Investigation of the noise sources in the electric field antenna on the ESA JUICE satellite

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1 Investigation of the noise sources in the electric field antenna on the ESA JUICE satellite Elias Odelstad Swedish Institute of Space Physics Uppsala, Sweden September 4, 2013

2 The Radio and Plasma Wave Investigation (RPWI) 3.3 INSTRUMENT DESCRIPTION

3 Outline Noise sources Nyquist (Thermal) noise Shot noise Quasi-thermal noise (QTN) Small signal equivalent circuit model Results Ganymede s ionosphere Jupiter s magnetosphere Discussion

4 Nyquist (Thermal) noise Thermal noise/nyquist noise/johnson noise Thermal agitation of charge carriers dissipative element R (noiseless) R = V n V 2 ω = 4k B TR = F { < V (t)v (t + τ) > }

5 Shot noise I Discrete nature of charge t I (t) = q k I 2 ω = 2qĪ δ(t t k ) ( V 2 ω = 2qĪ Z 2) Z I = I n Z

6 Quasi-thermal noise (QTN) Electric field fluctuations log V 2 ω plasma waves p Debye shielding temporal dispersion v th a V 2 ω = 1 (2π) 3 R 3 J i (k) E ij (k, ω) J j (k)dk 0 log f /f p

7 Two different models QTN dipole antenna DC electrostatic double-probes +Qe iωt Qe iωt V B, Q V B, Q V Z = 1 IT 2 E A (k) J A ( k)dk (2π)3 R 3 I B I B

8 Small signal equivalent circuit model V ph V s V qtn R ph R s I shot Z V out Linearized probe currents QTN antenna

9 Ganymede s ionosphere Cold and dense plasma: 300 cm 3, 0.1 ev V bias = 1 V V float = V Voltage spectral density [V 2 /Hz] ne =300 cm 3 Te = 0.1 ev Vbias= 1 V L/λDm = 44.2 Voltage spectral density [V 2 /Hz] ne =300 cm 3 Te = 0.1 ev Vbias= V L/λDm = Quasi-thermal noise Ambient plasma Nyquist noise Ambient plasma shot noise Photoelectron Nyquist noise Photoelectron shot noise Normalized frequency f/fp (fp = Hz) Quasi-thermal noise Ambient plasma Nyquist noise Ambient plasma shot noise Photoelectron Nyquist noise Photoelectron shot noise Normalized frequency f/fp (fp = Hz) Z P

10 Jupiter s magnetosphere Hot and tenuous plasma: 0.2 cm 3, 130 ev V bias = 1 V V float = V Voltage spectral density [V 2 /Hz] Quasi-thermal noise Ambient plasma Nyquist noise Ambient plasma shot noise Photoelectron Nyquist noise Photoelectron shot noise Voltage spectral density [V 2 /Hz] Quasi-thermal noise Ambient plasma Nyquist noise Ambient plasma shot noise Photoelectron Nyquist noise Photoelectron shot noise ne =0.2 cm 3 Te = 130 ev Vbias= 1 V L/λDm = ne =0.2 cm 3 Te = 130 ev Vbias= V L/λDm = Normalized frequency f/fp (fp = Hz) Normalized frequency f/fp (fp = Hz) Z P

11 Jupiter s magnetosphere Intermediate conditions: 50 cm 3, 40 ev V bias = 1 V V float = V Voltage spectral density [V 2 /Hz] ne =50 cm 3 Te = 40 ev Vbias= 1 V L/λDm = Voltage spectral density [V 2 /Hz] ne =50 cm 3 Te = 40 ev Vbias= V L/λDm = Quasi-thermal noise Ambient plasma Nyquist noise Ambient plasma shot noise Photoelectron Nyquist noise Photoelectron shot noise Normalized frequency f/fp (fp = Hz) Quasi-thermal noise Ambient plasma Nyquist noise Ambient plasma shot noise Photoelectron Nyquist noise Photoelectron shot noise Normalized frequency f/fp (fp = Hz)

12 Acknowlegdements Andris Vaivads (Supervisor) Mats Andre (A mnesgranskare) Lennart A hle n Anders Eriksson Jan-Erik Wahlund Wictor Pansar

13 Ganymede s ionosphere cience 49 (2001) L20105 EDBERG ET AL.: TITAN S COLD PLASMA Gurnett Eviatar 3. Electron density proles on Ganymede 2 obtained by means of PWS instrument on Galileo.

14 Jupiter s magnetosphere A few key properties, of importance for the plasma environment near the Galilean moons of Jupiter Body Io Europa Ganymede Radius (km) Distance from Jupiter (R j) Orbital period (days) Relative co-rotation velocity (km/s) Ne, Jovian magnetosphere (cm 3 ) Co-rotational dynamic pressure (npa) Average Ionospheric Te (ev) Average Ionospheric Ti (ev) Ionospheric thermal pressure (npa) Jovian magnetic field (nt) Intrinsic B field (eq. surface, nt) 1300? Small 700 Alfvén velocity (km/s) Acoustic velocity (km/s) Magnetosonic velocity (km/s)

15 QTN antenna impedance 300 cm 3, 0.1 ev 0.2 cm 3, 130 ev Antenna resistance (Re{Z}) Reactance (magnitude, Im{Z} ) Antenna capacitance 120 ne =300 cm 3 Te = 0.1 ev Vbias= 1 V 100 L/λDm = Antenna resistance (Re{Z}) Reactance (magnitude, Im{Z} ) Antenna capacitance ne =0.2 cm 3 Te = 130 ev Vbias= V L/λDm = x Impedance (Ω) Capacitance (pf) Impedance (Ω) Capacitance (pf) Normalized frequency f/fp (fp = Hz) Normalized frequency f/fp (fp = Hz) G J

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