To predict the satellite's motion or its re-entry, the density surrounding the satellite needs to be known as precisely as possible. Usually empirical models are used to estimate the neutral density of the thermosphere, which is the region of the neutrally charged atmosphere. Here, based on calibrated accelerations measured by instruments on board satellites, we compute daily global maps to correct modeled densities. During times of high solar activity, corrections of up to 28 % are necessary. Hide

Fast jets of solar wind particles drive through a slower environment in the magnetosheath, located sunward of the region dominated by the Earth’s magnetic field. THEMIS multi-spacecraft observations show that jets push ambient particles out of their way. These particles flow around the faster jets into the jets’ wake. Thereby, jets stir the magnetosheath, changing the properties of this key region whose particles and magnetic fields can directly interact with the Earth’s magnetic field. Hide

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