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Comparisons between Magnetic field Perturbations and model dipole moments at Europa

Comparisons between Magnetic field Perturbations and model dipole moments at Europa. Derek Podowitz EAS 4480 4/28/2011. Background. Europa has an induced dipole magnetic field Orientation of magnetic field measurements x: In direction of rotation and plasma flow

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Comparisons between Magnetic field Perturbations and model dipole moments at Europa

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  1. Comparisons between Magnetic field Perturbations and model dipole moments at Europa Derek Podowitz EAS 4480 4/28/2011

  2. Background • Europa has an induced dipole magnetic field • Orientation of magnetic field measurements • x: In direction of rotation and plasma flow • y: In direction of Jupiter • z: Opposite direction of the magnetic field C. Paty 2006

  3. Procedure and Data • Galileo magnetometer measurements from Planetary Data System: • Europa pass E12,Time increment: 1/3 seconds • Periodogram: sampling frequency = 3 Hz • Butterworth filter: Low Pass • Cut-off Frequency: 0.015 • Nyquist Frequency: 3/0.5 = 1.5

  4. Procedure and Data • Background Magnetic fields • Linear regression • Magnetic field Perturbations • Residual Analysis • Calculated Dipole vs. Perturbation • Distribution: Chi-squared analysis, student’s t-test • Equation: • Dipole moment = 2*m

  5. Background Magnetic Fields

  6. Magnetic field Perturbations • Residual calculation • Bperturbation = Bt – Bt-fit

  7. Observed vs. Modeled magnetic field • Chi-squared analysis was done to fit the dipole to the observed filtered perturbation data • moment = 9.6900e+018, n = 8176 points, dof = 997 • theoretical chi-squared value = 1071.6

  8. Conclusion • Low pass filter is a better choice to filter the data • Testing for permanent Dipole moment • Chi-squared test showed that Europa’s magnetic field signature is not a normal distribution: B_chi2 = 16153 • The student’s t test: The means are not equivalent • mean_difference = 37.1531 • Bt_mean = 36.8775 • 95% confidence interval = 34.2281 - 40.0780 • Dipole_mean 74.0306 • Other factors at play to produce signatures • Possible corrections: Using more strict parameters when analyzing background magnetic field to obtain better approximation of perturbations

  9. References • Kivelson M.G., et al. Galileo Magnetometer Measurements: Stronger Case for a Subsurface Ocean at Europa, Science289, 1340 (2000). • Paty, C. 'Ganymede’s Magnetosphere: Unraveling the Ganymede-Jupiter Interaction through Combining Multi-fluid Simulations and Observations.' PhD thesis. University of Washington, Seattle, WA. (2006). • PDS: The Planetary Data System. JPL/NASA. 2/2011. http://pds.jpl.nasa.gov/index.shtml. • Hand, Kevin P. and Christopher F. Chyba. Empirical constraints on the salinity of the europan ocean and implications for a thin ice shell. Icarus Volume 189, Issue 2, August 2007, Pages 424-438

  10. References • Project4480

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