**NSSDCA ID:** PSFP-00533

**Availability:** Archived at NSSDC, accessible from elsewhere

**Time span:** 1977-09-05 to

This description was generated automatically using input from the Planetary Data System.

Data Set Overview ================= This data set contains hour averages of the interplanetary magnetic field (IMF) measurements obtained by the triaxial fluxgate magnetometer experiment on Voyager 1. Identical instruments on Voyager 1 and 2 were designed to measure the IMF between Earth and Saturn (10 AU) during the primary Voyager mission. The design and performance yielded absolute accuracies to better than < 0.1 nT. In general, each component of the hourly average has an uncertainty of up to (+/- 0.05 nT) in the region beyond 10 AU. More accurate measurements can be obtained by special processing of the data, but it was not feasible to do this for the entire data set included here. The magnetic field magnitude in nT is provided along with angles of the field vector in the spacecraftcentered Heliographic (HG) coordinate system, also known as RTN. Coordinate System ================= Interplanetary magnetic field studies make use of two important coordinate systems, the Inertial Heliographic (IHG) coordinate system and the Heliographic (HG) coordinate system. The IHG coordinate system is use to define the spacecraft's position. The IHG system is defined with its origin at the Sun. There are three orthogonal axes, X(IHG), Y(IHG), and Z(IHG). The Z(IHG) axis points northward along the Sun's spin axis. The X(IHG) - Y(IHG) 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(IHG) axis. The X(IHG) axis drifts slowly with time, approximately one degree per 72 years. Magnetic field orientation is defined in relation to the spacecraft. Drawing a line from the Sun's center (IHG 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(IHG)-Y(IHG) plane too. The Z(HG) axis is chosen to complete the orthonormal triad. An excellent reference guide with diagrams explaining the IHG and HG systems may be found in Space and Science Reviews, Volume 39 (1984), pages 255-316, MHD Processes in the Outer Heliosphere, L. F. Burlaga [BURLAGA1984]. Data Formats ============ field description (data before 1990) ----- -----------------------------1. s/c id (1 = Voyager-1, 2 = Voyager-2) 2. UTC YY DDD HH where YY=year, DDD=day, and HH=hour 3. X X IHG position component (A.U. - IHG coordinates) 4. Y Y IHG position component (A.U. - IHG coordinates) 5. Z Z IHG position component (A.U. - IHG coordinates) 6. Range Heliocentric range = sqrt(X*X+Y*Y+Z*Z) 7. F1 Field magnitude (nT) ( avg(F2(48sec)) ) 8. F2 Field modulus (nT) ( norm (B1,B2,B3) ) 9. delta Latitudinal angle (degrees - HG coordinates) 10. lambda Longitudinal angle (degrees - HG coordinates) field descriptor (data after 1990) ----- ---------------------------1. s/c identification (FLT1=Voyager 1) (FLT2=Voyager 2) 2. Time (UTC) decimal year format (90.00000 is day 1 of 1990) 3. The magnetic field strength, F1, computed from high-resolution observations. 4. The elevation angle (degrees) in heliographic coordinates. 5. The azimuthal angle (degrees) in heliographic coordinates. 6. The magnetic field strength, F2, computed from hour averages of the components. The components of B can be computed from F2 and the two angles. MAG field components may be recovered using F2, delta and lambda. BR = F2*COS(lambda)*COS(delta) Fortran users need to convert BT = F2*SIN(lambda)*COS(delta) degrees to radians before BN = F2*SIN(delta) using trig functions. Contact Information =================== Principal Investigator: Prof. Norman F. Ness Bartol Research Institute Univerity of Delaware Newark, Delaware 19716-4793 Phone: (302) 831-8116 Fax: (302) 831-1843 Email: norman.ness@mus.udel.edu Data Contact: Dr. Len Burlaga Code 612.2 NASA Goddard Space Flight Center Greenbelt, MD 20771 Tel.: 301-286-5956 Fax: 301-286-1433 E-mail: len.burlaga@nasa.gov 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 Acknowledgement =============== Use of these data in publications should be accompanied at minimum by acknowledgements of the National Space Science Data Center and the responsible Principal Investigator defined in the experiment documentation provided here.

These data are available on-line from the Planetary Data System (PDS) at:

https://pds-ppi.igpp.ucla.edu/data/VG1-SW-MAG-4-SUMM-HGCOORDS-1HR-V1.0/

- VG1-SW-MAG-4-SUMM-HGCOORDS-1HR-V1.0

- Planetary Science: Fields and Particles

Questions and comments about this data collection can be directed to: Dr. Edwin V. Bell, II

Name | Role | Original Affiliation | |
---|---|---|---|

Dr. Norman F. Ness | Data Provider | University of Delaware |