Cold ion heating at the dayside magnetopause during magnetic reconnection

Cold ion heating at the dayside magnetopause during magnetic reconnection

Geophysical Research Letters, Volume 43, Issue 1, pp. 58-66 DOI : http://dx.doi.org/10.1002/2015GL067187

Toledo-Redondo, S.; André, M.; Vaivads, A.; Khotyaintsev, Yu. V.; Lavraud, B.; Graham, D. B.; Divin, A.; Aunai, N.

Cold ions of ionospheric origin are known to be present in the magnetospheric side of the Earth’s magnetopause. They can be very abundant, with densities up to 100 cm-3. These cold ions can mass load the magnetosphere, changing global parameters of magnetic reconnection, like the Alfvén speed or the reconnection rate. In addition they introduce a new length scale related to their gyroradius and kinetic effects which must be accounted for. We report in situ observations of cold ion heating in the separatrix owing to time and space fluctuations of the electric field. When this occurs, the cold ions are preheated before crossing the Hall electric field barrier. However, when this mechanism is not present cold ions can be observed well inside the reconnection exhaust. Our observations suggest that the perpendicular cold ion heating is stronger close to the X line owing to waves and electric field gradients linked to the reconnection process.

BV technique for investigating 1-D interfaces

BV technique for investigating 1-D interfaces

Published in Journal of Geophysical Research

Dorville Nicolas, Belmont Gerard, Rezeau Laurence, Aunai Nicolas Retinò, Alessandro

To investigate the internal structure of the magnetopause with spacecraft data, it is crucial to be able to determine its normal direction and to convert the measured time series into spatial profiles. We propose here a new single-spacecraft method, called the BV method, to reach these two objectives. Its name indicates that the method uses a combination of the magnetic field (B) and velocity (V) data. The method is tested on simulation and on Cluster data, and a short overview of the possible products is given. We discuss its assumptions and show that it can bring a valuable improvement with respect to previous methods.

The proton pressure tensor as a new proxy of the proton decoupling region in collisionless magnetic reconnection

The proton pressure tensor as a new proxy of the proton decoupling region in collisionless magnetic reconnection (ADS link, DOI) Aunai, N.; Retinò, A.; Belmont, G.; Smets, R.; Lavraud, B.; Vaivads, A. Cluster data is analyzed to test the proton pressure tensor variations as a proxy of the proton decoupling region in collisionless magnetic reconnection. The Hall electric potential well created in the proton decoupling region results in bounce trajectories of the protons which appears as a characteristic variation of one of the in-plane off-diagonal components of the proton pressure tensor in this region. The event studied in this paper is found to be consistent with classical Hall field signatures with a possible 20% guide field. Moreover, correlations between this pressure tensor component, magnetic field and bulk flow are proposed and validated, together with the expected counterstreaming proton distribution functions.