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:
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 = e+018, n = 8176 points, dof = 997
theoretical chi-squared value =

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 =
The student’s t test: The means are not equivalent
mean_difference =
Bt_mean =
95% confidence interval =
Dipole_mean
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, Science 289, 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/
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

10. References
Project4480