. (2001), but instead of the twelfth maxima of autocorrelograms used there, we use the first secondary maximum to derive the synodic rotation period. We estimate synodic rotation by Gaussian fit of the first secondary maximum. Vats et al. (2001) reported that the sidereal rotation period increases with increasing frequency. The variation found by them was from 23.6 to 24.15 days in this frequency range, with a difference of only 0.55 days. The present study finds that the sidereal rotation period increases with decreasing frequency. The variation range is from 24.4 to 22.5 days, and the difference is about three times larger (1.9 days). However, both studies give a similar rotation period at 925 MHz. In Vats et al. (2001) the Pearson’s factor with trend line was 0.86, whereas present analysis obtained a \({\sim}\,0.97\) Pearson’s factor with the trend line. Our study shows that the solar corona rotates more slowly at higher altitudes, which contradicts the findings reported in Vats et al. (2001). 相似文献
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Are droughts predictable? 总被引：2，自引：0，他引：2
From a study of rainfall series at several locations, it is shown that approximate but meaningful predictions of drought-prone intervals are possible only for regions where the rainfall series have prominent periodicities (of large amplitudes) in the long periodicity region (about 10 yr or more), provided the patterns do not change abruptly and drastically. Also, rainfall for individual years cannot be predicted accurately. 相似文献
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Spectral analysis of daily values of various solar indices viz. sunspot number, 10.7-cm flux, H Lyman-<alpha> and -<beta>, specific He, Fe and Mg lines and solar X-rays was carried out for two selected intervals. During interval A (May-August 1978, 123 days) the solar indices showed a prominent periodicity near 27 days, while during interval B (January-May 1979, 151 days) the solar indices showed a prominent periodicity near 13 days. For the same intervals, foF2 (max) and foF2 (average) during 1000–1500 LT were similarly analysed for the locations Cachoeira Paulista, SP, Brazil (23○S, 45○W), and Okinawa (26○N, 128○E) and Kokubunji (36○N, 139○E) in Japan. The 27-day and 13-day periodicities in solar indices were reflected in the foF2 series, but in different relative proportions at the three locations, probably due to the interference of local aerodynamical effects. Some other periodicities were common to solar indices and foF2, while some others were present in the solar indices but not in foF2, or vice versa. 相似文献
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A correlation analysis shows that the sunspot numbers at the peaks of the last eight solar cycles are well-correlated with the sunspot numbers in heliolatitudes 20°–40° (specially in the southern hemisphere) occurring in the solar minimum years immediately preceding the solar maximum years.On leave from Physical Research Laboratory, Ahmedabad, India. 相似文献
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The model of stellar origin of the anomalous component in the low energy cosmic rays for He to Fe ions observed in space vehicles is studied in the light of recent results. The model of heliospheric origin by Fisket al which has several attractive features cannot explain the long-term variations of intensity observed during 1974 to 1978 as pointed out by Nagashima and Morishita. The stellar origin model of Durgaprasad and Biswas, on the other hand, can easily account for the sudden appearance of the anomalous component in 1972 and its large decrease in intensity in 1978 on the basis of polarity reversal of the solar magnetic field as discussed by Nagashima and Morishita (1980). In this work, we show that in the stellar model energetic ions of He, C, N, O, etc. could originate in O-type stars which manifest very strong stellar wind with mass loss rate of 3·10?6 M⊙ per year. These have terminal velocities of about 1200 to 4000 km/sec and are typically a few times their escape velocity. These velocities correspond to ion energies of 10 to 100 keV/amu. These ions are in partly ionised state and are accelerated in the interstellar shock fronts to about 1 to 50 MeV/amu and thus account for the observed anomalous component of low energy cosmic rays. 相似文献
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B. R. Arora A. Rigoti I. Vitorello A. L. Padilha N. B. Trivedi F. H. Chamalaun 《Pure and Applied Geophysics》1998,152(2):349-375
—Magnetovariational fields recorded by an array of magnetometers in the equatorial region of north-northeast Brazil are analyzed to infer the configuration of internal induced currents in and around the extensive intracratonic Parnaíba basin. Only nighttime magnetovariational fields were used because of the prevailing uniform source field conditions. For periods exceeding 40 min. the vertical fields at all inland sites are dominated by the effects of electric currents originating in the northeast, in the deep Atlantic Ocean. Below this period, although best developed in the 12–15 min. period range, the anomalous signatures are principally controlled by two distinct continental current paths. The first is associated with a N60°E trending graben-like structure in the southeastern part of the basin (named the Parnaíba Basin Conductivity Anomaly—PBCA) and the second appears as a subsurface sedimentary channel, from the NW corner of the array to the central part of the basin. This is named the LINK anomaly, as it connects the northwestern Marajó basin with the Parnaíba basin. While the PBCA is shown to highlight the importance of basement tectonics in the geological evolution of the Parnaíba basin, the LINK anomaly provides strong geophysical evidence of the direction of the sea intrusion into the region of the basin and possibly indicates the connectivity of the Parnaíba basin to the adjoining Amazon basin through the Marajó basin. Frequency and polarization dependence suggest that the induction response of individual structures is not determined by the local conductivity alone but also by their interconnectivity as well as by their linkage to the continental shelf and deep oceanic region. 相似文献
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