PROPERTIES OF INTERPLANETARY DUST FROM INFRARED AND OPTICAL OBSERVATIONS .2. BRIGHTNESS, POLARIZATION, TEMPERATURE, ALBEDO AND THEIR DEPENDENCE ON THE ELEVATION ABOVE THE ECLIPTIC

In the first paper, by using the ''node of lesser uncertainty'' method , Dumont & Levasseur-Regourd (1988) have obtained the heliocentric gra dients of the local temperature, the local volume intensity (i.e. loca l brightness) and the local albedo in the symmetry plane of the zodiac al cloud (close to ecliptic plane). In the present work, by a new trea tment applied to the IRAS data, the values of the gradients are derive d more precisely. The method is also applied out of the ecliptic, to r etrieve the local values of brightness, polarization, temperature and albedo out of the symmetry plane, first towards the ecliptic pole, and then in the so-called tangential plane (i.e, plane tangent to the Ear th orbit and perpendicular to the ecliptic). Maps showing the changes of these local values (normalized at a solar distance of 1 AU and a ph ase angle of 90 degrees) with elevation above the ecliptic up to 0.4 A U, are drawn in this plane. The brightness, the polarization and the t emperature decrease, while the albedo increases, with increasing eleva tion. The decrease of the temperature is also established at a solar d istance of 1.5 AU and up to 1 AU above the ecliptic. These results can be interpreted in terms of at least two populations of dust with diff erent average orbital inclinations, originating from periodic comets a nd asteroidal dust bands, and from new comets.