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Session 49 - First Results from the Solar and Heliospheric Observatory (SOHO).
Oral session, Tuesday, June 11
Wisconsin Center,
The SOHO payload includes three experiments designed to make "in situ" particle measurements of the solar wind and solar energetic particles (CELIAS, D. Hovestadt PI; COSTEP, H. Kunow PI; ERNE, J. Torsti PI). The solar wind measurements that are the focus of this talk are primarily provided by the CELIAS CTOF and MTOF sensors. (CELIAS/STOF and COSTEP-ERNE measure solar and interplanetary suprathermal and energetic particle populations.) CELIAS/CTOF measures solar wind heavy ion elemental and charge state abundances, information which is used (for example) in identifying the type of solar wind flow and the ionization processes in the corona where the solar wind charge states become "frozen-in". CELIAS/MTOF provides heavy ion elemental and isotopic abundances that are important (for example) in the study of fractionation factors in coronal abundances (as in the so-called "FIP-effect") for the rarer elements not resolvable in conventional solar wind composition instruments, and in determining the isotopic make-up of the solar corona. MTOF is, by far, the most powerful solar wind mass spectrometer flown to date, and already has new science to report at the time of this writing. This happenstance is due to a combination of advanced technology in obtaining high mass resolution for ions at solar wind energies, and (2) increased statistics. The excellent counting statistics are largely due to continuous solar wind monitoring (with its position at L1, ``the Sun never sets on SOHO\/''), and the continuous sampling of the solar wind by the 3-axis stabilized spacecraft further enhanced by MTOF's novel, never previously flown deflection system that encompasses a very large dynamic range. As might be expected, this unique opportunity has allowed MTOF to identify a number of elements for the first time in the solar wind (e.g., P, Ti, Cr and Ni). A rich assortment of solar wind isotopes have been identified for the first time, many of which (e.g., Fe 54 and 56; Ni 58,60,62) have not been detected previously even in solar energetic particle populations nor remotely using spectroscopic techniques.
