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MMS 2 Digital Signal Processor (DSP) Search Coil Magnetometer (SCM), Magnetic Field Power Spectral Density, Level 2 (L2), Slow Mode, 16 s Data

The MMS magnetic field power spectral density (BPSD) is computed onboard by the Digital Signal Processor (DSP). The fast Fourier transform (FFT) calculation is performed on a digitized version of analog signals from the Search Coil Magnetometer (SCM) in the SCM123 coordinate system (scm1 = - x sensor; scm2 = -z sensor; scm3 = -y sensor). This data product is computed in space from individual components that are not synchronized to the 1 second pulse. Therefore, the timing between channels can be inaccurate by a fraction of a second. The samples times are interval start times taken from the x component. The spectra are calculated via a 1024-point FFT algorithm on piecewise continuous sets of waveform data. Nine signals can be processed simultaneously. Six of the twelve DC-coupled E, DC-coupled V, or SCM signals (16384 samples/s) are selected for spectral processing at 100% duty cycle. In addition, the three AC-coupled signals (262,144 kS/s) each can be processed at 6.25% duty cycle. Each of the nine signals has 16, 1024-point FFT operations every second; the field-programmable gate array (FPGA) performs 144 FFTs per second. The FFT is performed by an arithmetic logic unit (ALU), which is controlled by a state machine. Both are hard-coded into the FPGA. The operation starts by applying a 1024-point Hanning window onto a waveform. Next, an FFT is implemented. The FFT is broken into a series of "butterfly" operations performed by the ALU. The result has real and imaginary data. Power spectra are calculated by taking the sum of squares of real and imaginary values (the ALU includes a multiplier), which produces a power spectrum with 512 frequency bins. The frequency bins are then combined to give pseudo-logarithmic frequency spacing (del f)/f. The spectra are reduced to 88 frequency bins with (del f)/f between 6% and 12% when possible. Narrow-band emissions can be fit to an accuracy of (del f)/f ~3%, allowing for an accurate determination of plasma density. The spectra can be averaged in time. The fastest reporting rate of any signal is 16 spectra per second. Reporting rates can be as slow a one spectra every 16 s (averaging 256 spectra). The averaging process has 48-bit accuracy to maximize the dynamic range. The amplitudes undergo a pseudo-logarithmic compression to an 8-bit number representing over 120 dB of dynamic range at ~5% precision.

Thule Air Base (TAB) Ground-based Vector Magnetic Field (L2) 1.0 min Data

Thule Air Base, Greenland, Ground-based Vector Magnetic Field Level 2 Data, 1.0 min Time Resolution, Station Code: (TAB), Station Location: (GEO Latitude 76.5, Longitude 291.2), Norwegian Mag. Network

Pioneer Venus Orbiter (PVO) hourly merged magnetic field and plasma data

This is an hourly resolution, merged magnetic field and plasma data set created at NSSDC for COHOWeb. Magnetic field vectors and plasma flow direction angles are given in RTN coordinates. Spacecraft position data are given in Heliographic inertial (HGI coordinates).

Donna (DON) Ground-based Vector Magnetic Field (L2) 1.0 min Data

Donna, Norway, Ground-based Vector Magnetic Field Level 2 Data, 1.0 min Time Resolution, Station Code: (DON), Station Location: (GEO Latitude 66.1, Longitude 12.5), TGO Network

Nord (NRD) Ground-based Vector Magnetic Field (L2) 20.0 s Data

Nord, Greenland, Ground-based Vector Magnetic Field Level 2 Data, 20.0 s Time Resolution, Station Code: (NRD), Station Location: (GEO Latitude 81.6, Longitude 343.3), DTU Network

THEMIS-E: On Board Fast Fourier Transform (FFT) power spectra of Electric (EFI) and Magnetic (SCM) field measurements, for particle and wave burst survey modes.

On Board Fast Fourier Transform (FFT) power spectra of Electric (EFI) and Magnetic (SCM) field measurements for particle and wave burst survey modes. Spectra are produced only in Particle Burst and Wave Burst modes; only a preselected four of the signals listed in Table 1 are input at any time. Data fed through the FFT while not in Particle or Wave Burst modes is automatically disgarded. The FFTs (Cooley-Tukey algorithm) are conducted as an integral part of the power spectrum calculation by the Field Programable Gate Arrays (FPGAs). A CORDIC algorithm is used for sine/cosine calculations. The data has raw resolution of 1024 pts for 8,192 sample/sec signals and 2048 pts for 16,384 sample/sec signals (EAC measurements only). Signals at 8,192 samples/sec are handled by 1024-point FFTs, while those at 16,384 samples/sec go through 2048-point FFTs. Past and current signal configurations for specific spacecraft are listed bellow in Table 2. The spectra are arranged into log spaced frequency bins in steps of 16, 32, or 64. Cadence is adjusted to keep packet size constant (i.e. increasing the fequency resolution by a factor of 2 decreases the sampling rate by 1/2). The frequency bins cover a range of 0 Hz to 4 kHz. Table 1: FFT Input Signals. Signal Description SCMX, SCMY, SCMZ: Three axis magnetic fiend from SCM V1 through V6: Probe-spacecraft voltage for all six EFI sensors E12DC, E34DC, E56DC: DC-coupled electric field measured from opposing EFI sensors E12AC, E34AV, E56AC: AC-coupled electric field measured from opposing EFI sensors E12HF: High frequency electric field from EFI Table 2: Spacecraft specific configurations. All probes were initially set to use EDC34, EDC56, SCM2, and SCM3 signals for both particle and wave burst modes. Output was set to 16 frequency bins at 4 Hz. Configuration Changes: 23-27 June 2008: Particle burst spectra on all probes reconfigured to 64 bins at 1 Hz. Table 3: Instrument-Spacecraft Physical Configuration Instrument Alignment in Spacecraft Geometric coordinates (SPG). See THEMIS website for coordinate system details and mechanical drawings. EFI boom 1: Along positive X-axis EFI boom 2: Along negative X-axis EFI boom 3: Along positive Y-axis EFI boom 4: Along negative Y-axis EFI boom 5: Along positive Z-axis EFI boom 6: Along negative Z-axis SCM: *The SCM uses an instrument specific set of axes; an orthogonal system centered instrument with the X-axis 12.1 degrees from the SPG X-axis.

Savissivik (SVS) Ground-based Vector Magnetic Field (L2) 20.0 s Data

Savissivik, Greenland, Ground-based Vector Magnetic Field Level 2 Data, 20.0 s Time Resolution, Station Code: (SVS), Station Location: (GEO Latitude 76.0, Longitude 294.9), DTU Network

Vize Island (VIZ) Ground-based Vector Magnetic Field (L2) 1.0 min Data

Vize Island, Russia, Ground-based Vector Magnetic Field Level 2 Data, 1.0 min Time Resolution, Station Code: (VIZ), Station Location: (GEO Latitude 79.3, Longitude 76.5), AARI Network

Barentsburg (BBG) Ground-based Vector Magnetic Field (L2) 1.0 min Data

Barentsburg, Russia, Ground-based Vector Magnetic Field Level 2 Data, 1.0 min Time Resolution, Station Code: (BBG), Station Location: (GEO Latitude 67.9, Longitude 306.4), AARI Network

Hankasalmi (HAN) Ground-based Vector Magnetic Field (L2) 10.0 s Data

Hankasalmi, Finland, Ground-based Vector Magnetic Field Level 2 Data, 10.0 s Time Resolution, Station Code: (HAN), Station Location: (GEO Latitude 62.3, Longitude 26.6), IMAGE Network

Pueblo (PBLO) Ground-based Vector Magnetic Field (L2) 0.5 s Data

Pueblo, CO, Ground-based Vector Magnetic Field Level 2 Data, 0.5 s Time Resolution, Station Code: (PBLO), Station Location: (GEO Latitude 38.3, Longitude 255.4), THEMIS GBO Network

Ittoqqortoormiit (SCO) Ground-based Vector Magnetic Field (L2) 1.0 min Data

Ittoqqortoormiit, Greenland, Ground-based Vector Magnetic Field Level 2 Data, 1.0 min Time Resolution, Station Code: (SCO), Station Location: (GEO Latitude 70.4, Longitude 338.0), DTU Network

Stanford (STFD) Ground-based Vector Magnetic Field (L2) 0.5 s Data

Stanford, CA, Ground-based Vector Magnetic Field Level 2 Data, 0.5 s Time Resolution, Station Code: (STFD), Station Location: (GEO Latitude 37.4, Longitude 237.8), THEMIS GBO Network

Homer (HOMR) Ground-based Vector Magnetic Field (L2) 0.5 s Data

Homer, AK, Ground-based Vector Magnetic Field Level 2 Data, 0.5 s Time Resolution, Station Code: (HOMR), Station Location: (GEO Latitude 59.7, Longitude 209.5), University of Alaska Network

PENGUIn-4 (PG4) Ground-based Vector Magnetic Field (L2) 1.0 s Data

PENGUIn-4, Antarctica, Ground-based Vector Magnetic Field Level 2 Data, 1.0 s Time Resolution, Station Code: (PG4), Station Location: (GEO Latitude -83.3, Longitude 12.3), Antarctic Network

Ny Alesund (NAL) Ground-based Vector Magnetic Field (L2) 1.0 min Data

Ny Alesund, Norway, Ground-based Vector Magnetic Field Level 2 Data, 1.0 min Time Resolution, Station Code: (NAL), Station Location: (GEO Latitude 79.0, Longitude 11.9), TGO Network

Sitka (SIT) Ground-based Vector Magnetic Field (L2) 1.0 s Data

Sitka, AK, Ground-based Vector Magnetic Field Level 2 Data, 1.0 s Time Resolution, Station Code: (SIT), Station Location: (GEO Latitude 57.1, Longitude 224.7), USGS Network

Van Allen Probe A Electric Field and Waves Suite (EFW) Burst Mode 1 (512 Samples/sec) Electric and Magnetic Fields, Waveform, in Spacecraft Spin (UVW) Coordinates, Level 1 (L1), 1.95 ms Data

The EFW Burst Modes provide targeted Measurements over Brief Time Intervals of 3-D Electric Fields, 3-D Wave Magnetic Fields, and Spacecraft Potential. There are two EFW Burst Modes: BURST1 (B1), Medium-Rate 512 samples/s nominal and BURST2 (B2), Higher-Rate, 16384 samples/s nominal. The Burst 1 Mode Data includes three components of the Electric Field (E12_B1, E34_B1, E56_B1), six Components of the Spacecraft-Sensor Potential (V1_B1 through V6_B1), and three Components of the AC Magnetic Field (SCM_U_B1, SCM_V_B1, SCM_W_B1 from the EMFISIS Search Coil Magnetometer). The Burst 2 Mode Data returns a similar Complement of Electric Field (E_12ac_B2, E34ac_B2, E56ac_B2), Search Coil (SCM_B2, SCM_2B2, and SCM_B2 again from the EMFISIS Search Coil Magnetometer) and Single-ended Potential Measurements (V1ac_B1 through V6ac_B2) with the exception that in the Default Mode the Single-ended Potential and Electric Field Signals are AC coupled with a higher Gain. All Quantities are in "uvw" Coordinates where "u" and "v" are the Sensor Coordinates rotating with the Spacecraft and "w" points along the Spacecraft Spin Axis. Burst Waveform CDF Files are available. The three Data Types available are the Electric Field "E" the Searchcoil Magnetic Field "MSC" and Antenna Potential "V". The Suffix on each of these is either "B1" or "B2". B1 or Burst 1 is the Human-in-the-Loop Burst Type, meaning that both Collection and Playback (for arbitrary Lengths of Time) are requested on the Ground. B2 or Burst 2 is automatically telemetered as short Bursts based on an onboard Triggering Algorithm, typically set to trigger on large Amplitude Signals near 1 kHz. Sample Rates for B1 and B2 can and are changed depending on varying Science Goals.