Bipolar Sunspot Groups Research Articles

Solar eclipse observations of a magnetic loop structure at 2, 3.2, 8.2 and 21 cm

During the total eclipse of 1980 February 16, eclipse slope curves at 2, 3.2, 8.2 and 21 cm were obtained as the Moon occulted an active region with a bipolar sunspot group. From the peaks in these curves and the heights of the effective emission layers, the cores of the radio sources at the four wavelengths are located. Connecting these sites gives a magnetic loop structure. Relations between the locations, sizes, fluxes of the radio sources and the intensities, extensions, sizes and shapes of the bipolar sunspot field are analysed. The result at 8.2 cm is similar to the loop structure observed with the VLA at 6 cm. The radio flux spectrum shows that the gyro-radiation dominates over the thermal bremsstrahlung in this active region.

Geometrical relationship of flare-generated solar wind structures to the magnetic axes of bipolar sunspot groups adjacent to their originating solar flares

Occurrences of interplanetary shock waves near the Earth after the powerful isolated flares of 1957–1978 are investigated. The close connection between the occurrences of shock waves and the positions of magnetic axes of bipolar groups of sunspots is suggested on the basis of a statistical study. The shock waves are principally observed when the Earth finds itself near the planes that are projected through the flares in parallel to the appropriate magnetic axes of the nearest bipolar groups. This regularity is interpreted as an indirect argument for a three-dimensional geometry for the interplanetary shock waves which, when projected on these flattened to corresponding planes, are traces of large circular arcs. The typical angular scales of isolated interplanetary shock waves are estimated as ≈ 150° and ≈ 30° parallel and perpendicular, respectively, to the magnetic axes correspondingly.

Flux linkages of bipolar sunspot groups: A computer study

Past studies of the structure of solar magnetic fields have used magnetograph data to compute selected field lines for comparison with the morphology of structures seen in various spectral wavelengths. While those analyses examine one of the integral properties of magnetic fields (field lines), they are not complete since they fail to determine the other important integral property: the boundaries of the flux of field lines of given connectivity. In the present analysis we determine such a system of boundaries, called separatrices, for the current free field of two p-f spot pairs so as to exhibit the line of self-intersection, called the separator. The analysis is compared with previous analytical work. These computer results, confirming earlier studies carried out using iron fillings, show that the separatrix has the form of two intersecting ovoids, defining four flux cells. New features which have emerged from this study include the observation that the projections of the separatrix in a plane perpendicular to the separator at its highest point do not intersect at 90° as has been widely believed, but rather closer to 60° in the case studied. The separator is very nearly circular over most of its length. The two neutral points (B = 0) which appear at the photospheric ends of the separator have the mixed radial-hyperbolic form as expected, a feature requiring every field line lying on the separatrix to connect with at least one of the two neutral points. The rotation of line direction with height (shear) is graphically illustrated in the potential field case studied here. We also exhibit a magnetic arcade.

Note on the asymmetry of bipolar sunspot groups

It is shown that the analytical solution of the equilibrium plasma equation which is a superposition of the axial-symmetric solution and the solution with helical symmetry can describe asymmetry of elements for a bipolar sunspot group.

On the characteristics of the basic framework of solar active regions and the magnetohydrodynamical structure of the convection zone

The characteristics of the basic framework of structure and development of solar active regions are interpreted as good indicators of the magnetohydrodynamical structure of the convection zone, the magnetic field lines of which are twisted and are made wave-like by the action of the very large scale non-axisymmetric convection, called here the global convection. The characteristics discussed in this paper are: (i) the preponderance of preceding spots of bipolar sunspot groups in strength and life time relative to the following spots of the groups, (ii) the tilt of bipolar axes of the sunspot groups to the local parallels of latitude, (iii) the forward inclination of normal axes of sunspots inferred from the east-west asymmetry of the appearance and total area of sunspots, (iv) the faster rotation of sunspots than the averaged fluid rotation, and (v) the association of the characteristics of an active region with the presence of an older active region in its vicinity and with the relative disposition of the two active regions.

Slowly varying component spectrum of the solar radio emission at millimetre wavelengths

This paper deals with the observed data on the solar S-component sources at millimetre wavelengths. The observations were made in 1968 and 1969 using the 22-m radio telescope of the Crimean Astrophysical Observatory at six wavelengths: 2, 4, 6, 8, 13 and 17 mm. The enhanced intensity of the solar active region in comparison with the quiet Sun level varies proportionally to λ−2 if the wavelength λ is within the range of 2 ÷ 6 mm. In the wavelength band of 6 ÷ 17 mm almost flat spectra of the solar S-component sources is observed. Assuming the bremsstrahlung mechanism of the radio emission for the quiet Sun and the solar active regions an attempt has been made to treat the above presented data. It appears that the most probable explanation of the 2 ÷ 6 mm spectrum is that the S-component sources are opaque. In the 6 ÷ 17 mm wavelength band there are two possibilities: the active region may be either transparent or opaque. But in the last case the source brightness temperature must be proportional to λ2. Some differences in the spectra of the sources, identified with flocculi and with bipolar sunspot groups, were mentioned. The cold regions (as compared with the quiet Sun) were observed up to λ = 2 mm and identified with the filaments. However, its visibility falls when the wavelength decreases.

Solar and magnetic data, January to March, 1947, Mount Wilson Observatory

An immense complex bipolar sunspot group. Mount Wilson No. 8438, crossed the solar disk from March 3 to 16. It was the second largest spot group ever recorded, having been surpassed in size only by the great group of February 1946. Group 8438 was a return or at least an outgrowth of a large group, No. 8392, which crossed the solar disk from February 5 to 18.