Articles | Volume 33, issue 12
Ann. Geophys., 33, 1513–1524, 2015
Ann. Geophys., 33, 1513–1524, 2015

Regular paper 21 Dec 2015

Regular paper | 21 Dec 2015

Solar wind reconstruction from magnetosheath data using an adjoint approach

C. Nabert1, C. Othmer1,2, and K.-H. Glassmeier1,3 C. Nabert et al.
  • 1Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Braunschweig, Germany
  • 2Visiting Scholar, Department of Aeronautics and Astronautics, Stanford University, Stanford, CA, USA
  • 3Max Planck Institute for Solar System Research, Göttingen, Germany

Abstract. We present a new method to reconstruct solar wind conditions from spacecraft data taken during magnetosheath passages, which can be used to support, e.g., magnetospheric models. The unknown parameters of the solar wind are used as boundary conditions of an MHD (magnetohydrodynamics) magnetosheath model. The boundary conditions are varied until the spacecraft data matches the model predictions. The matching process is performed using a gradient-based minimization of the misfit between data and model. To achieve this time-consuming procedure, we introduce the adjoint of the magnetosheath model, which allows efficient calculation of the gradients. An automatic differentiation tool is used to generate the adjoint source code of the model. The reconstruction method is applied to THEMIS (Time History of Events and Macroscale Interactions during Substorms) data to calculate the solar wind conditions during spacecraft magnetosheath transitions. The results are compared to actual solar wind data. This allows validation of our reconstruction method and indicates the limitations of the MHD magnetosheath model used.

Short summary
The solar wind plasma interacts with a planetary magnetic field. A magnetohydrodynamic model is used to simulate the interaction and resulting plasma flow. The model uses solar wind inflow parameters as boundary condition. Spacecraft data of the interaction region are compared to the flow model. The solar wind boundary parameters are varied until the model matches the data. With a time-resolution of about 10min, the time-dependent solar wind boundary parameters were reconstructed from the data.