Detection de nanoparticules dans le milieu interplanétaire

Transcription

1 Detection de nanoparticules dans le milieu interplanétaire 1 Nicole Meyer-Vernet LESIA, Observatoire de Paris avec: M.Maksimovic 1, A.Lecacheux 1, K.Issautier 1, G.Le Chat 1, A. Czechowski 2, I. Mann 3, I. Zouganelis 7, K. Goetz 4, M.L. Kaiser 5, O.C. St. Cyr 5, S.D. Bale 6 2 Space Research Centre, Polish Academy of Sciences, Warsaw 3 School of Science and Engineering, Kindai University Kowakae, Osaka 4 School of Physics and Astronomy, University of Minnesota 5 NASA-GSFC 6 Space Sciences Laboratory, University of California 7 LPP, UPMC, Ecole Polytechnique & ISSI international team "Nano Dust in the Solar System: Formation, Interactions & Detection" nicole.meyer@obspm.fr 1 Meyer-Vernet- Seminaire 01/2010

2 Nanoparticules OUTLINE Particles, particles, particles... Poussières dans l'héliosphère Principe de détection avec un instrument "ondes" plasma micro dust nano dust Solar Orbiter Detections Perspectives 2 Meyer-Vernet- Seminaire 01/2010

3 Red blood cells: 7µ Flu virus 100nm DNA ~ 2 nm wide C nm 100 nm nanoparticles 1 nm PAH: C 24 H 12 bulk matter 0.1 µ Interplanetary medium at 1 AU: F EM /F G ~ /a 2 nm Lorentz force dominates 10 A molecules ions, electrons PLASMAS interaction with plasma, magnetic fields, solar wind ions 3 Meyer-Vernet- Seminaire 01/2010

4 surface/mass 1/size chemical reactivity large surface-to-mass ratio electric charge size large charge-to-mass ratio Lorentz force : F EM = q V X B a (particle size) Gravitational force : F G = mm G/d 2 a 3 (for 3-D particles) Interplanetary medium at 1 AU: F EM /F G ~ /a 2 nm > 1 Radiative force : F R = a 2 QL /d 2 a 3 for a < since Q a < F G Lorentz force dominant interaction with magnetic field interaction with solar wind ions 4 Meyer-Vernet- Seminaire 01/2010

5 Further consequences of small size: quantum effects p r h change optical, magnetic & electrical properties Small heat capacity energy of 1 photon h ~ c T stochastic heating [Draine & Li 2001] 5 Meyer-Vernet- Seminaire 01/2010

6 Nanoparticules Poussières dans l'héliosphère Principe de détection avec un instrument "ondes" Plasma Micro poussières Nano poussières Detections Perspectives 6 Meyer-Vernet- Seminaire 01/2010

7 NGC 7023 (Iris Nebula) far UV extinction a< /2 ~10 nm [Weingartner & Draine 2001] IR emission from nanoparticles IR emission [Sellgren 1984; Léger & Puget 1982, Draine & Li 2001] Indirect: photoelectric heating [Weingartner & Draine 2001] Dust scattering starlight Do interstellar nano-dust enter into the heliosphere? Scale of heliosphere:l ~ 200 AU Interstellar medium V Heliosphere electric charge q Gyroradius in magnetic field B: mv/qb << L B V Meyer-Vernet- Seminaire 01/2010

8 Interstellar nanodust cannot enter into heliosphere [Kimura & Mann 1999, Slavin & al. 2010] except included within larger grains Exclusion of interstellar nanodust from the heliosphere Dust density relative to value in ISM Heliopause a = 10 nm Solar wind termination shock Interstellar flow [Slavin et al. 2010] 8 Meyer-Vernet- Seminaire 01/2010

9 Detection zodiacal light (scattered sunlight) a> near the Sun: "F-corona" Fraunhofer lines IR thermal emission m Meteor trails - optical, radar - > 100 m ~ kg/year/on Earth S. Brunier Lunar micro craters m Marine isotope records ~ kg/year/on Earth [Peucher-Ehrenbrink 1996] 9 Meyer-Vernet- Seminaire 01/2010

10 10 Meyer-Vernet- Seminaire 01/2010

11 In situ collection near Earth LDEF (NASA) m ~ kg/year/on Earth ~100 tons/day [Love & Brownlee 1993; refs in Mann & al.ssrev 2010] In situ dust analysers on interplanetary probes penetration impact ionisation Cassini- CDA [Srama 2004] 11 Meyer-Vernet- Seminaire 01/2010

12 Conventional in situ dust detectors Calibration range saturation limit range: m detection threshold kg 50 nm Dust detectors in interplanetary space Ulysses measurements [Krüger et al. 2000] 70 km/s not calibrated for nanoparticles 12 Meyer-Vernet- Seminaire 01/2010

13 13 Meyer-Vernet- Seminaire 01/2010 Cumulative interplanetary flux based on data at 1 AU before STEREO (Wehry and Mann, 1999) Ulysses Dust 65 millions years 1 A 10 nm 1 m 5 km Itokawa Small bodies N. Meyer-Vernet 2007 (Basics of the Solar Wind, Cambridge U. P.) /year on Earth if ~ 2.5 g/cm 3

14 Cumulative interplanetary flux based on data at 1 AU before STEREO Collisional fragmentation 1 A (Wehry and Mann, 1999) Dust 10 nm 1 m 5 km Small bodies N. Meyer-Vernet 2007 (Basics of the Solar Wind, Cambridge U. P.) if equilibrium [Dohnanyi 1969] Total mass crushed in mass log interval independent on mass steeper slope less large particles yields less small particles decreases slope smaller slope... the reverse Note:distribution of fragments dn/da a -3.5 ~ 2.5 g/cm 3 14 Meyer-Vernet- Seminaire 01/2010

15 Cumulative interplanetary flux data at 1 AU Ulysses Serendipitous discovery A 10 nm 1 m 5 km if ~ 2.5 g/cm 3 Meyer-Vernet et al. 2009] 15 Meyer-Vernet- Seminaire 01/2010

16 SUN EARTH First detection at 1 AU not surprising since: agrees with collisional fragmentation equilibrium predicted from collisional fragmentation in interplanetary dust cloud and dynamics [Mann & al. 2007] detected near comets Halley [Utterback & Kissel 1990] PAH's in sample returned by Stardust to comet 81P/Wild2 [Sanford & al. 2006] and in Tempel2 ejecta? [Lisse et al 2006] detected near planets Loki on Io Jupiter [Zook & al. 1996, Krüger & al. 2006] Saturn [Kempf et al. 2005] 16 Meyer-Vernet- Seminaire 01/2010

17 Nanoparticules Poussières dans l'héliosphère Principe de détection avec un instrument "ondes" Plasma Micro poussières Nano poussières Detections Perspectives 17 Meyer-Vernet- Seminaire 01/2010

18 Measuring fast dust grains with a wave instrument Ultrasensitive radio receivers developed for space missions ISEE1, 2, 3 (ICE), Ulysses, Cluster, Wind, Cassini, STEREO, Bepi-Columbo,... STEREO 2006 Earth orbit ISEE 3/ICE 1978 sensitivity: a few nv/hz 1/2 Cassini 1997 Saturn Wind 1994 Earth orbit/l1 L1/ L2/ comet Ulysses AU/ out of ecliptic Ulysses/URAP <1990 STEREO 2005 Bepi-Colombo/SORBET cm 18 Meyer-Vernet- Seminaire 01/2010

19 Bepi-Colombo: SORBET instrument vibration tests (01/2010) Photo: JL Bougeret 19 Meyer-Vernet- Seminaire 01/2010

20 Measuring fast dust grains with a wave instrument Radio receivers on space missions designed to measure: radioemissions (EM waves) plasma waves f p in situ plasma measurement via spectroscopy of plasma quasi-thermal noise [Meyer-Vernet & Perche 1989] plasma electron Spacecraft plasma electron ~ V plasma electron equivalent cross-section of detector >> physical cross-section great sensitivity & accuracy (calibrates other devices) only device capable of measuring density & temperature of cold plasmas (comets, rings..) 20 Meyer-Vernet- Seminaire 01/2010

21 Example: solar wind electron measurements in routine on Ulysses/URAP Data points and best fit with 6 plasma parameters (electron density & core temperature, speed, suprathermal electron density & temperature) Temperature f p Density TIME 21 Meyer-Vernet- Seminaire 01/2010

22 BRUIT QUASI-THERMIQUE DU PLASMA TIME [Issautier & al. 1998] Vent solaire pole à pole (Ulysse) 2001 [Issautier & al. 2001] 1992 [Meyer-Vernet & al. 1992] 1998 Magnétosphère de Saturne (Cassini) 2004 [Moncuquet & al. 2005] 22 Meyer-Vernet- Seminaire 01/2010

23 Nanoparticules Nano-poussières dans l'héliosphère Principe de détection avec un instrument "ondes" Plasma Micro poussières Nano poussières Detections Perspectives 23 Meyer-Vernet- Seminaire 01/2010

24

25

26 Measuring fast dust grains with a wave instrument Measurement: Waveform (time domain sampler) Voltage Voltage rise decay and/or time t Instrumental filtering Voltage power spectrum Power spectral density (frequency receiver) 1/ decay (adapted from Meyer-Vernet 1985) 1/f 2 1/f 4 1/ rise frequency f time t 26 Meyer-Vernet- Seminaire 01/2010

27 Measuring fast dust grains with a wave instrument First (serendipitous) dust detection with wave instruments Voyager in Saturn G ring (micro-dust) Dust impacts produce voltage pulses on plasma wave instrument (Gurnett et al 1983) and Voltage power spectrum (Aubier et al. 1983) dipole antenna Voyager 2 / Saturn G ring monopole antenna PWS: PRA: Gurnett & al Aubier & al Tsintikidis & al Meyer-Vernet & al Voyager at Saturn, Uranus, Neptune monopole antenna: measures spacecraft potential dipole antenna: (measures potential between two booms) Signal on monopole much greater than signal on dipole and better calibrated Signal on dipole depends on dust via dissymetries of antennas 27 Meyer-Vernet- Seminaire 01/2010

28 Voyager in Uranus & Neptune rings detects micro dust Voyager/PRA (Planetary Radioastronomy instrument) Uranus Voyager at Saturn, Uranus, Neptune Meyer-Vernet et al Pedersen et al Meyer-Vernet- Seminaire 01/2010

29 Nanoparticules Poussières dans l'héliosphère Principe de détection avec un instrument "ondes" Plasma Micro poussières Nano poussières Detections Perspectives 29 Meyer-Vernet- Seminaire 01/2010

30 Preliminary interpretation of STEREO dust [Kaiser et al. 2008] Observed dust flux exceeds model by factor of 10000!! SOLUTION [Meyer-Vernet et al. 2009] Fast nanoparticles Same signal with smaller mass IF PARTICLES ARE FAST 30 Meyer-Vernet- Seminaire 01/2010

31 Planet. Space Sci (2001) 31 Meyer-Vernet- Seminaire 01/2010

32 Interplanetary nano dust: large charge-to-mass ratio Dust grain potential determined by balance of currents on uncharged grain: j ph >> j e >> j p charges until binds photoelectrons sufficiently to yield j ph ~ j e plasma electrons - secondary electrons j e + + protons >0 j p photoelectrons + j ph - - ionising photons photoelectron energy ~ a few ev ~ V Dust grain of radius a carries electric charge q ~ 4 For a ~10 nm, q ~ 70 e charge-to-mass ratio q/m~10-5 e/m p a -2 m -2/3 32 Meyer-Vernet- Seminaire 01/ a

33 Lorentz force: F L = q(v SW - v dust )X B SW >> gravitational force F G Larmor frequency: L= qb SW /m >> Kepler frequency: G= (M G/d 3 ) 1/2 For a ~10 nm: F L /F G ~ 200 d AU L / G ~ 20 at 1 AU Nano dust grains accelerated to ~ V SW if released farther than ~ 0.15 AU (Mann et al. 2007) Dust speed Mann et al : B inward in north pole -VXB towards heliosheet "focusing" Distance 33 Meyer-Vernet- Seminaire 01/2010

34

35 Nanoparticules Poussières dans l'héliosphère Principe de détection avec un instrument "ondes" Plasma Micro poussières Nano poussières Detections Perspectives 35 Meyer-Vernet- Seminaire 01/2010

36 Cassini in solar wind near Jupiter detects nano dust Io ejects nano dust Nano dust is ejected by Jupiter corotation electric field Nanodust is accelerated by solar wind Dust analyser not calibrated for nanodust But detected small signals explained by fast nano dust Wave instrument (RPWS) detects simultaneously nanodust with electric antennas 36 Meyer-Vernet- Seminaire 01/2010

37 RPWS Cassini in solar wind near Jupiter detects nano dust f -2 Jupiter stream quasithermal noise Meyer-Vernet, Lecacheux & al., Geophys. Res. Lett. 36, L03103 (2009) Same signal on the 3 monopoles Signal on dipole is much smaller Flux of nanodust deduced from wave instrument similar to simultaneous measurement with conventional dust detector 37 Meyer-Vernet- Seminaire 01/2010

38 STEREO in solar wind at 1 AU detects nano dust 38 Meyer-Vernet- Seminaire 01/2010

39 STEREO in solar wind at 1 AU detects nano dust WAVES Voltage power spectrum waveform Meyer-Vernet et al., Solar Phys. 256, 463 (2009) 39 Meyer-Vernet- Seminaire 01/2010

40 STEREO in solar wind at 1 AU detects nano dust V 2 f 4 hf voltage power spectrum: V 2 ~ 2 2 <SF( V/ ) 2 > / receiver gain surface of 2 target ~R MAX Flux from v(m) (dust dynamics) 4 2 f <..> = average during receiver acquisition time ~0.15 sec data at 1 AU 10 nm from Meyer-Vernet et al Meyer-Vernet- Seminaire 01/2010

41 Nanoparticules Poussières dans l'héliosphère Principe de détection avec un instrument "ondes" Detection plasma Detection micro Detection nano rapides Detections Perspectives 41 Meyer-Vernet- Seminaire 01/2010

42 Detailed analysis of Stereo & Cassini data Stereo A :3 years Improvement of detection method simulation of impact plasma [Pantellini & Landi in progress] response of wave receiver Origin of particles interplanetary dust cloud planets, comets, asteroids? Composition, shape Meyer-Vernet- Seminaire 01/2010

43 Interaction with solar wind electric charge of nanodust (transition dust/molecules) dynamics [Czechowski et al. in progress] size limit? (Coulomb explosion? since q>0 not limited by field emission) effects on solar wind ("inner source"...) Other detections Via radiation? Reanalysis of past detections (impacts from fast nano possibly misinterpreted as bigger & slower grains?) Wave detection of nanodust on future space missions Complementary to conventional dust detectors Solar Orbiter RPW large collecting area (whole spacecraft) not reliant on specific spacecraft attitude requires few resources (by-product of wave instrument) 43 Meyer-Vernet- Seminaire 01/2010