Relationship between geomagnetic storm development and the solar wind parameter ß

We have analyzed the dynamics of solar wind and interplanetary magnetic field (IMF) parameters during the development of 933 isolated geomagnetic storms, observed over the period from 1964 to 2010. The analysis was carried out using the epoch superposition method at intervals of 48 hrs before and 168 hrs after the moment of Dst minimum. The geomagnetic storms were selected by the type of storm commencement (sudden or gradual) and by intensity (weak, moderate, and strong). The dynamics of the solar wind and IMF parameters was compared with that of the Dst index, which is an indicator of the development of geomagnetic storms. The largest number of storms in the solar activity cycle is shown to occur in the years of minimum average values (close in magnitude to 1) of the solar wind parameter β (β is the ratio of plasma pressure to magnetic pressure). We have revealed that the dynamics of the Dst index is similar to that of the β parameter. The duration of the storm recovery phase follows the characteristic recovery time of the β parameter. We have found out that during the storm main phase the β parameter is close to 1, which reflects the maximum turbulence of solar wind plasma fluctuations. In the recovery phase, β returns to background values β~2‒3.5. We assume that the solar wind plasma turbulence, characterized by the β parameter, can play a significant role in the development of geomagnetic storms.

Relationship between geomagnetic storm development and the solar wind parameter β

We have analyzed the dynamics of solar wind and interplanetary magnetic field (IMF) parameters during the development of 933 isolated geomagnetic storms, observed over the period from 1964 to 2010. The analysis was carried out using the epoch superposition method at intervals of 48 hrs before and 168 hrs after the moment of Dst minimum. The geomagnetic storms were selected by the type of storm commencement (sudden or gradual) and by intensity (weak, moderate, and strong). The dynamics of the solar wind and IMF parameters was compared with that of the Dst index, which is an indicator of the development of geomagnetic storms. The largest number of storms in the solar activity cycle is shown to occur in the years of minimum average values (close in magnitude to 1) of the solar wind parameter β (β is the ratio of plasma pressure to magnetic pressure). We have revealed that the dynamics of the Dst index is similar to that of the β parameter. The duration of the storm recovery phase follows the characteristic recovery time of the β parameter. We have found out that during the storm main phase the β parameter is close to 1, which reflects the maximum turbulence of solar wind plasma fluctuations. In the recovery phase, β returns to background values β~2‒3.5. We assume that the solar wind plasma turbulence, characterized by the β parameter, can play a significant role in the development of geomagnetic storms.

POSSIBLE CONNECTION BETWEEN THE SEISMIC SHOCKS AND THE IMPACT OF SOLAR WIND ON THE LITHOSPHERE (LOCAL CASES)

Disruptions of unstable equilibrium in the corresponding tectonic structures causing the onset of earthquakes are put in relation to Sun spot flares and coronal mass ejections. They generate magnetic clouds of solar wind plasma moving at much higher speed than the constant background to the Earth. The author assumes that additional energy is introduced to shallow earthquake foci due to the action of breakthrough injections into the Earth’s near-surface region of plasma clumps of geoeffective solar wind components disconnected into the magnetosphere. As a research tool, we used the method of graphical correlation between bursts of geoeffective solar wind parameter values and the occurrence of subsequent starts and repetitions of earthquake shocks. The examples given for Europe, South Asia, the Indian and Pacific oceans coasts consistently confirm the validity of the author's analytical understanding of the earthquake shocks beginning as a result of the destruction of the subsurface by injections of solar wind plasma clots in earthquake-prone zones. The problem under study is considered to be relevant in connection with the implementation of targeted forecast work. In the General scientific plan, consideration of the influence of solar-meter origins of factors are proposed to be included in the programs of studying earthquakes as one of their items. The obtained results should serve as a dynamic addition to the information placed on the maps of seismic zoning.

Proton and electron fluxes in the plasma sheet transition region and their dependence on the solar wind parameters

<p>Proton and electron spectra in the plasma sheet usually consist of spectral core and high energy tail. These two populations are formed by different processes, driven by the various combinations of the solar wind parameters.These processes include different time delays and may act differently on protons or electrons. In this work we evaluate empirically the magnitude and the time delay of the impact of different solar wind parameter combinations on the protons and electrons with energies (30-300 keV) and reveal the mechanisms behind these impacts. To do this we build a model of the fluxes at different energy channels in the transition region (nightside central plasma sheet between 6 and 15 Re) for the THEMIS spacecraft observations in 2007-2018. We use normalized values of solar wind parameter combinations (incl. speed, density, pressure, electric field, etc) as inputs of the model, with regression coefficients indicating their impact magnitudes. We investigate different time delays up to 16 hours. The model obtained shows that protons and electrons are controlled differently by solar wind parameters: dynamic pressure is important for protons, whereas solar wind speed and VBs are important for electrons. Larger time delays are required to describe higher energy electron fluxes.</p>

INFLUENCE OF THE ß SOLAR WIND PARAMETER ON STATISTICAL CHARACTERISTICS OF THE Ap INDEX IN THE SOLAR ACTIVITY CYCLE

We have studied the effect of the β solar wind parameter (equal to the ratio of the plasma pressure to the magnetic pressure) on statistical characteristics of the Ap index reflecting the triggering behavior of the activity of Earth’s magnetosphere. The trigger effect of the dynamics of magnetospheric activity consists in the abrupt transition from the periodic mode to the chaotic mode in the solar activity cycle. It is shown that cumulative amplitude distribution functions and power spectra of the Ap index of both the periodic and chaotic modes are well approximated by power and exponential functions respectively. At the same time, the indices of power functions and the indices characterizing the slope of the Ap index spectrum differ significantly in magnitude for the periodic and chaotic modes. We have found that Ap nonlinearly depends on β for both the modes of magnetospheric dynamics. The maximum of the Ap index amplitude for periodic modes is observed when β>1; and for chaotic ones, when β<1. In almost every cycle of solar activity, the energy of the Ap index fluctuations of chaotic modes is higher than that of periodic ones. The results indicate intermittency and its associated turbulence of magnetospheric activity. The exponential character of the spectral density of the Ap index suggests that the behavior of magnetospheric activity is determined by its internal dynamics, which can be described by a finite number of deterministic equations. The trigger effect of magnetospheric activity is assumed to be due to the angle of inclination of the axis of the solar magnetic dipole to the ecliptic plane, on which the dynamics of the β parameter in the solar activity cycle depends.

INFLUENCE OF THE ß SOLAR WIND PARAMETER ON STATISTICAL CHARACTERISTICS OF THE Ap INDEX IN THE SOLAR ACTIVITY CYCLE

In this paper, we use numerical experiment methods to address the problem of determining characteristics of ULF (0.3–3 kHz) electromagnetic waves recorded in the surface layer and providing the maximum amount of information about the Earth–ionosphere waveguide. We have analyzed the effect of the horizontal spatial structure of electron density of the Earth–ionosphere waveguide on propagation of electromagnetic waves. We have identified characteristics that allow us to record them by instrumental methods in conditions of weakly disturbed ionosphere. The density profiles used in numerical experiments have been obtained from data acquired by the Partial Reflection Radar at the Polar Geophysical Institute, located at the radiophysical observatory Tumanny in the Murmansk Region (69.0° N, 35.7° E), and by the IRI2016 model during the March 15, 2013 solar flare and the subsequent magnetic storm on March 17, 2013. The electromagnetic signal propagation model used in this work is the adaptation of gas-hydrodynamic methods to electrodynamic applications. The model is based on the scheme of upwind approximation of spatial derivatives (Godunov’s method with correction of streams). We also use splitting by spatial directions and physical processes. Signal field attenuation due to conductivity and its rotation due to Hall conductivity of the medium are considered in separate splitting steps by analytical formulas.

Statistical study of the substorm onset: its dependence on solar wind parameters and solar illumination

Based on 1829 well-defined substorm onsets in the Northern Hemisphere, observed during a 2-year period by the FUV Imager on board the IMAGE spacecraft, a statistical study is performed. From the combination of solar wind parameter observations by ACE and magnetic field observations by the low altitude satellite CHAMP, the location of auroral breakups in response to solar illumination and solar coupling parameters are studied. Furthermore, the correspondence of the onset location with prominent large-scale field-aligned currents and electrojets are investigated. Solar illumination and the related ionospheric conductivity have significant effects on the most probable substorm onset latitude and local time. In sunlight, substorm onsets tend to occur 1h earlier in local time and 1.5° more poleward than in darkness. The solar wind input, represented by the merging electric field, integrated over 1h prior to the substorm, correlates well with the latitude of the breakup. Most poleward latitudes of the onsets are found to range around 73° magnetic latitude during very quiet times. Field-aligned and Hall currents observed concurrently with the onset are consistent with the signature of a westward travelling surge evolving out of the Harang discontinuity. The observations suggest that the ionospheric conductivity has an influence on the location of the precipitating energetic electron which causes the auroral break-up signature. Keywords. Ionosphere (Auroral ionosphere) – Magnetospheric Physics (Current systems; Magnetosphereionosphere interactions)