Alfvenic Aurora: Characteristic and Extreme

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This is a renewal proposal to continue and expand the investigation and modeling of auroral precipitation that was initiated under the previous 3-year NSF grant, AGS-0741344, which expired on March 1, 2011. Results from the previous grant provided the first quantitative estimates of the various contributions to auroral precipitation. They demonstrated that broadband electron precipitation, created by Alfvénic acceleration, is a surprisingly large contributor to the energy input into the ionosphere and upper atmosphere. Specifically, it was shown that Alfvénic aurora increases faster with increasing solar wind driving than any other type of aurora, and that there is a clear connection between substorm onset and enhanced Alfvénic aurora. The previous grant also produced the first empirical precipitation model with seasonal dependence and with the being used in real time space weather operations. In addition, the new model has proven to be a powerful research tool, capable of addressing issues such as the separate seasonal dependence of each type of aurora, and how these various auroral types differ over the course of a substorm cycle. The work builds on particle precipitation data from the DMSP satellites, and the team is providing DMSP raw data, spectrograms, and value added products from their web site (http://sd-www.jhuapl.edu/Aurora). This is a 3-year data analysis and modeling effort addressing several intriguing questions concerning broadband electron precipitation into the high latitude upper atmosphere, also called Alfvenic aurora because it is presumably caused by Alfvénic acceleration. A specific objective is the identification and characterization of extreme events. During geomagnetic storms Alfvénic aurora can reach exceptional values in energy flux and precipitating energy and they become the most important form of precipitation. Another objective is to further explore an observed exponential rise in Alfvénic aurora occurrence with increased solar wind driving and to explain this in terms of the basic coupling mechanisms between the magnetosphere and ionosphere, and the types of auroral precipitation that result. Finally, a simulation effort will be undertaken to help explain one of the more fascinating aspects of broadband acceleration, the tendency to have roughly constant differential energy fluxes over one or two orders of magnitude in electron energy range. The studies will utilize a comprehensive set of satellite particle precipitation data covering more than two solar cycles. The project will ensure continued public access and improvements to the empirical precipitation model based on the research results that constitutes a valuable asset both for space weather operations and other space science research projects. A successful educational activity that the team has established will also be continued for this project.