Space plasmas measurement techniques Milan Maksimovic CNRS & LESIA, Paris Observatory, France

Transcription

1 Space plasmas measurement techniques Milan Maksimovic CNRS & LESIA, Paris Observatory, France Maksimovic : Space plasmas measurement techniques 1

2 ESA mission with NASA participation (launcher + two instruments) Up to 0.28 AU with dedicated in situ & remote sensing instrumentation closest approach possible) Out of ecliptic observations 1st M class ESA Cosmic Vision (Launch ~Feb. 2019) Maksimovic : Space plasmas measurement techniques 2

3 Interplanetary high energy electron & Solar Radio Bursts Electrostatic Langmuir waves radio emission F N p e (khz) 1 R 2 N (au) e (cm -3 ) F p 1 R

4 All necessary measurements will be available on Solar Orbiter WIND 3DP Tens of sec Lin et al., plasmas measurements Np, Tp, Vp (16Hz) High cadence Ne Bx, By, Bz DC & AC (up to the plasma frequency) Adapted from [Ergun et al., 1998]

5 Particles measurements Electrons Ions & composition Energetic particles Waves measurements Outline Magnetic DC & AC sensors Measuring DC LF electric fields Measuring AC Electric Field: The Thermal Noise as an example Surprises, tricky data corrections and future challenges Maksimovic : Space plasmas measurement techniques 5

6 Astrophysical Plasmas accessibe to in situ measurements M-Sheath Aurora Lobes Maksimovic : Space plasmas measurement techniques 6

7 /. Lobes M-Sheath Aurora ~ Maksimovic : Space plasmas measurement techniques 7

8 A plasma particle is defined by a mass an electric charge a speed or kinetic energy Particle Energy Distributions Detector Maksimovic : Space plasmas measurement techniques 8

9 A plasma particle is defined by a mass an electric charge a speed or kinetic energy Particle Energy Distributions Detector The broad range of energies and fluxes require different instruments Faraday cup principle Maksimovic : Space plasmas measurement techniques 9

10 Electric charging in space : an example in the Solar Wind electrons For a plasma in quasi equilibrium with ~ protons In the Solar Wind ~ ~ ~ / ~ / Maksimovic : Space plasmas measurement techniques 10

11 Electric charging in space : an example in the Solar Wind electrons For a plasma in quasi equilibrium with ~ UV photons In the Solar Wind ~ ~ ~ / ~ / What are the average electron velocity and density at the surface of the Sphere? an be obtained applying Louville Theorem / ~ / And the photoelectron current? / Depends on the photo electric properties of the material ~ ~ / Finally the potential is obtained by assuming To be fully exhaustive one shall include the secondary electrons currents (important closer to the Sun) Maksimovic : Space plasmas measurement techniques 11

12 Cluster data Salem et al., 2001 Pedersen et al., 2008 Maksimovic : Space plasmas measurement techniques 12

13 Electron diagnostic in cold plasmas The Langmuir Probe Sweeping V and measuring I For a plasma in quasi equilibrium with ~ / In the saturation region / Segmented langmuir probe in order to measure the ion bulk speed Maksimovic : Space plasmas measurement techniques 13

14 Measuring the full 3D VDF Top Hat detectors Principles of Operation < 0 Incoming Electron Secondary Electrons Glass Channel Wall Electroding HV Semiconducting Layer Output Cascade Electrons A full 3D Velocity Distribution function is obtained by Scaning the energy ( ) Using the Top hat axis of symmetry and the spacecraft spin Hollow cylinders Maksimovic : Space plasmas measurement techniques 14

15 The Solar Orbiter EAS instrument Christopher «Chris» Owen, Mullard Space Sciences Lab., UK Maksimovic : Space plasmas measurement techniques 15

16 Particle Composition : Add a time of flight detector beneath the top hat analyser: Post- Acceleration Ion Aperture Stop Start U acc Electrostatic Analyser Τ V E/M (E/Q)* = (E/Q + U acc ) M/Q Time of Flight E/q Top hat section makes E/q selection as before : / Ions are then accelerated by an electric field into a thin carbon foil On passing through the foil the ion knocks out an electron The difference in travel time to the detector between the ion and electron can be used to determine the ions velocity, and hence E/M for the ion; Combining the two measurements gives M/Q Maksimovic : Space plasmas measurement techniques 16

17 Particle Composition : Add a time of flight detector beneath the top hat analyser: Composition Plot colours represent relative abundance of ions Top hat section makes E/q selection as before : / Ions are then accelerated by an electric field into a thin carbon foil On passing through the foil the ion knocks out an electron The difference in travel time to the detector between the ion and electron can be used to determine the ions velocity, and hence E/M for the ion; Combining the two measurements gives M/Q Maksimovic : Space plasmas measurement techniques 17

18 High Energy Particle Telescopes Robert "Bob" Wimmer Schweingruber University of Kiel, Germany Energy loss Bethe Block equation Javier Rodríguez Pacheco University of Alcala, Spain is the «first energy ionization» of the target Maksimovic : Space plasmas measurement techniques 18

19 Particles measurements Electrons Ions & composition Energetic particles Waves measurements Outline Magnetic DC & AC sensors Measuring DC LF electric fields Measuring AC Electric Field: The Thermal Noise as an example Surprises, tricky data corrections and future challenges Maksimovic : Space plasmas measurement techniques 19

20 Measuring DC/LF Magnetic Fields in space Flux Gate Magnetometer Nobody knows... best theory is that it is little pixies inside the cores. Vdrive Timothy "Tim" Horbury Imperial College, UK time Vsense ring cores of a highly magnetically permeable alloy around which are wrapped two coil windings B No external field : time time Maksimovic : Space plasmas measurement techniques 20

21 Measuring DC/LF Electric Field in space Flux Gate Magnetometer Nobody knows... best theory is that it is little pixies inside the cores. Vdrive Timothy "Tim" Horbury Imperial College, UK time Vsense B External field : ring cores of a highly magnetically permeable alloy around which are wrapped two coil windings time time Maksimovic : Space plasmas measurement techniques 21

22 Measuring AC Magnetic Fields in space The Search Coil Magnetometer (SCM) is an inductive sensor is based on Faraday's law of induction. Vladimir Volodya" Krasnoselskikh LPC2E Orléans, France SCMs On Solar Orbiter and Solar Probe Plus Coil Ferromagnetic Core Maksimovic : Space plasmas measurement techniques 22

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25 Measuring DC/LF Electric Field in space Maksimovic : Space plasmas measurement techniques 25

26 1 / 2 If the two probes are equally illuminated then and not necessarily equal to / Actually we do not measure and but rather / and / where we use the S/C as the potential ground If the ground is the same for the two probes then If an external is applied then Actually So if the experimental setup is appropriate then :! But life is not so simple because typical electric fields are tiny (a few mv/m)! Maksimovic : Space plasmas measurement techniques 26

27 10 ev, 100 cm -3 1 ev, 10 cm -3 Adding a Biasing current on the probe will solve the problem of the density fluctuations in the medium So if the experimental setup is appropriate and if one injects a BIAS current in the probes then! / Maksimovic : Space plasmas measurement techniques 27 ~ /

28 Measuring AC Electric Field: The Thermal Noise as an example In drifting plasma, spectral density at the antenna ports: V 2 2 (2 ) 3 d 3 k k.j k antenna 2 E 2 (k, k.v) plasma / Electrons passing within Electrons generating Langmuir waves Resistive / / Le Chat et al., AIP, 2009 Maksimovic : Space plasmas measurement techniques 28

29 Particles measurements Electrons Ions & composition Energetic particles Waves measurements Outline Magnetic DC & AC sensors Measuring DC LF electric fields Measuring AC Electric Field: The Thermal Noise as an example Surprises, tricky data corrections and future challenges Maksimovic : Space plasmas measurement techniques 29

30 Surprises : when an instrument allow unexpected observations Nanodusts with STEREO Spectral domain Picked up by the VXB field Temporal domain 30

31 Tricky data corrections techniques Maksimovic : Space plasmas measurement techniques 31

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34 Dipolar S/C potential correction Maksimovic : Space plasmas measurement techniques 34

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36 Some Challenges with Solar Orbiter Integrating all 10 instruments on the S/C platform is a real chalenge! Maksimovic : Space plasmas measurement techniques 36

37 Undertanding the electrostaic environment will be a challenge Maksimovic : Space plasmas measurement techniques 37

38 The Radio & Plasmas Waves instrument

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