Engineering topics

Ipavich, F. M.

Publications and source records attributed to Ipavich, F. M..

118 records · Page 7

NASA NTRS1975

Galactic winds driven by cosmic rays

Cosmic rays traveling through a magnetized plasma with mean velocity greater than the Alfven speed can become coupled to the plasma by the emission of magnetohydrodynamic waves. Using a time-independent, spherically symmetric, hydrodynamic treatment, we show that cosmic rays escaping from a galaxy can carry along thermal gas and produce a 'galactic wind'. Solutions indicate that a typical galaxy can lose mass at a rate of about 1 to 10 million solar masses per year and energy at a rate of about 10 to the 40th to 10 to the 42nd ergs per sec. The possible role of galactic winds in radio and X-ray sources is explored. A model is proposed to explain the X-ray emission observed from clusters of galaxies.

Ipavich, F. M.↗

NASA NTRS1975

Observations of protons not exceeding 1 MeV/nuc and ions during the September 1974 series of flares

Results are presented on observations of energetic particles made during an active solar period in September 1974, concentrating in particular on an ESP (Energetic Storm Particle) event observed in association with an interplanetary shock wave on 21 September. It is shown that the observed variations in the proton to alpha particle ratios and spectral indices can be explained either by pile-up or by acceleration models of ESP events.

Ipavich, F. M.↗

NASA NTRS1975

Analysis of the 31 Oct 1972 interplanetary shock wave and associated unusual phenomena

We analyze in detail the disturbed time period Oct. 31-Nov. 1, 1972 using magnetic field, plasma, and energetic particle data as well as magnetic field data. In particular, we discuss an interplanetary forward shock wave accompanied by a traditional shock-spike event in the energetic particles, a large tangential discontinuity correlated with a geomagnetic storm main phase, and a reverse interplanetary shock. This forward and reverse shock pair was caused by a 2N solar flare which occurred some 47 hours earlier. We also discuss an unusual rarefaction in the solar wind following (and probably related to) the shock pair, wherein the Alfven Mach number abruptly decreased from about 4.5 to about 1.5, allowing the earth's bow shock to move outward at least 20 earth radii beyond its nominal position.

Ipavich, F. M.↗

NASA NTRS1974

Possible acceleration of charged particles through the reconnection of magnetic field lines in interplanetary space

Prominent intensity spikes in the flux of protons and alphas with less than 0.5 MeV per charge have been observed in the region several hours behind an interplanetary shock front. The small spatial scale of these events and the high anisotropy of the particle flux suggest local acceleration. The spectra of the particles, which are cut off at equal energy per charge, suggest acceleration through an electric field. The possibility that these events have their origin in active magnetic neutral sheets in the shocked solar wind is examined.

Levy, E. H.↗

NASA NTRS1974

The Compton-Getting effect for low energy particles

The traditional first-order Compton-Getting effect, which relates particle distributions as observed in two frames of reference moving with constant relative velocity, is inadequate for the description of low-energy particles (less than a few hundred keV/nucleon) in the solar system. An exact procedure is given for recovering both isotropic and anisotropic distributions in the solar wind frame from observations made in a spacecraft frame. The method is illustrated by analyzing a particle event observed by an experiment on IMP-7 on Oct. 31, 1972.

Ipavich, F. M.↗

NASA NTRS1974

Post-shock spikes: A new feature of proton and alpha enhancements associated with an interplanetary shock wave

Abrupt and prolonged enhancements in the intensities of 100 to approximately 2000 keV nucleon protons and alpha particles observed in interplanetary space are interpreted as particle populations confined between an interplanetary shock front and a magnetic field discontinuity. Prominent intensity spikes observed only below approximately 400 keV per charge for both protons and alpha particles several hours behind the shock front suggest that some fraction of the confined particles is accelerated by an energy per charge dependent process.

Gloeckler, G.↗

NASA NTRS1974

Possible acceleration of charged particles through the reconnection of magnetic field lines in interplanetary space

Prominent intensity spikes in the flux of protons and alphas with less than 0.5 MeV per charge were observed in the region several hours behind an interplanetary shock front. The small spatial scale of these events and the high anisotropy of the particle flux suggest local acceleration. The spectra of the particles, which are cut off at equal energy per charge, suggest acceleration through an electric field. The possibility is examined that these events have their origin in active magnetic neutral sheets in the shocked solar wind.

Levy, E. H.↗

NASA NTRS1974

Post-shock spikes - A new feature of proton and alpha enhancements associated with an interplanetary shock wave

Description of the salient characteristics of temporal variations of greater than or about equal to 100 keV/nucleon protons and alpha particles during a ten-hour period associated with the passage of an interplanetary shock wave. In addition to extending measurements to energies considerably below previous observations for energetic storm particle and shock-spike events, the discovery of a new low energy feature, referred to as 'postshock spikes', is reported. The typical width of these spikes is several minutes, but they occur several hours after the passage of the shock front. Evidence is presented that spikes depends on the energy per charge of the particles.

Gloeckler, G.↗

NASA NTRS1974

The Compton-Getting effect for low energy particles

It was found that the traditional first-order Compton-Getting effect, which relates particle distributions as observed in two frames of reference moving with constant relative velocity, is inadequate for the description of low energy particles (less than a few hundred keV/nucleon) in the solar system. An exact procedure is given for recovering both isotropic and anisotropic distributions in the solar wind frame from observations made in a spacecraft frame. The method was illustrated by analyzing a particle event observed on IPM-7.

Ipavich, F. M.↗

NASA NTRS1970

Cosmic X rays and gamma rays

Diffuse cosmic X and gamma ray spectrum analysis, considering implications for Compton scattering models in intergalactic space

Ipavich, F. M.↗