Variations of the Near-Surface Electric field measured at Aragats during Geomagnetic Storms (2505.16271v1)

Abstract: At least two mechanisms effectively transfer interplanetary magnetic field (IMF) disturbances into the atmosphere. First, the inflow of solar wind into the ionosphere at low latitudes significantly enhances the total vertical electron content, increasing atmospheric conductivity. Second, Forbush decreases (FD) reduce the cosmic ray flux by a few percent, lowering ionization levels at middle latitudes and decreasing conductivity. Changes in atmospheric conductivity affect the global electric circuit and atmospheric electric field (AEF). However, to study the response of AEF to geomagnetic storms (GMS), it is necessary to carefully monitor atmospheric conditions before and during storms, as meteorological influences can be much stronger than those of GMS. Charged clouds above detectors, lightning flashes, and abrupt weather changes significantly impact near-surface electric field (NSEF) variations, which serve as a proxy for AEF measured at the Earth's surface. The facilities at Aragats station monitor all environmental parameters on a one-minute timescale. We analyze four GMS events described in previous studies, detailing the corresponding weather conditions to isolate the genuine influence of GMS on NSEF. The GMS of June 22, 2015, and September 8, 2017, occurred under fair-weather conditions, providing clear evidence of GMS influence on NSEF. These events were long-lasting, positive, and modest, ranging from 0.2 to 0.3 kV/m, and coincided with the depletion phase of FD. The sky was clear, no rain was detected, and lightning flashes from previous thunderstorms were more than 20 km from the station. The other two events did not meet favorable weather criteria, and their occurrence during GMS seemed incidental. We identify a feature that may indicate the solar (FD) origin of NSEF enhancement: a dip in the enhanced NSEF during the daytime.

Analysis of Near-Surface Electric Field Variations During Geomagnetic Storms

The paper titled "Variations of the Near-Surface Electric Field Measured at Aragats During Geomagnetic Storms" by A. Chilingarian offers a comprehensive examination of the interplay between geomagnetic storms (GMS) and near-surface electric fields (NSEF). The research underscores the importance of understanding how variations in atmospheric conductivity, driven by solar and cosmic phenomena, influence terrestrial electric environments.

The paper identifies two primary mechanisms transferring interplanetary magnetic disturbances into the Earth's atmosphere: the influx of solar wind enhancing ionospheric electron content, and Forbush decreases (FD) that diminish cosmic ray flux. Both phenomena subsequently influence atmospheric conductivity and the global electric circuit, thereby affecting the NSEF. This paper aims to isolate the specific impacts of GMS on NSEF amidst potentially confounding meteorological factors.

Four GMS events, including those on June 22, 2015, and September 8, 2017, were critically analyzed, with meteorological conditions meticulously monitored to mitigate local environmental noise. For these events, conducted under fair-weather conditions, clear evidence of GMS impact on NSEF was observed. The measurable changes ranged from 0.2 to 0.3 kV/m and aligned with the depletion phase of FDs. This data stood in contrast to two additional cases, where meteorological conditions were not strictly controlled, leading to inconclusive results regarding GMS influences.

Instrumentation at the Aragats Research Station facilitated these analyses, employing field mills, magnetometers, and particle detectors to gather comprehensive environmental data. Significantly, the NSEF changes during well-defined GMS coincided with DST index elevations and Kp index variations, confirming the correlation between solar activities and atmospheric electric parameters.

This research contributes valuable empirical evidence concerning the sensitivity of NSEF to solar and cosmic influences. The data supports models suggesting that increased atmospheric ionization due to solar wind incursions leads to observable enhancements in NSEF. Yet, the paper underscores the complexities within this relationship, noting that local atmospheric dynamics can overshadow the subtler effects of FDs and solar wind incursions.

Future research avenues could include extended observational campaigns under various atmospheric conditions to delineate further the mechanisms by which GMS influence NSEF. Moreover, integrating these observations with global datasets could enhance predictive models of electric field variations during space weather events.

Ultimately, this research enhances our understanding of space weather impacts on Earth. It highlights the intricate balance between cosmic phenomena and terrestrial electric environments, emphasizing the need for nuanced, high-resolution monitoring to capture the subtleties of these interactions.