Abstract
The FIELDS instrumentation suite on the Magnetospheric Multiscale (MMS) mission provides comprehensive measurements of the full vector magnetic and electric fields in the reconnection regions investigated by MMS, including the dayside magnetopause and the night-side magnetotail acceleration regions out to 25 Re. Six sensors on each of the four MMS spacecraft provide overlapping measurements of these fields with sensitive cross-calibrations both before and after launch. The FIELDS magnetic sensors consist of redundant flux-gate magnetometers (AFG and DFG) over the frequency range from DC to 64 Hz, a search coil magnetometer (SCM) providing AC measurements over the full whistler mode spectrum expected to be seen on MMS, and an Electron Drift Instrument (EDI) that calibrates offsets for the magnetometers. The FIELDS three-axis electric field measurements are provided by two sets of biased double-probe sensors (SDP and ADP) operating in a highly symmetric spacecraft environment to reduce significantly electrostatic errors. These sensors are complemented with the EDI electric measurements that are free from all local spacecraft perturbations. Cross-calibrated vector electric field measurements are thus produced from DC to 100 kHz, well beyond the upper hybrid resonance whose frequency provides an accurate determination of the local electron density. Due to its very large geometric factor, EDI also provides very high time resolution (∼1 ms) ambient electron flux measurements at a few selected energies near 1 keV. This paper provides an overview of the FIELDS suite, its science objectives and measurement requirements, and its performance as verified in calibration and cross-calibration procedures that result in anticipated errors less than 0.1 nT in B and 0.5 mV/m in E. Summaries of data products that result from FIELDS are also described, as well as algorithms for cross-calibration. Details of the design and performance characteristics of AFG/DFG, SCM, ADP, SDP, and EDI are provided in five companion papers.
Highlights
The paradigm of magnetic reconnection has been one of the central organizing principles of space physics since it was first comprehensively used by Dungey (1953) to explain explosive space plasma phenomena such as magnetic storms and solar flares, suggestions of the principles of reconnection were put forward earlier by Giovanelli (1946), Hoyle (1949), and Cowling (1953)
The above objectives are accomplished on Magnetospheric Multiscale (MMS) with six sensors integrated into the FIELDS suite, as diagrammed in Fig. 6, with the control and data flow managed by the Central Electronics Box (CEB)
The CEB directs the traffic of Electron Drift Instrument (EDI) and Digital Signal Processor (DSP) data, and uses some of those data for internal calculations of the Trigger Data Numbers that are used in the ground algorithms to determined selection of BURST data
Summary
The paradigm of magnetic reconnection has been one of the central organizing principles of space physics since it was first comprehensively used by Dungey (1953) to explain explosive space plasma phenomena such as magnetic storms and solar flares, suggestions of the principles of reconnection were put forward earlier by Giovanelli (1946), Hoyle (1949), and Cowling (1953). The authors confirm that the pressure terms and the inertial term, which would correspond to a parallel electric field, are impossible to determine from the time and energy resolution available with Cluster instrumentation, nor is there sufficient ion flux resolution to determine the U × B term in Ohm’s law on these time scales. This observation hints at intriguing reconnection dynamics occurring on the scale size of the electron diffusion region, the important discriminating mechanisms for the reconnection process are undetermined. Magnitude and distribution will discriminate among competing theories and simulations of reconnection
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