This data set includes the Voyager spacecraft number (1 or 2), the date-time in decimal year (90.00000 is day 1 of 1990), the magnetic field strength, F1, computed from high-resolution magnitudes, the elevation and azimuth angles in heliographic (RTN) coordinates, and the magnetic field strength, F2, computed from 1-hr averages of the components. The vector components of B can be computed from F2 and the two angles. The elevation angle is the latitude angle above or below the solar equatorial plane, and the azimuth angle is in the direction orbital motion around the Sun from the projection of the Sun-to-spacecraft axis into the solar equatorial plane. The Voyager MAG experiment and coordinates are further described in the following publication: Behannon, K.W., M.H. Acuna, L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M. Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2, Space Sci. Rev., 21 (3), 235-257, 1977. At the time of experiment proposal, it was expected that the required accuracy of the measurements would be 0.1 nT, determined by the combined noise of the sensors and the spacecraft field. The spacecraft magnetic field at the outboard magnetic field sensor, referred to as the primary unit, was expected to be 0.2 nT and highly variable, consistent with current estimates. Hence, the dual magnetometer design (Ness et al., 1971, 1973; Behannon et al., 1977). At distances > 40 AU, the heliospheric magnetic fields are generally much weaker than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about 0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting about 6 hours permits determination of the effective zero levels for the two independent magnetic axes that are perpendicular to the roll axis, which is nearly parallel to the radius vector to the Sun, at intervals of about 3 months. There is no roll calibration for the third magnetic axis. Comparison of the two derived magnetic vectors from the two magnetometers permits validation of the primary magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the uncertainties that must be considered when using these data is given in the Appendix of Burlaga et al. (1994) and in Appendix A of Burlaga et al. (2002). References: Behannon, K.W., M.H. Acuna, L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M. Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2, Space Science Reviews, 21 (3), 235-257, 1977. Burlaga, L.F., Merged interaction regions and large-scale magnetic field fluctuations during 1991 - Voyager-2 observations, J. Geophys. Res., 99 (A10), 19341-19350, 1994. Burlaga, L.F., N.F. Ness, Y.-M. Wang, and N.R. Sheeley, Jr., Heliospheric magnetic field strength and polarity from 1 to 81 AU during the ascending phase of solar cycle 23, J. Geophys. Res., 107 (A11), 1410, 2002. Ness, N., K.W. Behannon, R. Lepping, and K.H. Schatten, J. Geophys. Res., 76, 3564, 1971. Ness et al., 1973.
Coordinate Systems: Interplanetary magnetic field studies make use of two important coordinate systems, the Heliographic Inertial (HGI) coordinate system and the Heliographic (HG) coordinate system.
The HGI coordinate system is used to define the spacecraft's position. The HGI system is defined with its origin at the Sun. There are three orthogonal axes, X(HGI), Y(HGI), and Z(HGI). The Z(HGI) axis points northward along the Sun's spin axis. The X(HGI)-Y(HGI) plane lays in the solar equatorial plane. The intersection of the solar equatorial plane with the ecliptic plane defines a line, the longitude of the ascending node, which is taken to be the X(HGI) axis. The X(HGI) axis drifts slowly with time, approximately one degree per 72 years.
The magnetic field orientation is defined in relation to the spacecraft. Drawing a line from the Sun's center (HGI origin) to the spacecraft defines the X axis of the HG coordinate system. The HG coordinate system is defined with its origin centered at the spacecraft. Three orthogonal axes are defined, X(HG), Y(HG), and Z(HG). The X(HG) axis points radially away from the Sun and the Y(HG) axis is parallel to the solar equatorial plane and therefore parallel to the X(HGI)-Y(HGI) plane as well. The Z(HG) axis is chosen to complete the orthonormal triad.
An excellent reference guide with diagrams explaining the HGI and HG systems may be found in L.F. Burlaga, MHD Processes in the Outer Heliosphere, Space Sci. Rev., 39, 255-316, 1984.
Version:2.2.8
This data set includes the Voyager spacecraft number (1 or 2), the date-time in decimal year (90.00000 is day 1 of 1990), the magnetic field strength, F1, computed from high-resolution magnitudes, the elevation and azimuth angles in heliographic (RTN) coordinates, and the magnetic field strength, F2, computed from 1-hr averages of the components. The vector components of B can be computed from F2 and the two angles. The elevation angle is the latitude angle above or below the solar equatorial plane, and the azimuth angle is in the direction orbital motion around the Sun from the projection of the Sun-to-spacecraft axis into the solar equatorial plane. The Voyager MAG experiment and coordinates are further described in the following publication: Behannon, K.W., M.H. Acuna, L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M. Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2, Space Sci. Rev., 21 (3), 235-257, 1977. At the time of experiment proposal, it was expected that the required accuracy of the measurements would be 0.1 nT, determined by the combined noise of the sensors and the spacecraft field. The spacecraft magnetic field at the outboard magnetic field sensor, referred to as the primary unit, was expected to be 0.2 nT and highly variable, consistent with current estimates. Hence, the dual magnetometer design (Ness et al., 1971, 1973; Behannon et al., 1977). At distances > 40 AU, the heliospheric magnetic fields are generally much weaker than 0.4 nT; the average magnetic field strength near 40 AU and 85 AU is about 0.15 nT and 0.05 nT, respectively. The use of roll calibrations lasting about 6 hours permits determination of the effective zero levels for the two independent magnetic axes that are perpendicular to the roll axis, which is nearly parallel to the radius vector to the Sun, at intervals of about 3 months. There is no roll calibration for the third magnetic axis. Comparison of the two derived magnetic vectors from the two magnetometers permits validation of the primary magnetometer data with an accuracy of 0.02 to 0.05 nT. A discussion of the uncertainties that must be considered when using these data is given in the Appendix of Burlaga et al. (1994) and in Appendix A of Burlaga et al. (2002). References: Behannon, K.W., M.H. Acuna, L.F. Burlaga, R.P. Lepping, N.F. Ness, and F.M. Neubauer, Magnetic-Field Experiment for Voyager-1 and Voyager-2, Space Science Reviews, 21 (3), 235-257, 1977. Burlaga, L.F., Merged interaction regions and large-scale magnetic field fluctuations during 1991 - Voyager-2 observations, J. Geophys. Res., 99 (A10), 19341-19350, 1994. Burlaga, L.F., N.F. Ness, Y.-M. Wang, and N.R. Sheeley, Jr., Heliospheric magnetic field strength and polarity from 1 to 81 AU during the ascending phase of solar cycle 23, J. Geophys. Res., 107 (A11), 1410, 2002. Ness, N., K.W. Behannon, R. Lepping, and K.H. Schatten, J. Geophys. Res., 76, 3564, 1971. Ness et al., 1973.
Coordinate Systems: Interplanetary magnetic field studies make use of two important coordinate systems, the Heliographic Inertial (HGI) coordinate system and the Heliographic (HG) coordinate system.
The HGI coordinate system is used to define the spacecraft's position. The HGI system is defined with its origin at the Sun. There are three orthogonal axes, X(HGI), Y(HGI), and Z(HGI). The Z(HGI) axis points northward along the Sun's spin axis. The X(HGI)-Y(HGI) plane lays in the solar equatorial plane. The intersection of the solar equatorial plane with the ecliptic plane defines a line, the longitude of the ascending node, which is taken to be the X(HGI) axis. The X(HGI) axis drifts slowly with time, approximately one degree per 72 years.
The magnetic field orientation is defined in relation to the spacecraft. Drawing a line from the Sun's center (HGI origin) to the spacecraft defines the X axis of the HG coordinate system. The HG coordinate system is defined with its origin centered at the spacecraft. Three orthogonal axes are defined, X(HG), Y(HG), and Z(HG). The X(HG) axis points radially away from the Sun and the Y(HG) axis is parallel to the solar equatorial plane and therefore parallel to the X(HGI)-Y(HGI) plane as well. The Z(HG) axis is chosen to complete the orthonormal triad.
An excellent reference guide with diagrams explaining the HGI and HG systems may be found in L.F. Burlaga, MHD Processes in the Outer Heliosphere, Space Sci. Rev., 39, 255-316, 1984.
| Role | Person | |
|---|---|---|
| 1. | PrincipalInvestigator | spase://SMWG/Person/Norman.F.Ness |
| 2. | MetadataContact | spase://SMWG/Person/Robert.E.McGuire |
| 3. | MetadataContact | spase://SMWG/Person/Lee.Frost.Bargatze |
In CDF via ftp from SPDF.
In CDF via http from SPDF.
Access to ASCII, CDF, and plots via NASA/GSFC CDAWeb
Time, Beginning of Interval
Time, Beginning of Interval, 9.6-s Variables
Data Identifier, the Value is set to either HDR1 or LFM, List only
Telemetry Format, List only
Spacecraft Identification. 1 for Voyager 1, 2 for Voyager 2, List only
Decimal Day of Year, January 1 is Day 0
Decimal Day Count since August 20, 1977
Time Type, the Value is set to either SCET, the Spacecraft Event Time, or ERTS, the Earth Receive Time Start, List only
Time Period of the Data Block, 48-s
48-min Counter, 2^16 Sequence Counter of Data at Time of Telemetry Readout
48-s Counter, Modulo 60 Sequence Counter of Data at Time of Telemetry Readout
60-ms Counter, Line Counter of Data at Time of Telemetry Readout
MAG Instrument Status Word
MAG Instrument Command Word
Data Identifier, 2 denotes LFM, 8 denotes HDR1
Data Rate
MAG Data Confidence Flag, Indicates Reduced Data Confidence due to Software/Hardware Intervention
Number of Primary Data Words
Number of Secondary Data Words
Number of Primary Full Words
Number of Secondary Full Words
Record Number in File
Number of Words remaining in Logical Record
Voyager 1 Fixed Magnetic Field Error
Magnetic Field Magnitude by Method 1, F1, 9.6-s Average of 1.92-s Magnitudes
Magnetic Field Magnitude by Method 2, F2, 9.6-s Average derived from 9.6-s Averages of the B1, B2, and B3 Component Data by using sqrt(B1^2+B2^2+B3^2)
BR, B1, 9.6-s Average of 1.92-s Averages of the Magnetic Field Radial Component in Heliographic (HG) Coordinates
BT, B2, 9.6-s Average of 1.92-s Averages of the Magnetic Field Tangential Component in Heliographic (HG) Coordinates
BN, B3, 9.6-s Average of 1.92-s Averages of the Magnetic Field Normal Component in Heliographic (HG) Coordinates
Magnetic Field Magnitude by Method 1, F1, 9.6-s Average of 1.92-s Magnitudes, for 100 nT Plot Scale
Magnetic Field Magnitude by Method 2, F2, 9.6-s Average derived from 9.6-s Averages of the B1, B2, and B3 Component Data by using sqrt(B1^2+B2^2+B3^2), 100 nT
BR, B1, 9.6-s Average of 1.92-s Averages of the Magnetic Field Radial Component in Heliographic (HG) Coordinates, for 100 nT Plot Scale
BT, B2, 9.6-s Average of 1.92-s Averages of the Magnetic Field Tangential Component in Heliographic (HG) Coordinates, for 100 nT Plot Scale
BN, B3, 9.6-s Average of 1.92-s Averages of the Magnetic Field Normal Component in Heliographic (HG) Coordinates, for 100 nT Plot Scale
Magnetic Field Magnitude by Method 1, F1, 9.6-s Average of 1.92-s Magnitudes, for 10 nT Plot Scale
Magnetic Field Magnitude by Method 2, F2, 9.6-s Average derived from 9.6-s Averages of the B1, B2, and B3 Component Data by using sqrt(B1^2+B2^2+B3^2), 10 nT
BR, B1, 9.6-s Average of 1.92-s Averages of the Magnetic Field Radial Component in Heliographic (HG) Coordinates, for 10 nT Plot Scale
BT, B2, 9.6-s Average of 1.92-s Averages of the Magnetic Field Tangential Component in Heliographic (HG) Coordinates, for 10 nT Plot Scale
BN, B3, 9.6-s Average of 1.92-s Averages of the Magnetic Field Normal Component in Heliographic (HG) Coordinates, for 10 nT Plot Scale
Magnetic Field Magnitude by Method 1, F1, 9.6-s Average of 1.92-s Magnitudes, for 1 nT Plot Scale
Magnetic Field Magnitude by Method 2, F2, 9.6-s Average derived from 9.6-s Averages of the B1, B2, and B3 Component Data by using sqrt(B1^2+B2^2+B3^2), 1 nT
BR, B1, 9.6-s Average of 1.92-s Averages of the Magnetic Field Radial Component in Heliographic (HG) Coordinates, for 1 nT Plot Scale
BT, B2, 9.6-s Average of 1.92-s Averages of the Magnetic Field Tangential Component in Heliographic (HG) Coordinates, for 1 nT Plot Scale
BN, B3, 9.6-s Average of 1.92-s Averages of the Magnetic Field Normal Component in Heliographic (HG) Coordinates, for 1 nT Plot Scale
Magnetic Field Magnitude by Method 1, F1, 9.6-s Average of 1.92-s Magnitudes, for 0.1 nT Plot Scale
Magnetic Field Magnitude by Method 2, F2, 9.6-s Average derived from 9.6-s Averages of the B1, B2, and B3 Component Data by using sqrt(B1^2+B2^2+B3^2), 0.1 nT
BR, B1, 9.6-s Average of 1.92-s Averages of the Magnetic Field Radial Component in Heliographic (HG) Coordinates, for 0.1 nT Plot Scale
BT, B2, 9.6-s Average of 1.92-s Averages of the Magnetic Field Tangential Component in Heliographic (HG) Coordinates, for 0.1 nT Plot Scale
BN, B3, 9.6-s Average of 1.92-s Averages of the Magnetic Field Normal Component in Heliographic (HG) Coordinates, for 0.1 nT Plot Scale
Latitudinal Magnetic Field Angle in Heliographic (HG) Coordinates computed by using asin(B3/F2)
Longitudinal Magnetic Field Angle in Heliographic (HG) Coordinates computed by using 180°-atan(B2,-B1)
Root Mean Square of the Magnetic Field Radial Component, BR
Root Mean Square of the Magnetic Field Tangential Component, BT
Root Mean Square of the Magnetic Field Normal Component, BN
Number of 1.92-s Spacecraft Magnetic Field Averages per 9.6-s Average, 0<n<5
48-s Average of Spacecraft Magnetic Field Radial Component, BR
48-s Average of Spacecraft Magnetic Field Tangential Component, BT
48-s Average Spacecraft Magnetic Field Normal Component, BN
Norm of 48-s Spacecraft Magnetic Field Component Averages
Root Mean Square of 48-s Averaged Spacecraft Magnetic Field Radial Component, BR
Root Mean Square of 48-s Averaged Spacecraft Magnetic Field Tangential Component, BT
Root Mean Square of 48-s Averaged Spacecraft Magnetic Field Normal Component, BN
Number of 9.6-s Spacecraft Magnetic Field Averages per 48-s Average, 0<n<5
TN, Epic Day of Navigation Block Closest to Data Time
TP, Epic Day of Pointing Vector Block Closest to Data Time
Voyager 1 Spacecraft Position X Component in Heliographic Inertial (HGI) Coordinates
Voyager 1 Spacecraft Position Y Component in Heliographic Inertial (HGI) Coordinates
Voyager 1 Spacecraft Position Z Component in Heliographic Inertial (HGI) Coordinates
Voyager 1 Velocity X Component in Heliographic Inertial (HGI) Coordinates
Voyager 1 Velocity Y Component in Heliographic Inertial (HGI) Coordinates
Voyager 1 Velocity Z Component in Heliographic Inertial (HGI) Coordinates
Voyager 1 Radial Distance from the Sun
Voyager 1 Spacecraft Position Longitude in Heliographic Inertial (HGI) Coordinates computed by using atan(Y/X)
Voyager 1 Spacecraft Position Latitude in Heliographic Inertial (HGI) Coordinates computed by using asin(Z/R)
Matrix1, Rotation Matrix that Transforms a 3-Element Vector from Heliographic Inertial (HGI) Coordinates to Heliographic (HG) Coordinates
Matrix2, Rotation Matrix that Transforms a 3-Element Vector from Earth Mean Ecliptic, Equinox of 1950 (EME 50) Coordinates to Heliographic (HG) Coordinates
Matrix3, Rotation Matrix that Transforms a 3-Element Vector from Payload Coordinates to Heliographic (HG) Coordinates
Record Type, Header, List only
Telemetry Format, Header, List only
Spacecraft ID, Header, List only
Time, Header
Run Year, Header
Calendar Day, Header
Run Month, Header, List only
Run Day, Header
Run Type, Header, List only
Coordinate, Header, List only
Data ID, Header
Word 32, Header
EDR System, Header
MAG System, Header
Zero Name, Header, List only
Sensor Name, Header, List only
Record Type, Trailer, List only
Telemetry Format, Trailer, List only
Spacecraft ID, Trailer, List only
Time, Trailer
Run Year, Trailer
Calendar Day, Trailer
Run Month, Trailer, List only
Run Day, Trailer
Run Type, Trailer, List only
Coordinate, Trailer, List only
Data ID, Trailer
Word 32, Trailer
EDR System, Trailer
MAG System, Trailer
Zero Name, Trailer, List only
Sensor Name, Trailer, List only