HR: 0800h
AN: SH21B-0423    [Abstracts]
TI: A Model For EUV Flux Throughout The 3-Dimensional Heliosphere
AU: * McMullin, D R
EM: mcmullind@pxi.com
AF: Praxis, Inc., 2550 Huntington Avenue Suite 300, Alexandria, VA 22303 United States
AU: Auchere, F
EM: frederic.auchere@ias.u-psud.fr
AF: Institut d'Astrophysique Spatiale, Universit‚ Paris-Sud, bƒtiment 121, Orsay, F-91405 France
AU: Cook, J
EM: Cook@hrts.nrl.navy.mil
AF: US Naval Research Laboratory, 4555 Overlook Ave., SW, Washington, DC 20375 United States
AU: Newmark, J S
EM: newmark@midas.nrl.navy.mil
AF: US Naval Research Laboratory, 4555 Overlook Ave., SW, Washington, DC 20375 United States
AU: Quemerais, E
EM: quemerais@aerov.jussieu.fr
AF: Service d'a‚ronomie, Universit‚ Pierre et Marie Curie 4 place Jussieu, Paris, 75252 France
AU: von Steiger, R
EM: rudolf.vonsteiger@issi.unibe.ch
AF: International Space Science Institute, Hallerstrasse,6, Bern, CH-3012 Switzerland
AU: Witte, M
EM: Manfr.Witte@t-online.de
AF: Max Planck Institute for Solar System Resarch, Max-Planck-Str. 2, Katlenburg-Lindau, 37191 Germany
AB: After July 2001, when Ulysses moved from 30 to 80 degrees in solar latitude, the Ulysses GAS instrument measured an apparent increase in the neutral He density. This is more naturally interpreted as a latitudinal dependence (decrease) of the loss rate due to solar photoionization rather than a true increase of the neutral He density. We have developed a three-dimensional model for solar EUV fluxes observed at any heliospheric position, using daily SOHO EIT observations, over successive Carrington rotations, projected to any heliospheric position. The combined effects of solar rotational and latitude-dependent flux variability are explicitly treated in this model. The flux model has been directly compared with other direct irradiance observations in the ecliptic plane with the SOHO/SEM irradiance time series for validation. We then use this flux to compute the photoionization rate of the in-flowing neutral He, and compare the modeled change with time along the spacecraft trajectory with the direct measurements from the out -of -ecliptic Ulysses GAS observations. The 3-D model developed will be directly applicable to STEREO EUV images from the SECCHI instrument suite. As the two spacecraft separate, the amount of the solar surface observed will increase through the mission, providing more accurate solar inputs.
DE: 7538 Solar irradiance
DE: 2100 INTERPLANETARY PHYSICS
DE: 2194 Instruments and techniques
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting