Overview of TIMAS key parameters
Timas Key parameters are one minute averages of the density, temperature and velocity of H+, O+, He+ and He++ for one, two, or three mode dependent energy ranges.
The instrumental energy range is subject to change a few times per orbit. The key parameter Energy_Range_ID indicates which of the 3 instrumental energy ranges is currently active. Each instrumental energy range further divided into 3 Key Parameter (KP) energy channels (low – medium – and high). The table below gives the full energy range and limits of the thee KP energy ranges.
Energy_Range_ID=0: (Full instrumental energy range) ACTIVE AFTER June 26, 1996 Full range (0.015 - 33.3 keV/e) low KP channel (0.015 - 0.37 keV/e) mid KP channel (0.37 - 3.3 keV/e) high KP channel (3.3 - 33.3 keV/e) Energy_Range_ID=1: (Reduced instrumental energy range) ACTIVE BEFORE June 26, 1996 Full range (0.015 - 22.45 keV/e) low KP channel (0.015 - 0.37 keV/e) mid KP channel (0.37 - 3.3 keV/e) high KP channel (3.3 - 22.45 keV/e) Energy_Range_ID=2: (Low instrumental energy range) ACTIVE ONLY for short intervals over the polar cap
Not used after August 1996 Full range (0.015 - 2.18 keV/e) low KP channel (0.015 - 0.11 keV/e) mid KP channel (0.11 - 0.37 keV/e) high KP channel (0.37 - 2.18 keV/e)
TIMAS Key Parameters are written in the platform independent Common Data Format (CDF) developed by NASA.
The platform independent description of the TIMAS key parameters is given in TIMAS Key Parameter skeleton table
Three software packages are available to read and plot TIMAS key parameters.
- The NSSDC CDAWeb system.
- The Key Parameter Visualization Tool KPVT
- An IDL code used by TIMAS investigators
for diagnostic purposes.
A Selected Subset of TIMAS Key Parameters is available on-lne.
Important NoteVersion 2.0 of the KPGS software does not always provide accurate relative densities, temperatures, and velocities in the cusp.
Version 3.0 of the KPGS software will apply all known corrections
2/28/96 W.K. Peterson
The links below point to short descriptions of the Eight Types of variables in TIMAS Key Parameter Files:
< Time | Density | Velocity | Temperature | Quality | Position | Mode and Diagnostic | Descriptive (non record variable) >
Partial Density Variables
Units cm-3 — Energy Ranges are Mode Dependent
- Density_H [3 energy ranges (low,mid,hi) ]
- Density_O [3 energy ranges (low,mid,hi) ]
- Density_He_1 [1 energy range ]
- Density_He_2 [1 energy range ]
Three Dimensional Bulk Velocity Variables
Units km/s — Energy Ranges are Mode Dependent
The three velocity vectors are Despun and Aligned with the one minute average magnetic field. Specifically data are acquired in fixed platform coordinates. To transform to field aligned coordinates they are rotated about the Fixed Platform Z axis and then rotated again about a temporary Y axis so that the X axis is PARALLEL to the one minute average local magnetic Field. The Y axis remains in the spin plane. See the mode and diagnostic parameters for more information about the magnetic coordinate system.
- Vel_H_low Three components (x,y,z) of velocity from the low KP energy range.
- Vel_O_low Three components (x,y,z) of velocity from the low KP energy range.
- Velocity_H Three components (x,y,z) of velocity from the full instrumental energy range.
- Velocity_O Three components (x,y,z) of velocity from the full instrumental energy range.
Perpendicular and Parallel to the Magnetic Field
- Temp_H_low H+ Perp and Par Temp for the Low KP Energy Range
- Temp_O_low O+ Perp and Par Temp for the Low KP Energy Range
- Temperature_H H+ Perp and Par Temp for the Full Instrumental Energy Range
- Temperature_O O+ Perp and Par Temp for the Full Instrumental Energy Range
A Zero value indicates NO DATA acquired for this mass/energy range.
Calculation of the Quality Parameters depends on the instrumental background. A value of 999 indicates that no background counts were acquired.
- Quality_H [3 energy ranges]
- Quality_O [3 energy ranges]
- Quality_He_1 [1 energy range]
- Quality_He_2 [1 energy range]
See Table above for the mode dependent energy ranges.
- Geomagnetic_Position Invariant Latitude (degrees) Magnetic Local Time (decimal hours) and Geomagnetic latitude (degrees)
- Geographic_Position Latitude (degrees) Longitude (degrees) and Geocentric Distance ( R/Re in Earth radii)
Identification and Diagnostic Parameters
- Mode_IDThe Serial Number of the TIMAS ICP Table in use.
- Energy_Range_ID Integer indicating which of three instrumental energy range modes is active for each one minute key parameter averaging interval.
Key: 0=full, 1=reduced, 2=low See Table above for Full Energy Range Values
Units nT. The one minute average magnetic field in Fixed Platform Coordinates. These values are used by the TIMAS software to report values of Velocities and Temperatures in a magnetic field aligned coordinate system.
Fixed-Payload (FP) coordinates have the Z axis parallel to spin axis, The X axis perpendicular to the Z axis and in the meridian plane containing a radius vector to the Sun. The Y axis completes a right hand system.
NOTE: TIMAS_B values should NOT be used for analysis.
The following are NON record variable entries in the TIMAS Key Parameter Common Data Format file that are NOT updated by the TIMAS Key Parameter Code
Prepared by W.K. Peterson
Last updated 08/07/2005 by Daryl Carr