Effects of X2-class solar flare events on ionospheric GPS-TEC and radio waves over Brazilian sector

In this investigation, we present and discuss the effects of 6 X2-class solar flare events in the ionospheric F region over Brazilian sector that occurred during 2013 to 2015. For this investigation, we present the vertical total electron content (VTEC) observations from nearly 120 Global Positioning System (GPS) receivers all over the Brazilian sector for each event. Also, ionospheric sounding observations obtained in São José dos Campos (23.2°S, 45.9°W, dip latitude 17.6°S; hereafter referred to as SJC), under the southern crest of the equatorial ionospheric anomaly (EIA), Brazil, are presented. The observations show that the greatest TEC impact occurs with the EUV fluxes increases lasting for more than one hour and when the solar active region is located close to the solar disc center. We present a detailed study of the efficiency of the EUV flux with wavelengths ranging from 0.1 to 190?nm for the F region ionization. The largest increase of ΔTEC occurs below the magnetic equator line, covering mainly the central, northeast, southeast and south regions, which includes the equatorial ionospheric anomaly (EIA) region. The ionograms show partial or total fade out in the echoes traces observed causing blackouts of radio signals of up to 60?min, which can have serious consequences to technological systems of public and private agencies around Brazilian sector. This study can help to better understand the effects of solar flares in the ionospheric F region.     

Long-term (50 years) measurements of cosmic ray fluxes in the atmosphere

Since the middle of 1957 till present time the group of researchers of P.N. Lebedev Physical Institute of the Russian Academy of Sciences has carried out the regular balloon borne measurements of charged particle fluxes in the atmosphere. The measurements are performed at polar (northern and southern) and middle latitudes and cover the interval of heights from the ground level up to 30–35 km. Standard detectors of particles (gas-discharged counters) have been used. More than 80,000 measurements of cosmic ray fluxes in the atmosphere have been performed to the present time. In the data analysis the geomagnetic field and the Earth’s atmosphere are used as cosmic ray spectrometers.     

太阳帆技术综述

文章简要阐述了太阳帆的概念、主要结构和技术,参考美国L’Garde公司的太阳帆展开设计,对涉及的充气及刚化予以概述,为研究分析太阳帆的展开技术提供借鉴。     

The characteristics of valley phase as predictor of the forthcoming solar cycle

Is Solar Cycle 24 anomalous? How do we predict the main features of a forthcoming cycle? In order to reply such questions, this work partitions quantitatively each cycle into valley, ascend, peak, and descend phases, statistically investigate the correlations between valley phase and the forthcoming cycle. We find that the preceding valley phase may dominate and can be predictor of the forthcoming cycle: (1) The growth rate in ascend phase strongly negatively correlates to valley length and strongly positively correlates to cycle maximum. (2) The cycle maximum strongly negatively correlates to valley length, and strongly positively correlates to cycle minimum. (3) The cycle period strongly negatively correlates to the valley variation. Based on these correlations, we conclude that the solar cycle 24 is a relatively weak and long cycle which is obviously weaker than Cycle 23. The similarity analysis also presents the similar result. The Cycle 25 is also inferred possibly to be a weak cycle. These results can help us understanding the physical processes of solar cycles.     

The dynamics of the solar radiative zone

The picture of the solar radiative zone is evolving quickly. This review is separated in two parts. We first recall how the two powerful probes of the solar interior, namely the neutrinos and helioseismology have scrutinized the microscopic properties of the solar radiative plasma. Recent observations stimulate today complementary activities beyond the standard stellar model through theoretical modeling of angular momentum transport by rotation, internal waves or (and) by magnetic fields to get access to the dynamical motions of this important region of the Sun. So in the second part, we summarize the first impact of such processes on the radiative zone.     

The charge-sign dependent effect in the solar modulation of cosmic rays

The centennial anniversary of the discovery of cosmic rays was in 2012. Since this discovery considerable progress has been made on several aspects related to galactic cosmic rays in the heliosphere. It is known that they encounter a turbulent solar wind with an imbedded heliospheric magnetic field when entering the Sun’s domain. This leads to significant global and temporal changes in their intensity inside the heliosphere, a process known as the solar modulation of cosmic rays. The prediction of a charge-sign dependent effect in solar modulation in the late 1970s and the confirmatory observational discoveries can also be considered as a milestone. A short review is given of these predictions based on theoretical and numerical modelling work, the observational confirmation and related issues.