Interpretation of Auroral “Lightcurves” with Application to Jovian H+3Emissions

Abstract

Photometric observations of planetary aurorae may be used to constrain the time variation and spatial distribution of auroral emissions, thereby providing insight into planetary magnetic fields and magnetospheric dynamics. The variation of the total flux observed as a function of the planet's central meridian longitude (auroral “lightcurve”) is used to estimate the parameters of a simple auroral emission model. An inverse methodology based upon the singular-value decomposition of a matrix is used to estimate the model parameters and to characterize the uniqueness of the solutions obtained. The method of analysis is applied to images of Jupiter's polar regions at a 3.4-μm wavelength acquired during the first 4 months of 1992 using ProtoCAM at NASA's IRTF. The distribution and intensity of the H+3emission in Jupiter's auroral regions are estimated from the auroral lightcurves and compared with analyses of the actual images. Northern and southern auroral intensities covary, and for episodes of more intense activity during the period of observation, intensities observed in the north polar region generally exceeded those observed in the south. Auroral intensity varies with time in a manner that suggests considerable change in charged particle precipitation in Jupiter's magnetosphere, and energy deposition in Jupiter's atmosphere, on a time scale of months.