Donald A. Gurnett, PWI Principal Investigator
319-335-1697
(donald-gurnett@uiowa.edu)
Doug Menietti, PWI Operations/Science Data Manager
319-335-1919
(john-menietti@uiowa.edu)
Julie Dowell, PWI Key Parameter Software Development
319-335-1960
(julie-dowell@uiowa.edu)
All of the above are at:
Department of Physics and Astronomy
University of Iowa
Iowa City, Iowa 52242
The Plasma Wave Instrument (PWI) provides comprehensive measurements of plasma wave and radio emission phenomena in the high latitude auroral zones, the polar cusp, the dayside magnetosheath, the nightside equatorial plasmasheet and in the boundaries between these regions.
PWI uses the sensor system of EFI for electric field measurements. The EFI system consists of a pair of orthogonal two-sphere electric antennas in the spin plane of the spacecraft with sphere-to-sphere separations of 130m (Eu) and 100m (Ev) and a short two-sphere electric antenna (Ez) aligned along the spacecraft spin axis with a sphere-to-sphere separation of 14m.
For magnetic field measurements PWI uses a triaxial search coil magnetic antenna system (Bu, Bv, and Bz) mounted at the outboard end of a 6-m rigid boom and a magnetic loop antenna (L) mounted on the same boom with its axis oriented parallel to the Eu electric antenna. The mounting arrangement of the electric and magnetic antennas is illustrated in Figure 1 of Ref. 1.
The EFI electric antennas are designed to detect electric fields over a broad range of frequencies from DC to 125 MHz. The triaxial search coil magnetic antennas are designed to detect magnetic fields over a frequency range of 0.1 Hz to 50 kHz. The sensitivity constant of the search coil is 70 uV/nT-Hz. The magnetic loop antenna is designed to detect magnetic fields over a frequency range of 25 Hz to 800 kHz. The loop sensitivity constant is 110 uV/nT-Hz.
A detailed list of the physical characteristics of the electric and magnetic sensors is contained in Table III of Ref. 1.
A detailed list of the physical characteristics of the PWI receiver systems is contained in Table IV(a) and Table IV(b) of Ref. 1.
Five separate receiver systems are contained in PWI's main electronics unit: a narrowband sweep frequency receiver (SFR); a low frequency AC receiver (LFWR); a wideband receiver (WBR); a high-time-resolution multi-channel analyzer (MCA); and a high-frequency waveform receiver (HFWR). The PWI receiver systems are described in detail in Section 4 of Ref. 1. The PWI receivers can be connected to the electric and magnetic antennas in various antenna combinations, described in detail in Table IV(a) and Table IV(b) of Ref. 1.
Only data from the SFR are used to derive the PWI key parameters. The SFR consists of two single-sideband, phase matched, double-conversion receivers in parallel, with both amplitude and phase-measuring capability. The SFR provides amplitude and phase measurements in five frequency bands from 26 Hz to 808 kHz. Each receiver can be connected to one of four sensors, as listed in Table IV(a) of Ref. 1. Design features of the Sweep Frequency Receivers are provided in Table V of Ref. 1 and in the table labelled Design Features and Modes of Sweep Frequency Receivers.
A. Polar PWI Key Parameters
Key parameters for the Plasma Wave Investigation will be derived from the SFR data for any of the possible antenna combinations used by the pair of SFR receivers: Eu, Ev, Ez, L and Bz. All SFR data values will be 5-minute averages. Time tags and orbit parameters will be given for the start of the 5-minute averaging interval.
The key parameters consist of: the time for the start of the 5-minute averaging intervals in two formats; the data quality and SFR mode flags; the antenna configurations for the SFR receivers; the electric and magnetic spectral density values at 160 logarithmically-spaced frequency values (peak density values and RMS averages for each 5-minute time interval); the electron, proton and oxygen cyclotron frequencies averaged over the same 5-minute interval; and a selected set of orbit parameters, including magnetic latitude, magnetic local time, L-shell and geocentric radial distance.
LIST OF KEY PARAMETERS FOR POLAR PWI
1. Epoch Time Beginning of 299-sec interval
Units DD-MMM-YYYY-HH:MM:SS.SSS
Resolution msec
2. PB5 Time Beginning of 299-sec interval
Units YYYY DDD MSEC
Resolution msec
3. Electron cyclotron frequency
Units Hz
Ranges 25.0 // 1.1e+06
Resolution
4. Proton cyclotron frequency
Units Hz
Ranges 0.01 // 600.0
Resolution
5. Oxygen cyclotron frequency
Units Hz
Ranges 0.0005 // 37.5
Resolution
6. Magnetic Latitude
Units degrees
Ranges -90.0 // 90.0
Resolution
7. Magnetic Local Time
Units hours
Ranges 0.0 // 24.0
Resolution
8. L-Shell McIlwain Parameter
Ranges 1.0 // 100.0
Resolution
9. Geocentric Radial Distance
Units earth radii
Ranges 0.0 // 10.0
Resolution
10. SFRA Antenna Antenna configuration for SFRA
Value One of: 0 = Eu
1 = Ez
2 = Loop
3 = Bz
11. SFRB Antenna Antenna configuration for SFRB
Value One of: 0 = Eu
1 = Ev
2 = Ez
3 = Loop
12. SFRA Average Electric component of plasma waves
Electric Field detected by SFRA, averaged over
299 seconds for each of the 160
frequencies
Units (V/m)**2/Hz
Ranges 1.0e-23 // 10.0
Resolution 32 seconds for full spectrum in log mode
64 seconds for full spectrum in linear mode
13. SFRA Average Magnetic component of plasma waves
Magnetic Field detected by SFRA, averaged over 299
seconds for each of the 160 frequencies
Units (nT)**2/Hz
Ranges 1.0e-23 // 10.0
Resolution 32 seconds for full spectrum in log mode
64 seconds for full spectrum in linear mode
14. SFRB Average Electric component of plasma waves
Electric Field detected by SFRB, averaged over
299 seconds for each of the 160
frequencies
Units (V/m)**2/Hz
Ranges 1.0e-23 // 10.0
Resolution 32 seconds for full spectrum in log mode
64 seconds for full spectrum in linear mode
15. SFRB Average Magnetic component of plasma waves
Magnetic Field detected by SFRB, averaged over 299
seconds for each of the 160 frequencies
Units (nT)**2/Hz
Ranges 1.0e-23 // 10.0
Resolution 32 seconds for full spectrum in log mode
64 seconds for full spectrum in linear mode
16. SFRA Peak Electric component of plasma waves,
Electric Field peak value detected by SFRA during
299-second averaging interval for
each of the 160 frequency values
Units (V/m)**2/Hz
Ranges 1.0e-23 // 10.0
Resolution 32 seconds for full spectrum in log mode
64 seconds for full spectrum in linear mode
17. SFRA Peak Magnetic component of plasma waves,
Magnetic Field peak value detected by SFRA during
299-second averaging interval for
each of the 160 frequency values
Units (nT)**2/Hz
Ranges 1.0e-23 // 10.0
Resolution 32 seconds for full spectrum in log mode
64 seconds for full spectrum in linear mode
18. SFRB Peak Electric component of plasma waves,
Electric Field peak value detected by SFRB during
299-second averaging interval for
each of the 160 frequency values
Units (V/m)**2/Hz
Ranges 1.0e-23 // 10.0
Resolution 32 seconds for full spectrum in log mode
64 seconds for full spectrum in linear mode
19. SFRB Peak Magnetic component of plasma waves,
Magnetic Field peak value detected by SFRB during
299-second averaging interval for
each of the 160 frequency values
Units (nT)**2/Hz
Ranges 1.0e-23 // 10.0
Resolution 32 seconds for full spectrum in log mode
64 seconds for full spectrum in linear mode
20. Frequency 160 logarithmically-spaced values
Units Hz
Ranges 26.77 // 794452.88
Frequency 5% of bandwidth for frequencies <200 Hz
Resolution 1% of bandwidth for frequencies >200 Hz
21. SFR Mode Logarithmic or Linear Mode,
referring to spacing of the
frequency steps before mapping to
160 key parameter frequencies
Values 0 = Logarithmic
1 = Linear
2 = Mixed (when mode change occurs
during the averaging interval)
22. Data Quality Flag
Values 0 = Green, indicates good data.
1 = Yellow, indicates fair data.
2 = Red, indicates unreliable data.
23. Post Gap Flag Indicates number of missing frames
in the averaging interval
24. Label Pointer for PB5 Time
25. Unit Pointer for PB5 Time
26. Formats for PB5 Time
B. Algorithms
The electron and ion cyclotron frequencies are derived from the following: Fce = 0.028*B where B is the magnitude of the ambient magnetic field measured in nT and Fce is given in kHz. Fcp = Fce/1837 and FcO+ = Fcp/16 where Fcp and FcO+ are given in kHz. All frequencies in the key parameters are converted to Hz.
Since the SFR frequency steps vary with the mode (linear or logarithmic), the measured SFR frequencies will be mapped to a fixed array of 160 approximately logarithmically spaced frequency values, 32 frequency values for each of the five SFR channels. In the log mode, the 64 frequency steps of the fourth and fifth channels will be mapped to 32 frequency steps each, using geometric averaging. In the linear mode, the 448 linearly spaced frequency steps of the five frequency channels will be mapped to the fixed array of 160 logarithmically spaced frequency values using a windowing technique. The magnetic and electric field values corresponding to each SFR frequency step will be similarly mapped to 160-point fixed arrays corresponding to the mapped frequency array.
Parameters used to calculate the orbit parameters are extracted from the spacecraft housekeeping files. Geocentric radial distance is derived from the spacecraft altitude, using RE = alt/6378 where RE is given in earth radii and alt is in km. Magnetic local time L-shell, and magnetic latitude are derived from the spacecraft coordinates using the EDMLT KP subroutine.
C. Corrections To The Data
All electric and magnetic field values have been calibrated.
Other PWI parameters obtainable upon request include:
PWI key parameters will be obtained for both the SFR logarithmic mode and the SFR linear mode and for all antenna combinations [see SFR antenna modes]. The SFR bandwidth and dwell time vary with the SFR frequency bands. The time resolution varies with the SFR frequency bands and the SFR mode [see SFR Design Features]. The SFR has a 100% duty cycle.
Data from the remaining PWI receivers are not used in the generation of the PWI key parameters. The MCA bandwidth, like the SFR, is frequency-dependent and the time resolution is 1.3 seconds/spectra [see MCA Design Features]. The two MCA receivers, like the SFR receivers, have 16 different antenna modes available.The WBR has six bandwidth filters which can be combined with four front end filters to vary the frequency range from 0 kHz to 590 kHz. The sample rate and duty cycle vary with the bandwidth selected. The instantaneous dynamic range varies with the WBR A/D conversion compression mode. There are four antenna modes for the WBR receiver.
The HFWR has four filter modes and two telemetry modes. In the normal or default telemetry mode, data from the HFWR are stored on the spacecraft tape recorder and transmitted down the low-rate telemetry link. The three digital HFWR filter modes are only accessible when the HFWR is in the normal telemetry mode. All six HFWR channels can be selected to deliver an instantaneous three-axis snapshot of the electric and magnetic wave fields in one-second waveform segments. Fewer than six channels can also be selected to improve the capture rate, the number of samples per snapshot per channel and the snapshot length. The sampling rate and the frequency resolution vary with the HFWR filter.
In the high-rate telemetry mode the HFWR data is put into the high-rate telemetry link in place of the wideband data to allow fast 9.2-second waveform capture in real time. Only the 25 kHz analog filter is used in this mode.
There are two possible HFWR antenna modes. In the default mode, the six HFWR channels are connected to the three orthogonal electric antennas and the triaxial search coil magnetometer. The HFWR also has a special interferometry mode in which two of the channels are connected to the Ev+ and Ev- antennas to allow digitization of the single-ended waveform.
Under development