Magnetic holes as measured by two converging spacecraft

Space weather events largely depend on the turbulence in a solar wind stream perturbing the magnetosphere. The important elements of turbulence are magnetic holes (MHs), regions of decreased field intensities. Tracking the MHs dynamics in the solar wind is an actual task for the space weather studies. An opportunity for simultaneous measurements by two converging spacecraft was introduced in 2000, when the Wind was moved from the magnetosphere to the libration point L1, where the ACE spacecraft was located. While the Wind to ACE distance was decreasing from 140 to 70 Re, five high-speed solar wind streams with increased turbulence were observed. Figure shows the spacecraft trajectories. The study purpose was to compare the MH properties observed by two spacecraft as the distance between them changed. MHs with duration of up to 90 s were studied. In total, 29 MHs were identified, observed on both satellites with a delay between 480 and 2400 s. The MH dimensions in depth and in duration could both increase and decrease while moving from ACE to Wind. No explicit connection of the MH size and shape changes with the distance between the satellites was found. Both linear kinetic holes and holes with rotation of the magnetic field were observed. Considerations about the feasibility of magnetic holes studies using nano-satellite chains are put out.