Regular Article

On super-elastic collisions between magnetized plasmoids in the heliosphere

Università di Genova, Via Montallegro 1, 16145 Genova, Italy

^a e-mail: andrea.divita@ansaldoenergia.com

Received: 30 May 2017
Received in final form: 18 September 2017
Published online: 16 January 2018

Abstract

Recently, a unique collision between two large-scale magnetized plasmoids produced by coronal mass ejections in the heliosphere has been observed [C. Shen et al., Nat. Phys. 8, 923 (2012)]. Results suggest that the collision is super-elastic, i.e. the total linear kinetic energy of the two plasmoids after the collision is larger than before the collision, and that an anti-correlation exists, i.e. the lower the initial relative velocity of the plasmoids, the larger the relative increase in total kinetic energy. Following an old suggestion of Bostick [IEEE Trans. Plasma Sci. PS-14, 703 (1986)], here we start from first principles, retrieve some results of Ohsaki et al. [Astrophys. J. Lett. 559, L61 (2001)] and Kagan et al. [Mon. Not. R. Astron. Soc. 406, 1140 (2010)] and show that the anti-correlation is just a consequence of the properties of Joule and viscous dissipation inside the plasmoids. On the other end, if the initial relative velocity of the plasmoids is greater than the Alfvèn velocity times the global reconnection rate, then the plasmoids merge.