CONJUGATE AND CLOSELY-SPACED OBSERVATIONS OF AURORAL RADIO ABSORPTION .I. SEASONAL AND DIURNAL BEHAVIOUR

The paper gives results from nearly 2 yr of observation of auroral radio absorption at and around the magnetically-conjugate stations Great Whale River and Byrd. By using spaced observations with riometers (the spacing being achieved with oblique antennas) it was possible to measure the spatial gradient of absorption as well as the amount of absorption over the station. Analysis of about 600 absorption events shows that although the relative positions of event centres in the two hemispheres (possibly to be identified with conjugate points) varies seasonally by 100 km or so, this is insufficient to affect significantly the ratio of absorption seen between fixed conjugate stations. Therefore the seasonal and diurnal variations of relative absorption between conjugate stations, reported previously, must indicate a hemispheric difference of particle precipitation or of D-region chemistry. The first of these seems the more likely. The seasonal and diurnal changes are delineated more exactly than hitherto, and a small seasonal variation in the geographic position of the absorption zone is reported. © 1969.