SFA

The SFA provides spectral information on plasma wave amplitudes over the frequency range from 24 Hz to 800 kHz for the electric field and 24 Hz to 12.5 kHz for the magnetic field. The SFA consists of eight independent receivers covering 5 frequency bands for the electric fields and three frequency bands for the magnetic fields. The receiver specifications are listed in Table 1.

Table 1. Specification of SFA

Band	Frequency Range	Freq. Step	Bandwidth	Source	Sweep
1	24 Hz - 200 Hz	1.3 Hz	2.6 Hz	B and E	64sec
2	200 Hz - 1600Hz	10.7 Hz	10 Hz	Band E	64sec
3	1.6 kHz - 12.5 kHz	85.4 Hz	85 Hz	B and E	8 sec
4	12.5 kHz - 100 kHz	683 Hz	680 Hz	E only	8 sec
5	100 kHz - 800 kHz	5.47kHz	5.4 kHz	E only	8 sec

Each receiver has a very good frequency resolution of 1/128 of the receiver frequency band although their time resolution (64 sec for Bands 1 and 2, and 8 sec for Bands 3 - 5) is somewhat coarse.
The SFA measures one wave electric field component of either the E _U or E _V component and one wave magnetic field component of either the B_\alpha or B_\gamma component. The selection of which field component is measured is carried out by a telemetry command. Each receiver has an effective dynamic range of - 90 dB. The electric field receivers are placed in the High gain mode by stepping up the level in the Low gain mode by 30 dB. These two dynamic ranges are depicted in Fig.10(a).
The SFA has another mode of operation which can be used. Despite its operation as the SFA, we can also fix the measured frequency to one preset value in each frequency band. This mode provides very high time resolution for the observed signals at an arbitrarily selected frequency. The time resolutions in this mode are 0.5 sec for Bands 1 and 2, and 62.5 msec for Bands 3, 4, and 5, respectively. This mode change is also carried out by a telemetry command.