This is something we hope to help understand with this work. The Solar radiation below 200 nm consists of emission lines superimposed on a rapidly declining continuum. These emission lines arise in higher temperature layers of the outer solar atmosphere and are strongly related to the magnetic activity of the Sun. Understanding this relationship between magnetic morphology and EUV spectral irradiance is one of the overarching goals of this work. As this radiation is absorbed in the atmosphere it drives the temperature structure and ionization state of the upper atmosphere. In a modern technological world this has impacts on things such as GPS accuracy, high-frequency communications (used by aircraft) and satellite orbits. These types of effects are know as Space Weather, and understanding these effects is becoming increasingly important. The ProblemDue partly to the importance of space weather, we now are in the fortunate position to have several instruments measuring the solar EUV irradiance at the same time. The problem is that the irradiances reported by the various instruments do not always agree within the uncertainties claimed by the instrument teams. This is very similar to the discrepancies found in the total solar irradiance community, though we are not even starting to approach the 100 ppm quoted accuracies of those measurements. Measurements in the EUV are very difficult. The high-energy photons tend to degrade anything they hit, making material choices and instrument / spacecraft cleanliness imperative. even so, filters and detectors degrade with time, and understanding the degradation is an important goal of the present work. There are few facilities that can provide absolute calibration of the instruments (the NIST SURF, BESSY and NSLS synchrotron sources being the ones most often used) MembersThe working group currently comprises members from most of the current and past EUV Instruments, and various standards organizations. If you would like access to data and analysis programs please e-mail me: Andrew dot R dot Jones @ colorado dot edu |