Engineering topics

Burlaga, L. F.

Publications and source records attributed to Burlaga, L. F..

At least 253 records · Page 14

NASA NTRS1972

Discontinuities and shock waves in the interplanetary medium and their interaction with the magnetosphere.

The discontinuous structure of the solar wind is described with emphasis on properties related to geomagnetic impulses. Some of the discontinuities are clearly hydromagnetic shocks and tangential discontinuities, and can produce a significant change in the momentum flux at the magnetosphere boundary. Such a change generates an impulse which propagates through the magnetosphere to the earth where it is observed world-wide as an impulse in magnetograms. The propagation process is not reviewed here, but the relation between the initial cause (discontinuity) and the final effect (geomagnetic impulse) is reviewed in detail. The various types of impulses are examined, and are related qualitatively to the various types of discontinuities. The magnitude of an impulse is related to the change in the momentum flux. The propagation time and the rise time depend on the propagation process rather than on the initial state.

Burlaga, L. F.↗

NASA NTRS1972

The solar wind near the sun - The solar envelope.

Recent observational data and models for the structure of the solar envelope are discussed, with emphasis on those physical processes in the envelope which are decisive in determining solar wind states at 1 AU. Diffusion of relativistic solar flare protons, collisionless damping of a variable flux of hydromagnetic waves, heat transfer from electrons to protons, acceleration by Alfven waves, and magnetic field effects are examined from the viewpoint of possible contributions to solar wind behavior.

Burlaga, L. F.↗

NASA NTRS1972

Microstructure of the Interplanetary Medium

High time resolution measurements of the interplanetary magnetic field and plasma reveal a complex microstructure which includes hydromagnetic wave and discontinuities. The identification of hydromagnetic waves and discontinuities, their statistical properties, their relation to large-scale structure, and their relative contribution to power spectra are discussed.

Burlaga, L. F.↗

NASA NTRS1971

Hydromagnetic waves and discontinuities in the solar wind.

Development of a theory of hydromagnetic waves and discontinuities which is appropriate for the solar wind. The experimental evidence for the various waves, discontinuities, and some of the instabilities which are predicted by this theory is reviewed. Nearly all of the discontinuities given by the theory are shown to exist in the solar wind. These include tangential discontinuities, forward and reverse fast and slow shocks, perpendicular shocks, and Alfven shocks. Parallel shocks and contact discontinuities have not been found. A number of special cases are considered which show the basic physical properties of hydromagnetic waves in an anisotropic, multifluid, collisionless plasma. A treatment of discontinuities is presented which most resembles those of Chao (1970) and Hudson (1970). On the basis of the experimental results reviewed it is concluded that hydromagnetic theory is applicable to the solar wind.

Burlaga, L. F.↗

NASA NTRS1971

Reverse and forward slow shocks in the solar wind.

Probable reverse and forward slow shocks were found in plasma and magnetic-field data from Pioneer 6. The shocks were oblique and weak (Mach of approximately 1.2). No reverse fast shocks were found. Numerous (50) other discontinuities were found, most of which are probably tangential, since all the plasma parameters changed across most of them.

Burlaga, L. F.↗

NASA NTRS1971

The solar envelope

Processes which occur within the region between approximately 2 solar radii and 25 solar radii, which is called the solar envelope and the effect on the solar wind as seen at 1 AU are discussed. In the envelope the wind speed becomes supersonic and super-Alfvenic, the magnetic energy density is larger than the flow energy density, and the magnetic energy density is much larger than the thermal energy density. Large azimuthal gradients in the bulk speed are expected in the envelope, but the stream interactions near the outer edge of the envelope are probably relatively small. Cosmic ray observations suggest the presence of hydromagnetic waves in the envelope. The collisionless damping of such waves could heat protons out to approximately 25 solar radii and thereby cause an increase in V and T sub p consistent with the observed T sub p -V relation. A mechanism which couples protons and electrons would also heat and accelerate the wind. Alfven waves can accelerate the wind in the envelope without necessarily causing heating of protons; the Lorentz force might have a similar effect.

Burlaga, L. F.↗

NASA NTRS1971