The Electric Field Instrument (EFI) for THEMIS

Bonnell, J. W.; Mozer, F. S.; Delory, G. T.; Hull, A. J.; Ergun, R. E.; Cully, C. M.; Angelopoulos, V.

doi:10.1007/978-0-387-89820-9_14

Cited by 181 publications

(198 citation statements)

References 16 publications

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“…The THEMIS spacecraft are well equipped for measurement of electric fields near the plane of the ecliptic, with spinning 50 and 40 m baselines, and less so perpendicular to it, with only a 6.9 m baseline along the spin axis (Bonnell et al, 2008). We have used the spin-plane measurements with offsets negligible compared to the size of the signal, and determined the axial signal (roughly GSM E Z ) from them by requiring that E · B = 0.…”

Section: Electric Field Observationsmentioning

confidence: 99%

Magnetic flux transfer in the 5 April 2010 Galaxy 15 substorm: an unprecedented observation

2011

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Abstract.At approximately 08:25 UT on 5 April 2010, a CME-driven shock compressed Earth's magnetosphere and applied about 15 nT of southward IMF for nearly an hour. A substorm growth phase and localized dipolarization at 08:47 UT were followed by large dipolarizations at 09:03 UT and 09:08 UT, observed by GOES West (11) in the midnight sector, and by three THEMIS spacecraft near X = −11, Y = −2 R E . A large electric field at the THEMIS spacecraft indicates so much flux transfer to the inner magnetosphere that "overdipolarization" took place at GOES 11. This transfer is consistent with the ground and space magnetic signature of the substorm current wedge. Significant particle injections were also observed. The ensemble of extreme geophysical conditions, never previously observed, is consistent with the Near-Earth Neutral Line interpretation of substorms, and subjected the Galaxy 15 geosynchronous satellite to space weather conditions which appear to have induced a major operational anomaly.

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Section: Electric Field Observationsmentioning

confidence: 99%

Magnetic flux transfer in the 5 April 2010 Galaxy 15 substorm: an unprecedented observation

2011

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“…In the magnetospheric plasma, where binary collisions are almost absent, plasma waves are expected to ensure the collisionless dissipation requested by some of the substorm models, and, for guided waves, to allow a remote sensing of the dynamics of active regions. The Electric Field Instrument (EFI, see Bonnell et al 2008 for more details) and the Search Coil Magnetometer (SCM) instruments on THEMIS are tailored to investigating the possible role played by waves at substorm breakup and during the expansion phase. THEMIS SCM has a long heritage; earlier versions of the instrument have been built for GEOS 1 and 2, Ulysses, Galileo, Interball, and more recently for Cluster, and Cassini.…”

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confidence: 99%

The Search Coil Magnetometer for THEMIS

Roux¹,

Contel²,

Coillot³

et al. 2008

Space Sci Rev

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International audienceTHEMIS instruments incorporate a tri-axial Search Coil Magnetometer (SCM) designed to measure the magnetic components of waves associated with substorm breakup and expansion. The three search coil antennas cover the same frequency bandwidth, from 0.1 Hz to 4 kHz, in the ULF/ELF frequency range. They extend, with appropriate Noise Equivalent Magnetic Induction (NEMI) and sufficient overlap, the measurements of the fluxgate magnetometers. The NEMI of the searchcoil antennas and associated pre-amplifiers is smaller than 0.76 pT/ p Hz at 10 Hz.The analog signals produced by the searchcoils and associated preamplifiers are digitized and processed inside the IDPU, together with data from the EFI instrument. Searchcoil telemetry includes waveform transmission, FFT processed data, and data from a filter bank. The frequency range covered in waveform depends on the available telemetry. The searchcoils and their three axis structures have been precisely calibrated in a quiet site, and the calibration of the transfer function is checked on board usually once per orbit. The tri-axial searchcoils implemented on the five THEMIS spacecraft are working nominally

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“…In this case, all five IDPUs and FGMs were powered on and checked out during five consecutive passes, spanning 6 hours total. This approach worked very well as on-console staffing could be optimized and the operations and engineering support teams concentrated on one set of procedures at a The first probe to deploy its EFI spin-plane and axial booms was THEMIS C, beginning on LD+81 (Bonnell et al 2008). Detailed analyses showed that reeling out a section of the wire booms followed by a pulsed spin-up maneuver with two short pulses per spin revolution would not compromise dynamic stability (Auslander et al 2008).…”

Section: Instrument Commissioningmentioning

confidence: 97%

THEMIS Operations

et al. 2008

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THEMIS-a five-spacecraft constellation to study magnetospheric events leading to auroral outbursts-launched on February 17, 2007. All aspects of operations are conducted at the Mission Operations Center at the University of California at Berkeley. Activities of the multi-mission operations team include mission and science operations, flight dynamics and ground station operations. Communications with the constellation are primarily established via the Berkeley Ground Station, while NASA's Ground Network provides secondary pass coverage. In addition, NASA's Space Network supports maneuver operations near perigee. Following a successful launch campaign, the operations team performed on-orbit probe bus and instrument check-out and commissioning tasks, and placed the constellation initially into a coast phase orbit configuration to control orbit dispersion and conduct initial science operations during the summer of 2007. Mission orbit placement was completed in the fall of 2007, in time for the first winter observing season in the Earth's magnetospheric tail. Over the course of the first 18 months of on-orbit constellation operations, procedures for instrument configuration, science data acquisition and navigation were refined, and software systems were enhanced. Overall, the implemented ground systems at the Mission Operations Center proved to be very successful and completely adequate to support reliable and efficient constellation operations. A high degree of systems automation is employed to support lights-out operations during off-hours.

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The Electric Field Instrument (EFI) for THEMIS

Cited by 181 publications

References 16 publications

Magnetic flux transfer in the 5 April 2010 Galaxy 15 substorm: an unprecedented observation

Magnetic flux transfer in the 5 April 2010 Galaxy 15 substorm: an unprecedented observation

The Search Coil Magnetometer for THEMIS

THEMIS Operations

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