Rotation of the Solar Corona from Observations of Radio and X-Ray Solar Emission for Solar Activity Cycles 22–24

Geomagnetism and Aeronomy - The values of the radio and X-ray solar flux over the last three cycles of solar activity were studied for the presence of quasi-periodic oscillations via the...     

A review of: “Solar magnetohydrodynamics”

Abstract

By E. R. Priest, Geophys. and Astrophys. Monographs, Vol. 21, D. Reidel, Dordrecht, 1982. xx + 469 pp, Dfl. 235, US $99.00 (ISBN 90-277-1374-x).     

On The Question of North–South Asymmetry of Solar Activity

Geomagnetism and Aeronomy - The paper studies the dynamics of the distribution of the index of the north–south asymmetry of the sunspot number for the phase of the 11-year cycle, from cycle...     

Reconstruction of the Solar Activity in 1000–1700 Based on Auroral Data with Allowance for the Contribution of the Main Magnetic Field of the Earth

Geomagnetism and Aeronomy - A new reconstruction of the number of sunspots (SN) in 1000–1700, along with possible errors, has been obtained based on an analysis of auroral observations at...     

Drift of Polar Prominences in Solar Cycles 13–24

Geomagnetism and Aeronomy - A comparative analysis of the drift velocity of high-latitude prominences to the poles in solar cycles 13–24 is carried out. Data on the positions of prominences...     

Characteristic Features of Solar Cosmic Rays in the 21st–24th Solar-Activity Cycles According to Data from Catalogs of Solar Proton Events

Geomagnetism and Aeronomy - Homogeneous series of solar cosmic-ray events for four solar-activity cycles against the background of decreased activity in cycles 23 and 24 are considered. The number...     

Effects of Energetic Solar Emissions on the Earth–Ionosphere Cavity of Schumann Resonances

Schumann resonances (SR) are the electromagnetic oscillations of the spherical cavity bounded by the electrically conductive Earth and the conductive but dissipative lower ionosphere (Schumann in Z Naturforsch A 7:6627–6628, 1952). Energetic emissions from the Sun can exert a varied influence on the various parameters of the Earth’s SR: modal frequencies, amplitudes and dissipation parameters. The SR response at multiple receiving stations is considered for two extraordinary solar events from Solar Cycle 23: the Bastille Day event (July 14, 2000) and the Halloween event (October/November 2003). Distinct differences are noted in the ionospheric depths of penetration for X-radiation and solar protons with correspondingly distinct signs of the frequency response. The preferential impact of the protons in the magnetically unshielded polar regions leads to a marked anisotropic frequency response in the two magnetic field components. The general immunity of SR amplitudes to these extreme external perturbations serves to remind us that the amplitude parameter is largely controlled by lightning activity within the Earth–ionosphere cavity.     

Influence of Total Solar Irradiance on the Earth’s Climate

Geomagnetism and Aeronomy - The results of analysis of variations in the total solar irradiance in the 17–24th solar activity cycles and their relation to the climate global warming are...     

Evolution of Solar Active Regions Before Large Flares: Overview of the Events of 2010–2017

Geomagnetism and Aeronomy - The paper presents a study of the evolution of the photospheric magnetic field of active regions (ARs) of the Sun in which flares (larger than the M9 class in the...     

Estimates of Current Helicity and Tilt of Solar Active Regions and Joy’s Law

Geomagnetism and Aeronomy - The tilt angle, current helicity and twist of solar magnetic fields can be observed in solar active regions. We carried out estimates of these parameters by two ways....     

Results of Spectral Corona Observations in Solar Activity Cycles 17–24

The results of the work of the global observation network are considered, and a comparative analysis of the data of various coronal observatories is performed. The coronal activity index has been reconstructed for the period 1939–2016 based on the data of various observatories in Kislovodsk system. For this purpose, the corona daily intensity maps from the Sacramento Peak and Lomnický ?tít observatories according to the Solar-Geophysical Data journal have been digitized; they supplement the data of other observatories. The homogeneity and continuity of the corona observations at the Kislovodsk station, including activity cycle 24, is confirmed. Unfortunately, the only observatory at present that continues observation of the spectral corona in Fe XIV 5303 Å and Fe XIV 6374 Å lines is the Kislovodsk astronomical station Mountain Astronomical Station (MAS) of the Central Astronomical Observatory, Russian Academy of Sciences (Pulkovo). The data on the combined corona in 5303 Å line are analyzed. It is shown that there is a high correlation of the intensity index of green corona with solar radiation measurements in the vacuum UV region. Data on the beginning of the new 25th activity cycle in the corona at high latitudes are presented.     

Characteristics of Arc-Polarized Alfvén Waves in the Near-Earth Solar Wind

Geomagnetism and Aeronomy - The arc-polarized Alfvén waves observed in the near-Earth region of the heliosphere are studied with instruments of the WIND spacecraft in 1995–2011....     

Chronology of ‘killer’ electrons: Solar cycles 22 and 23

Measurements of >2 MeV electrons on GOES satellites from 1986 to 2007 are used to build a graphic chronology of outer radiation belt enhancements. Daily values of L=6.6 equivalent flux are colour coded and ordered by Carrington rotation to illustrate the pattern of occurrence frequency and intensity through the two solar cycles, and to contrast the form of recurrent and non-recurrent events. Highlighted are associations with high solar wind speed and southward interplanetary magnetic field that are clearly key to the energisation process, inducing high levels of geomagnetic activity during the growth phase. The chronology is offered as a simple background reference for the specific event case studies that are needed to understand the physical processes responsible for the production and dynamics of these relativistic electrons and their consequent internal electrostatic discharge threat to spacecraft systems. It is now possible to refine an empirical model for the solar cycle variation of this threat.     

Solar sources of interplanetary shocks on November 7–11, 2004

In a methodically independent manner compared to earlier works, an adjustment is performed to a series of solar sources, including six interplanetary shocks observed on November 7–11, 2004, during a very large solar-terrestrial storm. The results of different researchers are compared with one another and with this publication.     

The Effects of Solar Eclipse of August 1, 2008 on Earth’s Atmospheric Parameters

Several experiments were undertaken at Kolkata (latitude: 22°34′N, longitude: 88°30′E) on the solar eclipse day of August 1, 2008 to observe the effects of the solar eclipse on Fair Weather Field (FWF) and VLF amplitude and phase. The experimental results presented here show significant deviations of the observed parameters from their normal values, as they are determined by the average of the records obtained on 5 days adjacent to the day of the solar eclipse.     

Dynamics of Ionospheric Alfvén Resonances from the End of Cycle 21 through Cycle 24 of Solar Activity

Geomagnetism and Aeronomy - The results of the study of the dynamics of ionospheric Alfvén resonances (IARs) in a range of 0–10 Hz based on data from magnetic field observations at the...     

Features of the Earth’s Solar Climate Changes in the Present Epoch

Geomagnetism and Aeronomy - Calculated insolations of the Earth are analyzed. The main trends in the modern solar climate change are identified: increased latitudinal contrast and smoothed seasonal...     

Features of the Solar Wind Plasma Flow around the Earth’s Magnetosphere

Geomagnetism and Aeronomy - The change in the properties of the solar wind flow as it crosses the bow shock wave front and moves in the Earth’s magnetosheath are discussed. Solar wind data...     

Latitudinal Profiles of the Photospheric Magnetic Field in Solar Cycles 19–21

For various groups of photospheric magnetic fields differing in strength, averaged synoptic maps have been obtained from the data of the Kitt Peak National Solar Observatory (1976–2003). The latitudinal profiles of magnetic field fluxes are considered individually for each 5-G field strength interval. Changes in the maxima of the latitude profiles and their localization in the latitude are studied. The results are evidence that the latitudinal distribution of the magnetic fields changes significantly at field strengths of 5, 15, and 50 G. The magnetic flux for groups of fields differing in strength decreases monotonically as the strength increases, starting from B > 5 G; the fluxes of the southern hemisphere exceed those of the northern hemisphere. A very special group is formed by the weakest fields with B < 5 G, which are opposite in phase to stronger fields in terms of localization and time changes.     

Manifestation of the Lunar–Solar Tide and Free Oscillations of the Earth in the Variations of the Magnetic Field

The results of processing and analyzing the instrumental observations of the Earth’s magnetic field at the Geophysical Observatory Mikhnevo of the Institute of Geosphere Dynamics of the Russian Academy of Sciences (IGD RAS) for 2010–2015 are presented. Quasi-harmonic components with the periods close to the lunar–solar tidal waves are revealed in the spectra of geomagnetic variations over a period of 0.4 to 30 days. The elliptical S₁ tidal wave which is detected in the geomagnetic variations has modulations with periods of 1/3, 1/2, and 1 year. The spectra of the geomagnetic variations contain peaks corresponding to the free oscillations of the Earth. The analysis of the time series of the magnetic field for the period of the strong earthquakes in the absence of geomagnetic disturbances revealed the fine structure of the Earth’s fundamental spheroidal mode ₀S₂, which splits into five singlets. The established features of the spectrum of geomagnetic variations are helping the development of the new method for studying the deep structure of the Earth and the properties of the inner geospheres for estimating the viscosity of the Earth’s outer core and dynamics of the current systems in the outer (liquid) core, as well as for exploring, with the use of empirical data, the general regularities governing the regimes of energy exchange processes in the geospheres.