Rare observations of sprites and gravity waves supporting D, E, F-regions ionospheric coupling

We report rare simultaneous observations of columniform sprites and associated gravity waves (GWs) using the Transient Luminous Events (TLEs) camera and All-sky imager at Prayagraj (25.5° N, 81.9° E, geomag. lat. ~ 16.5° N), India. On 30 May 2014, a Mesoscale Convective System generated a group of sprites over the north horizon that reached the upper mesosphere. Just before this event, GWs (period ~ 14 min) were seen in OH broadband airglow (emission peak ~ 87 km) imaging that propagated in the direction of the sprite occurrence and dissipated in the background atmosphere thereby generating turbulence. About 9–14 min after the sprite event, another set of GWs (period ~ 11 min) was observed in OH imaging that arrived from the direction of the TLEs. At this site, we also record Very Low Frequency navigational transmitter signal JJI (22.2 kHz) from Japan. The amplitude of the JJI signal showed the presence of GWs with ~ 12.2 min periodicities and ~ 18 min period. The GWs of similar features were observed in the ionospheric Total Electron Content variations recorded at a nearby GPS site. The results presented here are important to understand the physical coupling of the troposphere with the lower and upper ionosphere through GWs.

Martian crustal magnetic fields: influences on the ionosphere

<p>Recent Mars Express and MAVEN observations have shown the extent to <br>which Mars's crustal fields, though weak in absolute magnitude, <br>nevertheless exert significant control over the structure of the ionosphere <br>over a range of altitudes. However, quantifying this control remains <br>challenging given the generally dynamic nature of the Mars solar wind <br>interaction, and the therefore naturally varying densities and temperatures <br>of the upper ionosphere in particular. In this study we examine MAVEN <br>Langmuir Probe and Waves data, and show for the first time a very clear <br>correspondence between the structure of the crustal fields and both the <br>measured electron temperatures and densities. Electron temperatures are <br>shown to be systematically lower in regions of strong crustal fields over a <br>wide altitude range. We speculate on the origins of this deviation.</p>

The solar eclipse effect on diffusion processes of O+ + O2 → O2+ + O reaction for the upper ionosphere over Kharkov

The Sun is the most effective factor in determining all processes in the ionosphere. For this reason, examining the effect of solar eclipses on the earth ionosphere provides a very important source of information about sudden and medium-scale changes in the ionosphere structure during a solar eclipse. In this study, the effect of solar eclipse on March 29, 2006 in Kharkov on self-diffusion of O+ + O2 ? O2+ + O reaction was investigated depending on the altitude (202, 252, and 303 km). As a result of the investigation, the minimum value of self-diffusion coefficient was seen at three altitudes on March 29, 2006 at the time of full covering in the solar. Self-diffusion coefficients were found to increase with increasing altitude. The results of the experimental study conducted to examine the effect of the eclipse on the ionosphere using high frequency wave propagation in Turkey where it was seen total eclipse on March 29, 2006 and the result that we obtained in this research are consistent with each other.

Origin of the zebra structure in the Jovian decameter radio emission

Context. We discuss the origin of quasi-harmonic emission bands that have been observed in the dynamic spectra of the Jovian decameter emission. Aims. We aim to show that the interpretation of the observed structure can be based on the effect of double plasma resonance (DPR) at ion cyclotron harmonics. Methods. According to the proposed model, in the extended source in the upper ionosphere of Jupiter, where the DPR condition is satisfied for one of the ion cyclotron frequency harmonics, the ion cyclotron waves are effectively excited at the frequency of the lower hybrid resonance. The observed electromagnetic radiation with a quasi-harmonic structure arises due to scattering of ion cyclotron waves by supra-thermal electrons. Results. Based on the VIP4 magnetic field model, we determine the longitudes at which the source of the considered radiation can be located. The obtained estimates of the plasma density and its height distribution in the source, as well as the energies of emitting ions and scattering electrons provide information about the plasma parameters in the upper ionosphere of Jupiter. Furthermore, these estimates are in good agreement with the observational data.

Density spikes in Titan’s upper ionosphere

<p>Titan, the largest moon of Saturn, has a dense and nitrogen-rich atmosphere, which is similar to that of early Earth before lived evolved. Solar EUV radiation and energetic particles ionizes the atmosphere and thereby forming a layer of plasma, the ionosphere, in the uppermost part of the atmosphere. The Cassini spacecraft flew past the moon Titan 127 times during its 14-year mission in the Saturn system. During most of these close flybys Cassini entered the ionosphere and some reached the ionospheric peak, located at some 1400 km above the moon surface. With the Langmuir probe instrument, we could study the plasma properties, e.g. ion and electron density, temperature etc., and a very dynamic ionospheric structure was found. In particular, significant and apparently sporadic density spikes in the upper ionosphere were found. These density peaks are manifested as a sudden increase in the measured density by some 10-100 cm<sup>-3</sup> over a time period of roughly minutes. These have so far been left unattended in our studies of Titan. We will present some statistics on their appearance and initial result on the mechanism forming them.</p> <p> </p> <p> </p>