SM52A-01 INVITED
Once Upon a Time in the Electron Radiation Belts
The classical concept of a hypothesis tested against experimental data leading to a valid theory remains a challenge when applied to space physics in general and the Earth's dynamic radiation belts in particular. While we have copious ongoing data for the energetic electrons in the trapped radiation environment many processes remain unobservable in principle or depend on parameters not directly measured at all, or not at the same time, or not at the right place. Wave generation from an unstable distribution of particles is a fast process not likely to ever be observable. Observed waves may have local and distributed remote sources. The effects of wave-particle interactions depend both on local densities, composition and wave parameters - AND on their distribution along a given field line. Net radial, pitch angle and energy diffusion effects depend on distributed processes an electron undergoes all along it's drift path. In the radiation belts very few of the processes leading to acceleration, loss or transport of energetic electrons can be observed directly - what we can however measure is their net effect on the distribution of energetic electrons in the radiation belts. The upcoming dual spacecraft RBSP mission, while carefully designed to provide key measurements in the right regions, cannot by itself overcome the endemic limitations listed above. To assess the effect of any mechanism we thus need to employ theory and models - which in turn depend on their own set of assumptions and limitations (like quasi-linear versus non-linear wave partcile interaction theory). By using sophisticated models that combine the effects of all the processes acting on energetic electrons we can develop our understanding of this interplay and test the net output of the models against our data. Success can be declared when our models are capable to reproduce a wide range of radiation belt dynamics - and not only work "once upon a time in the radiation belts". In this talk we outline some of the key data and measurements needed to successfully understand the energetic electron dynamics and present some of the pioneering work done in learning how to combine data and models in a "learning" loop aimed at deciphering the interplay of all the processes acting. We also highlight some of the key missing elements both in the data and modeling that need to be addressed before the launch of the RBSP mission.
SM52A-02 INVITED
Ground-based and Satellite Observational Constraints on Radiation Belt Dynamics
Recent studies have provided a range of observational evidence in support of various wave-particle interactions which may either drive the energisation of electrons to MeV energies in the Van Allen belts, or produce periods of enhanced loss. Statistical correlations have provided evidence that periods of enhanced VLF/ELF and ULF wave activity are associated with periods of enhanced MeV electron flux. Similarly, case studies have shown periods where causality of the wave-particle acceleration process can be inferred in the time domain. Given the close statistical relationship between the geomagnetic activity conditions which characterise intense intervals of both ELF/VLF and ULF wave activity, careful time-domain studies are required to extract causality from the observed correlations. I review observational studies which can be completed to look for signatures of competing wave acceleration hypotheses, and which together with appropriate simulation can be used to distinguish the dominant acceleration and loss processes which lead to observed radiation belt morphology. These archival studies can be used as a science preparation and focus in advance of forthcoming inner magnetosphere missions, such as the NASA RBSP mission and the CSA ORBITALS small satellite mission.
SM52A-03 INVITED
Waves in the Earth's Radiation Belt
The physics of the creation and loss of radiation belt particles is intimately connected to the electric and magnetic fields which mediate these processes. A large range of field regimes are involved in this physics from ring current magnetic fields to microscopic kinetic interactions such as whistler-mode chorus waves with energetic electrons. Of particular interest are the interactions of radiation belt particles with the wave modes of VLF hiss, equatorial magnetosonic waves, electrostatic electron cyclotron waves, electromagnetic ion cyclotron waves, and chorus. Data examples of these key waves along with their importance to radiation belt science are discussed.
SM52A-04
Data assimilation and parameter estimation using extended Kalman filtering.
Data assimilation models combine measurements and first principles models to provide the most realistic possible picture of the present condition or updates and corrections to the propagation of conditions forward in time. The Kalman filter incorporates measurements and physics based model according to underlined error structure of the model and data. It provides a powerful framework to estimate the state of the system in a way that minimizes mean of the squared errors. In particular for applications in the radiation belts, data at different L- shells can be combined with the model and will affect the forecasted fluxes at all radial locations. We present analysis of the phase space density measured on CRRES using Kalman filter and the radial diffusion model. The results indicate the presence of the local acceleration source at L~5.5. We also present results of the parameter estimation using extended Kalman filtering.