Title: Solar Irradiance At High Heliospheric Latitudes

Authors: Auch`ere, F., D. R. McMullin, R. von Steiger, J. S. Newmark, J. W. Cook and M. Witte

Reference: SOHO 11 Workshop, Davos, Switzerland, (2002)

For 6 years now, the EIT instrument on board SOHO has been continuously monitoring the solar activity in four EUV passbands. With the SOHO mission extended, it is likely that the final EIT data set will cover one complete solar cycle. This exceptional data set offers an unprecedented opportunity to investigate the long-term variations of the solar EUV irradiance. Furthermore, with the spatial resolution of the SoHO/EIT instrument, the data can also be used to study variations of the solar irradiance with heliospheric latitude. It is indeed clear that the wide intensity range of the various emitting regions (polar coronal holes, equatorial active regions, etc.) produces a latitude-dependant irradiance. To date, due to the small number of off-ecliptic measurements, very few attempts have been made to investigate these variations. We start here to use SoHO/EIT data to derive the solar EUV irradiance at high heliospheric latitudes. The knowledge of the off-ecliptic solar irradiance could have several applications in heliospheric physics.

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Last Update: 25 March 2003, Xuyu Wang