THE ARIA-I ROCKET CAMPAIGN

The Atmospheric Response in Aurora (ARIA) I rocket experiment was desi gned to measure the energy and momentum forcing of the atmosphere duri ng auroral disturbances and the resultant compositional and dynamical changes. It consisted of one instrumented rocket, three trimethyl alum inum chemical release rockets, and various ground-based optical instru ments. The rockets were launched from Poker Flat Research Range, Alask a, in March 1992. The instrumented payload included a set of eight ins truments for measuring various atmospheric and ionospheric quantities. This paper describes the contents of the program and the results of e lectrodynamic modeling and measurements. A substorm onset occurred app roximately 4 hours before launch of the instrumented payload, giving r ise to both particle and Joule heating in the vicinity of Poker Flat. By launch time, the substorm was well into recovery. We used optical m easurements, electron density measurements from the Langmuir probe ins trument, and model results from the Strickland electron transport code to specify latitudinal profiles of the height-integrated Pedersen con ductivity. Comparison with assimilated mapping of ionospheric electrod ynamics (AMIE) calculations of the Pedersen conductivities for this ev ent indicated that AMIE located the enhanced auroral conductivity regi on well. However, the magnitudes of the AMIE conductivities in the enh anced region were considerably less than the measurements due to local ized substorm-related particle precipitation enhancements not accounte d for by AMIE. Our conductivity profiles were used in conjunction with electric field values produced by the AMIE routine to examine the atm ospheric heating rates associated with the substorm. The latitudinally integrated Joule heating rate was initially less than the particle he ating rate, but rapidly increased to its maximum value at the time of the substorm maximum while the particle heating rate peaked prior to s ubstorm maximum. The particle and Joule heating were collocated during the expansion and maximum phase, but as the substorm recovered, the j oule heating moved to higher latitudes, so that by the time of launch, the two heating regions were completely separated by several degrees. The analysis indicates that the rocket was launched directly into the atmospheric region where the maximum heating had occurred.