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1.
Arild Gulbrandsen 《Planetary and Space Science》1973,21(11):2003-2011
Attention is drawn to the great statistical material on geomagnetic storms and solar activity, published mainly before the space age. By analyses of this material in connection with established correlations between geomagnetic activity and the interplanetary sector struc- ture, valuable information might be obtained that would significantly contribute to an increased understanding of solar and interplanetary sector magnetism.As an illustration of this, different analyses of solar-geomagnetic correlations have been considered in relation to the paper by Wilcox and Colburn (1972) on the observed sector struc- ture. Indications are found that (a) the interplanetary and solar sector pattern in the years 1919–1969 consisted of mainly 2 or 4 sectors per solar rotation, and (b) sector boundaries are related to bipolar magnetic regions on the Sun. 相似文献
2.
It is suggested that the observed differences in the periods of variation of some solar phenomena (solar brightness, appearance of sunspot maximum and interplanetary sector structure) occurring close to 27 days are due to differences in the rotation periods of the solar regions in which these phenomena are originated. Changes in periods during the solar cycle can be attributed to changes in the solar energy generation. On the basis of these considerations changes in the sign of the gradient of the Sun's angular velocity can be expected. 相似文献
3.
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
4.
P. Venkatakrishnan 《Solar physics》1982,81(1):193-195
The observed effects of solar flares and interplanetary sector crossings seem to indicate that particle precipitation in the Earth's upper atmosphere decreases cyclonic activity in the troposphere. As an extrapolation to longer term effects, it is suggested that the recurrence of prolonged periods of enhanced solar wind particle precipitation in the upper atmosphere during alternate solar minima could cause the recurrence of extreme droughts. 相似文献
5.
A phenomenological model of the interplay between the polar magnetic fields of the Sun and the solar sector structure is discussed. Current sheets separate regions of opposite polarity and mark the sector boundaries in the corona. The sheets are visible as helmet streamers. The solar sector boundary is tilted with respect to central meridian, and boundaries with opposite polarity change are oppositely tilted. The tilt of a given type of boundary [(+, ?) or (?, +)] changes systematically during the sunspot cycle as the polarity of the polar fields reverses. Similar reversals of the position of the streamers at the limbs takes place. If we consider (a) a sunspot cycle where the northern polar field is inward (?) during the early part of the cycle and (b) a (+, ?) sector boundary at central meridian then the model predicts the following pattern; a streamer at high northern latitudes should be observed over the west limb together with a corresponding southern streamer over the east limb. The current sheet runs now NW-SE. At sunspot maximum the boundary is more in the N-S direction; later when the polar fields have completed their reversal the boundary runs NE-SW and the northern streamer should be observed over the east limb and the southern streamer over the west limb. Observational evidence in support of the model is presented, especially the findings of Hansen, Sawyer and Hansen and Koomen and Howard that the K-corona is highly structured and related to the solar sector structure. 相似文献
6.
The possible relation between type I noise active regions and the polarity distribution of the interplanetary magnetic field is examined for the period from 13 March to 21 August, 1968 (Solar Rotation Numbers 1842–1847) by using data from ground-based and satellite observations. In general four type I radio regions appeared during each solar rotation period except for Rotation No. 1842. The number of type I regions is the same as the number of sector boundaries. This result suggests that the configuration of the photospheric magnetic field extending into the interplanetary space may be related to the origin of the type I radio regions. Statistically the passage of the sector boundaries is delayed by approximately 5 days after the central meridian passage of the type I noise regions on the solar disk.The position of the source of the sector boundaries and its relation to the type I radio regions are investigated by taking into account the mean bulk velocity of solar winds as observed by space probes. A model of the large-scale structure of type I radio regions and their relation to the sector structure of the magnetic field as observed in the interplanetary space is briefly discussed.NASA Research Associate at the University of Maryland. 相似文献
7.
The persistent large-scale coronal magnetic structure associated with a sector boundary appears to consist of a magnetic arcade loop structure extending from one solar polar region to the other in approximately the north-south direction. This structure was inferred from computed coronal magnetic field maps for days on which a stable magnetic sector boundary was near central meridian, based on an interplanetary sector boundary observed to recur during much of 1968 and 1969. 相似文献
8.
The solar wind velocity near Earth shows systematic structure in and around the heliospheric current sheet. The solar wind velocity measurements at IMF sector boundary crossings at 1 AU during 1972–1977 have been used to infer the azimuthal structure of the solar wind velocity in the current sheet. We found that the solar wind velocity in the in-ecliptic portion of the current sheet varies from longitude to longitude, where it originates from the corona. Also, the yearly average value of solar wind velocity in the HCS is found to vary with the phase of the solar cycle; with a maximum value around 1974. TheK-corona brightness on the source surface corresponding to the IMF sector boundary crossings during the period of study also shows a similar but opposite pattern of variation when the data are averaged over a long period. However, this relation is not observed when we considered them individually. So, we conclude that there exists a longitudinal variation of solar wind velocity in the heliospheric current sheet. 相似文献
9.
Distributions of the tangential discontinuity (TD) in the solar wind sector structure are investigated on the basis of the magnetic field data and the ion plasma parameters from the Explorer 33 satellite from 23 January to 23 March 1968. The TD is separated from the observed field fluctuations by calculating the direction of the plasma flow and also the direction of the minimum field fluctuation with respect to the ambient magnetic field direction.It is found that the TD is formed by the thin layered field-aligned currents (the current sheets), and that the TD is predominantly built up in the leading edge of the solar wind where the compression of the plasma and the magnetic field takes place.It is suggested that the current sheets might be locally generated in the leading edge in the turbulent conditions arising from collisions between the fast- and the slow-stream of the solar sector structure. 相似文献
10.
Paul F. Fougere 《Planetary and Space Science》1974,22(8):1173-1184
Inferred solar sector polarity given by the AC index of Svalgaard, has been intensively studied as a single time series and as a time series correlated with geomagnetic and solar activity. Power auto-spectra of the AC index yield a highly significant harmonic series with fundamental at 27 days period and possessing clear harmonics up to the sixth; and a very prominent peak at a period of 1 yr. The 27 day harmonic series clearly indicates the solar control of the index while the 1-yr period might be taken as confirmation of the work of Rosenberg and Coleman to the effect that the sector pattern observed on Earth depends upon Earth's heliographic latitude which has a 1-yr period.Cross correlation analysis and superposed epoch analysis are used to show that sectors inferred to be positive or away are associated with low geomagnetic and solar activity whereas sectors inferred to be negative or toward exhibit significantly enhanced geomagnetic and solar activity.These results appear to be in conflict with superposed epoch analyses by Wilcox and Ness using satellite observed sector polarities which showed that geomagnetic activity increased after passage of a sector boundary, independent of the nature, whether + ? or ? + of the boundary.The conflict is resolved here by noting that the yearly correlation coefficient, at zero time lag, between inferred sector structure and geomagnetic activity averaged about 0·5 for the year 1927–1958, dropped to low values by 1960, recovered by 1962 and then dropped sharply in 1963 by an order to magnitude; the correlation has remained essentially zero ever since. Thus, the satellite results, all obtained post 1963, would not show increased activity during either sector sign.The results cast doubt upon the accuracy of the early ‘inferred’ sector polarities because it is felt that the only simple explanation for the strange behavior of the correlation coefficient lies in some artifact of the data. 相似文献
11.
Phil H. Dittmer 《Solar physics》1975,41(1):227-231
A superposed epoch analysis of 1964–1970 solar flares shows a marked increase in flare occurrence within a day (13° of longitude) of (- +) solar sector boundaries as well as a local minimum in flare occurrence near (+ -)sector boundaries. This preference for (- +) boundaries is more noticeable for northern hemisphere flares, where these polarities match the Hale polarity law, but is not reversed in the south. Plage regions do not show such a preference. 相似文献
12.
A. A. Ruzmaikin 《Solar physics》1985,100(1-2):125-140
The basic features of the solar activity mechanism are explained in terms of the dynamo theory of mean magnetic fields. The field generation sources are the differential rotation and the mean helicity of turbulent motions in the convective zone. A nonlinear effect of the magnetic field upon the mean helicity results in stabilizing the amplitude of the 22-year oscillations and forming a basic limiting cycle. When two magnetic modes (with dipole and quadrupole symmetry) are excited nonlinear beats appear, which may be related to the secular cycle modulation.The torsional waves observed may be explained as a result of the magnetic field effect upon rotation. The magnetic field evokes also meriodional flows.Adctual variations of the solar activity are nonperiodic since there are recurrent random periods of low activity of the Maunder minimum type. A regime of such a magnetic hydrodynamic chaos may be revealed even in rather simple nonlinear solar dynamo models.The solar dynamo gives rise also to three-dimensional, non-axisymmetric magnetic fields which may be related to a sector structure of the solar field. 相似文献
13.
M.S. Bobrov 《Planetary and Space Science》1979,27(12):1461-1467
It is found that from the viewpoint of the magnetic field configuration there are only two types of solar wind: streams with closed field lines (flare-induced streams) and streams with open field lines (M-streams of various velocity and lifetime, and quiet solar wind). We emphasize that in the absence of flare-induced streams the Earth's magnetosphere is, as a rule, circum-flown not by a quiet but by a variably disturbed solar wind—M-streams. An important feature of M-streams is that within a given interplanetary magnetic field sector the sign (+ or −) of the stream magnetic field almost always coincides with that of the sector. These facts lead to the conclusion that M-streams are mainly responsible for the sector structure. 相似文献
14.
The orientations of tangential discontinuities seen by Mariner 4 are interpreted as implying a sector dependent asymmetry in the north-south component of the solar-wind flow. In two sectors, fast solar wind streams had a southward motion relative to slow streams, in one sector the reverse obtained, and in the remaining sector the asymmetry was not clearly defined. We interpret this as being due to greater pressure in the north hemisphere in two sectors and greater pressure in the south hemisphere in one. It is possible this asymmetry could produce a small average southward magnetic field component. 相似文献
15.
A Hale solar sector boundary is defined as the half (northern hemisphere or southern hemisphere) of a sector boundary in which the change of sector magnetic field polarity is the same as the change of polarity from a preceding spot to a following spot. Above a Hale sector boundary the green corona has maximum brightness, while above a non-Hale boundary the green corona has a minimum brightness. The Hale portion of a photospheric sector boundary tends to have maximum magnetic field strength, while the non-Hale portion has minimum field strength. 相似文献
16.
The relationship between coronal green line emission and solar sector magnetism has been studied statistically for the years 1965–1969. This period includes the rising portion and the maximum phase of solar cycle no. 20. In the years around solar maximum the results suggest the existence of longitudinal magnetic arcades at the solar sector boundaries. The arcades extend from at least 50°N to 50°S and are flanked by north-south oriented coronal holes about 90° apart. In the rising portion of the cycle the general picture consists of a high green line intensity structure to the west of the boundary and a region of low intensity several days wide to the east of it.Analyses of the calcium plage distribution in the years 1962–1969 show that, on the average, there is a tendency for the plage activity to peak near the sector boundaries. It is further concluded that the activity distribution suggested by Wilcox (1971a, b) is not typical of the behaviour of solar activity relative to the sector boundaries. 相似文献
17.
The brightness temperature distributions of the solar atmosphere in the polar region at the distances from one to two solar radii during the solar activity minimum are reported. Observations of the maximum phase of the solar eclipse of March 29, 2006 were carried out simultaneously on two sectors of the RATAN-600 radio telescope over a wide range of centimeter waves, 1–31 cm. This study is based on a comparison of models and observations carried out on the northeastern sector of the RATAN-600. 相似文献
18.
The hydrodynamic equations which describe the radial solar wind expansion are linearized and specialized to treat corotating perturbations. Approximate solutions are found which are time stationary in the corotating reference frame. The solutions predict the behavior of corotating structures for a given boundary condition close to the sun. In particular, the structure resulting from the interaction of fast and slow streams is described. Comparison with sector structure data shows reasonable qualitative and quantitative agreement. 相似文献
19.
M. P. Nakada 《Solar physics》1970,14(2):457-479
Effects of diffusion on the composition of the solar corona and solar wind have been examined. Multi-component diffusion equations have been solved simultaneously in attempts to account for the flux of He and heavier elements in the solar wind. Large enhancements of these elements at the base of the assumed isothermal corona appear to be required to give observed fluxes. Coronal conditions and solar wind fluxes that might account for the diffusive presence of Fe at high altitudes have been studied. 相似文献
20.
Valery P. Mikhailutsa 《Solar physics》1995,159(1):29-44
The evolution of the background magnetic field with the solar cycle has been studied using the dipole-quadrupole magnetic energy behaviour in a cycle. The combined energy of the axisymmetric dipole, non-axisymmetric quadrupole, and equatorial dipole is relatively lowly variable over the solar cycle. The dipole field changed sign when the quadrupole field was near a maximum, andvice versa. A conceptual picture involving four meridional magnetic polarity sectors proposed to explain these features may be in agreement with equatorial coronal hole observations. The rate of sector rotation is estimated to be 8 heliographic degrees per year faster than the Carrington rotation (P = 27.23d synodic). Polarity boundaries of sectors located 180° apart show meridional migrations in one direction, while the boundaries of the other two sectors move in the opposite direction. A simple model of how the magnetic field energy varies, subject to specifying reasonable initial photospheric magnetic and velocity field patterns, follows the observed evolution of the dipole and quadrupole field energies quite nicely. 相似文献