Charles L. Hyder

The polarization of emission lines in astronomy. iii - the polarization of coronal emission lines.

Resonance polarization theory to set limits on degree of polarization expected from coronal emission lines

A short-lived chromospheric flare-point with a lifetime of 20 seconds and rise and fall times of 5 seconds

We have observed a chromospheric brightening in the H alpha and Ca II K lines with a diameter of about 1 arc second. The time structure of this event, obtained with a relative resolution of 1 second, shows the rise time to be 4 seconds, the lifetime (FWHM) to be 20 seconds, and the decay time to be 5 seconds. This imposes new constraints on flare-point models. These restrictions can be accommodated easily by either an infall-impact flare model or a model invoking the precipitation of high-energy particles from the corona.

CORONAL IONIZATION BY TWO-STEP COLLISION PROCESSES

That ionization by electron impact for some coronal ions may take place via the double process of collisional excitation to metastable levels, thence collisional ionization from thess excited levels rather than by direct (onization from the ground state is suggested. The relative efficiency of this double- collision process depends primarily on the mean decay lifetimes for the excited levels. A specific computatlon based on estimated upper limits to the mean lifetimes of excited levels in the Fe x-Fe xv sequence shows a flatter spectrum of ion densities and a somewhat lower ionization temperature than is obtained from direct collisional ionization from the ground state, assuming that the abundance of Fe x equals that of Fe xiv. The two-step collision mechanism permits the possibility of a density dependence in the ionization equilibrium. (auth)

Random microscopic magnetic fields in a plasma.

Random plasma magnetic fields caused by electrons coming closer to plasma atom than mean interelectron distance and by electrons that pass at or beyond this distance