Journal Article

Cassini in situ observations of long-duration magnetic reconnection in Saturn’s magnetotail

André, N., Kidder, A., Volwerk, M., Lamy, L., Sergis, N., Poh, G.-K., Jia, X., Coates, A. J., Thomsen, M. F., Dougherty, M. K., Jackman, C. M., Slavin, J. A., Arridge, C. S., Walsh, A. P., Eastwood, J. P., Zarka, P., Radioti, A., Reisenfeld, D. B.

2016

Overview

Cassini’s encounter with Saturn’s magnetotail — the long magnetosphere region stretching into space — has revealed that plasma exits the magnetosphere through long-duration magnetic reconnection, which ejects ten times more mass than estimated. Magnetic reconnection is a fundamental process in solar system and astrophysical plasmas, through which stored magnetic energy associated with current sheets is converted into thermal, kinetic and wave energy 1 , 2 , 3 , 4 . Magnetic reconnection is also thought to be a key process involved in shedding internally produced plasma from the giant magnetospheres at Jupiter and Saturn through topological reconfiguration of the magnetic field 5 , 6 . The region where magnetic fields reconnect is known as the diffusion region and in this letter we report on the first encounter of the Cassini spacecraft with a diffusion region in Saturn’s magnetotail. The data also show evidence of magnetic reconnection over a period of 19 h revealing that reconnection can, in fact, act for prolonged intervals in a rapidly rotating magnetosphere. We show that reconnection can be a significant pathway for internal plasma loss at Saturn 6 . This counters the view of reconnection as a transient method of internal plasma loss at Saturn 5 , 7 . These results, although directly relating to the magnetosphere of Saturn, have applications in the understanding of other rapidly rotating magnetospheres, including that of Jupiter and other astrophysical bodies.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Publishing Group [2005-....],Nature
• Subject: 639/33/445/846 / 639/33/525/869 / 639/766/1960 / Astrophysics / Atomic / Aérospatiale, astronomie & astrophysique / Cassini mission / Classical and Continuum Physics / Complex Systems / Condensed Matter Physics / Current sheets / Diffusion / Jupiter / Jupiter (planet) / Kinetics / letter / Magnetic fields / Magnetism / Magnetospheres / Magnetotails / Mathematical and Computational Physics / Molecular / Optical and Plasma Physics / Physical, chemical, mathematical & earth Sciences / Physics / Physique, chimie, mathématiques & sciences de la terre / Planetary magnetospheres / Plasma / Plasma loss / Plasmas / Reconfiguration / Rotating bodies / Rotation / Saturn / Saturn (planet) / Solar system / Space science, astronomy & astrophysics / Spacecraft / Theoretical / Wave energy