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1.
We study the solar cycle evolution during the last 8 solar cycles using a vectorial sunspot area called the LA (longitudinal asymmetry) parameter. This is a useful measure of solar activity in which the stochastic, longitudinally evenly distributed sunspot activity is reduced and which therefore emphasizes the more systematic, longitudinally asymmetric sunspot activity. Interesting differences are found between the LA parameter and the more conventional sunspot activity indices like the (scalar) sunspot area and the sunspot number. E.g., cycle 19 is not the highest cycle according to LA. We have calculated the separate LA parameters for the northern and southern hemisphere and found a systematic dipolar-type oscillation in the dominating hemisphere during high solar activity times which is reproduced from cycle to cycle. We have analyzed this oscillation during cycles 16–22 by a superposed epoch method using the date of magnetic reversal in the southern hemisphere as the zero epoch time. According to our analysis, the oscillation starts by an excess of the northern LA value in the ascending phase of the solar cycle which lasts for about 2.3 years. Soon after the maximum northern dominance, the southern hemisphere starts dominating, reaching its minimum some 1.2–1.7 years later. The period of southern dominance lasts for about 1.6 years and ends, on an average, slightly before the end of magnetic reversal. 相似文献
2.
Photospheric magnetic fields were studied using the Kitt Peak synoptic maps for 1976?–?2003. Only strong magnetic fields (B>100 G) of the equatorial region were taken into account. The north–south asymmetry of the magnetic fluxes was considered as well as the imbalance between positive and negative fluxes. The north–south asymmetry displays a regular alternation of the dominant hemisphere during the solar cycle: the northern hemisphere dominated in the ascending phase, the southern one in the descending phase during Solar Cycles 21?–?23. The sign of the imbalance did not change during the 11 years from one polar-field reversal to the next and always coincided with the sign of the Sun’s polar magnetic field in the northern hemisphere. The dominant sign of leading sunspots in one of the hemispheres determines the sign of the magnetic-flux imbalance. The sign of the north–south asymmetry of the magnetic fluxes and the sign of the imbalance of the positive and the negative fluxes are related to the quarter of the 22-year magnetic cycle where the magnetic configuration of the Sun remains constant (from the minimum where the sunspot sign changes according to Hale’s law to the magnetic-field reversal and from the reversal to the minimum). The sign of the north–south asymmetry for the time interval considered was determined by the phase of the 11-year cycle (before or after the reversal); the sign of the imbalance of the positive and the negative fluxes depends on both the phase of the 11-year cycle and on the parity of the solar cycle. The results obtained demonstrate the connection of the magnetic fields in active regions with the Sun’s polar magnetic field in the northern hemisphere. 相似文献
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We study the longitudinal distribution of sunspot activity in 1917–1995 using vector sums of sunspot areas. The vector sum
of sunspots of one solar rotation gives a total vector whose amplitude characterizes the size of longitudinal asymmetry and
whose phase describes the location of the momentarily dominating longitude. We find that when the phase distributions are
calculated separately for the ascending phase and maximum (AM) on the one hand and for the declining phase and minimum (DM)
on the other hand, they behave differently and depict broad maxima around roughly opposite longitudes. While the maximum of
the phase distribution for the AM period is found around the Carrington longitude of 180°, the maximum for the DM period is
at the longitude of about 0°. This difference can be seen in both solar hemispheres, but it is more pronounced in the southern
hemisphere where the phase distribution has a particularly clear pattern. No other division of data into two intervals leads
to similar systematic differences. 相似文献
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Time variations in strong and weak photospheric magnetic fields have been considered based on synoptic maps from the Kitt Peak observatory for 1976?C2003. The magnetic fields of positive and negative polarities of the Northern and Southern hemispheres of the Sun and their imbalance were studied. It has been indicated that different groups of magnetic fields vary with 11-or 22-year periods depending on their values. The difference between positive and negative fluxes for each hemisphere always varies with a 22-year period. For weak fields, the 22-year cycle is related to the manifestation of the global solar magnetic field. For strong fields, the imbalance between positive and negative fluxes reflects the predominant role of leading sunspots in a given solar hemisphere. It has been detected that the total magnetic flux over the entire solar disk varies with an 11-year period in antiphase with the solar activity cycle for the weakest magnetic fields (0?C5 G). 相似文献
7.
Synoptic maps for 1976–2003 obtained at the Kitt Peak National Solar Observatory are used to analyze the longitudinal distribution
of the solar photospheric magnetic field. The superposition of synoptic maps gives different pictures for the rise-maximum
phase and the decline-minimum phase. Two characteristic periods correspond to different situations in the 22-year solar magnetic
cycle in the course of which both the global magnetic field and the magnetic field of the leading sunspot in a group change
their sign. 相似文献
8.
Vernova E. S. Tyasto M. I. Baranov D. G. Danilova O. A. 《Geomagnetism and Aeronomy》2018,58(8):1136-1143
Geomagnetism and Aeronomy - The distribution of positive and negative photospheric fields is considered based on the synoptic maps of the photospheric magnetic field from the National Solar... 相似文献
9.
Vernova E. S. Tyasto M. I. Baranov D. G. Danilova O. A. 《Geomagnetism and Aeronomy》2019,59(8):1029-1035
Geomagnetism and Aeronomy - The longitudinal asymmetry of the photospheric magnetic field distribution is studied based on data from the Kitt Peak National Solar Observatory (synoptic maps for... 相似文献
10.
Longitudinal distributions of the photospheric magnetic field studied on the basis of National Solar Observatory (Kitt Peak)
data (1976 – 2003) displayed two opposite patterns during different parts of the 11-year solar cycle. Helio-longitudinal distributions
differed for the ascending phase and the maximum of the solar cycle on the one hand and for the descending phase and the minimum
on the other, depicting maxima around two diametrically opposite Carrington longitudes (180° and 0°/360°). Thus the maximum
of the distribution shifted its position by 180° with the transition from one characteristic period to the other. Two characteristic
periods correspond to different situations occurring in the 22-year magnetic cycle of the Sun, in the course of which both
global magnetic field and the magnetic field of the leading sunspot in a group change their sign. During the ascending phase
and the maximum (active longitude 180°) polarities of the global magnetic field and those of the leading sunspots coincide,
whereas for the descending phase and the minimum (active longitude 0°/360°) the polarities are opposite. Thus the observed
change of active longitudes may be connected with the polarity changes of Sun’s magnetic field in the course of 22-year magnetic
cycle. 相似文献