We have studied fast plasma jets outside of Earth’s magnetic environment. Such jets are small-scale structures with a limited lifetime, which may be important in determining the properties of the near-Earth space environment, due to their concentrated kinetic energy. We have used data from the NASA Magnetospheric MultiScale (MMS) satellites to study their properties in detail, to understand how these jets are formed. We have found evidence that there are at least two different types of jets. Hide

The Harris–Fadeev–Kan–Manankova family of exact two-dimensional equilibria is generalized to reproduce the slow decrease of the normal magnetic component in the tailward direction, and the magnetotail current sheet bending and shifting in the vertical plane, arising from the Earth dipole tilting and the solar wind nonradial propagation. The analytical solution is found to fit the empirical T96 model, especially, at distances beyond 10–15 Earth radii at high levels of magnetospheric activity. Hide

Old diaries kept in Japan tell us a surprising fact. The 27-day solar rotational period in thunder and lightning activities had been persistent for the past 300 years. The intensity is found to be more prominent as solar activity increases. The physical mechanism of the Sun–Climate connection is yet uncertain, an important link surely exists between the solar activity and terrestrial climate even at a meteorological timescale. Hide

The Polar Cap (PC) indices, PCN (North) based on magnetic data from Qaanaaq (Thule) and PCS (South) based on Vostok data, reflect the transpolar convection of plasma and magnetic fields. The PC indices could be used, among others, to indicate the energy transfer from the solar wind to the magnetosphere–ionosphere–thermosphere system in space weather monitoring applications. The present IAGA-endorsed methods to derive PC indices in real time are found to generate inconsistent index values. Hide

Equatorial ionospheric irregularities have a significant detrimental impact on a variety of space application systems in navigation and communication areas that utilize satellites, especially the Global Navigation Satellite Systems (GNSS) network. The development of these irregularities in the nighttime ionosphere is controlled primarily by ionospheric electric fields and instabilities. The effect of magnetic disturbance on these electric fields and on the irregularities is investigated here. Hide

This paper presents a statistical study of the equatorward boundary of small-scale field-aligned currents (SSFACs) as observed by ESA's Swarm satellites and investigates the relation between this boundary and NASA’s Van Allen probe observed plasmapause (PP). It is found that the two boundaries are closely coincident in the midnight LT sector, where the new PP is formed. Our results point to the role of SSFACs in the creation of the PP and offer a unique tool to monitor PP dynamics. Hide

The midnight temperature maximum (MTM) is a phenomenon resulting from the constructive interference of the atmospheric tides. This paper brings the analysis of a long data set (846 nights) from the NATION network along with new analysis techniques (harmonic background removal and 2-D temperature interpolation) to detect the MTM in the mid-latitude range. Hide

This work presents an analysis of the scintillation onset over the southern Brazil based on data from two solar maximum periods and simulation of the ionospheric conditions before the scintillation onset. The results shows some patterns which may help to prevent several satellite-based technological applications suffering disruptions due to scintillation issues. Hide

With the powerful MAARSY radar, we detected 3D wind fields and the vertical winds show a non-Gaussian distribution. We further obtained the frequency spectrum of vertical wind. The distribution of the spectral slopes under different wind conditions is derived and their comparisons with the background horizontal winds show that the spectra become steeper with increasing wind velocities under quiet conditions, approach a slope of −5/3 at 10 m/s and then maintain this slope for even stronger winds. Hide

We present new results on the behavior of sporadic E layers (Es layers) using GPS (global positioning system) radio occultation (RO) measurements obtained from the FORMOSAT-3/COSMIC satellites and digisonde data over Cachoeira Paulista, a low-latitude station in Brazil. Hide

For subauroral polarization streams (SAPS) commencing at different universal times (UT), the strongest westward neutral winds exhibit large variations in amplitudes. The effect of a sine-wave oscillation of SAPS on the neutral wind also exhibits UT variations in association with the solar illumination. The reduction in the electron density and enhancement in the air mass density are strongest when the maximum solar illumination collocates with the SAPS. Hide

In this study we use multi-point spacecraft measurements of magnetic field and electron density derived from spacecraft potential to investigate the three-dimensional structure of solar wind plasma turbulence. We see that there is a dependence on the plasma beta (ratio of thermal to magnetic pressure) as well as a dependence on the type of wind i.e. fast or slow. Hide

The solar wind is a tenuous turbulent plasma permeating the interplanetary space and is not well understood. A complex process called magnetic reconnection can act as a source of solar wind turbulence. Here we study this process using statistics. We demonstrate that high-order statistics of the magnetic field display a parabolic relation that is enhanced when magnetic reconnection occurs. Our results can help us understand the nature of solar wind turbulence. Hide

We present observations of the Earth's upper atmosphere (ionosphere and thermosphere) near the Equator. Instruments such as cameras and radar systems are used to measure the characteristics of the this region and compare the different observations. One focus of the paper is on structured regions of low density and we find patterns in its development along with other new observations. We also show results of a local increase in temperature near midnight and investigate its extent and evolution. Hide

Thermospheric mass density from the GOCE satellite for Sun-synchronous orbits between 83.5° S and 83.5° N normalized to 270 km during 2009–2013 has been used to develop our GOCE model at dawn/dusk local solar time sectors based on the empirical orthogonal function (EOF) method. We find that both amplitude and phase of the seasonal variations have strong latitudinal and solar activity dependences, and the annual asymmetry and effect of the Sun–Earth distance vary with latitude and solar activity. Hide

We investigate what fraction of the hot hydrogen atoms recently found from Lyman-alpha measurements in the Earth's upper exosphere could have their origin as energetic neutral atoms via charge exchange from protons of the shocked solar wind ahead of the magnetopause. Our calculations show that this contribution, although definitely present at larger exospheric heights, cannot explain the observations at lower altitudes. Hide

Global coverage measurements made by satellites have provided observational studies which have shown the presence of four peaks in global longitudinal structures from global local time observations of equatorial ionization anomalies. The structures seen in the ionosphere are related to the diurnal non-migrating wave that comes from the troposphere and can be noticed in periods of low and high solar activity in the low-latitude ionosphere regions, mainly at altitudes from ~ 250 km up to ~ 800 km. Hide

This paper investigates the passage of the ozone secondary effect (OSE) over southern Brazil and Uruguay in October 2016 by using multi-instrumental data, i.e. ozonesonde, satellites and ground-based instruments, and the large OSE influence on the ozone concentration and on the temperature was shown. Hide

Ozone-poor air mass can be released and leave through the Antarctic ozone hole, thus reaching midlatitude regions. The objective of this study is to show how tropospheric and stratospheric dynamics behaved during the event. The ozone-poor air mass began to operate in the region on 20 October 2016. A reduction of ozone content of approximately 23 % was observed in relation to the climatology average. The advance of the ozone-poor air mass caused intense reductions in total ozone content. Hide

It has been shown that guide fields substantially modify the structure of reconnection layers. In this paper, we studied the electric field structures in magnetic reconnection under different initial guide fields (Bg). Once the amplitude of a guide field exceeds 0.3 times the asymptotic magnetic field B0, the traditional bipolar Hall electric field is clearly replaced by a tripolar electric field, which consists of a newly emerged electric field and the bipolar Hall electric field. Hide

Ionosonde data and crustal earthquakes with magnitude M ≥ 6.0 observed in Greece during the 2003–2015 period were examined. The ionospheric anomalies are identified on the observed variations of the sporadic E-layer parameters and foF2 at the Athens observatory. The empirical relationships between ionospheric anomalies and the earthquake magnitude and the epicentral distance are obtained. The possibility of using the relationships obtained for earthquake prediction is finally discussed. Hide

The relationship between the tropospheric convection and the ionospheric phenomenology have been investigated in recent decades. In this work a relation between the lightning strike activity and the characteristics of the equatorial spread-F events is analyzed over the Brazilian region, and the results seem to support the hypothesis of some indirect interrelationship between both distinct phenomena. Hide

Passive electromagnetic induction soundings in the far field live on the fact that natural electromagnetic field variations (their source signals) fulfill the plane-wave assumption. In the frequency range of geomagnetic pulsations some signals (upstream waves) do and others (field line resonances) do not meet this condition. The consequences for several branches of such soundings are shown. A consequence is that a remote reference site may be situated in another continent than the local site. Hide

Aerosols affect atmospheric dynamics because they absorb radiations (direct effects) and because they act as cloud condensation nuclei (indirect effects). The present study shows that aerosol indirect effects reduce summer precipitation in the Euro-Mediterranean region through reduction of the radiative heating of the surface and corresponding reductions of surface temperature, resulting in increased atmospheric stability in the presence of high aerosol loads. Hide

Swarm is the fourth Earth Explorer mission of the European Space Agency (ESA), launched on 23 November 2013. The mission provides an opportunity for better knowledge of the near-Earth electromagnetic environment. This study presents an initial attempt to derive an ultra low-frequency (ULF) wave index from low-Earth orbit satellite data. The technique can be potentially used to define a new product from the mission, the Swarm ULF wave index, which would be suitable for space weather applications. Hide

In the past years, the study of the temperature trend and its variability in the upper atmosphere has increased. However, most works were conducted in regions of medium and high latitude. Therefore, we aim to analyze a low-latitude region, the south of Brazil and surrounding areas. Using data from the TIMED/SABER instrument and applying the Trend-Run model for temperature trend analyses, no substantial temperature trend was found in the MLT region (80–100 km) from the years 2003 to 2014. Hide

On 3 October 2005, a mesospheric front was observed over São João do Cariri (7.4° S, 36.5° W) propagating to the northeast in the OH airglow images. One and a half hours later, it disappeared completely and ripples were observed in the eastern part of the images. After studying the background atmosphere, the main conclusion of this work was that the instability in the airglow layer did not allow the propagation of the front to the other side of the local zenith. Hide

The interaction between the magnetic field and the particles coming from outer space, which apparently have a relationship with tectonic plates, is studied. The major earthquakes of Maule (2010, 8.8 M_w), Sumatra (2004, 9.2 M_w) and Tohoku (2011, 9.0 M_w) were studied, similar frequencies being found in the vertical component of the magnetic field (microhertz range). The temporal evolution of the magnetic oscillations showed the possible link with the seismic movement of Maule in 2010. Hide

This article presents characteristics of periodic waves observed in the thermosphere from airglow images collected in the Northeast of Brazil. Using simultaneous measurements of the background wind in the airglow emission altitudes, it was possible to estimate the intrinsic parameters and the role of the wind in the propagation of the waves into the thermosphere. An anisotropy in the propagation direction of the waves was observed and it could be explained by the wind filtering process. Hide

This work presents four events of mesosphere fronts observed on King George Island, Antarctic Peninsula, in the year 2011. The atmospheric background environment was analyzed to investigate the propagation conditions for all cases. To investigate the sources for such cases, satellite images were used. In two cases, we found that strong tropospheric instabilities were potential sources, and in the other two cases, it was not possible to associate them with tropospheric sources. Hide