Comment on "MeV magnetosheath ions energized at the bow shock" by S.-W. Chang et al

• Published in: Journal of Geophysical Research. A. Space Physics 2003-08, Vol.108 (A8), p.n/a
• Main Authors: Chen, Jiasheng, Fritz, Theodore A., Sheldon, Robert B.
• Format: Article
• Language: English
• Subjects: bow shock; cusp; energetic particles; magnetopause boundary layer; magnetosheath
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2002JA009634

From a study of the 4 May 1998 storm event, Chang et al. [2001 ] (hereinafter referred to as CETAL01) suggested that "ions are accelerated at the quasi-parallel bow shock to energies as high as 1 MeV and subsequently transported into the magnetosheath during this event" and mentioned that "This is confirmed by a comparison of energetic ion fluxes simultaneously measured in the magnetosheath and at the quasi-parallel bow shock when both regions are likely connected by the magnetic field lines" (see their Abstract). After an inspection of the measured energetic ion data, however, one finds that CETAL01 have misplotted the observed ion energy spectrum in the "magnetosheath" (near the cusp) to lower energy which brings it in closer agreement to the flux measured near the quasi-parallel bow shock, making their analysis suspect. In fact, simultaneous measurements at this time indicate that (1) the energetic ion flux near the cusp was about one order of magnitude higher than that near the quasi-parallel bow shock, (2) the energetic ion time signatures were seen first near the cusp then near the bow shock, and (3) the energetic ion flux observed near he bow shock was independent of bow shock geometry. Each of these three facts is sufficient to demonstrate that the quasi-parallel bow shock was not the main source of the energetic ions near the cusp during this event.