Engineering topics

Anzer, U.

Publications and source records attributed to Anzer, U..

4 records

NASA NTRS1991

The fibril structure of prominences

It is suggested that the fibril structure of prominences may be caused by filamentation during its formation by radiative instability. Also discussed are the effects of other types of instability and a mechanism for the formation of vertical threads is given. The models indicate that highly inhomogeneous density structures can exist in the presence of smooth profiles for the plasma pressure and magnetic field. In the particular models the plasma pressure of a fibril prominence is higher and the vertical magnetical field is weaker than in a uniform prominence model, while the mass is substantially smaller.

Priest, E. R.↗

NASA NTRS1985

The global structure of magnetic fields which support quiescent prominences

Magnetic fields in quiescent prominences were observed, but only recently has it become possible to measure the full magnetic field vector. The component of the field along the line of sight, B (parallel) can be uniquely determined, whereas for the component perpendicular to the line of sight B (perpendicular) and -B (perpendicular) are indistinguishable. An ambiguity remains in the actual magnetic field vector, in particular with respect to its orientation relative to the prominence axis. A sample of more than 100 prominences were studied. A more detailed analysis of 10 prominences are presented, and then set these prominence fields into relation to the underlying photospheric fields. It is found from statistical analysis of several hundred prominences that in 25% of the cases the field penetrates the prominence directly, whereas in 75% the field orientation in the prominence is reversed.

Anzer, U.↗

NASA NTRS1980

The preflare state

The accumulation, storage and irreversible release of the free energy necessary for a solar flare are discussed on the basis of data obtained from the Apollo Telescope Mount on Skylab and other pertinent sources. Skylab and OSO 7 observations of possible flare precursors and flare evolution are presented, and the evolution of the flare of Sept. 5, 1973, the most completely observed flare of the Skylab program, is described in detail, with account given to magnetic structures and H alpha radiation. Theories of the preflare state are then reviewed, with attention given to the force-free fields and coronal arcades, thermal and magnetic structures and the MHD stability of coronal loops.

Van Hoven, G.↗

NASA NTRS1979

Mass flow in loop type coronal transients

Coronal transients having characteristics of a well-defined loop structure are examined, particularly with respect to temporal changes in the density and mass per unit length along the loop over periods of several days after the initial eruption. Measurements of mass distributions as a function of time are presented for eight transients, and one particular transient with a fairly simple configuration is investigated in more detail. Theoretical calculations are combined with the masses and densities derived from the observations to obtain estimates of the material flow in the transients; this flow is modeled on the assumption that magnetic forces drive and confine the loop. The flow field is found to be diverging everywhere, indicating that the density decreases in time. It is inferred that the transient legs are approximately in hydrostatic equilibrium and that most of the mass of the transient is lost from the sun during the initial phase.

Anzer, U.↗