Electron Density Distributions in Saturn's Ionosphere

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.Between 26 April and 15 September 2017, Cassini executed 23 highly inclined Grand Finale orbits through a new frontier for space exploration, the narrow region between Saturn and the D Ring, providing the first opportunity for obtaining in situ ionospheric measurements. During the Grand Finale orbits, the Radio and Plasma Wave Science instrument observed broadband whistler mode emissions and narrowband upper hybrid frequency emissions. Using known wave propagation characteristics of these two plasma wave modes, the electron density is derived over a broad range of ionospheric latitudes and altitudes. A two‐part exponential scale height model is fitted to the electron density measurements. The model yields a double‐layered ionosphere with plasma scale heights of 545/575 km for the northern/southern hemispheres below 4,500 km and plasma scale heights of 4,780/2,360 km for the northern/southern hemispheres above 4,500 km. The interpretation of these layers involves the interaction between the rings and the ionosphere

Logistics service provider selection for disaster preparation: a socio-technical systems perspective

Since 1990s, the world has seen a lot of advances in providing humanitarian aid through sophisticated logistics operations. The current consensus seems to be that humanitarian relief organizations (HROs) can improve their relief operations by collaborating with logistics service providers (CLSPs) in the commercial sector. The question remains: how can HROs select the most appropriate CLSP for disaster preparation? Despite its practical significance, no explicit effort has been done to identify the criteria/factors in prioritising and selecting a CLSP for disaster relief. The present study aims to address this gap by consolidating the list of criteria from a socio-technical systems (STS) perspective. Then, to handle the interdependence among the criteria derived from the STS, we develop a hybrid multi-criteria decision making model for CLSP selection in the disaster preparedness stage. The proposed model is then evaluated by a real-life case study, providing insights into the decision-makers in both HROs and CLSPs

Moonraker -- Enceladus Multiple Flyby Mission

Enceladus, an icy moon of Saturn, possesses an internal water ocean and jets expelling ocean material into space. Cassini investigations indicated that the subsurface ocean could be a habitable environment having a complex interaction with the rocky core. Further investigation of the composition of the plume formed by the jets is necessary to fully understand the ocean, its potential habitability, and what it tells us about Enceladus' origin. Moonraker has been proposed as an ESA M-class mission designed to orbit Saturn and perform multiple flybys of Enceladus, focusing on traversals of the plume. The proposed Moonraker mission consists of an ESA-provided platform, with strong heritage from JUICE and Mars Sample Return, and carrying a suite of instruments dedicated to plume and surface analysis. The nominal Moonraker mission has a duration of 13.5 years. It includes a 23-flyby segment with 189 days allocated for the science phase, and can be expanded with additional segments if resources allow. The mission concept consists in investigating: i) the habitability conditions of present-day Enceladus and its internal ocean, ii) the mechanisms at play for the communication between the internal ocean and the surface of the South Polar Terrain, and iii) the formation conditions of the moon. Moonraker, thanks to state-of-the-art instruments representing a significant improvement over Cassini's payload, would quantify the abundance of key species in the plume, isotopic ratios, and physical parameters of the plume and the surface. Such a mission would pave the way for a possible future landed mission.Comment: Accepted for publication in The Planetary Science Journa

Moonraker: Enceladus Multiple Flyby Mission

Enceladus, an icy moon of Saturn, possesses an internal water ocean and jets expelling ocean material into space. Cassini investigations indicated that the subsurface ocean could be a habitable environment having a complex interaction with the rocky core. Further investigation of the composition of the plume formed by the jets is necessary to fully understand the ocean, its potential habitability, and what it tells us about Enceladus’s origin. Moonraker has been proposed as an ESA M-class mission designed to orbit Saturn and perform multiple flybys of Enceladus, focusing on traversals of the plume. The proposed Moonraker mission consists of an ESA-provided platform with strong heritage from JUICE and Mars Sample Return and carrying a suite of instruments dedicated to plume and surface analysis. The nominal Moonraker mission has a duration of ∼13.5 yr. It includes a 23-flyby segment with 189 days allocated for the science phase and can be expanded with additional segments if resources allow. The mission concept consists of investigating (i) the habitability conditions of present-day Enceladus and its internal ocean, (ii) the mechanisms at play for the communication between the internal ocean and the surface of the South Polar Terrain, and (iii) the formation conditions of the moon. Moonraker, thanks to state-of-the-art instruments representing a significant improvement over Cassini's payload, would quantify the abundance of key species in the plume, isotopic ratios, and the physical parameters of the plume and the surface. Such a mission would pave the way for a possible future landed mission

Is Evolution of Blind Mole Rats Determined by Climate Oscillations?

The concept of climate variability facilitating adaptive radiation supported by the ‘‘Court Jester’’ hypothesis is disputed by the ‘‘Red Queen’’ one, but the prevalence of one or the other might be scale-dependent. We report on a detailed, comprehensive phylo-geographic study on the ,4 kb mtDNA sequence in underground blind mole rats of the family Spalacidae (or subfamily Spalacinae) from the East Mediterranean steppes. Our study aimed at testing the presence of periodicities in branching patterns on a constructed phylogenetic tree and at searching for congruence between branching events, tectonic history and paleoclimates. In contrast to the strong support for the majority of the branching events on the tree, the absence of support in a few instances indicates that network-like evolution could exist in spalacids. In our tree, robust support was given, in concordance with paleontological data, for the separation of spalacids from muroid rodents during the first half of the Miocene when open, grass-dominated habitats were established. Marine barriers formed between Anatolia and the Balkans could have facilitated the separation of the lineage ‘‘Spalax’’ from the lineage ‘‘Nannospalax’’ and of the clade ‘‘leucodon’’ from the clade ‘‘xanthodon’’. The separation of the clade ‘‘ehrenbergi’’ occurred during the late stages of the tectonically induced uplift of the Anatolian high plateaus and mountains, whereas the separation of the clade ‘‘vasvarii’’ took place when the rapidly uplifting Taurus mountain range prevented the Mediterranean rainfalls from reaching the Central Anatolian Plateau. The separation of Spalax antiquus and S. graecus occurred when the southeastern Carpathians were uplifted. Despite the role played by tectonic events, branching events that show periodicity corresponding to 400-kyr and 100-kyr eccentricity bands illuminate the important role of orbital fluctuations on adaptive radiation in spalacids. At the given scale, our results supports the ‘‘Court Jester’’ hypothesis over the ‘‘Red Queen’’ one

On the 1/f Spectrum in the Solar Wind and Its Connection with Magnetic Compressibility

We discuss properties of Alfv\'enic fluctuations with large amplitude in plasmas characterised by low magnetic field compression. We note that in such systems power laws can not develop with arbitrarily steep slopes at large scales, i.e. when $|\delta \bf{B}|$ becomes of the order of the background field $|\bf{B}|$. In such systems there is a scale $l_0$ at which the spectrum has to break due to the condition of weak compressibility. A very good example of this dynamics is offered by solar wind fluctuations in Alfv\'enic fast streams, characterised by the property of constant field magnitude. We show here that the distribution of $\delta B=|\delta \bf{B}|$ in the fast wind displays a strong cut-off at $\delta B/|{\bf B}|\lesssim2$, as expected for fluctuations bounded on a sphere of radius $B=|{\bf B}|$. This is also associated with a saturation of the rms of the fluctuations at large scales and introduces a specific length $l_0$ above which the amplitude of the fluctuations becomes independent on the scale $l$. Consistent with that, the power spectrum at $l>l_0$ is characterised by a -1 spectral slope, as expected for fluctuations that are scale-independent. Moreover, we show that the spectral break between the 1/f and inertial range in solar wind spectra indeed corresponds to the scale $l_0$ at which \left\sim1. Such a simple model provides a possible alternative explanation of magnetic spectra observed in interplanetary space, also pointing out the inconsistency for a plasma to simultaneously maintain $|\bf{B}|\sim$const. at arbitrarily large scales and satisfy a Kolmogorov scaling.Comment: 6 pages, 5 figures, Accepted by The Astrophysical Journal Letter

Moonraker: enceladus multiple flyby mission

Stars and planetary system

Moonraker — Enceladus Multiple Flyby Mission

Enceladus, an icy moon of Saturn, possesses an internal water ocean and jets expelling ocean material into space. Cassini investigations indicated that the subsurface ocean could be a habitable environment having a complex interaction with the rocky core. Further investigation of the composition of the plume formed by the jets is necessary to fully understand the ocean, its potential habitability, and what it tells us about Enceladus's origin. Moonraker has been proposed as an ESA M-class mission designed to orbit Saturn and perform multiple flybys of Enceladus, focusing on traversals of the plume. The proposed Moonraker mission consists of an ESA-provided platform with strong heritage from JUICE and Mars Sample Return and carrying a suite of instruments dedicated to plume and surface analysis. The nominal Moonraker mission has a duration of ∼13.5 yr. It includes a 23-flyby segment with 189 days allocated for the science phase and can be expanded with additional segments if resources allow. The mission concept consists of investigating (i) the habitability conditions of present-day Enceladus and its internal ocean, (ii) the mechanisms at play for the communication between the internal ocean and the surface of the South Polar Terrain, and (iii) the formation conditions of the moon. Moonraker, thanks to state-of-the-art instruments representing a significant improvement over Cassini's payload, would quantify the abundance of key species in the plume, isotopic ratios, and the physical parameters of the plume and the surface. Such a mission would pave the way for a possible future landed mission