Synthetic solar X-ray flares time series since AD 1968 /s2

TL;DR

This study constructs a synthetic time series of solar X-ray flare activity from 1968 to 2009 using regression models based on satellite and radio data, revealing cycle-specific flare patterns.

Contribution

It introduces a novel method to generate extended flare activity series by modeling satellite data, filling gaps before 1980 with high correlation accuracy.

Findings

Strong relationships between radio flux and X-ray flare numbers

Cycle 20 had more X-class flares than subsequent cycles

Synthetic series align well with observed data from 1980 onward

Abstract

On the base of the most qualitative GOES satellites data for the period AD 1980-2009 and multiple regression model the "synthetic" series of the monthly numbers of soft X-ray flares (separately for the classes C, M, X and total numbers) were built for the epoch AD 1968-2009. The earlier parts of the series before AD 1980 were derived on the base of the mentioned model . The monthly numbers of radio bursts at four frequencies (29-33, 609, 8800 and 15400 MHz) and the radio flux at 2800 MHz (F10.7) are used as factors. The relationships are very strong (correlation coefficients R are from 0.79 to 0.93 and Snedekor-Fisher's F parameter is in the range of 2.5-7). The earlier GOES X-ray data (AD 1975-1979) and the older SOLRAD satellite data (AD 1968-1974) are not enough certain, which suggests a probable reduction effect because of the low instrumental sensitivity. It has also been found that the relatively weak sunspot Zurich cycle No 20 is essentially richer of flares of the strongest class X than the next three cycles No 21-23.