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EFI Operation and First Results J. W. Bonnell With many thanks to:

EFI Operation and First Results J. W. Bonnell With many thanks to: F. Mozer, J. McFadden, C. Cully the THEMIS Engineering, Science, Mission Ops and SciSoft Teams. Outline. Milestones Operational Modes DC and AC Performance On-Orbit Deployed State and Bias Settings Systematic Errors

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EFI Operation and First Results J. W. Bonnell With many thanks to:

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  1. EFI Operation and First Results • J. W. Bonnell • With many thanks to: • F. Mozer, J. McFadden, C. Cully • the THEMIS Engineering, Science, Mission Ops and SciSoft Teams

  2. Outline • Milestones • Operational Modes • DC and AC Performance On-Orbit • Deployed State and Bias Settings • Systematic Errors • Cold Plasma Wakes • 20 July 2007 -- Hall fields at the M’Pause. • AC Performance • L1 and L2 Data and Data Analysis Support • Near-Term Efforts

  3. EFI Wants YOU! Coloumb Faraday Franklin Tesla We want YOU to join the EFI Team – • Travel to the far reaches of the terrestrial magnetosphere in search of E-fields! • Painstakingly detect and calibrate away significant systematic errors! • Measure quasi-DC fields associated with large-scale plasma physics at various magnetospheric boundaries! • Make quantitative measurements of the waves in wave-particle interactions! The Few – the Proud – THEMIS EFI

  4. EFI Milestones

  5. Operational Modes - EFI • Continuous coverage of lower-rate data through burst periods. • Slow Survey (time-tag commanded): • Filter Bank (2 channels (SCM1, EAC12), 6 frequencies + AKR, 1 spec/4 s). • Spin Fit V, E, and B. • NEW, since early July! Waveform V (6 channels, 4 samp/s) • NEW, since early July! Waveform E (3 channels, 4 samp/s) • Fast Survey (time-tag commanded) • Waveform V (6 channels, 4 samp/s). • Waveform E (3 channels, 8 samp/s). • Particle Burst (time-tag commanded; to be on-board triggered) • Waveform V (6 channels, 16 samp/s). • Waveform E (3 channels, 128 samp/s). • FFT Spectra (4 channels, 16 freq. bins, 4 spec/s; may be reassigned to SS). • Wave Burst (time-tag commanded; to be on-board triggered) • Waveform V (6 channels, 8192 samp/s). • Waveform E (3 channels, 8192 samp/s). • FFT Spectra (4 channels, 16 freq. bins, 4 spec/s).

  6. Calibration - EFI • Ground Electrical and mechanical calibrations completed in Oct ’05. • Results of In-Flight calibrations will be fed back into revised L1 CAL procs and data, and will be used in the production of L2 physical quantities: • Intercomparison between Vptcl and ExB -> Leff. • Intercalibration between Vsc and particle density -> n(Vsc). • Estimation of offsets due to differential photemission (sphere vs. sphere; the sunward E-field offset, etc.). • Optimization and estimation of sensor coupling parameters. • Deployed Boom Lengths (TH-C, D, and E): • X-axis (V1-V2), 49.6 m, sphere center-to-center. • Y-axis (V3-V4), 40.4 m, sphere center-to-center. • Z-axis (V5-V6), 5.63 m, whip center-to-center, 6.39 m tip-to-tip, whips are 0.76-m long each.

  7. Bias Settings, Other Caveats • Last set of Sensor Diagnostic Tests run on TH-C, D, and E over two orbits, 30 June – 2 July 2007 (3 runs/orbit/probe). • Last BIAS table updates -- 20 July 2007: • BIAS set to ~-175 nA/sensor (factor of ~2 increase in photoemission over <2 months; typical). • USHER and GUARD set to positive voltage. • DBRAID driven by V1. • Other Caveats: • One-sec timing glitches. • Occur on many data types. • Occur when IDPU processor is running heavy oreground tasks (e.g. compression during SlowSurvey just after exit from FastSurvey). • Can cause sudden 120-deg shifts in despun data. • Recoverable in L0->L1 processing (to be implemented soon).

  8. Waveform EFI Data • Waveform data similar between TH-C, D, E. • Data are available at full set of rates (FS, PB, and WB). • SC potential and ES wake effects more significant than on previous magnetospheric missions (Cluster, Polar).

  9. Spin Plane vs. Spin Axis E • Spin-plane E-field estimates are reasonable given past observations. • Spin-axis E-field estimates show significant common-mode (SC potential) effects.

  10. Axial E vs. Vsc • Significant correlation between v56 (axial E-field) and Vsc (avg(v1, v2)) over a broad range of spacecraft potentials (ambient densities). • Correlation is not strictly linear, and breakpoints probably represent changes in photocloud structure with SC potential.

  11. Vsc vs. Ambient Density • Typical two-slope correlation between Vsc and ambient ion density estimate (ESA). • Population of points below curve probably represent presence of cold plasma, e.g. Scudder et al., [2000] result for Polar.

  12. E vs. –VxB (EFI/FGM/ESA Inter-Calibration)

  13. Estimating Offsets and Eff. Boom Lengths Solar Wind, 30 June 2007 Magnetosheath, 30 June 2007

  14. Estimating Offsets and Eff. Boom Lengths When not affected by ES wake effects: • Sunward offsets are 1-2 mV/m (~Cluster and Polar). • Effective Boom Lengths are a factor of 1.5 to 1.7 times smaller than Physical Boom Length (significantly different than Cluster+Polar (~1.2 to 1.5), and predictions (~1.05 to 1.1 for vacuum)). • Correlation studies between EFI, ESA, and FGM to compare E with –VixB suggest that FGM spin axis offset can differ from calibrated value; ie. Best long-term fit between E and –VixB uses Bz offset different than std. FGM value (McFadden).

  15. ES Cold Plasma Wake • Waveforms non-sinusoidal. • Shorter boom pair (v34) has LARGER signal than long boom pair (v12). • Distortion reminiscent of cold plasma wake effect on Cluster [eg. Engwall et al., 2006] Figures courtesy C. Cully.

  16. Optimal DC Performance … When it all works right …

  17. Hall Fields, 20 July 2007 (1)

  18. Hall Fields, 20 July 2007 (2)

  19. Ground Processing and Software

  20. L1 and CAL, Analysis - EFI • L1 CDF files for each collected data type (FilterBank, SpinFit, FS Vs, PB Es, etc.). • L1 CAL procs and data currently account for Ground calibrations and deployed boom lengths. • Revised calibrations (offsets, effective boom lengths, etc.) based on in-flight testing will be included in subsequent releases. • Results to be produced in Despun Spacecraft (DSL) coordinates: • Standard spin-independent and -dependent offset estimation and removal will occur in intermediate coordinate systems (Probe Geometric, Spinning Spacecraft). • Options to enforce E dot B = 0, Eaxial = 0 will be included. • Data analysis based on exiting IDL TPLOT package and modified FAST fields processing routines (auto- and cross-spectra, etc.). • NEW !!! Old-School SDT-based data analysis fully-supported.

  21. Physical Qtys, L2 Data - EFI • Spacecraft potential and density proxy (spin resolution or better). • Waveform sensor potentials (V-channels) and 3-axis E-field estimates (E-channels); resolution as shown in Operational Modes. • Spin Fit E fields (spin-resolution). • Spectral Data Products: • Filter Banks (0-4 kHz + AKR). • PB and WB FFT spectra • Individual channels or on-board para/perp Derived Quantities. • Proposed L2 data quantities (spin-period resolution): • AKR power. • SC potential or derived density. • 3-axis E-field (E dot B=0, with Eaxial=0). • 0-4 kHz EFI spectrum (1 axis, derived from FilterBank).

  22. Near-term Efforts • Implementation and tuning of Derived Quantities spectra. • Evaluation of full-orbit FFT spectra support. • Preparation for boom deploys on final two probes. • Continued EFI/ESA/FGM inter-calibration efforts (E-field). • Determination of nominal offsets and effective antenna lengths. • ESA/EFI inter-calibration for n(Vsc). • Sub-spin-period density estimates. • Cold plasma detection. • Initial work on axial DC calibrations.

  23. Spare and Backup Slides

  24. Modeling of Potential Distribution All figures, courtesy C. Cully.

  25. Inter-Spacecraft Timing of dB and dn

  26. Hall Fields, 20 July 2007 (3) Discussion of first figure. 1. Shows comparison of E and –vXB during period of magnetopause xngs. 2. Can see the magnetopause in B (2nd from bottom) or density (3rd from bottom) 3. Comparison of E and –vxB in 3rd and 4th panels from top. Red is E 4. Many regions of agreement and disagreement. Disagree when ion density not equal to electron density (4rd from bottom) due to cold ions not measured 5. Disagreements of E and –vxB occur due to cold plasma wake. 6. EXCEPT FOR 1033 WHEN THERE IS NO COLD PLASMA WAKE.  THIS IS VERY LIKELY DUE TO HALL TERM (jxB/ne) IN REGION CARRYING MAGNETOPAUSE CURRENT!

  27. Hall Fields, 20 July 2007 (4) Discussion of 2nd figure • Event on 20 July 2007 at magnetopause crossing seen in B (bottom panel) or density (SC potential in 4th panel from bottom) • EX disagrees with (-vxB)x at the current layer. Discussion of 3rd figure. This figure plots EX, (-vxB)x and [(jxB/ne)x – (vxB)x] EX disagrees with –(vxB)x but agrees with [(jxB/ne)x – (vxB)x] Reason is E +vxB = jxB/ne + small terms So this is a direct observation of the Hall E-field, potentially in a reconnection layer. NOTE THAT THERE IS NO QUADRUPOLAR BY signature here.

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