The reported durations of GOES Soft X-Ray flares in different solar cycles

TL;DR

This paper analyzes the durations of GOES Soft X-Ray solar flares across different solar cycles, revealing inconsistencies in data collection criteria before and after May 1997 that impact solar physics research.

Contribution

It identifies and highlights significant differences in flare duration data before and after May 1997 due to changes in reporting criteria, affecting past and future analyses.

Findings

Significant differences in flare durations before and after May 1997.

Pre-1997 flare timings were based on different criteria than post-1997.

Implications for past research using flare durations before May 1997.

Abstract

The Geostationary Orbital Environmental Satellites (GOES) Soft X-ray (SXR) sensors have provided data relating to, inter alia, the time, intensity and duration of solar flares since the 1970s. The GOES SXR Flare List has become the standard reference catalogue for solar flares and is widely used in solar physics research and space weather. We report here that in the current version of the list there are significant differences between the mean duration of flares which occurred before May 1997 and the mean duration of flares thereafter. Our analysis shows that the reported flare timings for the pre-May 1997 data were not based on the same criteria as is currently the case. This finding has serious implications for all those who used flare duration (or fluence, which depends on the chosen start and end times) as part of their analysis of pre-May 1997 solar events, or statistical analyses of large samples of flares, e.g. as part of the assessment of a Solar Energetic Particle forecasting algorithm.