Expansion of interplanetary magnetic clouds observed in 2016-2019.

Vandas et al. (2015) studied expansion of 1996-2006 interplanetary magnetic clouds with elliptical cross-section. As the clouds pass the Earth’s orbit, their magnetic field magnitude B₀ decreases, and the minor and major semi-axes increase. The rate of these changes and geometrical parameters are determined. Our analysis of the magnetic clouds observed in recent years confirms that the approach interprets the events very well. The fitting procedure begins with determination of the orientation of the axis of the cloud by applying the Lundquist (1950) solution first, and then continues with adjustment of the determined Euler angles using Vandas and Romashets (2003) elliptical solution, by taking into consideration the expansion.