This dataset contains the files supporting the paper "The variable source of the plasma sheet during a geomagnetic storm" published in Nature Communications. Included are the following: 1) LEPI-HE2 contains cdf files of the He++ data of the LEPI instrument in the same format as the other species files available from the ERG science center (https://ergsc.isee.nagoya-u.ac.jp/) 2) WIND_SWE contains idl save sets with the results of the fits to the WIND/SWE data using two proton peaks and an alpha peak. The data is in the structure ppa.fits, with variable descriptions in ppa.pnames and ppa.pdesc. 3) The data that is plotted in Figures 3, 4, and 6. These are in tplot save formats that can be read with the spedas software (http://themis.ssl.berkeley.edu/software.shtml). IDL spedas programs (.pro) to read the data files and recreate the figures are also included.