Showing papers on "Coronal mass ejection published in 1977"
01 Jan 1977
TL;DR: In this paper, the first part of the Helios-1 mission was used to study the solar corona and the solar wind during the period between 0.3 and 1 AU and the separation of proton double streams and alpha-particles.
Abstract: The reported results are mainly based on data obtained during the first part of the Helios-1 mission. The sun was very quiet during the considered period. The data are, therefore, representative for comparatively stationary conditions in the solar corona. Data obtained concerning the protons were evaluated by means of a special computer routine. The significance of the data is discussed, taking into account the status of the corona and the interplanetary plasma during the considered part of the Helios-1 mission, fast stream structures in the region between 0.3 and 1 AU, radial gradients of fast and slow solar wind, and the separation of proton double streams and alpha-particles. Attention is also given to the 'strahl' in the electron distribution, differences between fast streams and slow plasma on the basis of the observed electron distributions, and radial gradients in the case of solar wind electron parameters.
273 citations
TL;DR: In this paper, the authors have confirmed the fact that the 11-year cycle consists of two events (maxima) having different features during the first maximum (it coincides in time with the maximum of the Wolf numbers) and the second maximum occurs 2-3 years after the first one.
Abstract: Investigation of sunspots, coronal lines intensity, flares and other solar and geophysical data have confirmed the fact that the 11-year cycle consists of two events (maxima) having different features During the first maximum (it coincides in time with the maximum of the Wolf numbers) the solar activity increases in all heliographic latitudes but it is maximal in latitude 25° in each hemisphere The far UV radiation and number of small spots, flares and geomagnetic disturbances with sudden commencements and without 27-day recurrences are maximum at this time During the second maximum, which appears 2–3 years after the first one, the activity is maximal in latitudes ± 10° At this time the biggest spots, big flares, aurora and geomagnetic disturbances with the gradual commencements and long series of 27-day recurrences appear The variations of averaged 5303 and 6374 A coronal line intensities may be interpreted as an increase of coronal density and temperature during the first maximum and a sharp decrease of density and temperature rise during the second one The temperature during the second maximum is higher than that during the first one The distribution of activity on time-latitude diagrams (so-called ‘butterflies’) is a result of superposition of two random distributions corresponding to the two maxima mentioned above
200 citations
01 May 1977
TL;DR: The influence of the geometry of the situation as well as the variability of the interplanetary magnetic field are both found to be important factors for the generation of geomagnetic activity as discussed by the authors.
Abstract: Current ideas about the interaction between the solar wind and the earth's magnetosphere are reviewed. The solar wind dynamic pressure as well as the influx of interplanetary magnetic field lines are both important for the generation of geomagnetic activity. The influence of the geometry of the situation as well as the variability of the interplanetary magnetic field are both found to be important factors. Semi-annual and universal time variations are discussed as well as the 22-year cycle in geomagnetic activity. All three are found to be explainable by the varying geometry of the interaction. Long term changes in geomagnetic activity are examined.
122 citations
TL;DR: In this paper, the effects of curvature drifts in an Archimedean-spiral magnetic field are shown to produce a significant effect on the modulation of galactic cosmic rays by the solar wind.
Abstract: Gradient and curvature drifts in an Archimedean-spiral magnetic field are shown to produce a significant effect on the modulation of galactic cosmic rays by the solar wind. The net modulation, heliocentric radial gradient, and average energy change of particles which reach the inner solar system are significantly reduced. The effects of drifts are due to the fact that cosmic rays for which the drift velocity is comparable to the wind velocity or larger, have more rapid access to the inner solar system than in the absence of drifts.
114 citations
TL;DR: In this article, it is suggested that there may be an association between density enhancements and solar coronal mass ejection events, and that aggregated events, when they are common, make a negligible contribution to the total mass and energy budget of the solar wind at 1 AU.
Abstract: When the bulk flow speed is nearly constant or falling, high densities are sometimes observed in the solar wind. These densities do not appear to be generated in interplanetary space. It is noted that the magnetic field is not enhanced within these events, and that the proton and/or electron temperatures are low, varying in opposition to the density. About 1/3 of these density events contains interplanetary magnetic field reversals, some of which are noisy and do not qualify as sector boundaries. It is estimated that the average event contains approximately 10 to the 16th g of material and 2.6 x 10 to the 31st ergs, so that aggregated events, when they are common, make a negligible contribution to the total mass and energy budget of the solar wind at 1 AU. It is suggested that there may be an association between density enhancements and solar coronal mass ejection events.
88 citations
TL;DR: In this paper, an eruptive prominence and coronal transient of 19 December, 1973 comprised one of the best-observed coronal mass ejection events during the skylab period (May, 1973-January, 1974).
Abstract: An eruptive prominence and coronal transient of 19 December, 1973 comprised one of the best-observed coronal mass ejection events during the skylab period (May, 1973–January, 1974). EUV observations show that the pre-eruptive quiescent prominence was (at 8000 K) not appreciably hotter than other quiescent prominences, but EUV radiation from it and its prominence-corona interface was unusually faint. The prominence material was distributed in helical threads which decreased in pitch angle during the early phases of eruption. No region of the prominence was markedly different from any other just prior to and during the eruption. For the first time, the temperature and density of rising prominence material were determined at great heights in the corona. At 3R
⊙, the prominence material was still confined in threads whose temperature and total hydrogen density were 2 × 104 K and ∼1.5 × 109 cm−3, respectively. Shortly after this observation (∼ 7hr after the start of the eruption), the prominence material expanded dramatically. A small portion (≲1%) of the prominence material was observed draining downward near the solar surface late in the event, and we infer that only a small fraction (∼10%) of the pre-eruptive prominence mass was expelled from the Sun. The remainder of the prominence apparently lay outside the instruments' fields of view. The bulk of the material expelled did not originate in the prominence. Both coronal and prominence material accelerated outward during the period of observations. A pre-existing streamer was disrupted by the outflowing material.
84 citations
TL;DR: In this article, observations of the solar velocity field with a diode array attached to the echelle spectrograph of a vacuum tower telescope are described which resolve the solar five-minute oscillatory motion into distinct bands of power.
Abstract: Observations of the solar velocity field with a diode array attached to the echelle spectrograph of a vacuum tower telescope are described which resolve the solar five-minute oscillatory motion into distinct bands of power. Previous observations are discussed which show that the solar five-minute oscillations can be resolved into frequencies having the character of nonradial p-mode eigenfrequencies of the solar envelope. The present observations confirm the observed frequencies and sharpen the previous resolution of the five-minute oscillations into ridges on the (wavenumber, frequency) plane. A comparison with earlier calculations indicates that the theoretical frequencies are in good but not perfect agreement with those observed. It is concluded that the identification of the five-minute oscillations as nonradial p-mode oscillations in the solar envelope is established beyond doubt.
67 citations
TL;DR: A summary of full-disk solar fluxes for the wavelength region 250-1940 A compiled from data obtained from six Air Force Geophysics Laboratory rocket spectrometers flown during the period 1969-1976 is presented in this article.
Abstract: A summary of full-disk solar fluxes for the wavelength region 250–1940 A compiled from data obtained from six Air Force Geophysics Laboratory rocket spectrometers flown during the period 1969–1976 is presented. The intense spectral lines in the wavelength region from 300 to 1220 A are emitted predominantly from the solar chromosphere and the chromosphere-corona transition region. The data indicate that the flux in this wavelength region increases generally by less than 10% with increasing values of the solar F10.7cm emission from 70 to 177 in units of 10−22 W m−2 Hz−1.
63 citations
TL;DR: In this paper, it was shown that the large decrease in the field observed near the dip equator is due to the reversal of the equatorial electrojet current, caused by the imposition of an additional westward electric field on the ionosphere which was originated by the interaction of solar wind with the interplanetary magnetic field.
Abstract: LARGE variations of the geomagnetic field observed at ground level during a geomagnetic storm are generally attributed to various magnetospheric changes following the arrival of the solar plasma ejected during the solar flare. Using the direct measurements of equatorial electric field during a geomagnetic storm, it is shown here that the large decrease in the field observed near the dip equator is due to the reversal of the equatorial electrojet current. This event is caused by the imposition of an additional westward electric field on the equatorial ionosphere which was originated by the interaction of solar wind with the interplanetary magnetic field.
60 citations
TL;DR: In this article, Skylab observations of the Sun in soft X-rays gave the first possibility to study the development of a complex of activity in the solar corona during its whole lifetime of seven solar rotations.
Abstract: Skylab observations of the Sun in soft X-rays gave us the first possibility to study the development of a complex of activity in the solar corona during its whole lifetime of seven solar rotations. The basic components of the activity complex were permanently interconnected (including across the equator) through sets of magnetic field lines, which suggests similar connections also below the photosphere. However, the visibility of individual loops in these connections was greatly variable and typically shorter than one day. Each brightening of a coronal loop in X-rays seems to be related to a variation in the photospheric magnetic field near its footpoint. Only loops (rarely visible) connecting active regions with remnants of old fields can be seen in about the same shape for many days. The interconnecting X-ray loops do not connect sunspots.
TL;DR: In this article, it was inferred that reported averages of the solar-wind speed for the 1973-1975 era are unusually large for that phase of the sunspot cycle, indicating that long-term variations in geomagnetic activity are closely coupled to long-time variations in the bulk flow speed of solar wind.
Abstract: Geomagnetic records from 1868 through 1975 indicate that geomagnetic activity during 1973-1975 was unusually enhanced for that phase of the sunspot cycle (5-7 years after solar maximum). Previous work indicates that long-term variations in geomagnetic activity are closely coupled to long-term variations in the bulk flow speed of the solar wind. Thus, it is inferred that reported averages of the solar-wind speed for the 1973-1975 era are unusually large for that phase of the sunspot cycle.
TL;DR: In this article, the variations in time of the electric potential of the ionosphere were derived from high-mountain observatories, under certain conditions, by recording atmospheric electric field and air-earth current density I on high mountain observatories.
01 Jun 1977
TL;DR: In this article, an analysis of Skylab coronagraph images of mass ejections from the solar corona is presented, which demonstrate the importance of mass-ejection coronal transients to the interplanetary medium and support the belief that magnetic forces are the primary mechanism driving mass ejection from the corona.
Abstract: Results obtained from analysis of Skylab coronagraph images of mass ejections from the solar corona are reviewed which demonstrate the importance of mass-ejection coronal transients to the interplanetary medium and which support the belief that magnetic forces are the primary mechanism driving mass ejections from the corona. Observations of 13 large ejection events are examined which indicate that coronal mass ejections contribute a nonnegligible fraction of the mass flux from the sun, especially toward the heliographic equator near the maximum of a solar activity cycle. It is shown that observed loop-shaped transients were associated with regions of increased magnetic field and with separations of unipolar field regions, that the forces driving the transients outward acted to great heights long after the onsets of the events, and that the behavior of the ejecta was magnetically controlled. It is concluded that mass ejections from the corona contributed at least 3% of the mass flux from the sun during the Skylab era and that the most common loop-shaped ejections are magnetically driven through the corona.
TL;DR: In this paper, the authors enumerate some of the limitations that must be considered before hydromagnetic waves are taken seriously, including the distance that each wave mode can travel, and for at least one mode it must be consistent with the size and location of the region where the waves are to act.
Abstract: Hydromagnetic waves are of interest for heating the corona or coronal loops and for accelerating the solar wind. This paper enumerates some of the limitations that must be considered before hydromagnetic waves are taken seriously. In the lowest part of the corona, waves interact so that a significant fraction of the coronal wave flux should have periods as ≈10 s. If the problem of interest determines either a flux of wave energy or a dissipation rate, the distance that each wave mode can travel can be specified, and for at least one mode it must be consistent with the size and location of the region where the waves are to act. Heating of coronal loops observed by X-rays can be explained if the strength of the magnetic field along the loop lies within a rather narrow range and if the wave period is sufficiently short. In general, Alfven waves travel furthest and reach high into the corona and into the solar wind. The radial variation of the magnetic field is the most important parameter determining where the waves are dissipated. Heating of coronal helmets by Alfven waves is probable.
TL;DR: In this article, it was shown that coronal ribbon-structures may be observed on the limb of the Sun as coronal streamers and that the prolongation of these structures into interplanetary space forms a curved surface.
Abstract: Analysis of observations of the white-light corona performed aboard OSO-7 is evidence for the existence of coronal ribbon-structures, which may be observed on the limb as coronal streamers. It is shown that prolongation of these structures into interplanetary space forms a curved surface; intersection of this surface is accompanied by a change of polarity of the interplanetary magnetic field, which existed in May–July 1973; and its connection with several phenomena in the solar atmosphere, has been found.
TL;DR: In this article, the authors present the development of the variational technique and apply it to a model of the solar wind interaction with Venus, and the use of these distributions in determining convective transport patterns of planetary ions is discussed.
TL;DR: In this article, the authors proposed that coronal magnetic bottles, produced by flares, serve as temporary traps for solar cosmic rays in some instances, which allows the expansion of these bottles at velocities of 300-500 km/s which allows fast azimuthal propagation of solar cosmic ray particles independent of energy.
Abstract: Key observations pertaining to the fast azimuthal propagation of solar cosmic ray particles are reviewed. Briefly, protons and electrons with a wide range of energies from 40/sup 0/ to 60/sup 0/ heliolongitude on either side of a flare site have access to the earth--sun interplanetary field line within an hour a flare onset. We propose that coronal magnetic bottles, produced by flares, serve as temporary traps for solar cosmic rays in some instances. It is the expansion of these bottles at velocities of 300--500 km/s which allows fast azimuthal propagation of solar cosmic rays independent of energy. As a result of the Rayleigh--Taylor instability, cosmic rays originally trapped inside the bottle are released into interplanetary space at a time of the order of 0.5-1 hour after the flare.
TL;DR: In this article, the authors attempt to merge conceptually planetary wind models of Jupiter's outer magnetosphere with reconnection models of the inner magnetosphere of the Jovian system.
Abstract: We attempt to merge conceptually planetary wind models of Jupiter's outer magnetosphere with reconnection models of Jupiter's outer magnetosphere. Solar wind reconnection scaling arguments predict 2-4 AU for the length of the Jovian tail, consistent with that inferred from Jovian cosmic ray propagation arguments. Two conceivable limits of solar wind reconnection driven internal magnetospheric convection emerge, depending upon whether or not the centrifugally driven planetary wind transports magnetic flux radially outward.
01 Mar 1977
TL;DR: In this article, the ion-acoustic wave turbulence detected in interplanetary space has characteristics essentially identical to bursts of electrostatic turbulence generated by protons streaming into the solar wind from the earth's bow shock.
Abstract: Plasma wave measurements on the Helios 1 and 2 spacecraft have revealed the occurrence of electric field turbulence in the solar wind at frequencies between the electron and ion plasma frequencies. Wavelength measurements with the IMP 6 spacecraft now provide strong evidence that these waves are short wavelength ion-acoustic waves which are Doppler shifted upward in frequency by the motion of the solar wind. Comparison of the Helios results with measurements from the earth-orbiting IMP 6 and 8 spacecraft shows that the ion-acoustic wave turbulence detected in interplanetary space has characteristics essentially identical to bursts of electrostatic turbulence generated by protons streaming into the solar wind from the earth's bow shock. In a few cases enhanced ion-acoustic wave intensities have been observed in direct association with abrupt increases in the anisotropy of the solar wind electron distribution. This relationship strongly suggests that the ion-acoustic waves detected by Helios far from the earth are produced by an electron heat flux instability, as suggested by Forslund. Possible related mechanisms which could explain the generation of ion-acoustic waves by protons streaming into the solar wind from the earth's bow shock are also considered.
TL;DR: In this paper, a thermalized plasma was recorded one hour after the shock followed two hours later by the plasma ‘piston' with a bulk velocity higher than 1700 km s-1.
Abstract: Solar wind and interplanetary magnetic field data were obtained by the PROGNOZ 1 and PROGNOZ 2 satellites during the period following the August 4, 1972 (06∶21 UT) solar flare. A thermalized plasma was recorded one hour after the shock followed two hours later by the plasma ‘piston’ with a bulk velocity higher than 1700 km s-1. The comparison between the PROGNOZ and PIONEER 9 solar wind data shows an attenuation of the plasma properties with the deflection from the flare's meridian.
TL;DR: In this paper, a spherically symmetric adiabatic single-fluid model is proposed to simulate the nonlinear time-dependent response of the corona to solar events that are simulated by perturbations in the appropriate physical variables from their steady-state values at the coronal base.
Abstract: A spherically symmetric adiabatic single-fluid model is outlined for simulating the nonlinear time-dependent response of the corona to solar events that are simulated by perturbations in the appropriate physical variables from their steady-state values at the coronal base. Several observed features of the coronal transient that occurred on June 10, 1973, are simulated by using a particular steady-state solar wind, a specific combination of density and temperature perturbations, and a particular time dependence of the perturbations. A different steady-state solar wind, a perturbation of shorter duration, and other perturbation combinations are also employed to simulate the same transient so that the effect of each quantity can be determined. It is found that the model cannot adequately simulate all the observational results for the investigated transient, that the steady-state solar wind is relatively unimportant in such numerical simulations, and that studies which attempt only to reproduce observed shock trajectories may lead to erroneous conclusions regarding the physics of the solar event that produced the transient.
TL;DR: The structure of the interplanetary magnetic field within the flare streams as well as associated variations of the geomagnetic disturbancy are considered in this article, where it is shown that in the main body of the flare stream the magnetic field is determined by the configuration of the large scale magnetic field on the Sun at the flare region.
Abstract: The structure of the interplanetary magnetic field within the flare streams as well as associated variations of the geomagnetic disturbancy are considered. It is shown that in the main body of the flare stream the magnetic field is determined by the configuration of the large scale magnetic field on the Sun at the flare region. Within the head part of the flare stream the magnetic field represents by itself the compressed field of the background solar wind and hence is determined by the distribution of the super large scale solar magnetic field outside the flare region.
TL;DR: In this article, the changes in different terms of the Fokker-Planck equation, which describes energetic particle propagation, were analyzed in a theoretical blast wave model, which incorporates the interaction with plane polarized Alfven waves.
Abstract: Energetic particles, ejected from the Sun during solar flare events, may encounter interplanetary plasma/field conditions, which deviate considerably from the quiet time values used normally to describe the particle propagation. This is due to the presence of a hydromagnetic shock, which is emitted from the Sun at the time of the explosion. In a theoretical blast wave model, which incorporates the interaction with plane polarized Alfven waves, we have analysed the changes in different terms of the Fokker-Planck equation, which describes energetic particle propagation. In this treatment, the shock influence on energy changes and on the transport coefficients are discussed.
TL;DR: A brief review of recent solar abundance results is given in this paper, where the relative abundance of 68 chemical elements is known for the sun and a brief review is given of solar abundance.
Abstract: A brief review is given of recent solar abundance results. The relative abundance of 68 chemical elements is known for the sun.
TL;DR: In this paper, the authors compared X-ray images of the solar corona taken by rocket-borne telescopes on September 16 and November 17, 1976 with data from the MIT detectors on the IMP 7 and 8 satellites and the SOLRAD 11B satellite.
Abstract: Solar wind data from the MIT detectors on the IMP 7 and 8 satellites and the SOLRAD 11B satellite for the solar-minimum period September-December, 1976, were compared with X-ray images of the solar corona taken by rocket-borne telescopes on September 16 and November 17, 1976. There was no compelling evidence that a coronal hole was the source of any high speed stream. Thus it is possible that either coronal holes were not the sources of all recurrent high-speed solar wind streams during the declining phase of the solar cycle, as might be inferred from the Skylab period, or there was a change in the appearance of some magnetic field regions near the time of solar minimum.
TL;DR: In this paper, a data set containing merged plasma and magnetic field measurements obtained aboard several spacecraft is presented, which is possible in about three quarters of the cases from June 1967 to July 1968 with the use of 6-hour averages.
Abstract: A data set containing merged plasma and magnetic field measurements obtained aboard several spacecraft is presented. By using simple formulas resulting from the constant velocity approximation the field magnitude and direction and the plasma density at 0.3 AU are calculated from this data set. This is possible in about three quarters of the cases from June 1967 to July 1968 with the use of 6-hour averages. The relation between streams and sectors is examined. The cross correlation between the various parameters is calculated. It is found that the directional fluctuations of the magnetic field on this time scale are mainly due to interplanetary processes; however, the amplitude fluctuations of the magnetic field are decreased by interplanetary processes. The high-speed portions of interplanetary streams arise in regions of low plasma density. Since the data are at solar maximum, the implication is that the Skylab results for the relation between coronal holes and solar wind sources may hold for the entire solar cycle.