[en] Neutrinos from the decay of ⁸B in the Sun have been observed in the Kamiokande-11 detector. Based on 802 live detector days in the time period January 1987 through July 1989, the measured flux for E_e ≥ 9.5 MeV is 0.39 ± 0.09 (stat.) ± 0.07 (syst.) of the value predicted by the standard solar model. The Kamiokande-II result confirms the accuracy of the ³⁷Cl radiochemical experiment, and also the existence of the so called solar neutrino problem. The data suggest with low statistical significance a decrease in the observed ⁸B solar neutrino flux during a 2.5 year interval in which the sunspot rate increased by approximately an order of magnitude. Within experimental errors, no evidence for either a day-night effect or a seasonal variation was found in the present data

[en] A model for high-energy solar flares is presented to explain prompt proton and electron acceleration within 1 sec to relativistic energies. The three-dimensional X-type current loop coalescence, where two crossed flux tubes interact in one point, is a fundamemtally new process as compared to the one- and two-dimensional cases studied earlier. It is shown that the strong implosion can be driven by the magnetic pinch in the region where two current loops interact. The strong inductive electric field can be excited during the implosion. A test-particle orbit under the EM fields derived from the MHD equations is studied. It is also shown that both protons and electrons can be promptly accelerated to about 100 GeV and 100 MeV, respectively. 26 refs

[en] The nature of umbral oscillations is investigated using an empirical model for the sunspot umbra, based on the model of Maltby et al. (1986). Approximating the sunspot as a thick flux tube of circular cross section, the axisymmetric normal modes of magnetoatmospheric waves were determined, and a diagnostic diagram was generated for different field strengths. The diagram shows the existence of avoided crossings in the solution of magnetoatmospheric modes in a sunspot atmosphere. It was found that, for low values of the radial wavenumber k, corresponding to observed oscillations, a simple global classification is not possible. The oscillations in the low photosphere and below are of either fast or mixed type, but tend to acquire a slow or acoustic character above the temperature minimum. 61 refs

[en] The recent observation at the ³⁷Cl experiment suggests that the (anti)correlation between the solar-neutrino flux and the sunspot activity seems to be real. We analyze the characteristic features of the time variation of the solar-neutrino flux in terms of the resonant spin-flavor rotation mechanism. Implications for the ongoing Kamiokande II experiment are discussed

[en] The results of the measurements of the solar wind velocity are presented for heliocentric distances between 3 and 80 solar radii R₀. The solar wind power is given as a function of radial distance R. It is shown that the velocity V increases from 40 to 250 km/s and the power L increases from 10¹⁸ to 3x10¹⁹W, while the distance changes from 8 to 20 R₀. In this region the solar wind velocity is becoming supersonic one. It is shown that large increasing of V and L in the acceleration region is caused by the motion of Alfven waves from the corona, the propagation of waves to the distances of (10-20) R₀ and following nonlinear dissipation

[en] Most large solar flares exhibit hard X-ray emission which is usually impulsive, as well as thermal soft X-ray emission, which is gradual. The beam-driven chromospheric evaporation model of solar flares was proposed to explain the origin of the soft X-ray emitting flare plasma. A careful evaluation of the issue under discussion reveals contradictions between predictions from the theoretical chromospheric evaporation model and actual observations from a set of large X- and M-type flares. It is shown that although the soft X-ray and hard X-ray emissions are a result of the same flare, one is not a result of the other. 33 refs

[en] Recently reported occurrence rates of coronal mass ejections (CMEs) are compared with the time scale for the long-term evolution of the global white light coronal density distribution. This time scale is estimated from the synoptic observations of the corona made from Mauna Loa, Hawaii, by a seies of K-coronameters. The data span a period of more than 20 years and show evolution rates which vary with time roughly in phase with the solar activity cycle. However, there are detailed differences between the sunspot number curve and the long-term behavior of this quantity. When the occurrence rates of CMEs observed from orbiting coronagraphs, available mainly during the descending phase of the activity cycle, are compared with this evolution time, it is found that the two quantities are inversely proportional. From energy considerations, it is unlikely that there is a causal relationship between CMEs and this coronal evolution. Rather, the result indicates that the processes which lead to the global evolution are intimately related to those which give rise to CMEs, a hypothesis consistent with current theories that CMEs arise from preexisting magnetic structures which become stressed by the global magnetic field rearrangement to the point of instability. copyright American Geophysical Union 1989

[en] Brief item

[en] A recently developed three-dimensional Fourier analysis results in the appearance of rings in the power spectrum of solar oscillations. These rings are the cross-sections at constant temporal frequency of trumpet surfaces, and are the analog of the familiar ridges. The shape of the rings provides information on the local dispersion relationship of the oscillations expressed as a simple power law. The exponent and constant in the power law are related to the thermodynamics of the region in the solar interior where the waves propagate. Asymptotic expressions for high-degree modes, coupled with the assumption that the upper part of the solar envelope is an adiabatic polytrope, predict that the exponent should be 1/2. The constant should depend on the polytropic index of the envelope, and on a phase factor resulting from wave leakage. Analysis of over 5000 rings results in an observed exponent ranging between 0.3 and 0.6, a polytropic index between 1 and 7, and a phase factor between -1.5 and 5

[en] The p-mode frequencies exhibit anomalous behaviour at degree 5 and frequencies below 2 mHz. We have investigated the implications of these data, and find no plausible solar model that is consistent with them. A density inversion including the low-degree five-minute data of Jimenez et al. (1988) implies that the density of the solar core is some 10 per cent greater than it is in the standard solar model 1 of Christensen-Dalsgaard (1982). Although that result is in keeping with previous suggestions either that the sun has a greater evolutionary age than is usually supposed or that there is a cloud of weakly interacting massive particles in the solar core and its environs, the behaviour of the sound speed in the core is not consistent with either hypothesis. Both the inferred sound-speed variation, and a secondary inversion for hydrogen abundance, provide some evidence for material redistribution in the energy-generating core. A sound-speed inversion for the entire radiative interior, using also frequencies of low and intermediate degree, confirms the earlier finding that the sound speed in the sun exceeds that of a standard solar model by up to 1 per cent in a region extending some 30 per cent of the solar radius and centred at r ≅ 0.4R. That is consistent with, though does not necessarily imply, that the opacity in the outer layers of the radiative interior at temperatures of up to about 4 x 10⁶K has been underestimated by some 20 per cent