Long-term observation of magnetic pulsations through the ELF Hylaty station located in the Bieszczady Mountains (south–eastern Poland)

Zenon Nieckarz,Grzegorz Michałek

doi:10.1051/swsc/2020063

Abstract

Ground-based measurements of ultra- and extremely low-frequency waves (ULF/ELF) carried out in 2005–2016 (the 23rd and 24th solar cycle) at the ELF Hylaty station in Bieszczady Mountains (south–eastern Poland) were used to identify the days (360 days) in which magnetic pulsation events (MPEs) occurred. To reveal sources of MPEs at the Sun we considered their correlation with the basic indices describing solar activity. Our analysis, like earlier studies, did not reveal a significant positive correlation between the MPE detection rate and the sunspot numbers (SSN). On the other hand, we showed that MPEs are strongly correlated (correlation coefficient ≈0.70) with moderate (Dst < −70 nT) and intense (Dst < −100 nT) geomagnetic disturbances expressed by the Disturbance Storm Index (Dst). We recognized all sources of these geomagnetic storms associated with the considered MPEs. Only 44% of the MPEs were associated with storms caused by CMEs listed in the CDAW LASCO CME catalog. 56% of the MPEs were associated with storms caused by other phenomena including corotating interaction regions (CIRs), slow solar wind or CMEs not detected by LASCO. We also demonstrated that the CMEs associated with the MPEs were very energetic, i.e. they were extremely wide (partial and halo events) and fast (with the average speed above 1100 km s−1). CMEs and CIRs generally appear in different phases of solar cycles. Because MPEs are strongly related to both of these phenomena they cannot be associated with any phase of a solar cycle or with any indicator characterizing a 11-year solar activity. We also suggested that the low number of MPEs associated with CMEs is due to the anomalous 24 solar cycle. During this cycle, due to low density of the interplanetary medium, CMEs could easily eject and expand, but they were not geoeffective.

Highlights

Earth’s vicinity is mostly controlled by solar activity, especially by energetic events such as Coronal Mass Ejections (CMEs) and solar flares. Both of these phenomena significantly affect space weather: solar flares can cause a sudden change in the ionization level in the ionosphere, while CMEs are responsible for solar energetic particle (SEP) events and geomagnetic storms (Gopalswamy et al, 2001a; Gopalswamy, 2002; Zhang et al, 2003; Kim et al, 2005; Moon et al, 2005; Manoharan et al, 2004; Manoharan & Agalya, 2011; Shanmugaraju et al, 2015; Klein & Dalla, 2017)
The analysis presented here clearly indicates that magnetic pulsation events (MPEs) are significantly associated with geomagnetic storms disturbances and their source must be at the Sun
In the present study the MPE occurrence rate recorded in the ELF Hylaty station located in the Bieszczady Mountains in Poland was studied

Summary

Introduction

Earth’s vicinity is mostly controlled by solar activity, especially by energetic events such as Coronal Mass Ejections (CMEs) and solar flares. Both of these phenomena significantly affect space weather: solar flares can cause a sudden change in the ionization level in the ionosphere, while CMEs are responsible for solar energetic particle (SEP) events and geomagnetic storms (Gopalswamy et al, 2001a; Gopalswamy, 2002; Zhang et al, 2003; Kim et al, 2005; Moon et al, 2005; Manoharan et al, 2004; Manoharan & Agalya, 2011; Shanmugaraju et al, 2015; Klein & Dalla, 2017).

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