Showing papers on "Earth's magnetic field published in 1979"
TL;DR: The Stare (Scandinavian twin auroral radar experiment) was used to measure ionospheric electric fields associated with Pc 5 geomagnetic pulsations as discussed by the authors.
Abstract: The Stare (Scandinavian twin auroral radar experiment) auroral radar system has been used to measure ionospheric electric fields associated with Pc 5 geomagnetic pulsations With this system, electric fields are derived from the drift velocity of radar auroral irregularities The spatial resolution is 20 km over a 200,000-km² grid, and the temporal resolution is 20 s It has been found that the oscillating electric field associated with a hydromagnetic field line resonance produces poleward moving, bandlike regions of radar aurora, which are aligned in the east-west direction The drift of the irregularities within these bands is alternately eastward and westward The Stare electric field data have been used in conjunction with the Biot-Savart Law and an assumed height-integrated conductivity of 8–10 Ω−1 to calculate the ground magnetic disturbance It has been found that the H and Z are well predicted, whereas D is generally underestimated These results are consistent with a 90° rotation of the magnetic polarization ellipse in the ionosphere By Fourier analyses of the Stare data it is found that the half-power latitudinal width of the field line resonance is typically 100 km in the ionosphere Moreover, the north-south electric field undergoes a 180° phase shift about the resonance as predicted by theory The data have been used to estimate equatorial plasma densities for 6 < L < 7, and values of the order of 20 cm−3 have been obtained However, these determinations are strongly affected by distortions of the geomagnetic field from a dipolar geometry In summary, (1) the experimental results strongly support the hydromagnetic field line resonance theory of pulsations; (2) the magnetic polarization ellipse is indeed rotated through 90° by the ionosphere; (3) the phenomena previously observed by auroral radar workers in association with Pc 5 pulsations were related to the electric field of the hydromagnetic wave near resonance; and (4) auroral radar measurements can be used to estimate the equatorial magnetospheric plasma density in the region 5 < L < 8
304 citations
TL;DR: In this article, the authors used a distribution of 2.5 minute averages of B sub Z as a function of position across the tail to find that more flux crosses the equatorial plane near the dawn and dusk flanks than near midnight.
Abstract: Over 3000 hours of IMP-6 magnetic field data obtained between 20 and 33 R sub E in the geomagnetic tail have been used in a statistical study of the tail configuration. A distribution of 2.5 minute averages of B sub Z as a function of position across the tail reveals that more flux crosses the equatorial plane near the dawn and dusk flanks than near midnight. The tail field projected in the solar magnetospheric equatorial plane deviates from the X axis due to flaring and solar wind aberration by an angle alpha = -0.9 y sub SM - 1.7 where Y sub SM is in earth radii and alpha is in degrees. After removing these effects the Y component of the tail field is found to depend on interplanetary sector structure. During an away sector the B sub Y component of the tail field is on average 0.5 gamma greater than that during a toward sector, a result that is true in both tail lobes and is independent of location across the tail.
291 citations
01 Sep 1979
263 citations
TL;DR: In this paper, the authors considered three possible sources of energy: radioactive heating in the core itself, loss of internal energy due to cooling and freezing of the outer core, and cooling of the whole core with consequent differentiation to form the inner core with release of gravitational energy.
Abstract: Summary. The persistence of the magnetic field of the Earth demands a constant energy source for the last three thousand million years, and this provides a constraint on the thermal evolution of the core. The equations of global energy and entropy balance are used to estimate the power source required for a specific magnetic field. The amount of power required depends on the exact nature of the source. Three possibilities are considered here: radioactive heating in the core itself, loss of internal energy due to cooling and freezing of the outer core to form the inner core, and cooling of the whole core with consequent differentiation to form the inner core with release of gravitational energy. The last of these includes all the sources except for radioactive heating, but the introduction of some radioactivity into this calculation would be a simple matter. For radioactive heating alone, 1013W is required for the dynamo. This is just within the limits set by the observed surface heat flux (4 x lOI3 W) and what some geochemists believe to be the heating due to K40. Cooling itself cannot release enough heat to power the dynamo because the required cooling rate is so high that the inner core would be a very recent feature of the Earth. The release of gravitational energy can produce a magnetic field of 100-200 gauss, with the inner core growing slowly to its present size over 4Ga, and a heat release of 2.5 x lO'*W. A lower heat flux is required because of the greater efficiency of conversion of gravitational energy into magnetic fields than heat. When pursuing the calculations backwards in time, the rate of energy release is found to be proportional to the mass of the inner core. A surprising feature of this model, which assumes a constant rate of cooling at the top of the core, is that the useful power available for the dynamo increases with time, so that the field should be stronger now than it was in the past, although only by about 30 per cent.
220 citations
TL;DR: In this paper, the problem of instantaneous transmission of the polar ionospheric electric field to the equator is solved analytically as an initial-boundary value problem by assuming a plane Earth-ionosphere waveguide system composed of the metallic ionosphere with vertical static magnetic field and the perfectly conducting Earth, the TM0 (zeroth-order transverse magnetic) waveguide mode excited by the polar electric field propagates instantaneously to the low-latitude accompanying the electric field with the same direction as the polar field.
212 citations
TL;DR: In this article, the dependence of cosmogenic isotope production on solar modulation and on geomagnetic field intensity has been calculated, and spallation yields based on the Silberberg-Tsao formalism have been determined.
Abstract: The dependence of cosmogenic isotope production on solar modulation and on geomagnetic field intensity has been calculated, and spallation yields based on the Silberberg-Tsao formalism have been determined. The stratospheric inventory of /sup 7/Be during the period 1970--1974 has been calculated to be about 4.5mCi, in good agreement with measured values. The calculated radiocarbon reservoir of 1.75 cm/sub e//sup -2/ s/sup -1/ (where results are integrated over the whole earth) is in good agreement with experimental value of 1.8. Geomagnetic and solar effects were taken into account.
205 citations
TL;DR: In this article, an extensive sampling has revealed a new feature of the Mono Lake geomagnetic excursion, where the previously known eastward and steepening of inclination are preceded by an even greater swing to westerly declination and shallow inclination.
Abstract: Extensive sampling has revealed a new feature of the Mono Lake geomagnetic excursion. The previously known eastward swing in declination and steepening of inclination are preceded by an even greater swing to westerly declination and shallow inclination. The duration of the entire excursion is estimated to be about 1000 years. Excellent agreement of paleomagnetic directions between four sites shows the excursion is a real expression of the geomagnetic field. Interpretation of natural remanent magnetization/anhysteretic remanent magnetization (NRM/ARM) ratios for one site indicates the field intensity may have fallen well below and then increased well above the dipole field intensity, suggesting the excursion is a manifestation of the nondipole field. The source can be modeled by a radial eccentric dipole at high northern latitudes and pointing outward during the first part of the excursion, and near the equator and pointing inward during the latter part. Movement of the source appears localized, displaying a complex pattern of eastward, westward, and even northward drift. The average moment of the hypothetical eccentric dipole during the excursion is comparable with the largest calculated for the 1945 field, and the maximum moment is almost twice as great.
177 citations
TL;DR: In this article, a model depicting the relationship between proton events in various magnetospheric regions is presented, which relates these initial proton populations directly to the substorm onset acceleration mechanism.
Abstract: High-energy (E > 0.3 MeV) proton increases within the magnetosphere both at synchronous orbit (6.6 RE) and in the plasma sheet (∼18 RE) have been studied. Measurements at 6.6 RE reveal that most (>80%) substorms have no associated injections of >0.3-MeV protons (above the typical ambient level of 5 × 10³ (cm² s sr MeV)−1). Those relatively rare substorms which produce large fluxes of high-energy particles show behavior ranging from drift echo to nondrift echo types of enhancements. The drift echo events are characterized by brief, well-defined pulses of protons which are observed to drift azimuthally about the earth several times before dispersing. The nondrift echo events exhibit clear flux enhancements, but they do not show very evident pulsed behavior. The relative occurrence probability of high-energy proton enhancements at 6.6 RE shows a strong positive correlation both with solar wind speed and with Kp. A substantial correlation with southward interplanetary magnetic field (IMF) is also found. Very similar Kp, solar wind, and IMF dependences are found for plasma sheet proton (Ep > 0.5 MeV) enhancements above a threshold of ∼10 (cm² s sr MeV)−1 as measured at 18 RE. The close similarity of differential energy spectra, Kp, solar wind, and IMF dependences at synchronous orbit and in the plasma sheet suggests a common acceleration source. Bursts of energetic protons (Ep ∼ 1 MeV) are also often observed simultaneously in data obtained in the interplanetary medium when proton enhancements are seen at 6.6 RE. A model depicting the relationship between proton events in various magnetospheric regions is presented. It is suggested that large transient (<1 min) induced electric fields exist within the plasma sheet at the time of those substorm onsets that occur during periods of high solar wind speed and southward IMF. Such electric fields then produce both the proton pulses seen at synchronous orbit and the previously reported plasma sheet ‘impulsive’ tailward flowing proton bursts. We relate these initial proton populations directly to the substorm onset acceleration mechanism. The more frequently observed type of plasma sheet proton enhancements which is observed in the expanding plasma sheet is, in the present model, attributed to previously injected protons from the outer radiation zone filling the plasma sheet volume during the recovery phase of substorms.
171 citations
TL;DR: In this article, a quasi-steady model of global lower atmospheric electricity is presented, which considers thunderstorms as dipole electric generators that can be randomly distributed in various regions and that are the only source of atmospheric electricity and includes the effects of orography and electrical coupling along geomagnetic field lines in the ionosphere and magnetosphere.
Abstract: A quasi-steady model of global lower atmospheric electricity is presented. The model considers thunderstorms as dipole electric generators that can be randomly distributed in various regions and that are the only source of atmospheric electricity and includes the effects of orography and electrical coupling along geomagnetic field lines in the ionosphere and magnetosphere. The model is used to calculate the global distribution of electric potential and current for model conductivities and assumed spatial distributions of thunderstorms. Results indicate that large positive electric potentials are generated over thunderstorms and penetrate to ionospheric heights and into the conjugate hemisphere along magnetic field lines. The perturbation of the calculated electric potential and current distributions during solar flares and subsequent Forbush decreases is discussed, and future measurements of atmospheric electrical parameters and modifications of the model which would improve the agreement between calculations and measurements are suggested.
162 citations
TL;DR: In this article, the steady state equations for current conservation were solved numerically by assuming (1) several divided regions of the global earth (such as the polar cap, auroral zone, and middle-low latitudes), (2) exponentially distributed anisotropic electric conductivities for each zone with a continuous change at the boundaries of the regions, and (3) exponential distributed downward and upward field-aligned current intensities in the auroral region, assumptions based on our current knowledge of auroral phenomena and geomagnetic variations as well as rocket and satellite measurements of field-
Abstract: Computer simulation studies of the electric fields and currents in the global ionosphere produced by field-aligned electric currents for quiet periods are conducted. The steady state equations for current conservation are solved numerically by assuming (1) several divided regions of the global earth (such as the polar cap, auroral zone, and middle-low latitudes), (2) exponentially distributed anisotropic electric conductivities for each zone with a continuous change at the boundaries of the regions, and (3) exponentially distributed downward and upward field-aligned current intensities in the auroral region, assumptions based on our current knowledge of auroral phenomena and geomagnetic variations as well as rocket and satellite measurements of field-aligned currents. Resultant computer-plotted diagrams include equipotential contours of the electric fields, vector distributions of the electric fields and currents, and electric current patterns equivalent to the magnetic field effect produced by the field-aligned and real ionospheric currents. One of the merits of this simulation method is that the three-dimensional current system can roughly be estimated from the equivalent current system obtained from ground-based geomagnetic data alone. This paper also provides a foundation for a similar study of substorms. The following main results are obtained: (1) Conductivity inhomogeneity alters considerably the electric field pattern that has previously been obtained by assuming the uniform conductivity distribution. (2) Even a slight conductivity enhancement along the nightside auroral belt results in a large modification of the electric field. (3) The existence of the strong conductivity gradients and the field-aligned currents in the equatorward half of the auroral oval reduces the electric field in the middle and low latitudes. This corresponds to the ‘shielding’ effect of the electric field inside the Alfven layer in the magnetotail. (4) Seasonal changes in the polar cap conductivities cause surprisingly large effects on the electric fields and currents. (5) The equivalent ionospheric currents differ significantly from real ionospheric currents in both intensity and direction.
157 citations
01 Jan 1979
TL;DR: In this article, a mechanism for the generation of field aligned currents during magnetospheric substorms is presented, where the energy which is injected to the geomagnetic tail is converted into plasma flow energy in solar and anti-solar directions.
Abstract: A mechanism for the generation of field aligned currents during magnetospheric substorms is presented. The energy which is injected to the geomagnetic tail is converted into plasma flow energy in solar and anti-solar directions. When the flow meets the inner magnetosphere, a viscous interaction occurs. This interaction creates time-increasing vorticities which produce field aligned currents upward in the pre-midnight sector and downward in the post-midnight sector.
TL;DR: In this article, the authors proposed that the magnetic field changes associated with the Matsushiro earthquake swarms were produced by electrokinetic currents, and they used electric field sensors to help in determining the source of any observed variations.
Abstract: Fluid motion in the vicinity of a vertical fault separating regions of different streaming potential coefficient can produce an external magnetic field of observable magnitude. If tectonic stress changes along the fault produce fluid motion, the magnetic field changes would be indicative of stress changes, and might precede severe fault motion. The largest component of the magnetic field is oriented parallel to the strike of the fault. Magnetic field changes produced by this mechanism will have electric fields associated with them with similar time variation; this is in contrast to magnetic field changes produced by changes in susceptibility or remanent magnetization, which have no associated electric field. Experiments aimed at the detection of tectonomagnetic effects should include electric field sensors to help in determining the source of any observed variations. The hypothesis of Mizutani and Ishido (1976) that the magnetic field changes associated with the Matsushiro earthquake swarms were produced by electrokinetic currents seems reasonable.
TL;DR: In this article, the Imp 6 and Hawkeye satellites were used in a study of very intense electrostatic waves near the upper hybrid resonance frequency in the region just outside the plasmapause, where the polarization of these waves is such that the wave electric field vector is oriented perpendicular to the geomagnetic field.
Abstract: Plasma wave measurements using instruments on the Imp 6 and Hawkeye satellites are utilized in a study of very intense electrostatic waves near the upper hybrid resonance frequency in the region just outside the plasmapause. Studies of these electrostatic disturbances show that the events occur at local times and at magnetic latitudes varying from the equator to 50 deg, and the polarization of these waves is such that the wave electric field vector is oriented perpendicular to the geomagnetic field. In most cases the center frequency of the intense waves corresponds to an (n + 1/2) fg(-) harmonic near the upper hybrid resonance frequency. The hot distribution on function is described for a few events showing temperature anisotropy and a loss cone distribution. A possible mechanism for producing intense waves near the upper hybrid resonance frequency is suggested, and evidence which indicates that the intense electrostatic waves may be a source of nonthermal continuum radiation is given.
TL;DR: The geomagnetic coast effect as mentioned in this paper is a phenomenon where the vertical component of the magnetic variation field is abnormally large near most coastlines and correlates positively with the inland horizontal component.
Abstract: Near most coastlines the vertical component of the geomagnetic variation field is abnormally large and correlates positively with the inland horizontal component. This phenomenon is known as the geomagnetic coast effect. The few coastal locations at which it is absent are tectonically anomalous. The ratio of vertical to horizontal components decreases inland at a rate which depends on the geological nature of the continent. The effect varies only slightly with period, reaching a broad maximum between periods of 30 and 90 min. A number of models have been investigated by either calculation or analogue modeling, but the complete problem dealing with finitely conducting irregular oceans overlying a less conducting lithosphere has not yet been solved. Eddy currents flowing entirely in the seawater would be induced only by the vertical component of the magnetic field. Observations, combined with analogue model experiments, suggest that induction by horizontal components is also important. This requires flow of current in the lithosphere beneath the oceans.
TL;DR: In this paper, the authors review paleomagnetic records of reversals and attempt to determine the geometry of transitional fields, based on which a proper documentation of reversal phenomena may yield useful ideas about the generation of the field.
Abstract: The reversal of polarity of the earth's magnetic field is one of the most remarkable features of our planet's magnetism. A proper documentation of reversal phenomena may therefore be expected to yield useful ideas about the generation of the field. Reversals are also of interest to geologist; they have given rise to a new stratigraphy, allowed us to map the history of the ocean basins and to trace the movement of plates. The subject of reversals was comprehensively reviewed by Bullard (1968) and again more recently by Jacobs (1976). In this paper, we review paleomagnetic records of reversals and attempts to determine the geometry of transitional fields.
TL;DR: In this article, the authors used the Isis 2 satellite to measure magnetic perturbations perpendicular to the main geomagnetic field, which fit a pattern similar to the usual two-cell convection pattern except in the noon cleft region, where the perturbation direction tends to be eastward when the IMF B/sub y/ component is positive and westward when it is negative.
Abstract: Particle and magnetic field measurements made on the dayside of the magnetosphere by the Isis 2 satellite are reported. Northern hemisphere magnetic perturbations perpendicular to the main geomagnetic field are obtained by subtracting a model field from the field measured at the spacecraft plotted as two-dimensional vectors, these perturbations, on the average, fit a pattern very similar to the usual two-cell convection pattern except in the noon cleft region, where the perturbation direction tends to be eastward whenthe IMF B/sub y/ component is positive and westward when it is negative. This relatively strong dependence of the perturbation direction on the sign of B/sub y/ is taken as further evidence for interconnection between the IMF and the geomagnetic field. Comparing various features of the magnetic perturbations with particle measurements, it is found that, on the average, the maximum perturbation in the noon sector falls within the region of cleft prcipitation lying near the poleward edge of cleft electrons and just poleward of the 40-keV electron boundary. The location of the maximum perturbation in this sector is identified with the polar cap boundary. In the dawn and dusk sectors a marked change in slope of the magnitude of the perturbation typically occursmore » at the poleward edge of the plasma sheet; this is also the poleward edge of the region 1 field-aligned currents defined by Iijima and Potemra (1976a) and identified here with the polar cap boundary.« less
Journal Article•
TL;DR: In this paper, a method of finding a first approximation to a crustal magnetization distribution from inversion of satellite magnetic anomaly data is described, where magnetization is expressed as a Fourier series in a segment of spherical shell.
Abstract: A method of finding a first approximation to a crustal magnetization distribution from inversion of satellite magnetic anomaly data is described. Magnetization is expressed as a Fourier series in a segment of spherical shell. Input to this procedure is an equivalent source representation of the observed anomaly field. Instability of the inversion occurs when high frequency noise is present in the input data, or when the series is carried to an excessively high wave number. Preliminary results are given for the United States and adjacent areas.
TL;DR: In this paper, the impulse response of the geomagnetic indices (Dst, AL, AU and AE) to the interplanetary magnetic field southward component (IMF-Bz) is calculated on the assumption that the magnetosphere acts as a linear system.
Abstract: The impulse response of the geomagnetic indices (Dst, AL, AU and AE) to the interplanetary magnetic field southward component (IMF-Bz) is calculated on the assumption that the magnetosphere acts as a linear system. Hourly data for 300 days are used in this analysis. The main results obtained are as follows: (1) Using interplanetary data, a fairly large portion of geomagnetic disturbances may be predicted with the assumption of a linear system. (2) The response of the Dst index and the AL index develops at two steps or has an oscillating property with a period of several hours. (3) The response of the AU index is rather different from that of the other indices. These results may suggest that the disturbances represented by the Dst and AL indices have a common origin associated with the interplanetary magnetic or electric field, whereas those indicated by the AU index have an origin somewhat different from it.
TL;DR: In this article, the Mead-Fairfield model of the geomagnetic field is used to estimate the standing wave periods of geOMagnetic pulsations for three different magnetospheric cold plasma regions, corresponding to waves guided in the plasmatrough, the extended plasmasphere and regions of enhanced proton density (detached plasma) within the plasphere.
TL;DR: In this article, a model of global atmospheric electricity used to examine the effect of upper atmospheric generators on the global electrical circuit is presented, where the model represents thunderstorms as dipole current generators randomly distributed in areas of known thunderstorm frequency; the electrical conductivity in the model increases with altitude.
Abstract: The paper presents a model of global atmospheric electricity used to examine the effect of upper atmospheric generators on the global electrical circuit. The model represents thunderstorms as dipole current generators randomly distributed in areas of known thunderstorm frequency; the electrical conductivity in the model increases with altitude, and electrical effects are coupled with a passive magnetosphere along geomagnetic field lines. The large horizontal-scale potential differences at ionospheric heights map downward into the lower atmosphere where the perturbations in the ground electric field are superimposed on the diurnal variation. Finally, changes in the upper atmospheric conductivity due to solar flares, polar cap absorptions, and Forbush decreases are shown to alter the downward mapping of the high-latitude potential pattern and the global distribution of fields and currents.
TL;DR: In this paper, the displacement between the geographic and geomagnetic poles has an important effect on the plasma drift patterns over the polar cap for a range of constant magnetospheric electric fields as well as for asymmetric electric fields with enhanced plasma flow on either the dawnside or the duskside of polar cap.
Abstract: We assumed that the ionospheric plasma at high latitudes has a tendency to corotate about the geographic pole and that magnetospheric convection is relative to the geomagnetic pole. With this assumption we calculated plasma drift patterns over the polar cap for a range of constant magnetospheric electric fields as well as for asymmetric electric fields with enhanced plasma flow on either the dawnside or the duskside of the polar cap. We calculated the drift patterns in both the geographic inertial and the geomagnetic inertial frame taking into account the displacement between the geographic and geomagnetic poles. We found that this displacement between the poles has an important effect on the plasma drift patterns. In particular, we found the following: (1) A time-independent magnetospheric electric field produces a flow pattern in the magnetic inertial frame that does not vary with universal time. (2) This flow pattern becomes UT dependent in the geographic inertial frame because of the motion of the geomagnetic pole about the geographic pole. (3) The UT variation of the plasma flow pattern in the geographic inertial frame occurs on a time scale that is comparable to satellite orbital periods and that is much less than typical plasma convection flow times over the polar cap. (4) In the geographic inertial frame the main region of very low speed flow is not centered at 1800 LT but moves from about 1300 to 2300 LT during the course of a day. (5) In the geographic inertial frame a throatlike feature appears at certain universal times owing to the relative motion of the geographic and geomagnetic poles. This feature is not seen in the geomagnetic inertial frame and is not connected with our model of the magnetospheric electric field. These results and others described in the paper have important implications for both the interpretation of satellite data related to high-latitude ionospheric dynamics and the formation of ionospheric troughs.
TL;DR: In this article, the magnetopause is regarded as a perfectly absorbing boundary for the trapped energetic particles, and boundary waves are often present, which is consistent with a large-scale radial motion having an approximately 10-min period plus superimposed boundary waves with a 90-to 150-sec period.
Abstract: The present analysis deals with energetic (above 24 keV) particle data from the Isee satellites during a series of magnetopause crossings. The primary energetic particle data employed in the analysis are the three-dimensional distributions from the Isee A satellite. Correlative magnetic field measurements are used to relate the particle behavior to magnetic field characteristics at and earthward of the magnetopause. It is shown that, to first order, the magnetopause may be regarded as a perfectly absorbing boundary for the trapped energetic particles, that it is nearly always in motion, and that boundary waves are often present. The observed dayside magnetopause motion is consistent with a large-scale radial motion having an approximately 10-min period plus superimposed boundary waves with a 90- to 150-sec period.
01 Jan 1979
TL;DR: The Birkeland currents play an important role in the coupling of energy between the magnetosphere and lower ionosphere and atmosphere and must form the basis of any three-dimensional current system over a wide range of magnetospheric conditions.
Abstract: During his polar expeditions of 1902–1903, Kristian Birkeland determined that large-scale ionospheric currents were associated with the aurora. Birkeland suggested that these currents originated far from the earth and that they flowed into and away from the polar atmosphere along the geomagnetic field lines. The existence of such field-aligned or Birkeland currents was disputed because it was not possible to unambiguously identify current systems that are field-aligned and those which are completely contained in the ionosphere only from a study of surface magnetic field measurements. The presence of Birkeland currents has been confirmed during the last decade with particle and magnetic field observations acquired from a variety of rocket and satellite experiments. The large-scale characteristics of Birkeland currents determined from a wide variety of observations, but principally from experiments on the near earth TRIAD and ISIS-2 satellites, are reviewed here. These include the relationship of the locations, flow directions, and intensities of Birkeland currents with the geomagnetic field, interplanetary magnetic field, visual and radar aurora, particle measurements, and auroral kilometric radiation. The Birkeland currents play an important role in the coupling of energy between the magnetosphere and lower ionosphere and atmosphere and must form the basis of any three-dimensional current system over a wide range of magnetospheric conditions. These same Birkeland currents are also the critical ingredient in a variety of complicated plasma phenomena that have important applications to this planet (associated with substorms and the aurora) to Jupiter (associated with Io-related radio emissions, Cloutier et al., 1978; Dessler and Hill, 1978), and to the galaxy (related to comets and double radio sources, Alfven, 1977).
TL;DR: In this article, it was shown that when averaged in 1000 year intervals, the archaeomagnetic intensity data for the past 5000 years can be interpreted in terms of a change in the intensity of the dipole field.
TL;DR: In this article, the authors report results from 6 days' continuous recording of pulsation activity on a chain of magnetometers aligned East-West at 56.5°N geomagnetic latitude.
TL;DR: In this paper, a semiquantitative study of the configurations of Joule heating and momentum force is performed in terms of series of spherical functions, each individual term drives corresponding wind systems which depend on latitude, longitude, local time and universal time.
TL;DR: In this paper, the applied magnetic flux of the southward component of the IMF in GSM coordinates (Bz-) which impinges upon the sunward magnetopause is compared to the time integral of the auroral AL index during 56 intervals within a 3-month period in 1969 when interplanetary records from Heos 1 and Explorer 35 were available.
Abstract: The applied magnetic flux of the southward component of the IMF in GSM coordinates (Bz-) which impinges upon the sunward magnetopause is compared to the time integral of the auroral AL index during 56 intervals within a 3-month period in 1969 when interplanetary records from Heos 1 and Explorer 35 were available The periods of magnetic activity were those for which Bz was greater than 0 and AL was less than 20gamma at the beginning and end of the interval It was found that for these intervals, the time integral of the AL index was proportional to the applied magnetic flux with a correlation coefficient of 094 In addition, the empirical relationships between magnetic flux transfer, applied southward flux, and the time integral of AL arrived at by Holzer and Slavin (1978) on the basis of expansion and contractions of the forward magnetosphere observed with OGO 5 are reexamined and improved
TL;DR: A palaeomagnetic record of geomagnetic secular variation during the last 7000 years has been obtained from the sediments of Loch Lomond, Scotland as mentioned in this paper, where magnetic direction fluctuations repeat well between cores and show greater detail than other European records.
TL;DR: In this paper, a review of the literature on heavy ions in the energy range between 100 eV and 100 keV is presented, which includes all species of ions having a mass per unit charge of 2 AMU or greater.
Abstract: For purposes of this review heavy ions include all species of ions having a mass per unit charge of 2 AMU or greater. The discussion is limited primarily to ions in the energy range between 100 eV and 100 keV. Prior to the discovery in 1972 of large fluxes of energetic O+ ions precipitating into the auroral zone during geomagnetic storms, the only reported magnetosphere ion species observed in this energy range were helium and hydrogen. More recently O+ and He+ have been identified as significant components of the storm time ring current, suggesting that an ionosphere source may be involved in the generation of the fluxes responsible for this current. Mass spectrometer measurements on board the S3-3 satellite have shown that ionospheric ions in the auroral zone are frequently accelerated upward along geomagnetic field lines to several keV energy in the altitude region from 5000 km to greater than 8000 km. These observations also show evidence for acceleration perpendicular to the magnetic field and thus cannot be explained by a parallel electric field alone. This auroral acceleration region is most likely the source for the magnetospheric heavy ions of ionospheric origin, but further acceleration would probably be required to bring them to characteristic ring current energies. Recent observations from the GEOS-1 spacecraft combined with earlier results suggest comparable contributions to the hot magnetopheric plasma from the solar wind and the ionosphere.
TL;DR: The results of the detailed analyses of two disturbance events are presented in this article, showing that the global scale current system associated with a bay-type disturbance undergoes large changes even within the duration of the disturbance.