Data Set Overview : This dataset contains Voyager 2 magnetometer data from the interplanetary cruise averaged to 48 second samples in Heliographic coordinates. Data Processing : The high resolution data submitted to the NSSDC has its origins in the original MVS 'Summary' data sets formally produced on the NSSC IBM MVS mainframe system. The original data sets contain a mix of engineering, electron, magnetic field and plasma data. The Voyager magnetometer (MAG) experiment now resides on a dedicated workstation where only MAG data are processed. All Voyager MAG data submitted to the NSSDC consists wholly of high resolution LFM averages. These files consist of a set of averages applied across all of the mission's differing telemetry modes. In the case of the Magnetometer Experiment, the records contain both 1.92 second, 9.6 second and 48 second averages. 1.92 second averages are created from the detail detail data, 9.6 second averages are created from 1.92 second averages and 48 second averages are created from the 9.6 second averages. All data in this NSSDC data set are interplanetary and in heliographic coordinates (see below). An ASCII formated data set containing key components of the 48 second magnetic field data and ephemeris data has been created allowing more convenient access to high resolution Voyager magnetometer data. 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 Format : field descriptor (pre 1990 data) ----- ---------------------------------- 1. s/c identification (FLT1:Voyager 1) (FLT2:Voyager 2) 2. coordinate system (HG:heliographic)used for this data set 3. Time (UTC) format YY DDD HH MM SS MSS YY : year DDD : day of year HH : hour MM : minute SS : second MSS : millisecond 4. field magnitude (nT) 5. field component 1 (nT) - HG 6. field component 2 (nT) - HG 7. field component 3 (nT) - HG 8. spacecraft radial distance (AU) 9. spacecraft x position (AU) - IHG 10. spacecraft y position (AU) - IHG 11. spacecraft z position (AU) - IHG field descriptor (temiantion shock data) ----- ---------------------------------- 1. s/c identification (2:Voyager 2) 2. Time (UTC) format YYYY DDD.DDDD YY : year DDD.DDDD : decimal day of year 3. F1 average field magnitude (nT) 4. Br field component (nT) - HG 5. Bt field component (nT) - HG 6. Bn field component (nT) - HG 7. 1 sigma error in F1 8. 1 sigma error in Br 9. 1 sigma error in Bt 10. 1 sigma error in Bn 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 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 have been extracted from the NSSDC archive for distribution by the PDS along with other Voyager solar wind data sets. These data were not submitted to the PDS for archive and have not been through the PDS peer review process. These data are provided by the PDS for the convenience of PDS users. Please exercise caution when using these data. Comments on the Voyager 2 48 sec termination shock data The average magnetic field strength produced by the spacecraft at the location of the outboard magnetometer of the dual magnetometers system on V2 varies between 0.1 - 0.2 nT, comparable to the most probable magnetic field strength in the inner heliosheath and significantly larger than the most probable magnetic field strength in the distant supersonic solar wind. The spacecraft magnetic field is a complex, time-dependent signal that must be removed from the measured magnetic field signal in order to derive the ambient magnetic fields of the solar wind and heliosheath. Corrections must also be made for spurious magnetic signals and noise associated with the telemetry system, ground tracking systems, and other factors. A non-periodic modulation of the spacecraft's magnetic field, with amplitudes comparable to the average ambient magnetic field strength and periods in the range from 1 to 12 hours, has been present approximately half the time in the V2 data since ~1990, beginning in ~1985. Finally, a spacecraft systems command during late 2006 had the unintended consequence of exposing the sensors to temperatures well beyond their design limits for more than one week. This command also rotated one set of dual triaxial sensors through a large angle and produced additional noise, drifts and spurious signals as a result of damage to the sensor assembly. Extracting the signal describing the solar wind and heliosheath from the many sources of uncertainty is a complex and partly subjective process that requires understanding of the instrument and judgment based on experience in dealing with the ever-changing extraneous signals. We estimate that the 1-sigma uncertainty in the 48 sec averages in the components of the magnetic field is typically ~ +/-0.03 nT. The uncertainties in F1, BR, BT, and BN can differ from one another and they may vary with time, but there is no practical way to determine these uncertainties more precisely at present.