Directory "particles_apl" provides access to hourly resolution energetic proton and alpha particle data from the JHU/APL Solar Proton Monitoring Experiment (SPME) on the IMP 4 spacecraft. IMP 4 is also known as IMP F and Explorer 34. ---------------------------------------------------------- A list of IMP 4 magnetopause crossings is available from ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/magnetopause_crossings/ and, with graphical display capability, from https://omniweb.gsfc.nasa.gov/ftpbrowser/magnetopause.html ----------------------------------------------------------------- Related data and directories: SPDF Data and Orbits Services NSSDC Master Catalog NSSDC Contact: Natalia Papitashvili , Please acknowledge NASA's National Space Science Data Center and Space Physics Data Facility for data usage. Authorizing NASA Official: Dr. R.E. McGuire, Head, SPDF, NASA Goddard Space Flight Center 301-286-7794, e-mail: Robert.E.McGuire@nasa.gov -----------------------------------------------------------------------