Cold ion demagnetization near the X-line of magnetic reconnection

Sergio Toledo-Redondo , M. André , Y. V. Khotyaintsev , A. Vaivads , Andrew P. Walsh , Wenya Li , Daniel B. Graham , Benoit Lavraud , A. Masson , Nicolas Aunai (1) , A. V. Divin , Jérémy Dargent (1, 2, 3) , Stephen Fuselier , D. J. Gershman , J. C. Dorelli , B. L. Giles , L. Avanov , Craig Pollock , Y. Saito , T. E. Moore , Victoria Coffey , Michael O. Chandler , Per-Arne Lindqvist , Roy Torbert , Christopher T. Russell

1 LPP - Laboratoire de Physique des Plasmas
2 IRAP - Institut de recherche en astrophysique et planétologie
3 CNRS - Centre National de la Recherche Scientifique

Although the effects of magnetic reconnection in magnetospheres can be observed at planetary scales, reconnection is initiated at electron scales in a plasma. Surrounding the electron diffusion region, there is an Ion-Decoupling Region (IDR) of the size of the ion length scales (inertial length and gyroradius). Reconnection at the Earth's magnetopause often includes cold magnetospheric (few tens of eV), hot magnetospheric (10 keV), and magnetosheath (1 keV) ions, with different gyroradius length scales. We report observations of a subregion inside the IDR of the size of the cold ion population gyroradius (˜15 km) where the cold ions are demagnetized and accelerated parallel to the Hall electric field. Outside the subregion, cold ions follow the E × B motion together with electrons, while hot ions are demagnetized. We observe a sharp cold ion density gradient separating the two regions, which we identify as the cold and hot IDRs.

Domaines: Physique des plasmas [physics.plasm-ph]; Astrophysique [astro-ph]

Sergio Toledo-Redondo, M. André, Y. V. Khotyaintsev, A. Vaivads, Andrew P. Walsh, et al.. Cold ion demagnetization near the X-line of magnetic reconnection. Geophysical Research Letters, 2016, 43 (13), pp.6759-6767. ⟨10.1002/2016GL069877⟩. ⟨hal-01551956⟩