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[en] The solar wind velocity data were analyzed with the purpose of determining their quasi-biennial oscillations. The solar wind data used had been recorded y probes at the distance of 1 AU from the Sun and they cover the 16-year period from November 1963 to May 1980. Periods of the quasi-biennial oscillations ranging from 1.8 to 2.2 years with an average of 2.0 years were found in the solar wind velocities in that time interval. A tendency for the mean period of the oscillations to decrease was observed: longer periods of about 23-26 Bartels rotations prevailed in the first half of the analyzed time interval (up to Bartels rotation No. 1910) and then in the second part shorter periods of about 21-22 Bartels rotations dominated. In the second half of 1970 a change in the phase of the oscillations was observed. Maximum oscillation amplitudes occurred on the decreasing branch of solar cycle No. 20, whereby both solar cycles Nos. 20 and 21 were begun with maxima of oscillation amplitudes. Certain differences between the quasi-biennial oscillations of solar wind and solar activity are pointed out in the paper. (author). 5 figs., 1 tab., 37 refs
[en] Central parts of high-speed flows in solar wind are shown to be mainly projected to quiet parts of solar surface, while during periods of speed increase and decrease they may be projected to the vicinities of eruptive-active formations. Probability to reach velocity higher than 700 km/s increases essentially of outflow area of high-speed flow is contigous to the actice area. Problem concerning relation of solar wind speed with processes in the active areas is discussed
[en] The Rutherford Appleton Laboratory (RAL) is contributing instruments and a spacecraft to several imminent and excitingly new explorations of the plasma phenomena arising from the interaction between the solar wind and the Earth, and the solar wind and a comet. The projects in which the Laboratory is engaged, in collaboration with university and other research groups in the UK and abroad, include the AMPTE mission, which will trace the flow of particles injected into the solar wind, the GIOTTO encounter with comet Halley, the VIKING exploration of the generation of the aurora, and the CRRES and ISTP missions to clarify the structure and dynamics of the Earth's magnetosphere. These projects are outlined, together with the results of recent studies of particle acceleration and pulsations in the aurora. (author)
[en] The cosmic-ray equatorial anisotropy inseide broad high-speed solar-wind streams ejected by coronal holes, i.e. in quasi-stationary condition, is analysed over the years 1973-1974. From the beginning to the end of the stream the amplitudes of the first and second harmonics of the anisotropy are found to decrease remarkably by factors 2.5 and 2.0, respectively, while the phases do not show systematic variations. The development of the stream structure in the interplanetary space together with the parker theory on the diurnal anisotropy in stationary condition give a possible explanation for the large variation observed in the first harmonic anisotropy. The behaviour of the second harmonic is tentatively interpreted in the light of current theories
[en] It is shown that variations of JPDP type pulsations in the cycle of solar activity are dictated by change of the character of active processes in solar wind. The maximal frequency of JPDP accurrence in the years of the lowest solar activity is formed due to pulsation excitation against the background of recurrent high-velocity fluxes. Intensive flare activity suppresses JPDP generation in the maximum of the cycle. The index of JPDP recurrenece is suggested as a characteristic of active process change
[en] The effects of viscosity on a steady, radial, spherically symmetric solar wind with an embedded, non-radial magnetic field are reconsidered. The correct expression for the classical viscosity in the presence of a non-radial magnetic field is shown to be different from that used in the past, and a means of describing non-classical viscosity is presented. A physical interpretation of the classical and nonclassical description of viscosity is provided, and observational inferences are used in discussing the nature and degree of viscous effects in the solar wind
[en] The prevalent theory describing the entry of solar wind energy into the magnetosphere involves the merging of solar wind and terrestrial magnetic field lines on the dayside magnetopause and the subsequent reconnection of those field lines across the neutral sheet in the Earth's magnetotail. The reconnection is thought to occur at a neutral line, whose location is often set at ∼100 Re behind the Earth. The location of this neutral line has not been verified experimentally to date, and in this paper we shall provide some constraints suggesting its average location to lie in the range -50 > X > -80 Re. We shall use AMPTE, ISEE, and IMP 8 magnetic field data to evaluate the falloff of Bz at the position of the neutral sheet as one moves back into the tail. From these measurements we construct an analytical representation of Bz as a function of downtail position. Using the Coroniti and Kennel relationship for the flaring of the magnetotail, we evaluate the average position of the equatorward edge of the polar cap, which we then assume to represent the poleward edge of the average auroral oval. From flux conservation considerations, we then evaluate the average width of the auroral oval. We conclude the paper by discussing how the mapping from the magnetotail is reflected in the scale sizes of auroral features in the midnight sector of the auroral oval. 34 refs., 4 figs., 3 tabs
[en] The purpose of the paper is generalization of the mechanism of electric field excitation on the front side of the magnetosphere due to solar wind pressure gradient along the magnetopause for the case of curved magnetic force lines. Motion of geomagnetic force tubes near the magnetopause from the front point in the direction of the magnetotail is considered. Models with n approximately L-4 (Gold relation), n approximately L-3 (straight force lines), n approximately L-6 (Chapmen-Ferraro model) are analyzed. Decrease in the tangential component of the magnetic field with removal from the front point in the head part of the magnetopause due to a reduction in the solar wind pressure caused by a change in the magnetopause inclination in relation to unperturbed solar wind velocity results in appearance of recurrent stream inside the magnetosphere with increase in the stream rate with removal from the front point and to the corresponding generation of the electric field component normal to the magnetopause. The rate of recurrent stream and electric field are determined by two parameters in the point of plasma stagnation: the Alfven speed and gas/magnetic pressure ratio
[en] It is shown that the nonlinear interaction between the magnetic field-aligned circularly polarized (CP) dispersive Alfvén waves and low-frequency electrostatic perturbations give rise to Alfvénic rogue waves in magnetized plasmas. Our results reveal the left-hand CP Alfvénic wave supports both supersonic and subsonic Alfvénic rogue waves. The latter can propagate for backward wave only. The right-hand CP Alfvénic rouge waves appear on account of the amplitude modulation of the waves by quasi-stationary density modulations. The amplitude of the right-hand CP Alfvénic rogue waves decreases with the increase of the plasma number density, but it increases with the increase of the magnetic field strength. However, the amplitude of the subsonic left-hand CP Alfvénic rogue wave becomes stronger with the excess of the plasma number density, but it shrinks with stronger magnetic field strength. Finally, we briefly discuss the relevance of our investigation to the role of the nonlinear Alfvén waves that power the solar wind. -- Highlights: ► Alfvénic rogue waves in magnetized plasmas are studied. ► NLS equation describes the propagation of the rogue waves. ► Left- and right-hand Alfvénic rogue waves can exist. ► Left-hand Alfvénic wave supports both supersonic and subsonic rogue waves. ► The model is applied to the nonlinear Alfvén waves that power the solar wind.
[en] Three mechanisms have been proposed to explain relativistic electron flux depletions (dropouts) in the Earth's outer radiation belt during storm times: adiabatic expansion of electron drift shells due to a decrease in magnetic field strength, magnetopause shadowing and subsequent outward radial diffusion, and precipitation into the atmosphere (driven by EMIC wave scattering). Which mechanism predominates in causing electron dropouts commonly observed in the outer radiation belt is still debatable. In the present study, we evaluate the physical mechanism that may be primarily responsible for causing the sudden change in relativistic electron pitch angle distributions during a dropout event observed by Van Allen Probes during the main phase of the 27 February 2014 storm. During this event, the phase space density of ultrarelativistic (>1MeV) electrons was depleted by more than 1 order of magnitude over the entire radial extent of the outer radiation belt (3 < L* < 5) in less than 6 h after the passage of an interplanetary shock. We model the electron pitch angle distribution under a compressed magnetic field topology based on actual solar wind conditions. Although these ultrarelativistic electrons exhibit highly anisotropic (peaked in 90°), energy-dependent pitch angle distributions, which appear to be associated with the typical EMIC wave scattering, comparison of the modeled electron distribution to electron measurements indicates that drift shell splitting is responsible for this rapid change in electron pitch angle distributions. This further indicates that magnetopause loss is the predominant cause of the electron dropout right after the shock arrival.