Bow Shock Crossing Dataset Description FILE_NAME = BOWSHOCK.TAB RECORD_TYPE = FIXED_LENGTH FILE_RECORDS = 1322 DATA_SET_ID = PVO-V-OETP-5-BOWSHOCKLOCATION-V1.0 SPACECRAFT_NAME = PIONEER VENUS ORBITER INSTRUMENT_NAME = ELECTRON TEMPERATURE PROBE TARGET_NAME = VENUS START_TIME = 1985-10-20T22:27:44.000Z STOP_TIME = 1992-10-06T20:38:35.000Z START_ORBIT_NUMBER = 2501 STOP_ORBIT_NUMBER = 5055 The Bow Shock File. This file gives the orbit-by-orbit times and locations of the bow shock crossings, which are characterized by distinct changes in Ne. Multiple shock crossing are listed if they are sufficiently separated to be resolved accurately. (Bow shock crossings will be evident in the High Resolution Ne File when they occurred within 30 minutes of periapsis). The ionopause and bow shock crossing times and locations are easily identified in the high resolution Ne measurements (Theis et al., 1980). These files contain the UT, altitude, latitude, SZA and local time of each crossing. The bow shock is a much more discrete feature in the data than the ionopause. Multiple shock crossings sometimes occur because the shock often moves at higher velocities than the satellite. In these cases, only the outer most shock crossing is recorded, unless the separation between the crossings is greater than a minute or two. The occurrence of multiple shocks in the Bow Shock File provides a record of the orbits in which the solar wind itself was probably highly variable. Because of the geometry of the orbit, most shock crossings were in the range of 45 to 135 deg. SZA. However, the nose region of the shock was explored between 1985 and 1987 when PVO periapsis was near the equator and was at altitudes between 2000 and 2300 km. During these years near solar minimum the nose of the shock often moved down into that altitude range (Russell et al, 1988). During the subsolar passages of these years, the orbit approximately paralleled the shock, sometimes inside, sometimes outside, thus providing interesting snapshots of its movements. DATA QUALITY/ACCURACY The bow shock is selected from 200 minute pass plots by marking the UT resolution of the shock crossing time is of the order of 1 minute on these plots, but this could be improved to a few seconds if expanded plots were used. There is no plan currently to provide the ultimate resolution available in bow shock crossing time and location. NOTE: The original submission by the P.I. was formatted for printing with header lines inserted every 50 orbits. PDS/PPI has removed these imbedded headers so that the file can be easily loaded into database or spreadsheet software. If a user would like a copy of this data file in its original format, the PPI Node of the PDS will provide a copy of that file electronically to the user. Please send e-mail to pds_operator@igpp.ucla.edu to request this data file. ----------------------------------------------------------------- Example data with header The "1" in column 1 indicates 8 lines of header are to follow. The only 1's in column 1 are these header block markers. ----------------------------------------------------------------- 1 ORBIT DATE PERIAPSIS INBOUND CROSSING OUTBOUND CROSSING HH:MM:SS SECS HH:MM:SS LAT LST ALT SZA SECS HH:MM:SS LAT LST ALT SZA 1 78339 15:11:12 51512 14:18:32 43.9 5.4 12044. 100.2 0 00:00:00 0.0 0.0 0. 0.0 2 78340 14:21:42 49079 13:37:59 49.1 5.8 9899. 96.4 0 00:00:00 0.0 0.0 0. 0.0 3 78341 14:31:46 50202 13:56:42 56.3 6.3 7725. 91.3 0 00:00:00 0.0 0.0 0. 0.0 4 78342 14:40:12 49872 13:51:12 45.1 5.8 11284. 96.2 57078 15:51:18 -67.8 2.0 16416. 109.1 REFERENCES Alexander, C. J., C. T. Russell, Solar cycle dependence of the location of the Venus bow shock, Geophys. Res. Lett., 12, 369, 1985. Brace, L. H., W. T. Kasprzak, H. A. Taylor, Jr., R. F. Theis, C. T. Russell, A. Barnes, J. D. Mihalov, and D. M. Hunten, The ionotail of Venus: Its configuration and evidence for ion escape, J. Geophys. Res., 92, 15, 1987. Brace, L. H., W. R. Hoegy, and R. F. Theis, Solar EUV measurements at Venus based on photoelectron emission from the Pioneer Venus Langmuir probe, J. Geophys. Res., 93, 7282, 1988. Brace, L. H., R. F. Theis, and J. D. Mihalov, The Response of the Venus Nightside Ionosphere and Ionotail to Solar EUV and Solar Wind Dynamic Pressure, J. Geophys. Res., 95, 4075, 1990. Elphic, R.C., L. H. Brace, R. F. Theis, and C. T. Russell, Venus Dayside Ionosphere Conditions: Effects of magnetic field and solar EUV flux, Geophys. Res. Lett., 11, 124, 1984. Krehbiel, J. P., L. H. Brace, J. R. Cutler, W. H. Pinkus, and R. B. Kaplan, Pioneer Venus Orbiter Electron Temperature Probe, IEEE Transactions on Geoscience and Remote Sensing, GE-18, 49, 1980. Mahajan, K. K, W. T. Kasprzak, L. H. Brace, H. B. Niemann, and W. R. Hoegy, Response of the Venus Exospheric Temperature Measured by Neutral Mass Spectrometer to the Solar EUV Measured by Langmuir Probe on the Pioneer Venus Orbiter, J. Geophys. Res., 95, 1091, 1990. Russell, C. T., E. Chou, J. G. Luhmann, P. Gazis, L. H. Brace, and W. R. Hoegy, Solar and interplanetary control of the location of the Venus bow shock, J. Geophysic. Res., 93, 5461, 1988. Theis, R. F., L. H. Brace, K. H. Schatten, C. T. Russell, J. A. Slavin, J. A. Wolf, The Venus ionosphere as an obstacle to the solar wind, Advances in Space Research, 1, 47, 1980. Theis, R. F., L. H. Brace, R. C. Elphic, and H. G. Mayr, New empirical models of the electron temperature and density of the Venus ionosphere, with applications to transterminator flow, J. Geophys. Res., 89, 1477, 1984.