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Overview

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.

Extended Information | Short Descriptions


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) >

Time Variables

  • Epoch The CDF Epoch variable
  • Time_PB5 [Year, Day of Year, Milliseconds of Day]

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Partial Density Variables

Units cm-3 — Energy Ranges are Mode Dependent

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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.

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Temperature Variables

Perpendicular and Parallel to the Magnetic Field

Units keV — Energy Ranges are Mode Dependent See the mode and diagnostic parameters for information on the field aligned coordinate system.

  • 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

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Quality Parameters

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.

See Table above for the mode dependent energy ranges.

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Position Variables

  • 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)

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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
  • TIMAS_B

    • 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.

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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

  • label_geomagnetic
  • units_geomagnetic
  • format_geomagnetic
  • label_geographic
  • units_geographic
  • format_geographic
  • label_time
  • units_time
  • format_time
  • Labels_for_TIMAS_B
  • Labels_for_Quality
  • label_Energy_ranges
  • label_H_density
  • label_O_density
  • label_H_Low_Velocity
  • label_O_Low_Velocity
  • label_H_Full_Velocity
  • label_O_Full_Velocity
  • label_H_Low_Temp
  • label_O_Low_Temp
  • label_H_full_Temp
  • label_O_full_Temp

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Prepared by W.K. Peterson

Last updated 08/07/2005 by Daryl Carr