This subsystem is provided by the University of Iowa. The MCA contains two spectrum analyzers with fixed frequency channel filters. It provides high time resolution data to complement the coarser time resolution data of the SFA. However, their frequency resolution is coarse because they have only four frequency channels per decade in frequency.
The input signal to the MCA is provided from the output of the common front-end circuit of the PWI system as well as to SFA and WFC receivers. One multi-channel spectrum analyzer is used to measure the electric field and is composed of 20 channels covering the frequency range from 5.62 Hz to 311 kHz. The other spectrum analyzer is used for magnetic field measurements and has 14 channels covering the frequency range from 5.62 Hz to 10 kHz. The bandwidths of the filters are \pm 15% of the channel center frequency in the frequency range below 10 kHz and \pm 7.5% of the center frequency for frequency above 10 kHz. The MCA instrument measures the wave electric field of either the EUor EV component (depending on which antenna is used) with a dynamic range of - 110 dB and the wave magnetic field of either the B\alphaor B\gamma component with a dynamic range of - 100 dB.
Signals from all channels are sampled simultaneously so that the ratio of the electric to magnetic field strength may be calculated accurately. The signals are sampled once (data acquisition time is 1.037 msec) every 250 msec in Format~2 (and every 500 msec in Format 1). Each channel of the spectrum analyzer has a suitable integration time in the linear detection of signal ranging from 500 msec in the lower frequency channels and decreasing to a few milliseconds for those channel above 3 kHz.