Engineering topics

Balogh, A.

Publications and source records attributed to Balogh, A..

122 records · Page 7

NASA NTRS1992

Ulysses - Interplanetary shocks between 1 and 4 AU

The complex solar events of March 1991 are evident as a large increase in the rate of occurrence of interplanetary shocks. Using Ulysses magnetic field and plasma measurements, 32 forward shocks and 7 reverse shocks have been identified in the 280 day interval from October 26, 1990 to August 1, 1991. The March events alone have produced 9 shocks, several in association with coronal mass ejections. The shocks have been identified and analyzed to find theta(BN), the speeds in the upstream solar wind, the Mach number, and the inertial speeds along the radial and magnetic field directions.

Burton, M. E.↗

NASA NTRS1992

The magnetic field investigation on the Ulysses mission - Instrumentation and preliminary scientific results

A fundamental feature of the heliosphere is the three-dimensional structure of the interplanetary magnetic field. The magnetic field investigation on Ulysses, the first space probe to explore the out-of-ecliptic and polar heliosphere, aims at determining the large-scale features and gradients of the field, as well as the heliolatitude dependence of interplanetary phenomena so far only observed near the ecliptic plane. The Ulysses magnetometer uses two sensors, one a Vector Helium Magnetometer, the other a Fluxgate Magnetometer. Onboard data processing yields measurements of the magnetic field vector with a time resolution up to 2 vectors/second and a sensitivity of about 10 pT. Since the switch-on of the instrument in flight on 25 October 1990, a steady stream of observations has been made, indicating that at this phase of the solar cycle the field is generally disturbed: several shock waves and a large number of discontinuities have been observed, as well as several periods with apparently intense wave activity. The paper gives a brief summary of the scientific objectives of the investigation, followed by a detailed description of the instrument and its characteristics. Examples of wave bursts, interplanetary shocks and crossings of the heliospheric current sheet are given to illustrate the observations made with the instrument.

Balogh, A.↗

NASA NTRS1992

The Ulysses Cosmic Ray and Solar Particle Investigation

The Ulysses experimental program termed Cosmic Ray and Solar Particle Investigation (COSPIN) is described, with special attention given to the scientific objectives of the COSPIN, the measurements performed, the initial postlaunch results, and the characteristics of the individual COSPIN instruments. The instrument package of the COSPIN experiment includes the Low Energy Telescope, the High Energy Telescope, the High-Flux Telescope, the Electron Telescope, the Digital Processing Unit, two Anisotropy Telescopes, and two dc/dc power converters. Preliminary results obtained from quick-look data from COSPIN telescopes showed that the instruments are functioning properly and that their design has achieved both the wide dynamic range and the precision required in this mission.

Simpson, J. A.↗

NASA NTRS1991

Multipoint observations of planar interplanetary magnetic field structures

IMF data made on November 1, 1984, by three spatially well-separated spacecraft in the solar wind are presented. The IMF measured by each of the spacecraft is found to consist of a multiplicity of structures within which the magnetic field varies in parallel planes. The orientations of these planes at the three spacecraft locations are similar. The planes are inclined at a large angle to the ecliptic, and they lie almost perpendicular to the nominal Parker spiral direction in the ecliptic. Intercomparisons of the measurements at the various spacecraft show that the IMF features at one spacecraft are clearly reproduced at another, with time delays required for signal propagation. From these time delays and the mutual separations of the spacecraft, it is inferred that the structures are convecting with the ambient flow. Simultaneous observations made downstream of the bow shock in the magnetosheath reveal that the magnetosheath magnetic field, too, is planar.

Farrugia, C. J.↗

NASA NTRS1991

Theory and observation of energetic ions in the lobes of the geomagnetic tail

The Owen et al. (1990) model, which attempts to explain the nature of the pitch angle distributions of energetic ions within the lobes of the distant geomagnetic tail is briefly reviewed. Energetic ion data from the ISEE-3 spacecraft obtained during early 1983, when the spacecraft made several traversals of the distant geomagnetic tail are then presented. The data demonstrate that during quiet periods in which the spacecraft is continuously located in the tail lobes, the pitch angle distribution is observed to be highly anisotropic, being peaked closely perpendicular to the magnetic field direction, but with a small net flow in the antisunward direction, in agreement with the model results. Further predictions of the model, concerning the variation of the lobe energetic ion distributions with position in the lobes, are compared to observations made as the spacecraft performed a traversal of the lobe. Finally, since the model indicates that a more isotropic distribution should exist in the tail lobe during solar particle events, data is presented from such a period for further comparison. In all the above cases, good agreement is demonstrated between the data and the expections of the model.

Owen, C. J.↗

NASA NTRS1991

Cometary water-group ions in the region surrounding Comet Giacobini-Zinner - Distribution functions and bulk parameter estimates

The bulk parameters (number density and thermal energy density) of cometary water-group ions in the region surrounding Comet Giacobini-Zinner have been derived using data from the EPAS instrument on the ICE spacecraft. The derivation is based on the assumption that the pick-up ion distribution function is isotropic in the frame of the bulk flow, an approximation which has previously been shown to be reasonable within about 400,000 km of the comet nucleus along the spacecraft trajectory. The transition between the pick-up and mass-loaded regions occurs at the cometary shock, which was traversed at a cometocentric distance of about 100,000 km along the spacecraft track. Examination of the ion distribution functions in this region, transformed to the bulk flow frame, indicates the occurrence of a flattened distribution in the vicinity of the local pick-up speed, and a steeply falling tail at speeds above, which may be approximated as an exponential in ion speed.

Staines, K.↗

NASA NTRS1991

Comparison of magnetosonic wave and water group ion energy densities at Comet Giacobini-Zinner

Measurements of the Comet Giacobini-Zinner (GZ) are presented to determine to what extent wave-particle scattering redistributed the initial pick-up energy of the ion population. Also examined is the difference between the ion thermal energy and the energy in the magnetic fields of the waves. In spite of uncertainty of about a factor of 2 noted in the pick-up and mass-loaded regions, it is shown that less than approximately 50 percent of the pick-up energy is converted into wave magnetic energy in the inbound pick-up region.

Staines, K.↗

NASA NTRS1991

Energetic water-group ions at Comet Giacobini-Zinner - An overview of observations by the EPAS instrument

An overview is presented of the observations of energetic (45-480 keV) cometary water group ions made by the EPAS instrument on the ICE spacecraft during the fly-by of Comet Giacobini-Zinner in September 1985. The discussion covers ion observations in the large-scale ion pick-up region surrounding the comet on about 10 exp 6 km spatial scales, observations of the cometary shock at about 100,000 km and the region of slowed mass-loaded flows which occur downstream, and the finite gyroradius effects which occur near the closest approach.

Cowley, S. W. H.↗

NASA NTRS1990

An interplanetary planar magnetic structure oriented at a large (about 80 deg) angle to the Parker spiral

Magnetic field structures in the solar wind, characterized by a variation of the field vectors within a plane inclined to the ecliptic ('Planar Magnetic Structures', PMSs), were reported recently (Nakagawa et al., 1989). These PMSs have the property that the plane of variation of the field also contains the nominal Parker spiral direction. An observation of a PMS where the direction of the line of intersection of the plane of field variation with the ecliptic plane makes a large (about 80 deg) angle to the Parker spiral direction is presented. Furthermore, the angular variables of the field (1) vary over a restricted range, and (2) are linearly related. The latter property is related to the former. Currently proposed models for the origin of PMS, inasmuch as they require field configurations which retain strict alignment with the Parker spiral direction from formation to observation, are probably incomplete.

Farrugia, M. W.↗

NASA NTRS1990

Pitch angle distributions of energetic ions in the lobes of the distant geomagnetic tail

A model is presented which accounts for observed pitch angle distributions of energetic ions in the lobes of the deep geomagnetic tail. Energetic (greater than 35 keV) ion data from the ISEE-3 spacecraft obtained during 1982-1983, when the spacecraft made a series of transversals of the distant geomagnetic tail (X sub GSE greater than -238 R sub E) is considered. Analysis indicates that under usual conditions the lobe pitch angle distribution is highly peaked at pitch angles closely perpendicular to the magnetic field direction while also showing a small downtail anisotropy. It is noted, however, that during periods of solar particle enhancements the lobe distributions become much more clearly isotropic. The proposed model successfully reproduces these features of the data and also accounts for the more isotropic ion population observed in the lobe during solar particle events, when the terrestrial component of the magnetosheath source may be considered negligeable in comparison to the enhanced solar component.

Owen, C. J.↗

NASA NTRS1988

The magnetic field investigation on Cluster

The magnetic field investigation of the Cluster four-spacecraft mission is designed to provide intercalibrated measurements of the B magnetic field vector. The instrumentation and data processing of the mission are discussed. The instrumentation is identical on the four spacecraft. It consists of two triaxial fluxgate sensors and of a failure tolerant data processing unit. The combined analysis of the four spacecraft data will yield such parameters as the current density vector, wave vectors, and the geometry and structure of discontinuities.

Balogh, A.↗

NASA NTRS1985

Pitch angle distributions of 35-1000 keV protons at quasi-perpendicular interplanetary shocks

The characteristic features of the scatter-free acceleration process near perpendicular shocks are examined in the upstream and downstream pitch angle distributions of 35 to 1000 keV protons. Reasonable quantitative agreement is found between theoretical predictions and observations. The role played by bottle geometries, leading to enhanced acceleration, is highlighted.

Balogh, A.↗

NASA NTRS1983

The magnetic-field investigation on ISPM

The International Solar Polar Mission (ISPM) onboard instrumentation for the magnetic field experiment to establish, on the basis of in-situ observations, the heliolatitude dependence of the interplanetary magnetic field, is described. The prime output consists of vector measurements, made by two triaxial magnetometers, of the ambient magnetic field along the orbit of the spacecraft. The onboard data processor generates two data streams to be transmitted through the spacecraft telemetry. The low speed, analog data stream consists of averaged and despun vector measurements, digitized in the spacecraft analog to digital converter (ADC). The despinning algorithm used in the analog processor is described. The high speed, digital data stream consists of vector measurements digitized in the instrument ADCs, generating up to two vector samples per sec. Multiple data-path switching is used to increase system reliability and to allow cross calibration of the ADCs. On board facilities for inflight calibration are described.

Balogh, A.↗

NASA NTRS1973

Higher order Compton-Getting anisotropies.

The Compton-Getting effect relates the distribution function of a particle population in a given frame of reference to that in another frame, moving at constant velocity V relative to the first. A study is made of the effects that arise when, contrary to previous assumptions, second-order terms in (V/v), where v is the particle velocity, are retained, and when the given distribution function is not isotropic. The importance of the extra terms is then examined in the specific case of low-energy solar protons in interplanetary space.

Balogh, A.↗