This proposal addresses the use of ground- and space-based proxies, along with space-based solar irradiance data sets, to help "define a range of relationships between them that will support the…

This is a $234,720.19 grant awarded by NASA to The University Corporation, a non-profit organization affiliated with California State University, Northridge (CSUN). The grant addresses NASA's initiative to develop consistent multi-instrument/multi-platform space-based data sets of solar irradiance, both total (TSI) and spectral (SSI). The project aims to use ground- and space-based proxies, along with space-based solar irradiance data sets, to help define relationships that can support the inference of longer-term solar irradiance records for use in global climate models. The University Corporation will develop a set of space-based feature-based solar indices from NASA's Solar Dynamics Observatory (SDO) data to serve as proxies, and compare them to ground-based proxies and spacecraft irradiance measurements. This work is intended to contribute to understanding the relationship between direct irradiance measurements and proxies to support long-term irradiance record development. The contract is not designated as a set-aside award.

This proposal addresses the use of ground- and space-based proxies, along with space-based solar irradiance data sets, to help "define a range of relationships between them that will support the inference of longer term solar irradiance records that can be used as input to global models so that effects of solar variations can be properly represented and their impacts on the earth system investigated." IT addresses NASA's initiative "to support the development of consistent multi-instrument/multiplatform space-based data sets of solar irradiance (both total and spectrally resolved)." the importance of solar irradiance as a primary external forcing to the variability and change in earth's climate and atmospheric composition cannot be understated. Solar irradiance can only be measured directly from space and has been since 1978 with the launch of nimbus-7. As technology has advanced, spacecraft instruments and calibration techniques have improved considerably; instrument reliability and longevity have increased. The goal has been to develop a single total solar irradiance record (and later SSI record), but because of time gaps between one operating spacecraft and the next, gaps in the irradiance data due to instrument issues, and different native scales among orbiting instruments, knitting together a long-term solar irradiance record has not always been easy. Because of this, solar proxies are often used as substitutes for solar spectral variability and are important in helping to understand the role of solar activity in TSI variations. A number of proxies, both space and ground-based, are used in the study of irradiance variability. In part, these proxies are needed because single disk-integrated irradiance measurements alone cannot explain the factors that contribute to variability. Ground-based images have proven to be useful in identifying the sources of this irradiance variability, both continuum and spectral. The ability to support space-based TSI measurements and irradiance composites comes from the fact that IT is possible to develop empirical models of total (TSI) and spectral (SSI) solar irradiance using two-component ground-based proxies of sunspot deficit (dark) and facular excess (bright) solar features. Full-disk photometric solar images reveal solar features, allowing US to compute their spatial and radiative properties; comparing feature-based data with disk-integrated TSI measurements from space helps US to understand how solar active regions contribute to irradiance changes. This has been done successfully at the SAN fernando observatory (SFO) with our 30-year set of full-disk photometric images used as proxies. We propose to develop a second set of similar proxies from space-based full-disk images provided by NASA's solar dynamics observatory (SDO), primarily HMI intensitygrams and AIA 1700A images, using the same methodology and software techniques as those applied to SFO images, developing a set of space-based feature-based solar indices to be used as proxies, especially in TSI reconstructions. We will continue to compare these proxy irradiance indices with future sorce measurements as well as with other experiments such as the TSI calibration transfer experiment (tcte) and the upcoming tsis-1 experiment, as well as comparing SFO and SDO data sets. Comparing these two proxy sets with spacecraft irradiance data sets, as well as with each other, will contribute to defining the relationship between direct irradiance measurements and proxies and "support the inference of longerterm solar irradiance records" that can be used to develop external forcing models. The results of this work will be published and our indices will be shared with the community.