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Accueil > Recherche > Plasmas Spatiaux > Thématiques scientifiques > Planetary magnetospheres

Planetary magnetospheres

Toutes les versions de cet article : [English] [français]

Sommaire

For the magnetized planets, the magnetosphere is the envelope that delimits the zone of influence of the intrinsic magnetic field of the planet.

LPP team :

P. Canu,T. Chust, N. Cornilleau-Wehrlin, D. Fontaine, A. Retino, F. Sahraoui

Selection of publications :

L. Z. Hadid, F. Sahraoui, K. Kiyani, A. Retinò, R. Modolo, P. Canu, A. Masters, M. K. Dougherty, Nature of the MHD and Kinetic Scale Turbulence in the Magnetosheath of Saturn : Cassini Observations, Ap. J. Letters, Volume 813, Issue 2, article id. L29, 6 pp., 2015
C. Tao, F. Sahraoui, D. Fontaine, J. de Patoul, T. Chust, S. Kasahara, A. Retinò, Properties of Jupiter’s magnetospheric turbulence observed by the Galileo spacecraft, Journal of Geophysical Research, 2015
N., Romanelli, R. Modolo, E. Dubinin, J.-J. Berthelier, C. Bertucci, J. E. Wahlund, F. Leblanc, P. Canu, N. J. T. Edberg, H. Waite,W. S. Kurth, D. Gurnett, A. Coates, M. Dougherty, Outflow and plasma acceleration in Titan’s induced magnetotail : Evidence of magnetic tension forces, Journal of Geophysical Research, 2014
A. Masters, L. Stawarz, M. Fujimoto, S. J. Schwartz, N. Sergis, M. F. Thomsen, A. Retinò, H. Hasegawa, B. Zieger, G. R. Lewis, A. J. Coates, P. Canu, M. K. Dougherty, Electron acceleration to relativistic energies at a strong quasi-parallel shock wave, Nature Physics, 2013

The context :

The universe consists almost entirely, 99%, of plasma. The Earth is only a small part of the remaining 1%, where the creation of plasmas and the control of its parameters remain difficult and complex tasks. Understanding the mechanisms governing this plasma relies, like any other field of physics, on a permanent confrontation between observations, theories and modeling. The plasmas of the solar system, the environment of the planets, the solar wind and their interactions will thus constitute a natural laboratory of primary importance where the in-situ observation of the plasmas will make it possible to identify the fundamental questions concerning their behavior, and constrain theories.

Space exploration :

The successive generations of satellites, with an always evolving instrumentation, has allowed to obtain an increasingly fine description of the terrestrial magnetosphere, its great regions, and its dynamics. The current generation, based mainly on constellations of satellites such as Cluster, Themis or MMS, addresses the main issues of fundamental mechanisms at work : turbulence, reconnection, acceleration, shocks , radio emissions, dissipation of the energy stored in the magnetic field. The exploration of the planets presently pursued by space probes, allows the discovery of the various ionized environments of the objects of the solar system, with conditions that are often very different from the terrestrial case. The variety of characteristics of the plasmas encountered, leads to parametric studies of the models that have been developed from terrestrial observations ;

Small and big planets :

Mercury is an example of a small body, with a global magnetic field but no noticeable atmosphere. His small magnetosphere, completely controlled by the solar wind must have very rapid reaction times. A first exploration by the Messenger probe (NASA) put into orbit in 2011, will be deepened by the 2 probes (ESA-JAXA) of the mission Bepi-Colombo to be launched in 2018, mission in which LPP is largely associated with two instruments (MSA and DBSC).

The giant planets, all magnetized, offer to space plasma physicists a fascinating diversity of ionized environments. Contrary to Earth’s case where the plasma and the free energy essentially come from the incident Solar Wind, Jupiter and Saturn possess internal plasma sources, originating from satellites circulating inside their magnetosphere (Io for Jupiter, Enceladus for Saturn). A large part of the energy transferred to the particles originates from the rapid rotation of these planets (9.8 h for Jupiter, 10.2 for Saturn). The mechanisms of transport of the plasma, its confinement and the dissipation of the accumulated energy, are notably different from the Earth’s case. The interaction of the various moons with this plasma makes each one a case study. The Ganymede satellite in orbit within the Jovian magnetosphere, which itself possesses a magnetic field, allows the study of the interaction between the magnetosphere of a small planet and that of a giant one. The example of Saturn’s ring systems offers a unique plasma interaction laboratory, the rings being both emitters of material in the magnetosphere and absorber of plasma circulating along the internal magnetic field lines.

Questions studied by LPP team :

The LPP space plasmas team was involved very early in this exploration of the magnetospheres of the giant planets, with instruments flown on space probes. After the first data acquired by the URAP instrument (PI : B. Stone, GSFC) during the flyby of the jovian magnetosphere by the Ulysses probe (ESA) in February 1992, the team participated in the deep exploration of Jupiter’s environment (Figure 1) with the PWS instrument (PI : D. Gurnett, University of Iowa), mounted on the Galileo probe, put on orb of the giant planet in December 1995. Data from the search-coil magnetic antennas, built by the team, largely contributed to the discovery of the mini magnetosphere of Ganymede.
The LPP is also involved in the in-depth exploration of the Saturn magnetosphere (Figure 2), the environment of its satellites, particularly Titan, and its ring systems, using in particular our instrumentation included in the RPWS instrument (PI : D. Gurnett, then W. Kurth, University of Iowa), mounted on the Cassini probe. It was launched in 1997, and was put in orbit around Saturn in July 2004. Its mission will end in September 2017.

: Figure 2
Magnétosphère de Saturne
Source : M. Kivelson, Science, 2006

The interest of the team to continue the study of the giant planets remains very strong. The team has been selected to provide the magnetic antennas of the RPWI instrument (PI : JE Wahlund, IRF, Uppsala) which will be flown onboard the Juice probe (ESA), whose launch towards Jupiter is scheduled for 2022. The main objective of Juice will be, beyond an in-depth study of the entire Jovian environment and an Europa flyby around 2030, an exploration of the magnetosphere of the moon Ganymede after being place in orbit around it.

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