Abstract

BackgroundTo examine the influence of solar cycle and geomagnetic effects on SLE disease activity.MethodsThe data used for the analysis consisted of 327 observations of 27-day Physician Global Assessment (PGA) averages from January 1996 to February 2020. The considered geomagnetic indices were the AP index (a daily average level for geomagnetic activity), sunspot number index R (measure of the area of solar surface covered by spots), the F10.7 index (measure of the noise level generated by the sun at a wavelength of 10.7 cm at the earth’s orbit), the AU index (upper auroral electrojet index), and high energy (> 60 Mev) proton flux events. Geomagnetic data were obtained from the Goddard Space Flight Center Space Physics Data Facility. A time series decomposition of the PGA averages was performed as the first step. The linear relationships between the PGA and the geomagnetic indices were examined using parametric statistical methods such as Pearson correlation and linear regression, while the nonlinear relationships were examined using nonparametric statistical methods such as Spearman’s rho and Kernel regression.ResultsAfter time series deconstruction of PGA averages, the seasonality explained a significant fraction of the variance of the time series (R2 = 38.7%) with one cycle completed every 16 years. The analysis of the short-term (27-day) relationships indicated that increases in geomagnetic activity Ap index (p < 0.1) and high energy proton fluxes (> 60 Mev) (p < 0.05) were associated with decreases in SLE disease activity, while increases in the sunspot number index R anticipated decreases in the SLE disease activity expressed as PGA (p < 0.05). The short-term correlations became statistically insignificant after adjusting for multiple comparisons using Bonferroni correction. The analysis of the long-term (297 day) relationships indicated stronger negative association between changes in the PGA and changes in the sunspot number index R (p < 0.01), AP index (p < 0.01), and the F10.7 index (p < 0.01). The long-term correlations remained statistically significant after adjusting for multiple comparisons using Bonferroni correction.ConclusionThe seasonality of the PGA averages (one cycle every 16 years) explains a significant fraction of the variance of the time series. Geomagnetic disturbances, including the level of geomagnetic activity, sunspot numbers, and high proton flux events may influence SLE disease activity. Studies of other geographic locales are needed to validate these findings.

Highlights

  • The Earth is immersed in a geomagnetic field (GMF) that deflects the flowing ionized particles of solar winds

  • Statistical methodologies As a first step we studied the components of the 27-day Physician Global Assessment (PGA) average time series, its trend, seasonality and noise

  • In what follows the estimated trend was denoted by Physician global assessment (PGA) time series decomposition The plot of the 27-day PGA average time series is shown in panel (a) of Fig. 1

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Summary

Introduction

The Earth is immersed in a geomagnetic field (GMF) that deflects the flowing ionized particles of solar winds. The GMF is impressed and altered by the solar winds [1]. These alterations in GMF are called geomagnetic disturbances. The GMF has different strength and direction in different areas of the Earth. Several periodic variations have been shown in GMF, mostly related to various solar cycles (especially the 11 year cycle), and others related to Earth’s rotation and situation in its orbit [2]. To examine the influence of solar cycle and geomagnetic effects on SLE disease activity

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