Investigating Effects of Solar Proton Events and Forbush Decreases on Ground‐Level Potential Gradient Recorded at Middle and Low Latitudes and Different Altitudes

Abstract

High‐energetic charged particles, such as solar protons, and phenomena such as Forbush decreases are eligible candidates to affect the global electric circuit. These effects have been studied by analyzing disturbances of the potential gradient in ground‐based measurements in fair weather regions. In this paper, we investigate deviations in the potential gradient diurnal curve, during solar proton events, and Forbush decreases, from the mean values obtained in fair weather conditions. In each situation, we select only events which are not accompanied or followed by the other. Using the superposed epoch analysis, in order to enhance the visualization of small effects, we study the potential gradient data recorded between January 2010 and December 2019 at two stations located at low and middle‐latitudes, and at two different altitudes: the Complejo Astronómico El Leoncito (CASLEO), Argentina: 31.78°S, 2550 m a.s.l., and the Geophysical Observatory in Świder (SWIDER), Poland: 52.12°N, 100 m a.s.l., respectively. For intense solar proton events (>100 MeV) we found a statistically significant increase of the potential gradient after solar proton events recorded at CASLEO and no such deviation in the potential gradient recorded at SWIDER. For Forbush decrease events (greater than 4%), no significant deviation of the potential gradient after the start of the event was found in both stations, however for very intense Forbush decreases (>7%) we found an increase of the potential gradient recorded at CASLEO.

Effects of Forbush Decreases on the Global Electric Circuit

“…Their amplitude A determined from AMS-02 measurements are 15.2% (4th), 19.4% (1st), and 14.2% (5th) respectively. These events were analyzed individually by Tacza et al (2022) and showed a significant PG increase during the FD. To see if these three events dominate the SEA analysis, we also remove these three events from our analysis to evaluate its impact on our results.…”

“…Over the past decades, they have been speculated to be also able to affect the global electric circuit (GEC), and through which, affecting the weather patterns such as thunderstorms and lightnings on the Earth. Tacza et al (2022) performed SEA on 17 large SEP events and showed that at the 2.5σ level, there is a correlation between SEP flux increase and PG increase at fair weather conditions. Less clear is the effect of FDs on PG.…”

“…Previous studies seem to have reached different conclusions. The work of Tacza et al (2022) examined three individual large FD events and showed that PGs in all three events increase shortly after the FDs reach their maximum GCR reduction.…”

“…However, the author pointed out that the results depended of the timing of the FD onset. Recently, Tacza et al (2022) examined FDs with magnitude greater than 4% as recorded by the IZMIRAN database and did not find any significant PG variations, as recorded at the CASLEO observatory (18 events, high altitude station) and at the SWIDER observatory (15 events, low altitude station). The authors also defined the FD onset as the start of the cosmic rays flux decrease.…”

“…In this work, we examine how the variations of primary cosmic ray intensity affects the GEC by using the amplitude reduction parameter proposed and computed in Wang et al (2023). Our current work is an extension of the analysis presented in Tacza et al (2022) and uses potential gradient data recorded between January 2010 and December 2019 at a high-altitude station in Complejo Astronómico El Leoncito.…”