A Multicomponent Magnetic Proxy for Solar Activity

doi:10.1029/2021SW002860

2021-12-15

PRE

Harry P. Warren *

Linton Floyd

Lisa Upton

DOI：10.1029/2021SW002860

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We present a new, multicomponent magnetic proxy for solar activity derived from full disk magnetograms that can be used in the specification and forecasting of the Sun's radiative output. To compute this proxy we project Carrington maps, such as the synchronic Carrington maps computed with the Advective Flux Transport (AFT) surface flux transport model, to heliographic cartesian coordinates and determine the total unsigned flux as a function of absolute magnetic flux density. Performing this calculation for each day produces an array of time series, one for each flux density interval. Since many of these time series are strongly correlated, we use principal component analysis to reduce them to a smaller number of uncorrelated time series. We show that the first few principal components accurately reproduce widely used proxies for solar activity, such the the 10.7 cm radio flux and the Mg core-to-wing ratio. This suggests that these magnetic time series can be used as a proxy for irradiance variability for emission formed over a wide range of temperatures. Plain Language Summary Proxies for solar activity are often used to extend solar irradiance measurements in time or forecast future variability. Widely used proxies, such as the 10.7 cm radio flux, can include emission formed from different mechanisms, which limits their ability to accurately reproduce some irradiance time series. Other proxies, such as the Mg core-to-wing ratio, perform better, but are taken from different space instruments, whose long-term calibration can be difficult to understand. In this paper we show how to use images of the solar photospheric magnetic field to create a multicomponent proxy for solar activity that overcomes some of the limitations of existing proxies.

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