CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE

1. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE Laboratoire de Physique et Chimie de l'Environnement et de l’Espace 3A, avenue de la Recherche Scientifique F-45071 Orléans cedex 02, France Mutual Impedance MEasurements, MIME as part of the EJSM JGO/RPWI Jean Gabriel TROTIGNON and the MIME Team LPC2E, CNRS, Université d’Orléans, Orléans, France EJSM JGO/RPWI Team Meeting, Warsaw, 10-11 Jan. 2011 Phone: (33 2) 38 25 52 63; Fax: (33 2) 38 63 12 34; E-mail: Jean-Gabriel.Trotignon@cnrs-orleans.fr

2. EJSM JGO/RPWI Team Meeting, 10-11 Jan. 2011 Mutual Impedance MEasurements, MIME as part of the EJSM JGO/RPWI Presentation Outline MIME general status Mutual-Impedance considerations Conclusion Olivier Le Duff presentation Téléphone: (33 2) 38 25 52 63 Secrétariat: (33 2) 38 25 52 64 Télécopie (Fax): (33 2) 38 63 12 34 E-mail: Jean-Gabriel.Trotignon@cnrs-orleans.fr

3. MIME general status • MIME actions: • To fill in DPU, RPWI DCDC, Mechanical, and Miscellaneous Questionnaires (Done). • To estimate instantaneous data rate, compression factor, compressed data rate to S/C OBDH, and total data volume to be downlinked (Done). • To sign “Non-disclosure agreement and declaration of non-interest for participants in the EJSM/Laplace DOI instrument study teams” (Done). • Application for funding (submitted to CNES, and funding secured for 2010 and 2011). • To provide the list of people in charge of MIME (to be updated) • Science: Jean Gabriel Trotignon • Jean Louis Rauch • + AurélieMarchaudon and Jean Pierre Lebreton • Technology: Olivier Le Duff (TM) • + Fabrice Colin

4. MIME general status (cont’d) • MIME actions (cont’d): • RPWI-13: Include Active Measurements Capability (Done) • “Mutual Impedance Measurements, MIME”, by J. G. Trotignon, • J. L. Rauch, and F. Colin • 1 Introduction • 2 How do standard impedance probes work? • 2.1 Self-impedance measurements • 2.2 Mutual-impedance measurements • 3 Advantages of quadripole probes • 4 The MIP mutual impedance probe onboard ROSETTA • 5 The MIME Mutual Impedance MEasurements • 5.1 MIME scientific objectives • 5.2 MIME principle of measurements • 5.3 Expected MIME range of measurements • 5.4 MIME measurement point definition • 5.5 MIME possible working modes • 5.6 MIME telemetry resources • 5.7 Electric-field antenna/LP occupancy • 5.8 MIME power and mass resources • 5.9 How to implement active plasma measurements • onboard EJSM/JGO • 6 Conclusion

5. Mutual-Impedance considerations • A classical impedance probe consists in the probe itself and the electronics that measure the impedance: • The probe comprises transmitting/receiving electrodes immersed in the plasma. • The electronics measure the dynamic impedance between the electrodes at several fixed frequencies over a range that includes the electron plasma frequency, from which the total plasma density is directly derived. • As the impedance depends on the parameters of the ambient plasma, such as the electron density and temperature, impedance probes are powerful tools for plasma diagnostics.

6. Mutual-Impedance considerations (cont’d) Let us consider an infinite homogeneous plasma in which there is an alternating point source Q = Qo exp jωt , where ω is the angular frequency. The source emits a current I that produces an electric field E(r) . In the quasi-electrostatic approximation (which is valid provided that the distance r is small compared with the wavelength of any electromagnetic wave that can be propagated in the plasma at the given frequency) E = - gradV. The point-source transfer impedance function of the plasma is defined as: Z(ω,r) = V(ω,r) / I = V(ω,r) / jωQ, indeed I = dQ/dt = jwQ. (In vacuum Vo(ω,r) = Q / (4πεo r), therefore Zo(ω,r) = 1 / (4πjωεo r). Let us now assume a cold plasma in the absence of a magnetic field, its dielectric constant is given by : εr = 1 – (ωpe2/ω2) / (1 – j ν/ ω), where ωpe is the angular plasma frequency and v the collision frequency of electrons with heavy particles.

7. Mutual-Impedance considerations (cont’d) • In a uniform isotropic dielectric, the potential distribution set up by a point charge is: • V(ω,r) = Q / (4πεoεr r) = Vo / εr , • and thenZ = Zo / εr = Zo / [1 – (ωpe2/ω2) / (1 – j ν/ ω)]. For a square aray quadripole probe, we obtain: Z (ω) / Zo (ω,d) = 0,414 / [1 – (ωpe2/ω2) / (1 – j ν/ ω)], with Zo (ω, d) = 1 / (4πjωεo d), where d is half the diagonal length. And whenever the collision frequency ν is negligible, Z (ω) / Zo (ω,d) = 0,414 / [1 – (ωpe2/ω2)] .

8. Mutual-Impedance considerations (cont’d) If there are no collisions (dotted curve), Z (ω) / Zo (ω,d) = 0,414 / [1 – (ωpe2/ω2)], the transfer impedance tends to infinity as the frequency approaches the plasma frequency (i.e. there is a resonance). In the presence of collisions (solid curve), there is a simple maximum at a frequency slightly higher than the plasma frequency. The height of the maximum and the width of the peak depend on the ratio v/ωpe. v/ωpe = 0 v/ωpe = 0.1 ω /ωpe

9. Mutual-Impedance considerations (cont’d) • Considering a cold plasma in the presence of B, but in the absence of collisions. • It is anisotropic, and εr is now a tensor: • | S j D 0 | • εr = | - j D S 0 | , • | 0 0 P | • Its diagonal elements are: S = 1 - Σiωpi2 / (ω2 - ωci2) • and P = 1 - Σiωpi2 / ω2~ 1 - ωpe2 / ω2~ εro (B = 0, and no collisions). • Note: P is the dielectric constant in the absence of B; • P = S and D = 0 in the absence of B, the tensor is then diagonal. • After some computations that are out of the scope of this presentation, the point-source transfer impedance function Z(ω,r) for a cold and magnetized collisionless plasma: • Becomes infinite at the upper and lower hybrid frequencies, and under conditions corresponding to the oblique resonance; • May be very large at the composite plasma frequency; and • Vanishes at the electron and ion gyrofrequencies.

10. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE Laboratoire de Physique et Chimie de l'Environnement et de l’Espace 3A, avenue de la Recherche Scientifique F-45071 Orléans cedex 02, France Mutual Impedance MEasurements, MIME as part of the EJSM JGO/RPWI J. G. Trotignon and the MIME Team Conclusion Mutual Impedance probes, and in particular quadripole probes (in asymmetrical and/or symmetrical configurations) can be used for measuring characteristic frequencies of a magnetoplasma, thus allowing powerful plasma diagnoses to be done. MIME may therefore contribute to the study of the Jupiter’ system and also help out with in-flight sensor calibrations. EJSM JGO/RPWI Team Meeting, Warsaw, 10-11 Jan. 2011 Phone: (33 2) 38 25 52 63; Fax: (33 2) 38 63 12 34; E-mail: Jean-Gabriel.Trotignon@cnrs-orleans.fr