@article{RodriguezZuluagaStolleYamazakietal.2019,
  author    = {Rodriguez-Zuluaga, Juan and Stolle, Claudia and Yamazaki, Yosuke and L{\"u}hr, H. and Park, J. and Scherliess, L. and Chau, J. L.},
  title     = {On the balance between plasma and magnetic pressure across equatorial plasma depletions},
  series = {Journal of geophysical research : Space physics},
  volume    = {124},
  journal   = {Journal of geophysical research : Space physics},
  number    = {7},
  publisher = {American Geophysical Union},
  address   = {Washington},
  issn      = {2169-9402},
  doi       = {10.1029/2019JA026700},
  pages     = {5936 -- 5944},
  year      = {2019},
  abstract  = {In magnetized plasmas such as the ionosphere, electric currents develop in regions of strong density gradients to balance the resulting plasma pressure gradients. These currents, usually known as diamagnetic currents decrease the magnetic pressure where the plasma pressure increases, and vice versa. In the low-latitude ionosphere, equatorial plasma depletions (EPDs) are well known for their steep plasma density gradients and adverse effect on radio wave propagation. In this paper, we use continuous measurements of the magnetic field and electron density from the European Space Agency's Swarm constellation mission to assess the balance between plasma and magnetic pressure across large-scale EPDs. The analysis is based on the magnetic fluctuations related to diamagnetic currents flowing at the edges of EPDs. This study shows that most of the EPDs detected by Swarm present a decrease of the plasma pressure relative to the ambient plasma. However, EPDs with high plasma pressure are also identified mainly in the vicinity of the South Atlantic magnetic anomaly. From the electron density measurements, we deduce that such an increase in plasma pressure within EPDs might be possible by temperatures inside the EPD as high as twice the temperature of the ambient plasma. Due to the distinct location of the high-pressure EPDs, we suggest that a possible heating mechanism might be due to precipitation of particle from the radiation belts. This finding corresponds to the first observational evidence of plasma pressure enhancements in regions of depleted plasma density in the ionosphere.},
  language  = {en}
}
@article{CervantesVillaShpritsAseevetal.2019,
  author    = {Cervantes Villa, Juan Sebastian and Shprits, Yuri Y. and Aseev, Nikita and Drozdov, Alexander and Castillo Tibocha, Angelica Maria and Stolle, Claudia},
  title     = {Identifying radiation belt electron source and loss processes by assimilating spacecraft data in a three-dimensional diffusion model},
  series = {Journal of geophysical research : Space physics},
  volume    = {125},
  journal   = {Journal of geophysical research : Space physics},
  number    = {1},
  publisher = {American Geophysical Union},
  address   = {Washington},
  issn      = {2169-9380},
  doi       = {10.1029/2019JA027514},
  pages     = {16},
  year      = {2019},
  abstract  = {Data assimilation aims to blend incomplete and inaccurate data with physics-based dynamical models. In the Earth's radiation belts, it is used to reconstruct electron phase space density, and it has become an increasingly important tool in validating our current understanding of radiation belt dynamics, identifying new physical processes, and predicting the near-Earth hazardous radiation environment. In this study, we perform reanalysis of the sparse measurements from four spacecraft using the three-dimensional Versatile Electron Radiation Belt diffusion model and a split-operator Kalman filter over a 6-month period from 1 October 2012 to 1 April 2013. In comparison to previous works, our 3-D model accounts for more physical processes, namely, mixed pitch angle-energy diffusion, scattering by Electromagnetic Ion Cyclotron waves, and magnetopause shadowing. We describe how data assimilation, by means of the innovation vector, can be used to account for missing physics in the model. We use this method to identify the radial distances from the Earth and the geomagnetic conditions where our model is inconsistent with the measured phase space density for different values of the invariants mu and K. As a result, the Kalman filter adjusts the predictions in order to match the observations, and we interpret this as evidence of where and when additional source or loss processes are active. The current work demonstrates that 3-D data assimilation provides a comprehensive picture of the radiation belt electrons and is a crucial step toward performing reanalysis using measurements from ongoing and future missions.},
  language  = {en}
}