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THEMIS Electric Field Instrument (EFI) Dr. John Bonnell Space Sciences Laboratory UC Berkeley PowerPoint PPT Presentation


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THEMIS Electric Field Instrument (EFI) Dr. John Bonnell Space Sciences Laboratory UC Berkeley. Performance vs. Specifications. EFI has met or exceeded on-orbit performance requirements and specifications (all requirements and specs included in appendix):

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THEMIS Electric Field Instrument (EFI) Dr. John Bonnell Space Sciences Laboratory UC Berkeley

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Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

  • THEMIS

  • Electric Field Instrument (EFI)

  • Dr. John Bonnell

  • Space Sciences Laboratory

  • UC Berkeley


Performance vs specifications

Performance vs. Specifications

  • EFI has met or exceeded on-orbit performance requirements and specifications (all requirements and specs included in appendix):

    • 30 sensors still functional and in spec after 33 months on-orbit, including long- and short-duration eclipses (lifetime; thermal).

    • No obvious signs of degradation in performance:

      • no dramatic increases in offsets or shifts in gain.

      • no increases in power consumption.

      • no loss of current- or voltage-bias control.

      • no problems with commanding or configuration control.

    • 2D DC and 3D AC E-field estimates from EFI have been made in support of all three mission objectives:

      • Substorm Onset (E-fields in tail to 1 mV/m)

      • Radiation Belt Acceleration Processes (AC measurements to 4-8 kHz.

      • Dayside Magnetopause Observations (E fields at M’Pause to few mV/m).

    • On-orbit calibration and offset estimation and removal allow for accuracies better than 1 mV/m, if cold plasma wake effects are not present.


Assessment of data products 1

Assessment of Data Products (1)

  • L1 EFI data products are sufficient to meet Level-1 Science Requirements (EFI-1 to -4):


Assessment of data products 2

Assessment of Data Products (2)

  • L1 EFI data products are sufficient to meet Level-1 Science Requirements (EFI-5 to -10):


Assessment of data products 3

Assessment of Data Products (3)

  • L1 EFI data products are sufficient to meet Level-1 Science Requirements (EFI-11 to -13):


Assessment of data products 21

Assessment of Data Products (2)

  • L1 EFI data products support investigations beyond L1 science requirements:

    • Hall E-field measurements at the dayside magnetopause (e.g. Mozer et al., 2008).

    • Hall E-field measurements in tail dipolarization events (McFadden, private comm., 2008-9).

    • Coordinated E- and B-field measurements in geomagnetic pulsation studies (spin-fit and waveform) (e.g. Liu et al., 2009).

    • Double layer and electron hole observations in magnetotail (e.g. Andersson et al., 2009; Ergun et al., 2009).


Data maturity 1

Data Maturity (1)

  • L1 EFI data reprocessed several times in order to remove on-board data collection anomalies:

    • Time Tagging, prior to correction in FSW.

    • Spikes in high-rate (WaveBurst) data (impacts << 0.1% of WB data).

  • L1 data is accessible through TDAS package (IDL crib sheets and procs), as well as the Science Data Tool (old-school E-field community).

  • Calibration has both fixed (gains, sunward offsets) and time-dependent elements.

    • Fixed calibration parameters (gains sunward/dawn-dusk offsets) computed using cal runs in magnetosheath.

    • Time-dependent element is computed on-the-fly in TDAS and SDT processing, both for DC (FastSurvey) and AC (Pburst, Wburst) data types.

  • Accuracy is at least 1 mV/m for 2D spin plane fields, with few tens of mV/m for the axial estimate (after heavy processing).

  • Description and discussion of calibration and error sources in Bonnell et al. (2008), as well as on EFI Instrument web page.


Data maturity 2

Data Maturity (2)

  • Preliminary quality flags available, but not formalized:

    • detection of wake effect fields through comparison of long- and short-antenna results.

    • Limitation of E∙B=0 estimates of Eperp to limited ranges of (Bspin/Baxial).

  • L2 EFI data processing in the works, but data still needs significant care in use and interpretation.


Efi lessons learned

EFI Lessons Learned

  • Wake effect fields due to flowing cold plasma have significant impact (tens of mV/m) on magnetospheric side of dayside magnetopause, as well as in inner magnetosphere →

    • longer booms.

    • SC potential control.

    • continuous waveform measurements, or spin-fit of both spin plane signals, rather than just one.

  • 7-m tip-to-tip axial antennas are too short for making 1 mV/m 3D DC measurements →

    • longer booms.

    • adjustable boom lengths on-orbit.

  • Photoelectron fluxes returning to SC and body-mounted particle detectors can be significant and can impact low-energy (few to tens eV) e- measurements →

    • GUARD surfaces run at positive, rather than negative potentials.

    • adjust voltage biasing scheme of DBRAID surfaces during sensor eclipse season.


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

  • BACKUP SLIDES:

  • References.

  • Requirements and Specs.

  • On-Orbit Operation and Calibration.

  • Measurement Challenges.


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

References

  • Andersson et al., New features of electron phase space holes observed by the THEMIS mission, PRL, accepted, 30 Apr 2009.

  • Bonnell et al., The electric field instrument (EFI) for THEMIS, SSR, doi:10.1007/s11214-008-9469-2.

  • Bortnik et al., An Observation Linking the Origin of Plasmaspheric Hiss to Discrete Chorus Emissions, Science 324, 5928, 775 - 778, doi: 10.1126/science.1171273.

  • Cully et al., THEMIS Observations of Long-lived Regions of Large-Amplitude Whistler Waves in the Inner Magnetosphere, GRL, doi:10.1029/2008GL033643.

  • Ergun et al., Observations of Double Layers in Earth’s Plasma Sheet , PRL, 102, 155002.

  • Li et al., Global Distribution of Whistler-mode Chorus Waves Observed on the THEMIS Spacecraft, GRL, 2009.

  • Liu et al, Solar wind influence on Pc4 and Pc5 ULF wave activity in the inner magnetosphere, GRL, accepted, 2009.

  • Mozer et al., THEMIS observations of modified Hall fields in asymmetric magnetic field reconnection, GRL, doi:10.1029/2007GL033033.

  • Segeev et al., THEMIS observations in the near-tail portion of the inner and outer plasma sheet flux tubes at substorm onset, JGR, doi:10.1029/2008JA013527.

  • Sergeev et al., Kinetic structure of the sharp injection/dipolarization front

  • in the flow-braking region, GRL,doi:10.1029/2009GL040658.


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

Lifetime, Radiation


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

Mass, Power, Thermal


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

Cleanliness; Elect., Mech. ICD


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

Environmental Testing


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

Science Requirements


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

Performance Requirements


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

Performance Requirements


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

EFI Board Requirements


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

EFI Board Requirements


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

EFI Boom Requirements


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

  • ON-ORBIT OPERATION AND CALIBRATION


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

On-Orbit Current and Voltage Bias Sweeps

“Sensor Diagnostic Test (SDT)”


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

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


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

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


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

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


Vsc vs ambient density

Vsc vs. Ambient Density

  • Typical two-slope correlation between Vsc and ambient ion density estimate (iESA).


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

  • MEASUREMENT CHALLENGES


Themis electric field instrument efi dr john bonnell space sciences laboratory uc berkeley

ES Cold Plasma Wake

  • Waveforms non-sinusoidal and significant amplitude (tens of mV/m).

  • Shorter boom pair (E34) has LARGER signal than long boom pair (E12).

  • Occurrance consistent with ESA cold plasma observations, when available:

    • ne>ni

    • cold (few eV) flowing ions present in iESA spectrum

  • Distortion reminiscent of cold plasma wake effect on Cluster [eg. Engwall et al., 2006].

  • Rate of occurrence on THEMIS is high; initial estimates of 60-80% of duskside passes.

  • Significant for MMS, RBSP E-field measurements.

  • PIC simulation by Engwall & Eriksson (CLUSTER booms)


Short booms axial e vs vsc

Short Booms: Axial E vs. Vsc

  • Significant correlation between v56 (axial E-field) and Vsc over a broad range of spacecraft potentials (ambient densities) – ≈ 4 ((mV/m)/V)

  • Correlation is not strictly linear, and breakpoints probably represent changes in photocloud structure with SC potential.

  • Partly explained by the shift in the electrostatic center caused by the mag booms (≈ 6 cm shift!).


What s calibration error and what s e

What’s Calibration Error and What’s E||?


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