Modeling of the Atmosphere Magnetosphere Ionosphere System (MAMI)

Example of the image analysis using DE data

Auroral images in the UV wavelength show the auroral oval even in the sunlit dayside of the globe (left image). Scattered sunlight drowns the aurora in the visible part of the spectrum (right image - the sunlit part is blocked out to protect the instrument), and allows a quantitative auroral analysis only of the nightside part of the auroral oval.

UV Image     Image at 557.7 nm

The brightness of some auroral emissions is proportional to the energy flux of the electrons that cause the aurora. A good example are the first negative emissions of the N₂⁺ ion at 391.4 nm wavelength. Other emissions, particularly those in the UV wavelength range suffer absorption in the atmosphere. Their brightness is also dependent on the altitude of the emission which in turn depends on the characteristic energy of the auroral electrons. Using our auroral model, we can relate the brightness of the aurora in different wavelength regimes to the energy flux and characteristic energy of the particle precipitation.

The auroral images from the DE satellite can thus be interpreted to give characteristics of the particles that cause the aurora. The following two images show maps of the energy flux and the characteristic energy of the auroral electrons.

Knowing these parameters, we can use our model to see how the ionosphere responds to such an aurora. Ionospheric properties of particular interest that can be found in this manner are the height integrated conductivities, the Hall and Pedersen conductance. These are shown in the next two images.

Since all shown ionospheric parameters are derived from auroral images they are only known where the instruments could actually detect aurora. Additional ionization of the ionosphere is caused by solar EUV and the photoelectrons. Both these sources need to be included to obtain a complete picture of the conductances. This is done in the AMIE model.