DOI: 10.5281/zenodo.17526151
title: Magnetospheric Multi-Scale Mission Fast Plasma Investigation example of Ion Density and Velocity at 0.15 s cadence derived from on-board moments

description: This dataset contains examples of  MMS FPI trigger ion density and sign bit estimated velocity. The data is derived from ground calibration of the on-board 0th and 1st ion moments at 0.15 s cadence during fast mode intervals for two days. Unfortuanately the sign bit of the 1st moment was removed before the data was telemeterd, so the central part of this study is recovering the sign bit and generating calibrated velocity moments. This method works best when the spacecraft are in the magnetosheath and its boundary layer. The goal is to derive such a dataset over the entire MMS mission in ISTP CDF format and archive it at the Space Physics Data Facility. The examples here are in idl save format.  This data is used in a demonstration paper titled "MMS Fast Plasma Investigation ‘trigger’ data derived Ion velocities used to analyze magnetosheath ion cyclotron waves " by Boardsen S.A., et al. to be submitted to JGR space physics.
description:   

The files in IDL SAVE format are 

mms1_trigger_ion_velocity_density_2015-10-07T06:02:00.169Z-2015-10-08T17:39:36.165Z.svmms1_trigger_ion_velocity_density_2015-12-30T00:00:00.577Z-2015-12-31T23:59:59.014Z.svmms2_trigger_ion_velocity_density_2015-10-07T06:02:21.872Z-2015-10-08T17:39:25.287Z.svmms2_trigger_ion_velocity_density_2015-12-30T00:00:00.175Z-2015-12-31T23:59:59.103Z.svmms3_trigger_ion_velocity_density_2015-10-07T06:02:17.235Z-2015-10-08T17:39:54.021Z.svmms3_trigger_ion_velocity_density_2015-12-30T00:00:00.403Z-2015-12-31T23:59:59.995Z.svmms4_trigger_ion_velocity_density_2015-10-07T06:02:07.401Z-2015-10-08T17:39:32.405Z.svmms4_trigger_ion_velocity_density_2015-12-30T00:00:03.934Z-2016-01-01T00:00:00.910Z.sv

IDL is used to load the files, although python routines exist that can load idl save files.

IDL> restore,'mms1_trigger_ion_velocity_density_2015-10-07T06:02:00.169Z-2015-10-08T17:39:36.165Z.sv',/v% RESTORE: Restored variable: Q1.IDL> help, q1,/str** Structure <1b80c008>, 17 tags, length=71700408, data length=71700404, refs=1:   SC              STRING    '1'   EPOCHI          LONG64    Array[556680]    ; in CDF TT2000 format, which is time in nano-seconds this J2000.   VI_BSC          DOUBLE    Array[3, 556680] ; trigger ion velocity in BSC coordinates in km/s   VI_DBSC         DOUBLE    Array[3, 556680] ; trigger ion velocity in DBSC coordinates in km/s   DENICAL         FLOAT     Array[556680]    ; trigger ion density in cm^{-3}   VI_FLAG         FLOAT     Array[3, 556680] ; sign bit error flag for VI_BSC, 0 ok,  1 possible error in sign bit estimation   SPEEDICAL       FLOAT     Array[556680]    ; trigger ion speed   VF_DBSC         FLOAT     Array[3, 556680] ; FSAT mode ion velocity in DBSC spline interpolated to trigger times   VF_BSC          DOUBLE    Array[3, 556680] ; FSAT mode ion velocity in BSC spline interpolated to trigger times   DENSF           FLOAT     Array[18556]   M0              FLOAT     Array[556680]   ; M 0, X, Y, Z unsigned uncalibrated trigger moments   MX              FLOAT     Array[556680]   MY              FLOAT     Array[556680]   MZ              FLOAT     Array[556680]   EPOCHF          LONG64    Array[18556]    ; FAST mode epoch   VF_DBSCF        FLOAT     Array[3, 18556] ; FSAT mode ion velocity in DBSC   ISIGNBITERRCUTOFF                   FLOAT           1.00000

 Calibrated ion trigger data are used in the paper areDENICAL         FLOAT     Array[556680]     ; ion density in cm^{-3}VI_BSC          DOUBLE    Array[3, 556680]  ; ion velocity in BSC coordinates in km/sVI_DBSC         DOUBLE    Array[3, 556680]  ; ion velocity in DBSC coordinates in km/s

whose time stamps are 

EPOCHI          LONG64    Array[556680]  ; in CDF TT2000 format, which is time in nano-seconds this J2000.   

BSC - Body Spacecraft coordinates which spins with the spacecraft bodyDBSC - Despun Body Spacecraft coordinates which in despun spacecraft coordinate, note DBSC is within a couple of degrees of GSE (Geocentric Solar Ecliptic).