A method to reconstruct magnetic fields from multi-spacecraft measurements

A method to reconstruct magnetic fields from multi-spacecraft measurements

Project title: Heating and Acceleration through Magnetic Reconnection in Space Plasma Turbulence
PI: Daniel Verscharen (MSSL, University College London)
DiRAC Resource: Data Intensive at Leicester (DIaL)

Jeffersson A. Agudelo Rueda, Daniel Verscharen

Advances in space technology have led to the dawn of a new era for multi-spacecraft science missions to explore our solar system. Missions such as THEMIS, CLUSTER, and MMS have proven extremely valuable for our understanding of plasma physics in the Earth’s space environment. Building on this strong heritage, newer multi-spacecraft mission concepts such as HelioSwarm and MagneToRE have been developed that will take the multi-spacecraft approach further by deploying even greater numbers of scientific spacecraft than in these earlier missions. The success of these new missions requires the development of new multi-point techniques for data analysis.

Multi-point measurements of the complex magnetic field in space plasmas are of particular interest for our understanding of the transport and transfer of energy in the near-Earth space environment. In this context, the reconstruction of the magnetic field topology from a finite ensemble of measurements is a specific goal of these new missions. MagneToRE is a dedicated mission concept designed to address this question and to shed light on the geometry and topology of the magnetic field with unprecedented multi-point measurement resolution. MagneToRE will use a mission configuration consisting of one main spacecraft (hub) and a large number (∼24) of 6U cubesats (probes) that will carry magnetometers to sample the magnetic field at the locations of the probes. MagneToRE will study and characterize the interplanetary magnetic field at scales corresponding to the inertial range of space-plasma turbulence.

In preparation for MagneToRE, we develop a new method for magnetic field reconstruction from multi-point measurements. We use our DiRAC particle-in-cell (PIC) simulations of anisotropic Alfvénic plasma turbulence as a numerical testbed for this novel reconstruction method.

Panel a) in Figure 1 shows the presence of magnetic structures that form in our simulation domain. Panel b) depicts one of four spatial configurations that we use to sample the simulated magnetic field data. We trace artificial spacecraft trajectories through the simulation box to emulate the paths of spacecraft crossing through the plasma volume. We record the local fields from the simulation along these trajectories and apply our reconstruction method to the artificial dataset. Panel c) shows traced magnetic field lines based on the information available from the entire domain of our DiRAC simulations. Panel d) shows the reconstructed magnetic field lines based on the limited information taken along the trajectories of the artificial spacecraft.

Tracing artificial spacecraft trajectories through our DiRAC simulation allows us to evaluate the quality of our and other reconstruction methods against the ground truth of our 3D simulation data.

Figure 1. DiRAC particle-in-cell simulation of plasma turbulence. a) Our simulation domain, colour-coded with the strength of the magnetic field showing magnetic structures of different sizes. b) Configuration of our spacecraft swarm. c) Magnetic field lines from the simulation (ground truth). d) Reconstructed magnetic field lines based on artificial spacecraft data.