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Barouch, E.

Publications and source records attributed to Barouch, E..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

The Crab pulsar light curve in the soft gamma ray range: FIGARO II results

The FIGARO II experiment (a large area, balloon borne, crystal scintillator detector working from 0.15 to 4.3 MeV) observed the Crab pulsar on 1990 Jul. 9 for about seven hours. The study of the pulse profile confirms some structures detected with a low significance during the shorter observation of 1986, and adds new important elements to the picture. In particular, between the two main peaks, two secondary peaks appear centered at phase values 0.1 and 0.3, in the energy range 0.38 to 0.49 MeV; in the same energy range, a spectral feature at 0.44 MeV, interpreted as a redshifted positron annihilation line, was observed during the same balloon flight in the phase interval including the second main peak and the neighboring secondary peak. If the phase interval considered is extended to include also the other secondary peak, the significance of the spectral line appears to increase.

Massaro, E.↗
NASA NTRS1976

Three-dimensional interplanetary stream magnetism and energetic particle motion

Cosmic rays interact with mesoscale configurations of the interplanetary magnetic field. A technique is presented for calculating such configurations in the inner solar system, which are due to streams and source conditions near the sun, and maps of magnetic field are constructed for some plausible stream and source conditions. One effect of these mesoscale configurations on galactic cosmic rays is shown to be an out-of-the-ecliptic gradient drift sufficient to explain Forbush decreases. The effects on solar energetic particles include small polar drifts due to the field gradients and a possibly large modification of the time-intensity profiles and anisotropy characteristics due to the formation of mirror configurations in space. If a diffusion model is applicable to solar particles, the true diffusion coefficient will be masked by the effects of streams. A conceptual model which incorporates these ideas and those of several other models is presented.

Barouch, E.↗
NASA NTRS1976

Interplanetary stream magnetism - Kinematic effects

The particle density and the magnetic-field intensity and direction are calculated for volume elements of the solar wind as a function of the initial magnetic-field direction and the initial speed gradient. It is assumed that the velocity is constant and radial. These assumptions are approximately valid between about 0.1 and 1.0 AU for many streams. Time profiles of the particle density, field intensity, and velocity are calculated for corotating streams, neglecting effects of pressure gradients. The compression and rarefaction of the magnetic field depend sensitively on the initial field direction. By averaging over a typical stream, it is found that the average radial field intensity is inversely proportional to the square of the heliocentric distance, whereas the average intensity in the direction of the planets' motion does not vary in a simple way, consistent with deep space observations. Changes of field direction may be very large, depending on the initial angle; but when the initial angle at 0.1 AU is such that the base of the field line corotates with the sun, the spiral angle is the preferred direction at 1 AU. The theory is also applicable to nonstationary flows.

Burlaga, L. F.↗
NASA NTRS1975

Interplanetary magnetic fields, their fluctuations, and cosmic ray variations

The cause of Forbush decreases is examined using neutron monitor data and measurements of the interplanetary magnetic field. It is found that for the period examined (Dec. 15, 1965 to April 23, 1966) large enhancements of the interplanetary magnetic field correlate well with decreases in cosmic ray intensity, while various parameters connected with the fluctuations in the field do not display such good correlation. The inference is drawn that Forbush decreases are not related to the turbulence or random motions in the field but to the large scale features of the field.

Barouch, E.↗
NASA NTRS1975

Causes of Forbush decreases and other cosmic ray variations

The relationship between neutron monitor variations and the intensity variations of the interplanetary magnetic field is studied by using Deep River data and Imp series satellite data. In over 80% of the cases studied in 1968, identifiable depressions of the cosmic ray intensity are associated with magnetic field enhancements of several hours duration and intensity above 10 gamma. Conversely, almost every magnetic field enhancement has an identifiable effect (though not necessarily a marked depression) on the cosmic ray intensity. Perpendicular gradient drifts are suggested as one possible mechanism producing the individual decreases, and some ideas on the recovery processes are presented. Long-lasting Forbush decreases are found to be the consequence of the action of several successive magnetic field enhancements. Evidence is presented that indicates that most of these enhancements are caused by the steepening of streams in interplanetary space.

Barouch, E.↗
NASA NTRS1975

A survey of the interplanetary magnetic field

All interplanetary magnetic field measurements from near-earth satellites have been collected in the form of hourly averages for the years 1963-1974. Solar cycle variations of the field and the exceptional events of this cycle are discussed in relation to the associated cosmic ray events, and statistical properties of the field over this period are presented. The presence of magnetic blobs as a permanent feature of the field is demonstrated and explained. The implications of these results for the theory of cosmic ray modulation are presented and analyzed.

Barouch, E.↗
NASA NTRS1975

Enhanced interplanetary magnetic fields as the cause of Forbush decreases

A strong correlation is observed between neutron monitor variations and variations in the interplanetary magnetic field intensity. It is thought that the cosmic ray intensity depressions are caused by perpendicular gradient drifts. The perpendicular gradient drift velocity for particles with energies exceeding 500 MeV in a magnetic field configuration produced by a representative stream is at least a few times the solar wind velocity. Thus particles can be swept away from the ecliptic by such a blob faster than the blob advances. It is suggested that this mechanism might be the cause of Forbush decreases and other cosmic ray variations near 1 AU.

Burlaga, L. F.↗
NASA NTRS1974

Interplanetary stream magnetism: Kinematic effects

The particle density, and the magnetic field intensity and direction are calculated in corotating streams of the solar wind, assuming that the solar wind velocity is constant and radial and that its azimuthal variations are not two rapid. The effects of the radial velocity profile in corotating streams on the magnetic fields were examined using kinematic approximation and a variety of field configurations on the inner boundary. Kinematic and dynamic effects are discussed.

Burlaga, L. F.↗
NASA NTRS1974

Causes of forbush decreases and other cosmic ray variations

The relationship between neutron monitor variations and the intensity variations of the interplanetary magnetic field is studied, using Deep River data and IMP-series satellite data. In over 80% of the cases studied, identifiable depressions of the cosmic ray intensity are associated with magnetic field enhancements of several hours duration and intensity above 10 gamma. Conversely, each magnetic field enhancement has an identifiable effect (though not necessarily a marked depression) on the cosmic ray intensity. Long lasting Forbush decreases are found to be the consequence of the successive action of several such features. An explanation is presented and discussed.

Barouch, E.↗
NASA NTRS1974

Two views of cosmic ray propagation in the solar system

Diffusion and scatter free cosmic ray propagation theories are discussed in terms of the quality of their alternate viewpoints. A hypothetical model of conditions in interplantary space is described which aids in the comparison. A plot of the intensity of the interplanetary magnetic field over a long period is presented, and the association of these regions with high velocity streams is shown to support the scatter free viewpoint.

Barouch, E.↗