The SCM (Search-Coil-Magnetometer) is an inductive sensor that measures all three components of the AC magnetic field between 3 Hz and 1 MHz. The instrument, which consists of three 10 cm antennas, is located at the end of the 3.5 meter boom at the rear of the Parker Solar Probe spacecraft [Jannet et al., 2020]. Lower-frequency fluctuations of the magnetic field are captured by the MAG triaxial magnetometer, which covers the frequency range from DC up to typically 30 Hz. Both instruments are part of the same FIELDS suite [Bale et al., 2016].
The SCM has two different types of antennas: one triaxial set that covers the LF band up to 10 kHz and one single MF antenna (Bu) that covers the 1 kHz 1 MHz band. The three components are labelled as (Bu, Bv, Bw) and are not aligned with the spacecraft coordinates (x,y,z). he rotation matrix to convert from sensor (u,v,w) to spacecraft (x,y,z) coordinates is
(Bx) ( 0.81654 -0.40827 -0.40827 ) (Bu)
(By) = ( 0.00000 -0.70715 0.70715 ) (Bv)
(Bz) ( -0.57729 -0.57729 -0.57729 ) (Bw)
SCM anomaly : as of 3 March 2019 the LF Bu antenna has suddenly lost sensitivity below 1 kHz. This problem occurs whenever the sensor is cold, i.e. at perihelion. At the same time, the sensitivity of the LF Bu antenna to periodic spikes associated with heater cycling has increased by two orders of magnitude. The data are correct for encounter 1 (October-November 2018) only. For subsequent encounters, only Bv and Bw should be used, or Bu above 1 kHz.
The analogue recordings of the SCM are processed by two instruments: the Digital Fields Board (DFB) [Malaspina et al., 2016] and the Time Domain Sampler (TDS). The main data product consists of waveforms produced by DFB of each of the three magnetic components. These waveforms are usually sampled at 292.97 Hz (so-called survey mode) during a two-week period at each perihelion. There are also various burst modes, some recorded by the DFB at 150 kHz and others by the TDS at 1.92 MHz. The latter apply to the MF Bu antenna only. Other data products include spectra and bandpass-filtered data, see [Jannet et al., 2020].
One data product of particular interest is the SCAM merged magnetic field [Bowen et al., 2020], in which MAG and SCM data have been merged into one single magnetic field product that covers the frequency range from DC up to 292.97 Hz. This product has been made public for encounter 1 only (October November 2018).
Additional data sets from the SCM (burst data, recordings outside of perihelion, etc.) and data from other FIELDS instruments can be found on the FIELDS Data Center (https://fields.ssl.berkeley.edu/data/).
For further information, contact: Thierry Dudok de Wit (LPC2E, Orleans) ddwit@cnrs-orleans.fr
References:
Bale, S. et al. (2016), The FIELDS Instrument Suite for Solar Probe Plus. Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients, Space Science Reviews, Volume 204, Issue 1-4, pp.49-82, doi:10.1007/s11214-016-0244-5
Bowen, T. et al. (2020), A Merged Search-Coil and Fluxgate Magnetometer Data Product for Parker Solar Probe FIELDS, Journal of Geophysical Research: Space Physics, 125(5):e2020JA027813
Jannet, G. et al. (2020), Measurement of magnetic field fluctuations in the Parker Solar Probe and Solar Orbiter missions, Journal of Geophysical Research: Space Physics, 125, e2020JA028543
Malaspina, D., et al. (2016), The Digital Fields Board for the fields instrument suite on the Solar Probe Plus mission: Analog and digital signal processing, Journal of Geophysical Research: Space Physics, 121:5088-5096