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THEMIS-FGM: Operation and first results

THEMIS-FGM: Operation and first results. H.U. Auster 1 , D. Constantinescu 1 , D. Fischer 2 , K.H. Fornacon 1 , E. Georgescu 3 , K.H. Glassmeier 1 , W. Magnes 2 , F. Plaschke 1 , H. Schwarzl 4 1: IGEP, TU Braunschweig 2: IWF, Graz 3: MPE, Garching 4: UCLA, Los Angeles.

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THEMIS-FGM: Operation and first results

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  1. THEMIS-FGM: Operation and first results H.U. Auster1, D. Constantinescu1, D. Fischer2, K.H. Fornacon1, E. Georgescu3, K.H. Glassmeier1, W. Magnes2, F. Plaschke1, H. Schwarzl4 1: IGEP, TU Braunschweig 2: IWF, Graz 3: MPE, Garching 4: UCLA, Los Angeles

  2. Commissioning Results • All five instruments are working well. This includes IDPU, PSU, telemetry, boom deployment, ground operation ... • During Commissioning instrument functionality and parameters were checked. • No anomaly at all could be detected up to now • Timing deltas between FGH, FGL, FGE and Spinfit data have been investigated and corrected (thanks Jim, Michael and Peter !)

  3. Calibration Status • The Cluster Calibration Software has been adapted to THEMIS data by Edita Georgescu • Application of calibration files, data despinning and link to auxiliary data is done by Hannes Schwarzl • Calibration is performed by K.H. Fornacon on a weekly basis • All parameters (offsets, sensitivities and axis alignments) are in the expected range • UCLA inputs • spin axes offsets available • spin phase under investigation • Calibration files available from launch to mid of July • Achieved accuracy: ±0.2nT for fields less than 100nT

  4. Offset Stability Required stability: 0.2nT / 12 hours Standard deviation X: 0.14 nT Y: 0.12 nT Spinplane Offsets March-July 2007, Probe A

  5. Offset Stability Requirements on Stability: 0.2 nT / 12 hours Standard Deviation of Spinplane Offsets March-July 2007, Probe A-D

  6. Offset Stability Sensor temperature and offset behaviour after eclipse Temperature drop down during eclipse March: -15°C April: -10°C May: -6°C June: -4°C Probe A, March 7, total influence less than 1 nT; after 4 hours within 0.2 nT

  7. FGM Noise Level Requirements on noise level: 30pT/√Hz at 1 Hz No. Number of sensors (15) vs. inflight noise level (FGM & Spacecraft)

  8. Spacecraft Disturbances • Solar cells generated interferences: • Amplitude: 0.2 nT maximum (Probe D) • Frequency: spin tone & harmonics • Problem: elimination of spin tone and first harmonics in field magnitude are inflight calibration criteria • Solution approach: spin tone and second harmonics has been modelled (David Fischer) and shall be removed from raw data. • Expected result: interference will be suppressed below 0.05 nT • Caution: data cosmetics by modifying calibration parameters to remove spin tones leads to wrong data!

  9. Spacecraft Disturbances • 11 Hz + harmonics noise • Amplitude: 0.3nT maximum (Probe D) • Frequency: spin frequency/32 & harmonics • Source: sectoring of particle experiments, interference disappears if ETC processing is switched off • Problem: it is not a narrow line (not precisely fspin/32) and it is variable in time • Solution approach: has to be accepted as it is

  10. Open software tasks • Removal of DAC steps at higher fields – already written by Dragos Constantinescu • Recovery of data after non frame correlated range switching (Dragos) • Compensation of field generated by solar array currents, analysisalready done by David • Analysis of possibility to recover eclipse data by studying the MoI behaviour during & after eclipse by FGM data (Harald, Edita, Uli)

  11. The May 9, 2007 Event Birkeland

  12. Spacecraft Positions 12:00 UT 04:00 UT 02:00 UT 02:00 UT

  13. High-speed stream ? Solar Wind Environment: ACE XACE=255 RE 45 minutes delay time

  14. Relative Positions along Orbit

  15. THEMIS Chapman Overview LLBL oscillations MP oscillations MP: ~02:20 LLBL

  16. FGM-Overview with MP Crossings Magnetopause

  17. MP Crossings en Detail 02:21:20 02:20:00 02:19:35 02:19:30

  18. MP Crossings and Inward Motion Decelerated inward motion x x VN,MP ≈ 75 km/s x

  19. MP Oscillations: Chapman

  20. C D B E 02:00 UT MP Oscillations: Chapman Ion density

  21. Five on One Stroke: BX

  22. LLBL Oscillations Period: 800 s

  23. Magnetospheric Waves Period: 250 s

  24. First Synopsis MP crossing LLBL waves ULF waves

  25. MP and LLBL Oscillations: Hypothesis We see an inward moving, oscillating boundary

  26. ULF Waves: Hypothesis No field line resonance effect LLBL oscillations are too slow to cause any compression, i.e. velocity of boundary motion much slower than Alfven speed in the magnetosphere

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