Influence of Geomagnetic Disturbances at Different Times of Day on Locomotor Activity in Zebrafish (Danio Rerio)

The influence of magnetic fields and natural geomagnetic storms on biological circadian rhythms are actively studied. This study reveals an impact of local natural perturbations in the geomagnetic field that occurred at different times of the day on circadian patterns of locomotor activity of zebrafish. A decrease in zebrafish swimming speed was observed during the geomagnetic disturbances before or after the fluctuations of diurnal geomagnetic variation. However, if the geomagnetic perturbations coincided with the fluctuations of diurnal geomagnetic variation, the decrease in zebrafish swimming speed was insignificant. This result suggests that the biological effects of geomagnetic disturbances may depend on synchronization with the diurnal geomagnetic variation. It implies that the previously published correlations between geomagnetic activity and medical or biological parameters could result from a disruption in circadian biorhythms.

Statistics of Large Impulsive Magnetic Events In The Auroral Zone

Impulsive geomagnetic variations, latitudinally localized to the auroral zone, have been observed over the period from 2015-2020. These impulsive events have been observed mostly in the pre-midnight sector as upward vertical perturbations. Diurnal variations in geomagnetically-triggered harmonic distortion events observed in Hydro-Québec's Système de Mesure de Décalage (SMDA) synchrophasor measurement system have been found to have a peak in the number of events around midnight. This was similar to diurnal rates of occurrence of negative B z geomagnetic impulsive events, observed at nearby auroral zone magnetometers. Superposed epoch analysis demonstrates the impulses are regularly associated with increases in harmonic distortion observed at a nearby substation transformer. These large impulsive vertical geomagnetic perturbations appear to be local vortical ionospheric disturbances.

Analytical and empirical modelling of the origin and heliospheric propagation of coronal mass ejections and space-weather applications

The focus is on the physical background and comprehension of the origin and the heliospheric propagation of interplanetary coronal mass ejections (ICMEs), which can cause most severe geomagnetic disturbances. The paper considers mainly the analytical modelling, providing useful insight into the nature of ICMEs, complementary to that provided by numerical MHD models. It is concentrated on physical processes related to the origin of CMEs at the Sun, their heliospheric propagation, up to the effects causing geomagnetic perturbations. Finally, several analytical and statistical forecasting tools for space weather applications are described.

Sources of hazardous geoelectric fields in the United States during magnetic storms

<p>Geomagnetic perturbations related to various phenomena in the near-Earth space environment can induce electric fields within the electrically conducting Earth. The geoelectric field is an important link between magnetospheric/ionospheric phenomena and geomagnetically induced currents in grounded electricity transmission networks. In evaluations of contiguous United Sates hazards, most previous studies have been focused on either 1-minute resolution geoelectric field measurements or geoelectric field time series derived from convoluting 1-minute geomagnetic field data with surface impedance tensors. To investigate sources of hazardous geoelectric fields during magnetic storms, including geoelectric fields induced by ultra-low frequency (ULF: 1 mHz to 1 Hz) waves, we use directly measured 1-second geoelectric field data from magnetotelluric survey stations that are distributed across the contiguous United States. Temporally-localized perturbations in measured geoelectric fields with a prominence of at least 0.5 V/km are detected during magnetic storms with a Dst minimum of at least -100 nT from 2008 to 2019. Most of these perturbations cannot have been resolved with 1-minute data since they correspond to phenomena that vary on smaller timescales and higher frequencies. The sources of geomagnetic perturbations inducing these extreme geoelectric fields can be categorized as interplanetary shocks, substorms, and ULF waves. We compare the geoelectric fields associated with the three sources and characterize their features. Extreme geoelectric fields related to these sources can have amplitudes of 1-2 V/km, comparable to the thresholds commonly used to identify hazardous events.</p>

A Study on the Characteristics of the Ionospheric Gradient under Geomagnetic Perturbations

The Earth’s ionosphere is greatly influenced by geomagnetic activities, especially geomagnetic storms. During a geomagnetic storm, the ionosphere suffers many perturbations, leading to a spatial gradient that are neglected during geomagnetically quiet periods. An ionospheric gradient generates potential hazards for a ground-based argumentation system (GBAS) by enlarging the errors in the delay corrections between ground monitor stations and users. To address this problem, this work investigates the characteristics of the ionospheric gradient under geomagnetic storms. Global Navigation Satellite System (GNSS) observations from the continuously operating reference station (CORS) network were used to analyze the ionospheric gradients during the geomagnetic storm on 8 September 2017. The statistical behavior of the ionospheric gradient was further discussed. Experiments show that strong geomagnetic perturbations lead to large ionospheric gradients, and the gradients also vary with the geomagnetic location.

About determination of coordinates of sources of geomagnetic perturbations according to the world network of magnetic observatories

<p>A method for determining the coordinates of geomagnetic perturbation sources based on joint data processing of the world network of magnetic observatories is proposed. A large statistical material showed the relationship of large geomagnetic storms with the interaction of two or more magnetic clouds formed as a result of coronal mass ejections. To determine the coordinates of the sources of perturbations, it is proposed to use the data of magnetic observatories of the "INTERMAGNET" international network, which has more than 100 observation points distributed around the world and equipped with modern identical hardware. The results of geomagnetic field measurement obtained by magnetic observatories are brought to a single coordinate system. It was achieved by rotation of the axes of local stations, which allows determining the coordinates of the sources of perturbations and evaluating the accuracy of specifying the coordinate system of each local observatory.</p>