A configuration of field-aligned currents (FACs) that can explain the rapid variation in the geomagnetic field in mid-latitude Europe on 29 October 2003 was recently proposed. Interestingly, this specific system of the FACs might also explain the famous Carrington event on 2 September 1859. By analysing the declination observed in mid-latitude Europe on 29 October 2003, we confirmed an important feature of the proposed current system, the westward movement of one of the FACs.

It is often the case that only magnetic field data are available for in situ planetary studies using spacecraft. Either plasma data are not available or the data resolution is limited. Nevertheless, the theory of plasma instability tells us how to interpret the magnetic field data (wave frequency) in terms of flow speed and beam velocity, generating the instability. We invent an analysis tool for Mercury's upstream waves as an example.

Magnetopause is a shielding boundary of planetary magnetic field. Many mathematical models have been proposed to describe or to reproduce the magnetopause location, but they are restricted to the real-number functions. In this work, we analytically develop a magnetopause model in the complex-number domain, which is advantageous in deforming the magnetopause shape in a conformal (angle-preserving) way, and is suited to compare different models or map one model onto another.