File vy1mgd.txt ------------------------------------------------------------------------- VOYAGER-1 INTERPLANETARY DATA The main science objectives for the VOYAGER interplanetary mission are as follows: - investigate the structure of the solar wind magnetic fields and plasma in the inner and outer heliosphere; - conduct long term study of heliospheric evolution during different phases of the twenty-two year solar magnetic cycle and the eleven-year solar activity cycle; - study the long term solar modulation and determine the elemental and isotopic abundances of galactic cosmic ray particles in the heliosphere; - measure radial gradients, spectra, and nuclear abundances of the anomalous component of cosmic rays from acceleration at the solar wind termination shock; - investigate local particle acceleration in the interplanetary medium from solar flare shocks and corotating interaction regions; - study propagation of solar energetic particles in the heliosphere. This directory contains hourly averages of parameters for the interplanetary magnetic field, solar wind plasma and spacecraft trajectory coordinates VOYAGER-1 data have been reprocessed to ensure a uniformity of content and coordinate systems relative to data from other deep- space missions: - All spacecraft trajectory data were transformed to a Heliographic Inertial (HGI) coordinate system. - calculation of the RTN Cartesian components of interplanetary magnetic field from the RTN spherical components: BR=|B|*cos(THETA)*cos(PHI) BT=|B|*cos(THETA)*sin(PHI) BN=|B|*sin(THETA) where THETA - spherical RTN latitude, PHI- spherical RTN longtitude - calculation of RTN Spherical components of the solar wind velocity from RTN cartesian components: V = (Vr^2 + Vt^2 + Vn^2)^0.5 THETA=asin(Vn/V) PHI=atan(Vt/Vr) where THETA - spherical RTN latitude, PHI- spherical RTN longtitude - calculation of given thermal speed Vth into temperature T (Kelvin): T=60.5*Vth^2 (Vth in km/s) - merging of trajectory coordinates, magnetic field data, and plasma data files into a single annual file VY1_YR.DAT, where YR is the year; - Data gaps were filled with dummy numbers for the missing hours or entire days to make all files of equal length. The character '9' is used to fill all fields for missing data according to their format, e.g. ' 9999.9' for a field with the FORTRAN format F7.1. Note that format F7.1 below really means (1X,F6.1),etc. For the daily resolution data (one file), simple averages were taken over the hourly values. The format is identical to that for the hour averages However, the "hour" field has 0 as a value.and the "Magnitude of Average Vector" field is the simple average of the 24 hourly values of this parameter. [Note added in November of 2014]: we added Proton fluxes from LECP and CRS instruments to records. More details user can find at are at: http://omniweb.sci.gsfc.nasa.gov/ftpbrowser/flux_spectr_m.html FORMAT DESCRIPTION WORD ASCII MEANING UNITS/COMMENTS 1 I4 Year 1977, 1978, 1979, etc. 2 I3 Decimal Day January 1 = Day 1 3 I3 Hour 0,1,...,23 4 F7.2 Spacecraft Heliographic Astronomical units distance 5 F7.1 Heliographic Inertial latitude Degrees, +/-90. of the Spacecraft 6 F7.1 Heliographic Inertial longitude Degrees, 0-360 of the Spacecraft 7 F8.3 Field Magnitude Average |B| 1/N SUM |B|, nT 8 F8.3 Magnitude of Average Field sqrt(Bx^2+By^2+Bz^2), nT 9 F8.3 BR RTN-Coordinate System nanoteslas 10 F8.3 BT RTN-Coordinate System nanoteslas 11 F8.3 BN RTN-Coordinate System nanoteslas 12 F7.1 Proton flow speed, RTN km/s 13 F7.1 THETA-elevation angle degrees of flow velocity vector (RTN-cordinate system) 14 F7.1 PHI- azimuth angle of degrees flow velocity vector. (RTN-coordinate system) . 15 F9.5 Proton density [n/cc] 16 F9.0 Protom Temperature (calculated degrees, K from thermal speed width T=60.5*Vth*Vth) 17 E10.3 0.57-1.78 H MeV,H, LECP 1/(cm^2 sec ster MeV) 18 E10.3 3.40-17.6 H Mev,H LECP 1/(cm^2 sec ster MeV) 19 E10.3 22.0-31.0 H MeV,H LECP 1/(cm^2 sec ster MeV) 20 E12.5 1.894-2.605 MeV, H, CRS 1/(cm^2 sec ster MeV) 21 E12.5 4.200-6.240 MeV H, CRS* 1/(cm^2 sec ster MeV) 22 E12.5 3.256-8.132 MeV H, CRS* 1/(cm^2 sec ster MeV) 23 E12.5 3.276 - 8.097 MeV H, CRS* 1/(cm^2 sec ster MeV) 24 E12.5 6.343 - 42.03 MeV H, CRS* 1/(cm^2 sec ster MeV) 25 E12.5 17.88 - 26.81 MeV H, CRS* 1/(cm^2 sec ster MeV) 26 E12.5 30.29 - 69.47 MeV H, CRS* 1/(cm^2 sec ster MeV) 27 E12.5 132.8 - 242.0 MeV H, CRS* 1/(cm^2 sec ster MeV) * Originally CRS fluxes have 6-hr resolution ----------------------------------------------------------------------- Notes on Voyager 1 and 2 Magnetometer Data After 1989. 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; 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 »0.15 nT and »0.05 nT, respectively. The use of roll calibrations lasting »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 »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 nT - 0.05 nT. For further detail informaion look at http://cohoweb.gsfc.nasa.gov/html/cw_data.html#vy_mag DESCRIPTION OF COORDINATE SYSTEMS The Heliographic Inertial (HGI) coordinates are Sun-centered and inertially fixed with respect to an X-axis directed along the intersection line of the ecliptic and solar equatorial planes. The solar equator plane is inclined at 7.25 degrees from the ecliptic. This direction was towards ecliptic longitude of 74.36 degrees on 1 January 1900 at 1200 UT; because of precession of the celestial equator, this longitude increases by 1.4 degrees/century. The Z axis is directed perpendicular and northward from the solar equator, and the Y-axis completes the right-handed set. This system differs from the usual heliographic coordinates (e.g. Carrington longitudes) which are fixed in the frame of the rotating Sun. The RTN system is fixed at a spacecraft (or the planet). The R axis is directed radially away from the Sun, the T axis is the cross product of the solar rotation axis and the R axis, and the N axis is the cross product of R and T. At zero Heliographic Latitude when the spacecraft is in the solar equatorial plane the N and solar rotation axes are parallel. Hour averages of the interplanetary solar wind data from, and hourly heliocentric coordinates of, Voyager1/2 and other interplanetary spacecraft may be also be accessed and plotted on-line through the COHOWeb service http://cohoweb.gsfc.nasa.gov/ Acknowledgement: Use of these data in publications should be accompanied at minimum by acknowledgements of the Space Physics Data Facility and the responsible Principal Investigator defined in the experiment documentation provided here. Citation of SPDF's Coordinated Heliospheric Observations (COHO) data base would also be appreciated, so that other potential users will be made aware of this service. ------------------------------------------------------- For questions about this data set, please contact: Dr. N. Papitashvili, Natalia.E.Papaitashvili@nasa.gov, GSFC-Code 672 ------------------------------------------------