This paper presents a statistical analysis of soft X-ray flares during the period January 1986 to June 2017 covering the last three solar cycles (SCs) 22, 23, and 24. We have analyzed the distribution of flare number, the relationship between the occurrence rate of soft X-ray flares and solar activity, and the duration of different intensity class (B, C, M, and X) solar flares during the period of investigation. The total occurrence rates of M and X class flares are 10.33%, 6.77%, and 5.45% in SCs 22, 23, and 24, respectively, which indicates that SC 22 is an SC with frequent large flares. Meanwhile, the M and X class flares are mainly concentrated in solar maximum (71.13%) in SC 22. The correlation coefficients between the annual number of flares and solar F10.7 index, X-ray flux in 0.1–0.8 nm, and EUV flux in 0.1–50 nm in SC 24 (0.91, 0.88, and 0.96) are greater than that in SCs 23 (0.87, 0.85, and 0.86) and 22 (0.88 and 0.81). The median values of the duration of M and X class flares are 39.00 and 71.50 minutes in SC 22, 21.00 and 26.50 minutes in SC 23, and 19.00 and 24.00 minutes in SC 24. The duration of M and X class flares in SC 22 is obviously longer than that in SCs 23 and 24. In addition, the duration of flares increases with the increase of flare intensity.

中文翻译：

---

太阳周期 22、23 和 24 期间软 X 射线太阳耀斑的统计分析

本文介绍了 1986 年 1 月至 2017 年 6 月期间软 X 射线耀斑的统计分析，涵盖了最近三个太阳活动周期 (SC) 22、23 和 24。我们分析了耀斑数的分布、发生之间的关系软 X 射线耀斑和太阳活动的速率，以及调查期间不同强度等级（B、C、M 和 X）太阳耀斑的持续时间。M和X级耀斑在SC 22、23和24的总发生率分别为10.33%、6.77%和5.45%，表明SC 22是一个频繁发生大耀斑的SC。同时，M级和X级耀斑主要集中在SC 22的太阳极大期（71.13%）。 耀斑年数与太阳F10.7指数、0.1-0.8 nm X射线通量和EUV的相关系数SC 24 (0.91, 0.88, 和 0.96) 大于 SC 23 (0.87、0.85 和 0.86) 和 22 (0.88 和 0.81)。M 和 X 级耀斑持续时间的中值在 SC 22 中为 39.00 和 71.50 分钟，在 SC 23 中为 21.00 和 26.50 分钟，在 SC 24 中为 19.00 和 24.00 分钟。 SC 22 中 M 和 X 级耀斑的持续时间为明显长于SC 23和24。此外，耀斑持续时间随着耀斑强度的增加而增加。