Showing papers on "Coronal mass ejection published in 1979"
TL;DR: In this article, a strong correlation between mass ejection transients and chromospheric Hα activity was found, with three-quarters of the transients apparently originating in or near active regions.
Abstract: Coronal mass ejection transients observed with the white light coronagraph on Skylab are found to be associated with several other forms of solar activity. There is a strong correlation between such mass ejection transients and chromospheric Hα activity, with three-quarters of the transients apparently originating in or near active regions. We infer that 40% of transients are associated with flares, 50% are associated with eruptive prominences solely (without flares), and more than 70% are associated with eruptive prominences or filament disappearances (with or without flares). Nine of ten flares which displayed apparent mass ejections of Hα-emitting material from the flare site could be associated with coronal transients. Within each class of activity, the more energetic events are more likely to be associated with an observable mass ejection.
474 citations
TL;DR: In this article, a magnetohydrodynamic stability analysis of a model loop by the energy method suggests that the main reason for stability is the fact that the ends of the loop are anchored in the dense photosphere.
Abstract: Solar coronal loops are observed to be remarkably stable structures. A magnetohydrodynamic stability analysis of a model loop by the energy method suggests that the main reason for stability is the fact that the ends of the loop are anchored in the dense photosphere. In addition to such line-tying, the effect of a radial pressure gradient is incorporated in the analysis.
378 citations
TL;DR: In the dayside ionosphere of the Venus Orbiter, magnetic field measurements made by the Pioneer-Venice Orbiter spacecraft reveal a very low average field strength within the daysides ionosphere, typically only a few nanoteslas, in contrast to fields of several tens of nanotelas just outside the ionosphere as mentioned in this paper.
Abstract: MAGNETIC field measurements made by the Pioneer Venus Orbiter spacecraft reveal a very low average field strength within the dayside ionosphere of Venus, typically only a few nanoteslas, in contrast to fields of several tens of nanoteslas just outside the ionosphere1. Thus, at least in the range of solar zenith angles (65–90°) initially probed by the orbiter, the compressed interplanetary magnetic field of the shocked solar wind plasma (the magnetosheath) is effectively shielded from the ionosphere by currents flowing on the ionopause, the boundary between the ionosphere and the magnetosheath. In addition, the magnetic field pressure just outside the ionopause approximately balances the ionosphereic thermal plasma pressure2,3. However, within this generally low-field region the spacecraft occasionally passes through regions of very large field strength which can sometimes exceed that observed external to the ionosphere. These intense, short-lived enhancements are described here and interpreted to be due to the passage of the spacecraft through ‘flux ropes’, bundles of twisted magnetic field lines surrounded by ionospheric plasma.
162 citations
TL;DR: In this article, neither sunspots, flares, other solar activity, nor the solar wind, are found to be responsible for the 22-yr solar cycle period found in the [D/H] climate indicator.
Abstract: Neither sunspots, flares, other solar activity, nor the solar wind, are found to be responsible for the 22-yr solar cycle period found in the [D/H] climate indicator. This period may be due to a periodic variation in solar luminosity induced by a deeply buried magnetic field.
71 citations
TL;DR: In this paper, direct evidence of solar flare modification of stratospheric electric fields is presented through comparison of atmospheric electric field variations with fluxes of solar protons that bombarded the atmosphere during the August 1972 solar flares.
Abstract: Direct evidence of solar flare modification of stratospheric electric fields is presented through comparison of atmospheric electric field variations with fluxes of solar protons that bombarded the atmosphere during the August 1972 solar flares. Observed order of magnitude variations of the vertical electric field at 30-km altitude in anticorrelation with the intensity of solar protons are quantitatively interpreted in terms of atmospheric conductivity variations produced by solar proton ionization of the air. Other geophysical data are presented which indicate the state of the magnetosphere during this epoch and which further indicate a phenomenological coupling between atmospheric and extraterrestrial events.
71 citations
TL;DR: In this paper, the structure and parameters of flare streams in relation to the location of the flare and to the configuration of the large-scale magnetic field on the sun are considered. And the following results are obtained: (1) the flare streams spread in a rather wide angle (λm ≈ ±60°).
Abstract: The structure and parameters of flare streams in relation to the location of the flare and to the configuration of the large-scale magnetic field on the sun are considered. The following results are obtained: (1) The flare streams spread in a rather wide angle (λm ≈ ±60°). (2) The velocity of the streams ejected by the flares in the sun’s western hemisphere is 1.5 times higher than that of the streams ejected by eastern flares. (3) The sign of Bz being fixed, the sign of Bx within the stream is determined by the location of the flare with respect to the solar equator. (4) The exponent of the polytrope for the solar wind plasma (γ = 1.4–1.7) is close to or less than the adiabatic one.
56 citations
TL;DR: In this paper, the authors investigated the decrease of the volume of the dayside Hermaean magnetosphere with an increase in solar wind pressure, taking into account the effects of a conducting planetary core.
Abstract: The decrease of the volume of the dayside Hermaean magnetosphere with an increase in solar wind pressure is investigated, taking into account the effects of a conducting planetary core A two-layer conductivity model is used to simulate the metallic core and outer silicate mantle of Mercury, and the magnetic field of the magnetosphere is modelled by a pure planet-centered axial dipole, the magnetopause current system by a pure axial dipole on the Mercury-sun line and the tail field by a semiinfinite current sheet Results confirm the compression of the magnetic field and the increase in magnetic field pressures under most increased solar wind pressures in the presence of a planetary core, allowing a direct impact of the solar wind on the Hermaean surface to occur only 02% of the time
56 citations
Book•
01 Jan 1979
54 citations
TL;DR: In this article, a description of observations made at the Stanford Solar Observatory during the time from 1975 to the present, which seem to support the reports by Severny et al.
Abstract: Severny et al. (1976) have reported oscillations of the sun with a period near 160 min. A description is presented of observations made at the Stanford Solar Observatory during the time from 1975 to the present which seem to support the reports by Severny et al. At Stanford the relative velocity between a central circular area of radius 0.5 solar radius on the solar disk and most of the remaining area of the solar disk is measured. A superposed epoch analysis of the observations using a period of 160 min is discussed. An apparent agreement in phase between the obtained observational data and those reported by Severny et al. tends to support the interpretation that solar oscillations are being observed.
45 citations
TL;DR: In this paper, the authors observed a significant anti-correlation between solar activity and the brightnesses of two Solar System objects, namely, the planet Neptune and its satellite Titan, and hypothesised that what they observed are changes in planetary albedos induced by solar activity.
Abstract: IP WE have observed a significant anti-correlation between solar activity and the brightnesses of two Solar System objects. Both the planet Neptune and Saturn's satellite Titan increased in brightness by several per cent between 1972 and 19761 and subsequently became fainter by comparable amounts2. This period corresponds to the decline of solar activity at the end of solar cycle 20 (1972–76), followed by the rapid increase of activity at the beginning of cycle 21. Solar minimum and the maximum observed brightness of Titan and Neptune both occurred in 1976. (The maximum of cycle 21 is forecast for late 1979 or early 1980, with a sunspot number ∼1503.) We hypothesise that what we have observed are changes in planetary albedos induced by solar activity. Such changes may have an important bearing on the energy balances of the outer planets and their satellites.
TL;DR: In this paper, a theoretical study of the interactions between interstellar grains streaming through the solar system and the solar wind is presented, and it is shown that although elongated core-mantle interstellar particles of a characteristic radius of about 0.12 microns are subject to a greater force due to radiation pressure than to gravitational attraction, they are still able to penetrate deep inside the solar systems.
Abstract: Results of a theoretical study of the interactions between interstellar grains streaming through the solar system and the solar wind are presented. It is shown that although elongated core-mantle interstellar particles of a characteristic radius of about 0.12 microns are subject to a greater force due to radiation pressure than to gravitational attraction, they are still able to penetrate deep inside the solar system. Calculations of particle trajectories within the solar system indicate substantial effects of the solar activity cycle as reflected in the interplanetary magnetic field on the distribution of 0.12- and 0.0005-micron interstellar grains streaming through the solar system, leading to a 50-fold increase in interstellar grain densities 3 to 4 AU ahead of the sun during years 8 to 17 of the solar cycle. It is noted that during the Solar Polar Mission, concentrations are expected which will offer the opportunity of detecting interstellar grains in the solar system.
TL;DR: In this paper, it was shown that the simultaneous consideration of observed values of the solar wind proton flux density at 1 AU and of the electron pressure at the base of solar corona leads to relatively strong constraints on the coronal temperature in the region of subsonic solar wind flow.
Abstract: It is shown that the simultaneous consideration of observed values of the solar wind proton flux density at 1 AU and of the electron pressure at the base of the solar corona leads to relatively strong constraints on the coronal temperature in the region of subsonic solar wind flow. The extreme upper limit on the mean coronal temperature in the subsonic region is found to be about 2.6 × 106 K, but this upper limit is reduced to about 2.0 × 106 K if reasonable, rather than extreme, assumptions are made; the limit on the maximum temperature is about 0.5 × 106 K greater than the limit on the mean. It is also found that the same two observations limit the rate of momentum addition possible in the region of subsonic solar wind flow.
TL;DR: In this article, the Hartle-Sturrock model of the coronal expansion was used to determine the long-term variations near the earth of solar wind electron data measured between 1971 and 1978.
Abstract: Imp solar wind electron data measured between 1971 and 1978 were studied with the aim of determining long-term variations near the earth. Two separate sets of parameter variations were observed: (1) in 1976-1977 the solar wind density, the electron temperature, and the interplanetary electrostatic potential were all enhanced, and (2) the halo density and associated electron parameters were all depressed during a 1 1/2-year period centered on the last 6 months of 1976. Although interpretation of these results in terms of corresponding coronal and interplanetary variations is not unique, it may be significant that measured solar wind parameters near the minimum of solar cycle 20 agree better with the Hartle-Sturrock model of the coronal expansion than they do during other epochs.
TL;DR: The relationship between the geomagnetic activity of the three years preceding a sunspot minimum and the peak of the next sunspot maximum confirms the polar origin of the solar wind during one part of a solar cycle.
Abstract: The relationship between the geomagnetic activity of the three years preceding a sunspot minimum and the peak of the next sunspot maximum confirms the polar origin of the solar wind during one part of the solar cycle Pointing out that the polar holes have a very small size or disappear at the time of the polar field reversal, we suggest a low latitude origin of the solar wind at sunspot maximum and we describe the cycle variation of solar wind and geomagnetic activity In addition we note a close relationship between the maximum level of the geomagnetic activity reached few years before a solar minimum and its level at the next sunspot maximum Studying separately the effects of both the low latitude holes and the solar activity, we point out the possibility of predicting both the level of geomagnetic activity and the sunspot number at the next sunspot maximum As a conclusion we specify the different categories of phenomena contributing to a solar cycle
TL;DR: In this paper, the energy distributions of nonthermal electrons were derived from hard X-ray spectra taken during the impulsive phase of two 2B flares in February 1969.
Abstract: The energy distributions of nonthermal electrons are derived from hard X-ray spectra taken during the impulsive phase of two 2B flares in February 1969. They are used to calculate the fluxes of nonthermally excited X-ray lines of hydrogen-like and helium-like ions. These fluxes are compared to the total line fluxes observed at the same time with crystal spectrometers. The nonthermal excitation is found to give only small contributions to the total line intensities. This implies that the impact polarization which is to be expected for anisotropic velocity distributions of the energetic electrons, will be low. Nevertheless it should be feasible to detect line polarization during the impulsive phase of strong X-ray flares.
TL;DR: In this paper, the authors show that a bow shock of Venus forms as a result of the direct interaction of the solar wind with the ionosphere, and that the shape and position of the Venus bow shock correspond to a very weak dissipation of solar wind energy in ionosphere.
Abstract: The results of Soviet and American spacecraft plasma and magnetic experiments show that a bow shock of Venus forms as a result of the direct interaction of the solar wind with the ionosphere. The shape and the position of the Venus bow shock, in general, correspond to a very weak dissipation of solar wind energy in the ionosphere.
Journal Article•
TL;DR: In this paper, a procedure was developed to generate a computerized time intensity profile of the solar proton intensity expected at the Earth after the occurrence of a significant solar flares on the Sun.
Abstract: A procedure was developed to generate a computerized time intensity profile of the solar proton intensity expected at the Earth after the occurrence of a significant solar flares on the Sun. A combination of many pieces of independent research and theoretical results are included. A construction of selected experimental and theoretical results from the entire domain of solar terrestrial physics is given.
TL;DR: In this article, a chain of processes leading to solar flares is considered, including the dynamo process in the photospheric level in the vicinity of bipolar sunspots, the formation of a sheet current in the lower coronal level, the interruption of the sheet current, the subsequent diversion of it to the chromosphere, the development of a potential drop along magnetic field lines, the acceleration of current-carrying electrons and their impact on the chromospheric, producing a pair of flare ribbons.
Abstract: Assuming that basic plasma processes associated with magnetospheric substorms and solar flares are similar and thus assuming also that a flare ribbon is produced by the impact of field-aligned current-carrying electrons on the chromosphere, a chain of processes leading to solar flares is considered, including the dynamo process in the photospheric level in the vicinity of bipolar sunspots, the formation of a sheet current in the lower coronal level, the interruption of the sheet current, the subsequent diversion of it to the chromosphere, the development of a potential drop along magnetic field lines, the acceleration of current-carrying electrons and their impact on the chromosphere, producing a pair of flare ribbons.
TL;DR: In this paper, it was shown that the solar wind was of the simplest variety, analogous to that described in models of the so-called "quiet solar wind" and that closed magnetic loops would have been absent and extended energy deposition in the corona would have far less important than today.
TL;DR: In this paper, the authors discuss and evaluate the suggestions made by these authors on how to possibly reconcile the observed temperature enhancements at temperature-minimum levels in solar flares with some form of theoretical heating mechanism.
Abstract: As a sequel to the work by Machado et al. (1978), we discuss and evaluate the suggestions made by these authors on how to possibly reconcile the observed temperature enhancements at temperature-minimum levels in solar flares with some form of theoretical heating mechanism. After establishing the H− LTE assumption used by Machado et al., we then consider EUV irradiation, and joule heating by steady currents, as heating mechanisms. We find that, unless there are strong inhomogeneities associated with either mechanism, neither can reasonably be reconciled with observations. It is concluded that detailed, high resolution (both spatial and temporal) measurements are necessary to further our understanding of the flare process at temperature-minimum levels.
TL;DR: A survey of the origin, expansion, and acceleration of the solar wind and the plasma physics of the interplanetary medium can be found in this paper, where the relationship between coronal holes and solar-wind streams, and the associated revision of ideas about solar wind acceleration and heating are reviewed.
Abstract: The paper surveys topics related to the origin, expansion, and acceleration of the solar wind and the plasma physics of the interplanetary medium. The study of the relationship between coronal holes and solar-wind streams, and the associated revision of ideas about solar wind acceleration and heating are reviewed. In addition, topics of hydromagnetic waves and turbulence, and interplanetary electrons, as items of particular importance during the past quadrennium, are discussed. While the research discussed was concerned with data taken near solar minimum, further solar-wind studies will concentrate on observations from the rising and maximum phases of the solar cycle.
TL;DR: In this paper, the power flux into the magnetosphere from the solar wind was analyzed using the model of polar cap electric fields described by D'Angelo (1977), and it was shown that the substorm parameter proposed by Akasofu (1978) to predict the probability of a substorm can be interpreted as the portion of solar wind electromagnetic power flux which penetrates the magnetic field at a given moment.
TL;DR: The first very large array (VLA) synthesis maps of solar active regions are presented in this paper, where the observational capabilities and basic techniques of using the VLA to observe the Sun are described.
Abstract: The first very large array (VLA) synthesis maps of solar active regions are presented here. The observational capabilities, and the basic techniques of using the VLA to observe the Sun are also described. Comparisons of VLA maps with magnetograms are also made.
01 Jan 1979
TL;DR: The early effect of solar flares on the mid-latitude troposphere has been studied in this article, where the early effect is explained by strong convergence of air over large areas in the lower stratosphere.
Abstract: Strong solar flares cause atmospheric circulation changes (or alternatively changes in the mass and temperature distribution) at middle and high latitudes, starting less than 12 h after the solar eruption. This early effect lasts approximately one day, is strongest in winter and most pronounced at certain geographical locations. Delayed effects are reported having a maximum 2 to 4 days after a flare. In general, the connection between these effects is insufficiently known. This also applies to the possible role of solar flares in solar-climatic relationships. The observed early effect in the troposphere is plausibly explained by strong convergence of air over large areas in the lower stratosphere. However, a mechanism causing this convergence is still unknown. The early effect itself by changing the baroclinic stability in the mid-latitude troposphere could lead to some of the observed delayed effects.
15 Feb 1979
TL;DR: In this paper, a study on the differences of rotation properties, based on the lifetime of coronal features, has been performed for the period 1972-1974, and the short-lived component of the green corona associated with solar activity is differentially rotating, while long-lived coronal feature persisting more than one synodic rotation period, show little or no differential rotation.
Abstract: A study on the differences of rotation properties, based on the lifetime of coronal features, has been performed for the period 1972–1974. The short-lived component of the green corona associated with solar activity is differentially rotating, while long-lived coronal features persisting more than one synodic rotation period, show little or no differential rotation. These two components coexist at a same latitude within a wide latitude range at least in one of the solar hemispheres.
TL;DR: In this article, the solar EUV radiation from the whole solar disk for wavelengths between 15.5 and 103.76 nm was measured by the AEROS-EUV spectrometer during the period December 1972 through August 1973.
TL;DR: The representation of the sector boundaries, published by Svalgaard (1974, 1975) in a superposed 27-days Bartels format, showed that they have a significant preference to occur in certain days of the solar rotation.
Abstract: The representation of the sector boundaries, published by Svalgaard (1974, 1975) in a superposed 27-days Bartels format showed that they have a significant preference to occur in certain days of the solar rotation Further study of these data, as well as of the polarized days in the vicinity of them, pointed out that during the epoch of extrema of the 11-year cycle there is a well-established 2-sector structure, on the average On the contrary, a mean 4-sector structure is more prominent during the intermediate years