The ultimate goal of my research is to bridge the gap between macroscale and microscale descriptions of the Earth’s radiation belts in order to develop a more accurate understanding of their dynamics.
One of the most fundamental changes the world has seen in recent decades is globalization. An increasingly important side effect of this shift is that human productivity, communications, and economics now rely on satellite services. The function and viability of satellite services are dependent on space weather. Radiation belt dynamics are particularly important in this context for two reasons:
- Most spacecraft must pass through radiation belts
- They have been proven to be hazardous to space operations [ex: Baker et al., 1998; Horne et al., 2013]
The enhanced sensors onboard Van Allen Probes have unveiled observations that traditional theories had not anticipated or can hardly explain. This underscores the need for new knowledge on a broad range of timescales.
Past and Present Research
In the course of my Ph.D. studies, I have focused on how the low frequency perturbations of the electromagnetic field can transform radiation belt populations. In particular, I questioned the concept of radial diffusion; a concept introduced at the beginning of the Space Age which has suffered from multiple misconceptions and misinterpretations. I set up a new theoretical model based on a scale-changing technique, on which I built new analytical, numerical, and observational approaches. Starting with UC Berkeley I changed spatial and temporal scales drastically and I got interested in how the Time Domain Structures (TDS) can locally modify radiation belt electron distributions on very short time scales. In particular, I searched for observational evidence of the connection between TDS and auroras. I substantiated the idea that time domain structures can effectively and rapidly produce field-aligned electron distributions such that auroral light is generated. In parallel, I continued research in the lower frequency / broader scale picture and conducted investigations on the generation of the “zebra stripes”, the structured peaks and valleys that appear in the high energy resolution spectrograms reported by the Van Allen Probes in the inner belt (< L~3). Using a simple theoretical model, I argued that these features were an imprint of the ionospheric dynamo on the radiation belts. I am currently looking for observational evidence that would support or question this theory, which means that I am studying the Van Allen Probe electric drift measurements (ExB). I have recently analyzed observations close to perigee at one given altitude (L shell). Because of the extreme accuracy required for such a study, the objective was first and foremost to ensure that the quantities reported were consistent with the expectations that one could derive from observations by an incoherent scatter radar located at Arecibo (Puerto Rico). This preliminary study delivered promising results. It demonstrated that Van Allen Probes can measure ExB with great accuracy close to perigee, a result of interest for both the magnetospheric and ionospheric communities.
In the immediate future, my intent is to analyze Van Allen Probes measurements of the ExB electric drift on different L shells, up to approximately L=3 (an arbitrary altitude at which electric fields are most likely of magnetospheric origin); to assess the drivers of ExB variations (e.g. magnetic local time, season, magnetic activity, etc.); and to quantify the effect on radiation belt dynamics based on refreshed theoretical grounds. It is important to determine how much the ionospheric dynamo disrupts the traditional picture of the radiation belts dynamics because of the multiple unexpected observations that have been reported but left unexplained in the inner belt. Of additional importance is to determine how local non-linear wave-particle effects are best contextualized into the bigger picture of global radiation belt dynamics. State-of-the-art radiation belt models, for instance, are currently unable to render non-linear wave-particle effects. My objective is, therefore, to pave the way for the new generation of models and to contribute to the understanding of how electrons are accelerated (or lost) in the radiation belt particles due to local effects. Thus, my immediate intent is to analyze the wealth of Van Allen Probe high time resolution measurements of linear and non-linear features in the electromagnetic field to contribute to the RBSP-EFW joint effort.
In short, my research plans are designed to maintain a multifaceted approach to radiation belt dynamics. As a scientist, I believe a great way to build our collective knowledge is to gather information from totally different sources, to (re-) assess traditional modes of understanding, and to produce a fair synthesis for the benefit of all.