We combined the observed diurnal VLF amplitude variation in the D region with standard measurements of the E and F regions to perform a diagnostic investigation of coupled geomagnetic storm effects in order to understand the observed storm-induced variations in VLF narrowband based on state and responses of the ionosphere. The dayside VLF amplitude showed a tendency for attenuation following geomagnetic storms, and the h’E and h’F variations confirmed strong storm response over the signal paths.

We develop a new criterion to determine E_s, i.e., when the mean value of the absolute value of the difference between the normalized SNR is greater than 3 times the standard deviation. We show that E_s have strong seasonal variations, with the highest occurrence rates in the summer season at midlatitudes mainly located at 90–110 km at 14:00–20:00 LT. The comparison of E_s altitudes from radio occultation profiles with ionosonde revealed a large correspondence between both measurement techniques.

The pulsating auroral generation mechanism has been investigated by observing precipitating electrons using rockets or satellites. However, it is difficult for such observations to distinguish temporal changes from spatial ones. In this study, we reconstructed the horizontal 2-D distribution of precipitating electrons using only auroral images. The 3-D aurora structure was also reconstructed. We found that there were both spatial and temporal changes in the precipitating electron energy.

The polar light in its various colors and forms has fascinated human beings since ancient times. It is less well known that there are also radio emissions generated in the aurora at higher altitudes. Not just Earth, but some other planets of the solar system also have auroras and corresponding radio emissions. In our publication, we investigate and classify the spectral fine structures of a radio emission called Saturn kilometric radiation to find out more about this radiation process.

In this work, we use the Disturbance Ionosphere indeX (DIX) to study equatorial plasma bubble (EPB) events over the Brazilian equatorial and low latitudes. Our results showed that the DIX detected EPB disturbances in terms of their intensity and occurrence times. Therefore, these responses agreed with the ionosphere behavior before, during, and after the studied EPBs. Finally, these disturbances tended to be higher (lower) in high (low) solar activity.

The Arecibo radar was used to probe free electrons of the ionized atmosphere between 70 and 100 km altitude. This is also the altitude region were meteors evaporate and form secondary particulate matter, the so-called meteor smoke particles (MSPs). Free electrons attach to these MSPs when the sun is below the horizon and cause a drop in the number of free electrons, which are the subject of these measurements. We also identified a different number of free electrons during sunset and sunrise.

In this study, we use a multipoint analysis of conjugate magnetospheric and ionospheric observations to investigate the magnetospheric and ionospheric responses to fast flow bursts that are associated with different space weather conditions. The results show that ionospheric currents are connected to the magnetospheric flows for different space weather conditions. The connection is more apparent and global for flows that are associated with a geomagnetically active condition.

Eruptions from the Sun can pose a hazard to Earth's power grids via, e.g., geomagnetically induced currents (GICs). We study magnetic measurements from Fennoscandia to find ways to understand and forecast GIC. We find that the direction of the time derivative of the magnetic field has a short reset time, about 2 min. We conclude that this result gives insight on the current systems high in Earth’s atmosphere, which are the main driver behind the time derivative’s behavior and GIC formation.