361 research outputs found
Space Weathering on Near-Earth Objects investigated by neutral-particle detection
The ion-sputtering (IS) process is active in many planetary environments in
the Solar System where plasma precipitates directly on the surface (for
instance, Mercury, Moon, Europa). In particular, solar-wind sputtering is one
of the most important agents for the surface erosion of a Near-Earth Object
(NEO), acting together with other surface release processes, such as Photon
Stimulated Desorption (PSD), Thermal Desorption (TD) and Micrometeoroid Impact
Vaporization (MIV). The energy distribution of the IS-released neutrals peaks
at a few eVs and extends up to hundreds of eVs. Since all other release
processes produce particles of lower energies, the presence of neutral atoms in
the energy range above 10 eV and below a few keVs (Sputtered High-Energy Atoms
- SHEA) identifies the IS process. SHEA easily escape from the NEO, due to
NEO's extremely weak gravity. Detection and analysis of SHEA will give
important information on surface-loss processes as well as on surface elemental
composition. The investigation of the active release processes, as a function
of the external conditions and the NEO surface properties, is crucial for
obtaining a clear view of the body's present loss rate as well as for getting
clues on its evolution, which depends significantly on space weather. In this
work, an attempt to analyze the processes that take place on the surface of
these small airless bodies, as a result of their exposure to the space
environment, has been realized. For this reason a new space weathering model
(Space Weathering on NEO - SPAWN), is presented. Moreover, an instrument
concept of a neutral-particle analyzer specifically designed for the
measurement of neutral density and the detection of SHEA from a NEO is proposedComment: 36 page
Neutral Solar Wind Detector (NSWD) for Solar Orbiter
The Neutral Solar Wind Detector (NSWD), to be flown on board Solar Orbiter, consists of a neutral atom sensor able to detect and characterize (in terms of velocity and direction) the energetic neutrals flowing together the ionised particles within the solar wind, between âŒ0.05 keV/nuc and âŒ5 keV/nuc. This may be a stand-alone instrument (indicated as high priority augmentation payload in the Solar Orbiter PDD), but it is also suitable for inclusion in the solar wind particle package SWA.
The NSWD primary scientific objectives may be summarized as in the following:
âą observation of neutral solar wind flux;
âą velocity, density and temperature of the neutral solar wind;
⹠comprehension of solar Ly-α corona, i.e. deduction of solar wind plasma velocity distributions
anisotropy perpendicular and along the solar magnetic field lines from neutral solar wind
observations;
âą study of the solar wind acceleration region via the detection of the neutral solar wind
hydrogen atoms and investigation of the temporal and spatial details of the solar wind using
the co-aligned movement of the Solar Orbiter spacecraft with respect to the solar rotation;
âą observation of the fast and slow neutral solar wind in different solar conditions, potentially
including transitions regions and CMEs;
âą resolution of the "inner source" pick-up ion puzzle thought to originate from solar wind
plasma - dust interaction in the solar atmosphere region within 0.2 AU
Setting up of an experimental site for the continuous monitoring of water discharge, suspended sediment transport and groundwater levels in a mediterranean basin. Results of one year of activity
The study of suspended sediment transport requires continuous measurement of water discharge to better understand the sediment dynamics. Furthermore, a groundwater monitoring network can support the stream discharge measures, as it reveals how the interactions between surface water and groundwater may affect runoff and consequently sediment transport during flood events. An experimental site for the continuous monitoring of water discharge, suspended sediment transport and groundwater levels was set up in the Carapellotto basin (27.17 km2), which is located in Apulia, Southern Italy. Seven flood events that occurred in the operation timespan were covered with a full record of both water discharge and sediment concentration. Some monitoring problems, largely due to the clogging of the float by mud, suggested to improve the experimental set up. The results show high values of suspended sediments concentration which indicate the sub-basinâs key role in the sediment delivery to the whole river system, while counter-clockwise hysteresis loops are the most frequent due to the basin characteristics. The effects of the interaction between surface water and groundwater are related not only to the flood magnitude but also to the hydrogeological features in the hyporheic zone
Lineamientos generales para una propuesta didĂĄctica de FilosofĂa PolĂtica
Al enseñar filosofĂa surge una serie de preguntas ineludibles: quĂ© enseñar, cĂłmo y para quĂ©. En este trabajo intentaremos responder a estos interrogantes didĂĄcticos, centrĂĄndonos especĂficamente en la enseñanza de la FilosofĂa PolĂtica en el Bachillerato de Bellas Artes.En particular, en el presente artĂculo se propondrĂĄn ciertos lineamientos con el objetivo de incluir una unidad de FilosofĂa PolĂtica en los programas de sĂ©ptimo año de la mencionada instituciĂłn empleando como marco teĂłrico a la hermenĂ©utica de Gadamer, la cual representa a nuestro entender un enriquecimiento de la modalidad histĂłrica propuesta por G. Obiols y A. Cerletti para la enseñanza de la filosofĂa
Low energy high angular resolution neutral atom detection by means of micro-shuttering techniques: the BepiColombo SERENA/ELENA sensor
The neutral sensor ELENA (Emitted Low-Energy Neutral Atoms) for the ESA
cornerstone BepiColombo mission to Mercury (in the SERENA instrument package)
is a new kind of low energetic neutral atoms instrument, mostly devoted to
sputtering emission from planetary surfaces, from E ~20 eV up to E~5 keV,
within 1-D (2x76 deg). ELENA is a Time-of-Flight (TOF) system, based on
oscillating shutter (operated at frequencies up to a 100 kHz) and mechanical
gratings: the incoming neutral particles directly impinge upon the entrance
with a definite timing (START) and arrive to a STOP detector after a flight
path. After a brief dissertation on the achievable scientific objectives, this
paper describes the instrument, with the new design techniques approached for
the neutral particles identification and the nano-techniques used for designing
and manufacturing the nano-structure shuttering core of the ELENA sensor. The
expected count-rates, based on the Hermean environment features, are shortly
presented and discussed. Such design technologies could be fruitfully exported
to different applications for planetary exploration.Comment: 11 page
Geodetic Constraints on the 2014 M 6.0 South Napa Earthquake
On 24 August 2014, the M 6.0 South Napa earthquake shook much of the San Francisco Bay area, leading to significant damage in the Napa Valley. The earthquake occurred in the vicinity of the West Napa fault (122.313° W, 38.22° N, 11.3 km), a mapped structure located between the Rodgerâs Creek and Green Valley faults, with nearly pure rightâlateral strikeâslip motion (strike 157°, dip 77°, rake â169°; http://comcat.cr.usgs.gov/earthquakes/eventpage/nc72282711#summary, last accessed December 2014) (Fig. 1). The West Napa fault previously experienced an M 5 strikeâslip event in 2000 but otherwise exhibited no previous definitive evidence of historic earthquake rupture (Rodgers et al., 2008; Wesling and Hanson, 2008). Evans et al. (2012) found slip rates of âŒ9.5ââmm/yr along the West Napa fault, with most slip rate models for the Bay area placing higher slip rates and greater earthquake potential on the Rodgerâs Creek and Green Valley faults, respectively (e.g., Savage et al., 1999; dâAlessio et al., 2005; Funning et al., 2007)
Solar perturbations transits in Mercury exosphere
The link existing between the dayside Na exospheric patterns of Mercury and the solar wind-magnetosphere-surface interactions is investigated thanks to the synergy of Earth-based observations with the THEMIS solar telescope and the in-situ measurements of the Interplanetary Magnetic Field (IMF) and proton ïŹuxes at the magnetic cusp regions by MESSENGER. Frequently, two-peak patterns of variable intensity are observed, located at high latitudes in both hemispheres. Occasionally, Na signal is instead diïŹused above the sub-solar region. In a special case, the Na signal is diïŹused above the subsolar region, when the MESSENGER data detect the transit of two Coronal Mass Ejections (CMEs). Na emission patterns results to be clearly related to the solar wind conditions at Mercury. Hence, the Na exospheric patterns, observed from ground, could be considered as a natural monitor of solar disturbances when transiting near Mercury
The collapse of BĂĄrĂ°arbunga Caldera, Iceland
Lying below Vatnajökull ice cap in Iceland, BĂĄrĂ°arbunga stratovolcano began experiencing wholesale caldera collapse in 2014 August 16, one of the largest such events recorded in the modern instrumental era. Simultaneous with this collapse is the initiation of a plate boundary rifting episode north of the caldera. Observations using the international constellation of radar satellites indicate rapid 50 cm d^(â1) subsidence of the glacier surface overlying the collapsing caldera and metre-scale crustal deformation in the active rift zone. Anomalous earthquakes around the rim of the caldera with highly nondouble-couple focal mechanisms provide a mechanical link to the dynamics of the collapsing magma chamber. A model of the collapse consistent with available geodetic and seismic observations suggests that the majority of the observed subsidence occurs aseismically via a deflating sill-like magma chamber
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