Relationship between X-ray, ultraviolet, and kilometric radiation in the auroral region

An investigation is made of the simultaneous emission of X-ray and UV photo ns as a function of time and location in the auroral oval, and comparisons are made of their time variations with the intensity variations of Auroral Kilometric Radiation (AKR). The X rays were measured with the Polar Ionosph eric X-ray Imaging Experiment (PIXIE) instrument on the Polar satellite, an d ultraviolet emissions were acquired with the UVI instrument also on the P olar satellite. AKR was measured using the Plasma Wave Instrument (PWI) car ried on the Geotail satellite. For the events studied the time profiles of AI(R were compared with those of electron precipitation into the auroral at mosphere as measured by the emission of X rays and ultraviolet radiation. T he latter emissions exhibited fluctuations which on a scale of minutes to t ens of minutes were coherent over several hours of magnetic local time (MLT ). The polar region images of X-ray and UV emissions were usually very simi lar. The cross-correlation coefficients between X-ray and ultraviolet emiss ions were as high as 0.8 over a wide range of MLT, indicating that the time variations of these different emissions were similar, although the UV obse rvations were limited to the nightside of the Earth and to the field-of-vie w of the UVI. The correlation coefficient between AKR and precipitation as a function of the MLT of the precipitation often exceeded 0.8, usually near midnight, but was >0.5 over several hours of MLT. This widespread correspo ndence of AKR and precipitation fluctuations is traced to the large-scale c oherence of precipitation fluctuations around the auroral oval.