Engineering topics

Tsurutani, B. T.

Publications and source records attributed to Tsurutani, B. T..

At least 235 records · Page 13

NASA NTRS1986

International Cometary Explorer encounter with Giacobini-Zinner - Magnetic field observations

The vector helium magnetometer on the International Cometary Explorer observed the magnetic fields induced by the interaction of comet Giacobini-Zinner with the solar wind. A magnetic tail was penetrated about 7800 kilometers downstream from the comet and was found to be 10,000 kilometers wide. It consisted of two lobes, containing oppositely directed fields with strengths up to 60 nanoteslas, separated by a plasma sheet about 1000 kilometers thick containing a thin current sheet. The magnetotail was enclosed in an extended ionosheath characterized by intense hydromagnetic turbulence and interplanetary fields draped around the comet. A distant bow wave, which may or may not have been a bow shock, was observed at both edges of the ionoshpeath. Weak turbulence was observed well upstream of the bow wave.

Smith, E. J.↗

NASA NTRS1986

Energetic particle beams in the plasma sheet boundary layer following substorm expansion - Simultaneous near-earth and distant tail observations

Simultaneous observations of ions and electron beams in the near-earth and deep magnetotail following the onset of substorm are analyzed in terms of the substorm neutral line model. The observations were collected on March 20, 1983 with ISSE 1 and 3. Energy fluxes and intensity-time profiles of protons and electrons are studied. The data reveal that the reconnection at the near-earth neutral line produces ions and electrons for the plasma sheet boundary layer. The maximum electric potential along the neutral line is evaluated.

Scholer, M.↗

NASA NTRS1986

Comet-solar wind interaction - Dynamical length scales and models

ICE magnetometer measurements at Comet Giacobini-Zinner and model simulations of comet-solar wind interactions are analyzed. The magnetometer data reveal the existence of intense hydromagnetic turbulence, a draping of the magnetic field lines to form a magnetotail, a weak shock, and a magnetic barrier region in the magnetosphere. The global models of the comet-solar wind interaction are described. The observed data and models are compared and good correlation is displayed.

Mendis, D. A.↗

NASA NTRS1986

The bow wave of Comet Giacobini-Zinner - ICE magnetic field observations

Fitting of a Mach 2 shock surface to the ICE magnetic field data obtained near Comet Giacobini-Zinner has provided subsolar bow wave distances that infer neutral gas outflow rates comparable to previous measurements, and orientations of the bow wave symmetry axis that are consistent with the plasma measurements and motion of the comet relative to the solar wind. Mach values of 1.5-2 and transition thicknesses of the order of 10,000 km are inferred when the field magnitude and variance data are compared. Cross spectra of the transverse field components in and near the bow wave exhibit a peak near 0.01 Hz, or near the cyclotron frequency of ions from the water group. However, the level of turbulence is not consistent with that observed for similar configurations at planetary bow shocks.

Jones, D. E.↗

NASA NTRS1986

Strong hydromagnetic turbulence associated with Comet Giacobini-Zinner

The turbulence surrounding Comet Giacobini-Zinner reached intensities three orders of magnitudes above that of 'intermediate' solar wind conditions, was characterized by Delta B/B0 almost equal to one, and extended to cometocentric distances beyond one-million km. The strong spectral peak at 0.01 Hz and the general intensity profile of the turbulence are in excellent agreement with generation by plasma instabilities associated with the pickup of H2O(+) group ions. The total energy of the magnetic turbulence near 0.01 Hz is estimated to be 5 x 10 to the 15th joules and that of ion energization due to solar wind pickup 6 x 10 to the 13th watts. It thus takes a minimum of 100 s to build up the magnetic turbulence. This scale is approximately the linear growth rate of the ion pickup instability, giving a consistent picture of the energy source of the turbulence.

Tsurutani, B. T.↗

NASA NTRS1986

Hydromagnetic waves and instabilities associated with cometary ion pickup - ICE observations

The hydromagnetic turbulence surrounding comet Giacobini-Zinner is characterized by two dominant components: large amplitude, linearly polarized waves with periods near 100 s and circularly polarized wave packets with periods near 3 s. The latter appear in association with variations in field magnitude produced by the long period waves. A third, commonly observed feature is identified, consisting of a partial rotation of the magnetic field (a hook-like structure) which also appears to be triggered by the long period waves. The possibility that the long period waves are generated by the pickup of freshly ionized cometary neutrals has been investigated. A resonant instability identified by Wu and Davidson (1972) appears able to account for the long period waves in terms of the pickup of cometary ions of the water group. Application of the theory also indicates that the growth rate of proton cyclotron waves, as a consequence of hydrogen ion pickup, is somewhat lower, due to both higher neutral velocities and longer ionization times.

Tsurutani, B. T.↗

NASA NTRS1986

Giacobini-Zinner magnetotail - Ice magnetic field observations

A well developed magnetotail with a diameter of about 10,000 km has been revealed 7800 km downstream of the nucleus of Comet Giacobini-Zinner by International Cometary Explorer magnetic field observations. The tail is composed of two lobes of opposite magnetic polarity that are separated by an approximately 1500 km-thick plasma sheets. The field magnitude increases by a factor of 2 between the outer portions of the lobe and the central regions, where peak fields of about 60 nT were measured. Flaring is lowest in the high field regions of the central tail and greatest in the outer portions of the lobes, where minimum variance analyses on the magnetopause crossings furnishes flare angles of 20-40 deg. The Alfven field line draping model of type I cometary tails is confirmed by these observations.

Slavin, J. A.↗

NASA NTRS1986

Statics and dynamics of Giacobini-Zinner magnetic tail

The data gathered by the International Cometary Explorer during its traversal of Comet Giacobini-Zinner's tail are subjected to stress balance requirements, yielding estimates of unmeasured quantities. It is noted that the comet's tail is embedded in an ionosheath whose static pressure is nearly equal to the solar wind stagnation pressure, leading to a large lobe field strength. A systematic variation is found in the ion temperature across the tail, implying the variation of the pickup velocity of new ions. Axial stress balance yields an expression for the strength of the lobe field which reveals weak variation with axial distance.

Siscoe, G. L.↗

NASA NTRS1986

ISEE 3 observations during a plasma sheet encounter at 140 earth radii - Evidence for enhancement of reconnection at the distant neutral line

A plasma sheet encounter of the ISEE-3 spacecraft in the distant tail at 140 earth radii on March 20, 1983 is studied using magnetic field, energetic particle, and plasma electron data sets. The H-component magnetograms from auroral magnetometer stations, intensity-time profiles, high resolution magnetic field measurements, and electron and proton angular distributions are analyzed. The dynamics of the plasma sheet displayed by the strong tailward and earthward directed ion beams, large northward and southward magnetic fields excursions, and short tailward and earthward plasma flows are described.

Scholer, M.↗

NASA NTRS1986

Twisting of the geomagnetic tail

Theory and models indicate that the IMF causes the magnetotail to produce an observable twist, predicting that the torque should bring the north lobe south of the GSM xy plane on one flank of the magnetotail, and the south lobe north of the plane on the other flank. In this paper, ISEE-3 geotail observations are compared with simultaneously made IMP 8 IMF observations supplemented by inferred IMF B(y) polarities to demonstrate the IMF-induced magnetotail twist. The results indicate that twisting is the single most important factor accounting for observations of the north lobe south of the GSM xy plane and the south lobe north of the plane. The value of the observed magnetotail twist about its aberrated axis is about 18 deg.

Sibeck, D. G.↗

NASA NTRS1985

Electromagnetic ion beam instabilities. II

The results of Gary et al. (1984) on the properties of the right-hand resonant and nonresonant electromagnetic ion beam instabilities for relatively cool beam temperatures are extended. In particular, the parametric dependence of the real frequency at maximum growth of these modes is examined. It is demonstrated that the right-hand resonant ion beam instability can have maximum growth at frequencies near the ion-cyclotron frequency if the beam main component relative drift speed is about twice the Alfven speed and at least one of two conditions holds: that the ion beta or the beam main component relative temperature are sufficiently small, or the perpendicular-to-parallel beam temperature ratio is sufficiently large. These results support the identification of the right-hand resonant instability as the source of the large amplitude magnetic fluctuations observed upstream of slow shocks in the earth's magnetotail.

Gary, S. P.↗

NASA NTRS1985

Observations of the right-hand resonant ion beam instability in the distant plasma sheet boundary layer

Examples of the onset of a resonant ion beam instability are illustrated on the basis of ISEE 3 observations of 66 large amplitude wave events at the plasma sheet boundary layer. Analysis of the observational data showed that the observed wave and ion beam parameters were, in general, in agreement with linear theoretical predictions of resonant ion beam instability. The distribution of ion energies at the onset of the instability is given in a table.

Tsurutani, B. T.↗

NASA NTRS1985

Magnetic field properties of the distant magnetotail magnetopause and boundary layer

Models incorporating merging between dayside magnetosheath and magnetosphere field lines predict the location of the magnetotail boundary layer and bending of magnetotail field lines in the direction of the IMF. Previous observations supporting these models are reviewed, and a case of dense magnetotail boundary layer plasma and strongly bent field lines observed by ISEE 3 is examined. Observations of boundary layer plasma within a tangential discontinuity magnetopause are discussed. The model to explain this phenomenon requires that interconnected magnetotail and magnetosheath field lines leave the magnetotail via a narrow 'window'. Field lines in the dense boundary layer plasma veer away from the aberrated x axis more than those in the void magnetotail lobes in order to pass through the windows. Magnetosheath plasma must enter the magnetotail lobes through the windows at all downstream distances in order to supply he observed tailward flux of lobe plasma.

Sibeck, D. G.↗

NASA NTRS1985

Propagation mechanism of daytime Pc 3-4 pulsations observed at synchronous orbit and multiple ground-based stations

Observational data obtained during the last two decades show that the amplitude of daytime Pc 3-4 magnetic pulsations is controlled by the solar wind conditions. The high degree of correlation between the solar wind parameters and Pc 3-4 pulsations in the dayside magnetosphere suggests that the ultimate cause of the daytime Pc 3-4 pulsations must be the interaction of the solar wind with the earth's magnetosphere. The present paper is concerned with details regarding the control of the properties of the Pc 3-4 pulsations by the solar wind parameters, taking into account observations made at multiple ground-based stations. It is attempted to establish the relation between the daytime Pc 3-4 pulsations at the ground stations and the compressional Pc 3-4 waves in the magnetosphere. Attention is given to the most probable propagation mechanism of the daytime Pc 3-4 pulsations in the magnetosphere.

Yumoto, K.↗

NASA NTRS1985

Observations of 35- 10 1600-keV protons and low-frequency waves upstream of interplanetary shocks

The present investigation is concerned with a comparison of measurements of energetic protons in the range from 35 to 1600 keV and low-frequency waves (periods of approximately 6 s) on ISEE 3 associated with the passage of the large oblique shock of April 5, 1979, which exhibits an extended foreshock. An attempt is made to identify the energy of the particles which are responsible for the waves. Intensity profiles of both waves and particles as a function of upstream distance are compared, taking into account the relation between the energy of the particles and the period of the waves. The considered approach makes it possible to identify protons with energies of a few hundred keV as being responsible for the waves in the extended foreshock. It is believed that the high energy density of the high-energy solar flare protons preceding the shock could be responsible for 'seed' waves which provide the scattering centers necessary for the acceleration of the lower-energy protons via a first-order Fermi mechanism.

Sanderson, T. R.↗

NASA NTRS1985

The distant magnetotail's response to a strong interplanetary magnetic field By - Twisting, flattening, and field line bending

During an interval of strong interplanetary magnetic field (IMF) By, while ISEE 3 was in the distant magnetotail, the north lobe was observed south of the ecliptic plane. Lobe field lines were strongly bent in the direction of the IMF, and a dense boundary layer plasma was observed. During the interval, magnetopause normals pointed in the z direction, although ISEE 3 was near the dawnside ecliptic plane. The observations are interpreted in terms of field line bending within a twisted and flattened magnetotail.

Sibeck, D. G.↗

NASA NTRS1985

Correlated observations of substorm effects in the near-earth region and the deep magnetotail

Simultaneous observations of energetic particle measurements from the geosynchronous satellite 1982-019 and magnetic field, electron plasma, and energetic proton and electron measurements obtained with ISEE 3 in the deep tail are presented. The data are supplemented by ground magnetograms. A substorm occurred on March 22, 1983, close to 0300 UT as identified in the ground magnetograms and by a particle injection at geosynchronous orbit. About 10 min later, ISEE 3 observed (at a distance of approximately 130 RE in the deep tail) magnetic field, plasma, and energetic particle signatures consistent with the passage of a plasmoid. After the passage of the plasmoid the satellite enters shortly into a lobelike environment, in which an energetic proton beam is observed. High-resolution magnetic field data are indicative of small-scale structures in the postplasmoid plasma sheet. From the plasma sheet flow speed during the plasmoid's passage it is concluded that the 0300 UT substorm is responsible for its origin. This allows an approximate timing of the plasmoid release at a near-earth neutral line and of the plasma sheet recovery after substorm onset, and it indicates a close relationship between processes in the near-earth plasma sheet and the deep tail during substorms.

Scholer, M.↗

NASA NTRS1985

Coupling between the solar wind and the magnetosphere - CDAW 6

It is pointed out that an extensive study of the causes and manifestations of geomagnetic activity has been carried out as part of the sixth Coordinated Data Analysis Workshop, CDAW 6. The present investigation has the objective to determine the coupling between the solar wind and the magnetosphere for the two selected analysis intervals, taking into account, as a basis for the study, the interplanetary field and plasma observations from ISEE 3 and IMP 8 and the geomagnetic activity indicators developed by CDAW 6 participants. The method of analysis employed is discussed, giving attention to geomagnetic indices, upstream parameters, and a cross-correlation analysis. In a description of the obtained results, the March 22, 1979 event is considered along with the March 31 to April 1, 1979 event, and an intercomparison of the events. The relationship between interplanetary indices and the resulting geomagnetic activity for the two CDAW 6 intervals is illustrated.

Tsurutani, B. T.↗