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1.
Ester Antonucci 《Solar physics》1974,34(2):471-476
A cross-correlation analysis of coronal green line intensity (5303 Å) and interplanetary magnetic field polarity for the period 1947–1970 shows that the coronal features are organized in a constant pattern with respect to the 4-sector structure through the solar cycle. A sudden inversion of the coronal pattern with respect to the sector structure takes place at the solar minima. The high emission regions of the green corona are located near the solar magnetic sector boundaries having polarities (?, +), (+, ?), (?, +) during cycles 18, 19, 20 respectively in the northern hemisphere, and (+, ?), (?, +), (+, ?) in the southern hemisphere. 相似文献
2.
Arild Gulbrandsen 《Planetary and Space Science》1973,21(4):703-707
An analysis on the variation of coronal λ5303 intensity relative to the solar magnetic sector boundaries is presented. The location of the boundaries has been extrapolated from the observed interplanetary sector structure. The results indicate that in the years 1962–1964 the solar activity is in general high to the west and low to the east of a solar sector boundary. Such a distribution of solar activity contradicts with the one assumed up to now. Nevertheless, this distribution is in general in agreement with results of investigations on the correlation between solar and geomagnetic activity. 相似文献
3.
Photospheric and heliospheric magnetic fields 总被引：1，自引：0，他引：1
The magnetic field in the heliosphere evolves in response to the photospheric field at its base. This evolution, together with the rotation of the Sun, drives space weather through the continually changing conditions of the solar wind and the magnetic field embedded within it. We combine observations and simulations to investigate the sources of the heliospheric field from 1996 to 2001. Our algorithms assimilate SOHO/MDI magnetograms into a flux-dispersal model, showing the evolving field on the full sphere with an unprecedented duration of 5.5 yr and temporal resolution of 6 hr. We demonstrate that acoustic far-side imaging can be successfully used to estimate the location and magnitude of large active regions well before they become visible on the solar disk. The results from our assimilation model, complemented with a potential-field source-surface model for the coronal and inner-heliospheric magnetic fields, match Yohkoh/SXT and KPNO/He?10830 Å coronal hole boundaries quite well. Even subject to the simplification of a uniform, steady solar wind from the source surface outward, our model matches the polarity of the interplanetary magnetic field (IMF) at Earth ～3% of the time during the period 1997–2001 (independent of whether far-side acoustic data are incorporated into the simulation). We find that around cycle maximum, the IMF originates typically in a dozen disjoint regions. Whereas active regions are often ignored as a source for the IMF, the fraction of the IMF that connects to magnetic plage with absolute flux densities exceeding 50 Mx cm?2 increases from ?10% at cycle minimum up to 30–50% at cycle maximum, with even direct connections between sunspots and the heliosphere. For the overall heliospheric field, these fractions are ?1% to 20–30%, respectively. Two case studies based on high-resolution TRACE observations support the direct connection of the IMF to magnetic plage, and even to sunspots. Parallel to the data assimilation, we run a pure simulation in which active regions are injected based on random selection from parent distribution functions derived from solar data. The global properties inferred for the photospheric and heliospheric fields for these two models are in remarkable agreement, confirming earlier studies that no subtle flux-emergence patterns or field-dispersal properties are required of the solar dynamo beyond those that are included in the model in order to understand the large-scale solar and heliospheric fields.
相似文献4.
Analysis of the green line corona for the interval 1947–1970 suggests the existence of largescale organization of the emission. The green line emission at high northern latitudes (≈ 40°–60°) is correlated with the emission at high southern latitudes 6, 15 and 24 days later, while the low latitude green corona seems to be correlated on both sides of the equator with no time lag. These coronal features are recurrent with a 27-day period at all latitudes between ± 60 °, and we associate these large-scale structures with the solar magnetic sector structure. The high correlation between northern and southern high-latitude emission at 15 days time lag is explained as a signature of a two-sector structure, while four sectors are associated with the 6 and 24 day peaks. 相似文献
5.
G. D. Parker 《Solar physics》1973,31(1):259-269
The coronal green line intensity is inappropriate for correlation studies of galactic cosmic ray variations. Being a non-monotonic function of coronal temperature, the green line intensity is a good index of neither coronal temperature nor solar wind speed. A more appropriate measure of coronal activity is the intensity of the electron corona. Two-dimensional observations of the K-corona trace changes in coronal morphology during the solar cycle. An index based on four years of K-coronal measurements made in Hawaii shows that activity in the lower corona is not better correlated than sunspot number with long-term modulation. Correlation analysis defines the time lag of modulation much too poorly to permit its use in estimating the size of the heliosphere. 相似文献
6.
7.
In the declining phase of solar cycle 20 (1970–74) three pulses of activity occurred and resulted in two well defined ‘stillstands’ in the smoothed means of sunspot, 2800 MHz, and calcium plage data. Marked diminutions in spot and 2800 MHz flux took place in 1970 and 1971, respectively, and were accompanied by concomitant decreases in flare-occurrence. Studies of the latitude distribution of spots and flares show the extent of the dominance of the northern hemisphere in cycle 20 and the marked phase shift between northern and southern hemispheres. In the years studied, the longitudes of centers of activity clustered in identifiable zones or hemispheres for relatively long intervals of time. From mid-1973 to mid-1974 the Sun had a relatively inactive hemisphere centered on ～0° longitude. The relationship of certain well defined ‘coronal holes’ to this inactive hemisphere of the chromosphere is noted. The first two spot groups of the new cycle formed in November 1974 and January 1975 in the longitude zone associated with relatively high levels of old cycle activity, a repetition of the pattern observed in 1963–64. 相似文献
8.
Doppler shift measurements on the green coronal line—evidence for largescale macroscopic mass motion
Fabry-Perot interferometric observations on the green coronal line (λ 5303 å) carried out during the total solar eclipse of 1980 February 16 have yielded relative Doppler shift velocities with an accuracy of ± 7 km s-1. The values show a peak in the 30–50 km s-1 range indicating largescale macroscopic mass motion in the solar maximum corona. 相似文献
9.
The intensity of Fe XIV 530.3-nm green coronal line is compared quantitatively with the strength of magnetic fields of small and large scales and also with total sunspot areas for 1977–2001. A degree of similarity of appropriate synoptic maps is evaluated using correlation analysis. The green line intensity maps are constructed from data of its daily monitoring. Strengths of magnetic fields are calculated in a potential approximation using the photosphere observations of Wilcox Solar Observatory for a distance of 1.1 The calculations are performed separately for fields of large and small spatial scales. The total area of sunspots is obtained using data from the Greenwich Catalogue and its continuation by USAF/NOAA. The correlation has been calculated for the aggregate of areas (with a size of 20° in latitude and 30° in longitude) coinciding spatially on all maps. It is found that the most correlation between the green line intensity and coronal fields of small scales is observed in a zone of 0°–20°. The correlation with total sunspot areas (i.e., with local fields at the photosphere level) is substantially less here. In the higher-latitude zone 20°–40°, correlation of the green-line intensity with spot areas and small-scale coronal fields decreases. The large-scale fields have little influence on the green-line emission in the spot-formation zone. These results are the evidence of a complex nature of the effect of different-scale fields, arising as a result of dynamo activity in the subsurface (leptocline) and deep-lying (tachocline) layers of the convective zone, on the processes of the Sun’s corona heating and green coronal line emission. 相似文献
10.
The relation between coronal green line intensity and high-speed streams of solar wind emitted by coronal holes or by loop structures of the corona is studied. As well as these exclusive regions of coronal radiative emission, other factors of solar activity have been taken into account in this relation, such as proton events, sunspot number, faculae, and solar magnetic fields.Although the investigated time period (1964–1974) is very short, because of lack of data, we attempted to define the intensity of the coronal green line as an integrated index of the solar activity which can express all the photospheric and coronal phenomena of the Sun. The contraction of the low-density coronal-hole regions and the presence of bright loops during solar maximum provide a theoretical explanation of the above-mentioned relation. 相似文献
11.
Relation of the coronal green line intensity to magnetic fields and sunspot areas in the solar cycle
The intensity of the green coronal Fe XIV λ530.3-nm line is correlated with sunspot areas and the magnetic field strength calculated for a distance of 1.1R ⊙. The relation of the green line emission to large-scale and local magnetic fields is shown to change differently with cycle phase. Large-scale coronal magnetic fields play a decisive role at the ascending phase, while a slightly higher correlation of the green line intensity with the local magnetic fields of sunspots is observed at the descending phase. Our results can be used to construct and test various solar coronal heating models. 相似文献
12.
NSO Sacramento Peak Caii K images are analyzed for the years 1992 through September 1996 with about a 50% coverage. The plage, decayed plage, enhanced network, and quiet-Sun features are identified on each image with an algorithm that uses the criteria of intensity, size, and filling factor. These algorithms can be adapted for analyzing spectroheliograms from ground-based or space-based observatories. Plage and enhanced network indices, for these time periods, are shown. We present intensity contrasts for the plage, decayed plage, and enhanced network. We also find that these contrasts, which are an average of the structures intensity relative to the quiet Sun over the whole disk, remain essentially constant over the solar cycle. 相似文献
13.
H. Daene 《Astronomische Nachrichten》1966,289(6):279-283
It is shown from measurements of type III bursts at 234 MHz, III MHz and 23 MHz during the foregoing solar cycle that the type III activity has a relative minimum in 1959 and apparently a second maximum in 1960. This is in accordance with the statement of GNEVYSHEV relating at first to the intensity of the green coronal line. He also pointed out that the second maximum is closely correlated to some terrestrial features. It can be stated from a comparison of the three observing frequencies that the lowest frequency corresponding to the highest coronal level shows the strongest enhancement of type III activity during the second part of the solar cycle. By an indirect method it can be concluded that the percentage of polarized bursts at low levels is well correlated with the WOLF number. The suggestion is discussed that type III activity is not only an attendant effect of solar activity but it is also connected more directly with terrestrial features by contribution to the solar wind. 相似文献
14.
The power spectra of the daily peak electron content measured at Hawaii are estimated via covariance estimations, bivariate autoregressive estimations and fast Fourier transforms for a year of data close to minimum solar activity (1965) and a year of data close to maximum solar activity (1969). The strong peaks about 6 days and 15 days in the 1965 and 1969 power spectra, respectively, suggest an influence of the interplanetary magnetic sector structure on the electron content at low latitude (21·3°N, geographic). The daily solar flux (Sa) at 2800 MHz of 1965 and 1969 are analysed similarly. The decrease in energy content with period range of 3–7 days in the 1969 Sa power spectrum supports the above point of view. 相似文献
15.
A green line intensity variation is associated with the interplanetary and photospheric magnetic sector structure. This effect depends on the solar cycle and occurs with the same amplitude in the latitude range 60° N–60° S. Extended longitudinal coronal structures are suggested, which indicate the existence of closed magnetic field lines over the neutral line, separating adjacent regions of opposite polarities on the photospheric surface.Supported by an ESRO/NASA fellowhip.On leave from Torino University, Italy; now at Istituto di Fisica, Universita di Torino, Italy. 相似文献
16.
D.S. Peacock 《Planetary and Space Science》1973,21(10):1661-1670
In recent years several papers have indicated that the solar coronal green line emission (λ=5303Å) is the ‘best’ indicator of cosmic ray modulation. This paper questions this result for the following reasons: (a) the problems of green line measurement obscure the true meaning of the resulting observations; (b) there is a lack of any direct physical mechanism relating green line intensity and modulation; (c) a negative result came from a careful attempt to relate the cosmic ray diurnal variation and green line emission. 相似文献
17.
The analysis of the daily measurements of the coronal green line intensity, which have been extensively tested for homogeneity and freedom of trends observed at the Pic-du-Midi observatory during the period 1944–1974, has revealed some characteristic asymmetric variations. A north-south asymmetry of the green line intensity is the main feature of the period 1949–1971 while a south-north one is obvious within 1972–1974 and the minor statistical significance span 1944–1948. On the other hand a significant W-E asymmetry has been confirmed in the whole period 1944–1974. It is noteworthy that the period 1949–1971, where the N-S asymmetry takes place consists a 22-yr solar cycle which starts from the epoch of the solar magnetic field inversion of the solar cycle No. 18 and terminates in the relevant epoch of the cycle No. 20.The combination of N-S and S-N asymmetry with a W-E one makes the NW solar-quarter to appear as the most active of all in the 22-yr cycle 1949–1971, while in the periods 1944–1948 and 1972–1974 the SW quarter is the most active. Finally, from the polar distribution of the green line intensity has been derived that the maximum values of the asymmetries occur in heliocentric sectors ± 10°–20° far from the solar equator on both sides of the central meridian.Physical mechanisms which could contribute to the creation of both N-S and E-W asymmetries of the solar activity and the green line intensity as an accompanied event, like different starting time of an 11-yr solar cycle in the two solar hemispheres, the motion of the Sun towards the Apex, and short-lived active solar longitudes formed by temporal clustering of solar active centers, have been discussed. 相似文献
18.
Prediction of the exact date of the maximum of the 11-year solar activity cycle is a matter of disagreement among solar scientists
and of some importance to satellite operators, space-system designers, etc. Most predictions are based on physical conditions
occurring at or before the solar-cycle minimum preceding the maximum in question. However, another indicator of the timing
of the maximum occurs early in the rise phase of the solar cycle. A study of the variation over two previous solar cycles
of coronal emission features in Fe xiv from the National Solar Observatory at Sacramento Peak has shown that, prior to solar
maximum, emission features appear above 50° latitude in both hemispheres and begin to move towards the poles at a rate of
8° to 11° of latitude per year. This motion is maintained for a period of 3 or 4 years, at which time the emission features
disappear near the poles. This phenomenon has been referred to as the `Rush to the Poles'. These observations show that the
maximum of solar activity, as seen in the sunspot number, occurs approximately 19 ± 2 months before the features reach the
poles. In 1997, Fe xiv emission features appeared near 55° latitude, and began to move towards the poles. Using the above
historical data from cycles 21 and 22, we will see how the use of progressively more data from cycle 23 affects the prediction
of the date of solar maximum. The principal conclusion is that the date of solar maximum for cycle 23 could be predicted to
within 6 months as early as 1997. For solar cycle 24, when this phenomenon first becomes apparent later this decade, the average
parameters for cycles 21–23 can be used to predict the date of solar maximum. 相似文献
19.
Maurizio Ternullo 《Solar physics》1987,112(1):143-151
This work is a study of the rotational properties of the solar calcium plages, during the time interval 1967–1977; only plages older than 4 days have been the object of this research. We have looked systematically for any significant change occurring during the course of the solar cycle, and any kind of ‘anomaly’ or fine structure in the differential rotation latitudinal profile. We find that such a profile undergoes a cyclic transformation, making it assume the highest steepness at the solar maximum; a sudden flattening then occurs in the first years of declining activity; the last years of the cycle, as the first years of the next one, are characterized by intermediate steepness values. Moreover, we find that, in spite of the general belief that the angular rotation rate is continuously decreasing with increasing heliographic latitude, at least two inversions do exist of such an overall tendency:
- A narrow, minimal angular-rotation-rate strip lies very close to the equatorward margin of the plage production band; this feature shifts continuously, in a wave-like manner, throughout the solar cycle, from 15/18° to 3/6° latitude.
- A narrow, maximal angular-rotation-rate strip has been observed lying in the neighbourhood of the poleward margin of the activity band; a process of continuous transformation of the rotation rate profile is always active, in a narrow latitude strip on the equatorward side of such a feature, generating new features of the same kind, which replace the older ones, that disappeared due to the equatorward shift of the plage zone. All that simulates an equatorward shift of the observed ‘anomalies’; we observed them until the minimum activity epoch (1976), at 15/18° latitude. Some relations of these features with both torsionai waves (Howard and LaBonte, 1980) and magnetic activity are briefly discussed.
20.
Werner M. Neupert 《Solar physics》1998,177(1-2):181-190
Using extreme ultraviolet (EUV) images of the solar corona, we have carried out a region-by-region study of the association of coronal emission of Feix–Fexvi with Caii K plage areas and intensities reported in Solar-Geophysical Data. We find that emission is dependent on the area and brightness of the plage, with specific correlations varying with the temperature of formation of the emitting coronal ion. If confirmed and extended, this approach may provide a means of estimating coronal EUV levels associated with solar activity and ultimately a proxy method that is more accurate than the sole use of the centimetric radio flux for estimating the coronal component of solar EUV emission. 相似文献