Auroral electron precipitating energy during magnetic storms with peculiar long recovery phase features / Energia de precipitação auroral de elétrons durante tempestades magnéticas com características peculiares de longa fase de recuperação

Flavia Reis Cardoso

Aurora, light emissions generated by collisions between energetic electrons and atmospheric particles, is often seen in the polar region. Although much is known about the aurora, there are still many questions unanswered. For example, it is not well known what is the source of the energetic particles or by what processes the particles are energized. Understanding the behavior of the aurora is an important scientific problem because it provides information about the processes occurring during the solar wind-magnetosphere interaction. The auroral zone is significantly affected by magnetic storms and substorms. Occasionally, magnetic storms exhibit a long recovery phase which can last for several days. During such events, the auroral electrojet can display high-intensity, long duration activity. These events are known as HILDCAA events (High Intensity Long Duration Continuous AE Activity). The power input to the magnetosphere/ionosphere carried by precipitating electrons is an important parameter which can be estimated by the Ultraviolet Imager (UVI) on board the Polar satellite. This instrument monitors the spatial morphology and temporal evolution of the aurora in the far ultraviolet range in both sunlight and darkness. Applying the necessary instrument corrections and the dayglow removal, it is possible to evaluate the energy coming into the auroral zone. Our goal is to obtain quantitative information about the energy source for magnetic storms with long (LRP) and short (SRP) recovery phases by estimating the amount of precipitation energy input. Precipitation energy has been found highly variable for LRP. A significant energy input during long storm recovery phases implies additional energy source to maintain the magnetic activity in the auroral electrojet which is believed to be related to the fluctuating solar wind magnetic field and velocity. On the other hand, IMF (interplanetary magnetic field) remained southward for a while in SRP events. All the results suggest LRP could be a consequence of a solar wind driven system and SRP would be associated to an energy unloading process.

Auroral electron precipitating energy during magnetic storms with peculiar long recovery phase features / Energia de precipitação auroral de elétrons durante tempestades magnéticas com características peculiares de longa fase de recuperação

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