Freja F2 On-board FFT Summary Plots
Freja F2 On-board FFT Summary Plots
Plot Description:
The top panel contains a 0-256 Hz frequency-time spectrogram made up of
individual 512 point FFTs of spin-axis (z-axis) high-pass filtered (ac)
magnetic field data. The high-pass filter has a 3 dB point at 1.5 Hz and
an anti-alias filter at 256 Hz. The spectral power has been corrected for
the high-pass filter attenuation at low frequencies (plots with FC=1 label
under color bar).
The spectrogram is color coded in units of log spectral density (nT2/Hz).
The bottom panel contains the average spectral density in the frequency
range from 5-30 Hz (green) and 30-255 Hz (red).
Prepared and Maintained by J.B. Gary,
jim.gary@jhuapl.edu
Name Last modified Size Description
![[DIR]](/icons/back.gif)
Parent Directory -
![[DIR]](/icons/folder.gif)
00000/ 17-Oct-1997 15:54 -
00100/ 17-Oct-1997 16:01 -
00200/ 17-Oct-1997 16:01 -
00300/ 17-Oct-1997 16:01 -
00400/ 17-Oct-1997 16:01 -
00500/ 27-May-1998 16:10 -
00600/ 27-May-1998 16:14 -
00700/ 27-May-1998 16:15 -
00800/ 27-May-1998 16:16 -
00900/ 27-May-1998 16:17 -
01000/ 27-May-1998 16:17 -
01100/ 27-May-1998 16:18 -
01200/ 27-May-1998 16:18 -
01300/ 27-May-1998 16:18 -
01400/ 27-May-1998 16:19 -
01500/ 27-May-1998 16:20 -
01600/ 27-May-1998 16:20 -
01700/ 27-May-1998 16:20 -
01800/ 27-May-1998 16:27 -
01900/ 27-May-1998 16:29 -
02000/ 27-May-1998 16:30 -
02100/ 27-May-1998 16:32 -
02200/ 17-Oct-1997 16:01 -
02300/ 17-Oct-1997 16:01 -
02400/ 17-Oct-1997 15:54 -
02500/ 17-Oct-1997 16:02 -
02700/ 17-Oct-1997 15:54 -
04400/ 17-Oct-1997 16:02 -
04500/ 17-Oct-1997 15:55 -
04600/ 17-Oct-1997 15:55 -
04700/ 17-Oct-1997 15:55 -
04800/ 17-Oct-1997 16:02 -
04900/ 17-Oct-1997 16:02 -
05000/ 17-Oct-1997 16:02 -
05100/ 17-Oct-1997 16:03 -
05200/ 17-Oct-1997 16:03 -
05300/ 17-Oct-1997 16:03 -
05400/ 17-Oct-1997 16:03 -
05500/ 17-Oct-1997 16:03 -
05600/ 17-Oct-1997 16:03 -
05700/ 17-Oct-1997 16:03 -
05800/ 17-Oct-1997 16:04 -
05900/ 17-Oct-1997 16:04 -
06000/ 17-Oct-1997 16:04 -
06100/ 17-Oct-1997 16:04 -
06200/ 17-Oct-1997 16:04 -
06300/ 17-Oct-1997 16:04 -
06400/ 17-Oct-1997 15:54 -
06500/ 17-Oct-1997 15:55 -
06600/ 17-Oct-1997 15:55 -
06700/ 17-Oct-1997 15:56 -
06800/ 17-Oct-1997 15:56 -
06900/ 17-Oct-1997 15:56 -
07000/ 17-Oct-1997 15:56 -
07100/ 17-Oct-1997 15:56 -
07200/ 17-Oct-1997 15:57 -
07300/ 17-Oct-1997 15:57 -
07400/ 17-Oct-1997 15:57 -
07500/ 17-Oct-1997 15:57 -
07600/ 17-Oct-1997 15:57 -
07700/ 17-Oct-1997 15:58 -
07800/ 17-Oct-1997 15:58 -
07900/ 17-Oct-1997 15:58 -
08000/ 17-Oct-1997 15:58 -
08100/ 17-Oct-1997 15:58 -
08200/ 17-Oct-1997 15:58 -
08300/ 17-Oct-1997 15:58 -
08400/ 17-Oct-1997 15:59 -
08500/ 17-Oct-1997 15:59 -
08600/ 17-Oct-1997 15:59 -
08700/ 17-Oct-1997 15:59 -
08800/ 17-Oct-1997 15:59 -
08900/ 17-Oct-1997 15:59 -
09000/ 17-Oct-1997 15:59 -
09100/ 17-Oct-1997 16:00 -
09200/ 17-Oct-1997 16:00 -
09300/ 17-Oct-1997 16:00 -
09400/ 17-Oct-1997 16:00 -
09500/ 17-Oct-1997 16:00 -
09600/ 17-Oct-1997 16:00 -
09700/ 17-Oct-1997 16:00 -
09800/ 17-Oct-1997 16:01 -
09900/ 17-Oct-1997 16:01 -
10000/ 17-Oct-1997 16:01 -
10100/ 17-Oct-1997 16:04 -
10200/ 17-Oct-1997 16:05 -
10300/ 17-Oct-1997 16:05 -
11200/ 17-Oct-1997 15:54 -
11300/ 17-Oct-1997 16:01 -
11400/ 17-Oct-1997 16:01 -
![[ ]](/icons/p.gif)
sort.pl 16-May-1996 17:27 1.3K
sort_aux.pl 12-Aug-1997 17:56 1.2K
On-Board FFT Description:
The Freja F2 Magnetic Field Experiment (MFE) uses a three-axis ring core
fluxgate sensor and electronics unit which digitizes, filters, processes,
and stores signals from the sensor. The Freja MFE records both "dc" vector
magnetic fields for investigation of large scale field-aligned currents and
"ac" vector magnetic fields for investigations of small-scale size structures
and plasma waves. The "ac" vector magnetic field, provided by high-pass
filtering the "dc" channel prior to digitization, is sampled at 128 Hz and
digitized using 16 bits for a resolution of 20 pT. The "ac" channel high
pass 3-pole filter has a 3 dB point set at 1.5 Hz to attenuate oscillations
induced by the satellite spin in the earth's magnetic field at a rate of 0.16
revolutions per second. In order to further extend the frequency range, the
"ac" signals from the z-axis were also sent to the MFE processor which
performed 512 point fast Fourier transforms (FFT) of the signals with a
Nyquist frequency of 256 Hz. A three-pole anti-alias filter set at 256 Hz
was used for this signal. These data are referred to as the
"Freja F2 On-board FFT" data. The resulting spectra are calculated at 1 Hz
resolution and then are time-averaged, providing one complete spectra every
2 or 3 seconds.