Modelling and ObservatioNs of Asymmetric magNetic Reconnection – MON-ANR

Our work is based on the complementary usage of numerical simulations and data analysis of in situ measurements. We develop and use parallel simulation codes of type Particle-In-Cell to account for all plasma kinetic effets important in collisionless systems. We use spacecraft data, in particular from THEMIS and CLUSTER, and soon from the NASA Magnetospheric MultiScale, which we confront to numerical data and predictions

Our results show so far:
- the observation with the THEMIS satellites enabled us to show that reconnection tends to orient itself so that the reconnection rates is the largest.
- numerical simulation, fully kinetic and hybrid, allowed us to show the physical origin of electron scale signatures of the non ideal electron region. These signatures will later be confronted to observations with MMS data.
- numerical simulation have allowed us to show that the kinetic nature of electons do not alter the nature of a recently found kinetic asymmetric equilibrium.

Many points will be investigated:

- parametric study of the effect of the magnetic shear at the Earth magnetopause
- study the impact of a slowly varying plasma asymmetry
- study the impact of minor ion species in magnetopause reconnection and its observational signatures
- understand the 3D effects on magnetic reconnection and where it occurs on the magnetopause surface

Articles:

M. Hesse, N. Aunai, J. Birn, P. Cassak, R. E. Denton, J. F. Drake, T. Gombosi, M. Hoshino, W. Matthaeus, D. Sibeck, and S. Zenitani Theory and Modeling for the Magnetospheric Multiscale Mission Resubmitted to Space Science Reviews

M. Hesse, N. Aunai, M. Kuznetsova, S. Zenitani, and J. Birn“Magnetic Reconnection in Different Environments: Similarities and Differences AGU Geophysical Monograph, in press

R. Smets, N. Aunai, G. Belmont, C. Boniface, J. Fuchs. On the relationship between quadrupolar magnetic field and fast reconnection. Phys. Plasmas 21, 062111 (2014); dx.doi.org/10.1063/1.4885097

R. Smets, N. Aunai, G. Belmont, C. Boniface, J. Fuchs. On the relationship between quadrupolar magnetic field and fast reconnection. Phys. Plasmas 21, 062111 (2014); dx.doi.org/10.1063/1.4885097

M. Hesse, N. Aunai, M. Kuznetsova, S. Zenitani, J. Birn. Magnetic Reconnection in Different Environments: Similarities and Differences. Accepted in AGU Books

N. Dorville, G. Belmont, L. Rezeau, N. Aunai, A. Retino. BV technique for investigating 1-D interfaces Accepted in Journal of Geophysical Research. doi:10.1002/2013JA018926 pdf


Présentations orales:

N. Aunai et al. Electron Scale Signatures of Asymmetric Collisionless Reconnection Obtained from Particle-in-Cel Models. Dec. 2014, AGU 2014 (Invited)

N. Aunai et al. Electron scale mechanisms in collisionless magnetic reconnection – hybrid and fully kinetic modeling. May. 2014, US-Japan workshop on Magnetic reconnectionTokyo University, Japan. (Invited)

N. Aunai et al. Electron non-ideal physics in symmetric and asymmetric magnetic reconnection. March. 2014, Seminar at Delaware Uni., USA.

N. Aunai et al. Electron nongyrotropy and field line connectivity the electron jet of symmetric magnetic reconnection. March. 2014, Meeting MMS, Iowa City, USA


N. Aunai et al. Kinetic modeling of magnetopause reconnection. Fev. 2014, PNST 2014, Sete, France.

Magnetic reconnection is a universal phenomenon enabling large scale transfer of magnetic energy to plasma kinetic energy and affecting its macroscopic transport by changing its magnetic connectivity. Among many systems in the universe, the Earth magnetopause, being close and “easily” targeted by spacecraft missions, is a fantastic laboratory to study the reconnection process in great details, besides being, by itself, an important space weather actor, as reconnection there critically couples the solar wind to our magnetosphere, leading to geomagnetic activity. The magnetopause is a three-dimensional collisionless asymmetric magnetic boundary separating the solar wind from the magnetospheric plasma, and through which the magnetic field is sheared between the interplanetary magnetic field (IMF) and the Earth dipole. Although we know magnetopause reconnection is overall greatly influenced by the IMF orientation, we do not understand how the magnetic shear affects the microphysics resulting in this large scale perspective. Besides the asymmetrical magnetopause configuration distinguishes it from the majority of reconnection models, mostly focused on magnetotail-like, symmetric current sheets, which guide our intuition although, strictly speaking, are quite singular.
This three year project proposes to tackle the crucial issue of the impact of mesoscale environmental properties on collisionless magnetic reconnection, focusing on the impact of i) varying the magnetic shear angle in a fixed, asymmetric, reconnecting current sheet ii) the impact of a slowly varying degree of asymmetry of the current sheet on the reconnection process with a fixed magnetic shear and iii) the three-dimensional aspect of the problem. Such a systematic survey will lead to much clearer results than the simulation of a unique and arbitrary shear angle and high degree of asymmetry. We will use state-of-the-art 2D fully and hybrid kinetic simulations, later confronted to 3D kinetic and fluid simulations, and always in a close relationship with multi-mission space observations, at the magnetopause and in the solar wind, making an heavy use of innovative tools developed at the Institute for Research in Astrophysics and Planetology (IRAP), improving them and developing new ones. In october 2014, NASA will launch the major mission Magnetospheric MultiScale (MMS) to study the reconnection microphysics down to electron scales, and will explore the dayside magnetopause during its first phase. Our ambitious objectives are highly relevant to the MMS science priorities and very competitive. They will be reached by the gathering of the complementary strengths of the French space plasma community in theory, numerical modeling and space observations, together with the world leading experts in reconnection physics and its kinetic modeling, in a new and strong international collaboration, on a cross-disciplinary topic that is widely recognized as one of the most important and challenging one in experimental, spatial and astrophysical plasma communities.
The project will be mainly performed at IRAP, but will also involve researchers from the Laboratory of Plasma Physics (LPP) and NASA Goddard Space Flight Center (GSFC). If the latter, building the MMS four satellites is obviously deeply engaged in the mission, IRAP and LPP are also strongly involved, as they both contribute to the spacecraft instrumentation. This project is at the heart of the IRAP Geophysical and Space Plasma group’s scientific activities, to which it will bring, as well as to the French astrophysical plasma community as a whole, a highly desirable expertise on numerical modeling of collisionless magnetic reconnection. It will be decomposed in five tasks, among which the coordination one and four scientific tasks based on a very strong theory/observation/simulation synergy and designed to deliver key results on reconnection physics, original databases, codes and innovative observational tools for the community.