Data Descriptions
Which set of data would you like to see info about:
| ESA | SST | EFI | MOM | SCM | FGM | FBK | FFT | FIT | ASI | GMAG | STATE | GMOM |
THEMIS Level 2 EFI file info:
Files thx_l2_efi_yyyymmdd_v01.cdf (where x = a,b,c,d or e):
Electric Field Instrument (EFI) Electric field measurements. This L2 product is a 3D estimate including Eperp derived from the spin plane E-field measurements assuming E dot B = 0, using relevant FGM (Flux-Gate Magnetometer) data. Includes spin-averaged and Fast-survey field data. Spin-averaged (EFS_DOT0) data has approximately 3 second time resolution. Fast-survey (EFF_DOT0) data has 1/8 second time resolution.
Files thx_l2_efp_yyyymmdd_v01.cdf (where x = a,b,c,d or e):
Electric Field Instrument (EFI) Electric field measurements. This L2 product is a "cleaned" 3D field, for particle burst mode, using the SPEDAS IDL procedure THM_EFI_CLEAN_EFP, which is described below.
Files thx_l2_efw_yyyymmdd_v01.cdf (where x = a,b,c,d or e):
Electric Field Instrument (EFI) Electric field measurements. This L2 product is a "cleaned" 3D field, for wave burst mode, using the SPEDAS IDL procedure THM_EFI_CLEAN_EFW, which is described below.
| Link to the EFI Data Variable Descriptions | Link to EFI Instrument Information | |
| Link to the EFI Data Processing History |
THEMIS Level 2 EFI "clean" processes:
Here follows a brief description of the IDL processes that are used to "clean" the particle and wave burst data that is distributed in THEMIS EFP and EFW Level 2 data files. More information can be found in the documentation headers for the programs:
andTHM_EFI_CLEAN_EFP:
1) Inputs data, needs EFP, FGH, Spin data. Uses DSL coordinates. Inputs SC potential using THM_EFI_GET_POTENTIAL; uses VAP data for potential, not On-board PXXM_POT.
2) Clips data to the timerange, this program can be called on a full day, but can also be called on smaller time ranges. In particular, there are different default values of various fit parameters for daylight and night.
3) Calls THM_LSP_FIND_BURST to split the data into individual bursts. Simple process; data is split up when the time between data points dt is dt GT 2*median(dt).
FOR EACH BURST:
4) If the burst is too short, then data is set to NaN. Duration_threshold is an optional keyword with a default of 15 seconds.
5) Calls THM_EFI_CLEAN_EFP_DECONVOL_INST_RESP to remove the instrument response:
5a) THM_COMP_EFI_RESPONSE returns the voltage gain as a function of frequency.
5b) Take inverse FFT of 1/boom_resp. This results in a time profile that is then convolved with the input E field using the IDL BLK_CON function.
6) Clips the spacecraft potential and removes spintone, using THM_LSP_REMOVE_SPINTONE: THM_QFIT is used to get a smoothed version of the spinfit data, and this is subtracted from the input data.
7) Removes the spintone from the Efield data.
8) Uses THM_LSP_REMOVE_POTENTIAL to remove the SC potential from Ez component.
9) Removes spikes from E data, using THM_LSP_REMOVE_SPIKES.
10) Removes spin tones again.
11) Removes spin tones from B field.
12) Smooths B.
13) Next batch
14) Stores data in tplot variables, 'thx_efp_clean'.
15) Gets FAC, field aligned E field, not saved in L2 files.
THM_EFI_CLEAN_EFW:
1) Inputs data, needs EFP, EFW, FGH, Spin data. Uses DSL coordinates. Inputs SC potential using THM_EFI_GET_POTENTIAL; uses VAW data for potential, not on-board PXXM_POT. EFP data is used for spike removal, but process will not stop if there is no EFP data.
2) Clips data to the timerange, this program can be called on a full day, but can also be called on smaller time ranges. The process will fail if there is a shift between AC and DC coupling during the time range, so occassionally full-day processes will fail. When this is the case, split the day's data into AC or DC coupled intervals.
3) Calls THM_LSP_FIND_BURST to split the data into individual bursts. Simple process; data is split up when the time between data points dt is dt GT 2*median(dt).
4) Sets up a kernel, the transfer function, for deconvolving the EFI response, including: plasma-probe response, anti-aliasing filter response, ADC interleaving timing, DFB digital filter response. Calls THM_COMP_EFI_RESPONSE, THM_EAC_FILTER_RESP, THM_ADC_RESP, THM_DFB_DIG_FILTER_RESP.
FOR EACH BURST:
5) Interpolates over NaN values, if there are more than half NaN values, then the full burst is set to NaN.
6) Subtracts median value from each field component to minimize offsets.
7) Finds spin period for this burst.
8) Calls THM_LSP_FILTER_HIGHPASS for a high-pass filter. This is optimized for sample rates above 8192 per second, but will return values for lower sample rates.
9) Removes spikes, using THM_LSP_REMOVE_SPIKES, and THM_LSP_FIND_SPIKES, which compares values to median to find spikes.
10) Deconvolves the transfer function using the IDL BLK_CON function.
11) Gets FAC, field aligned E field, not saved in L2 files.
12) All done, next burst
13) Creates tplot variables for cleaned data.