•State of the art of the lithosphere–atmosphere–ionosphere coupling (LAIC) mechanisms.•Earthquake-related case studies are shown together with unrelated cases.•Models of LAIC are proposed with future ...trends of research.
A systematic multi-parameter and multi-platform approach to study the slow process of earthquake preparation is fundamental to gain some insights on this complex phenomenon. In particular, an important contribution is the integrated analysis between ground geophysical data and satellite data. In this paper we review some of the more recent results and suggest the next directions of this kind of research. Our intention is not to detect a particular precursor but to understand the physics underlying the various observations and to establish a reliable physical model of the preparation phase before an impending earthquake. In this way, future investigation will search for suitable fore-patterns, which the physical model of multi-layers coupling predicts and characterizes by quasi-synchronism in time and geo-consistency in space. We also present alternative explanations for some anomalies which are not actually related to earthquakes, rather to other natural or anthropic processes.
The ATHENA X-ray observatory is the second large-class mission in the ESA Cosmic Vision 2015–2025 science programme. One of the two on-board instruments is the X-IFU, an imaging spectrometer based on ...a large array of TES microcalorimeters. To reduce the particle-induced background, the spectrometer works in combination with a cryogenic anticoincidence detector (CryoAC), placed less than 1 mm below the TES array. The last CryoAC single-pixel prototypes, namely AC-S7 and AC-S8, are based on large-area (1
cm
2
) silicon absorbers sensed by 65 parallel-connected iridium TES. This design has been adopted to improve the response generated by the athermal phonons, which will be used as fast anticoincidence flag. The latter sample is featured also with a network of aluminum fingers directly connected to the TES, designed to further improve the athermals collection efficiency. In this paper, we will report the main results obtained with AC-S8, showing that the additional fingers network is able to increase the energy collected from the athermal part of the pulses (from the 6% of AC-S7 up to the 26 % with AC-S8). Furthermore, the finger design is able to prevent the quasiparticle recombination in the aluminum, assuring a fast pulse rising front (
L
/
R
limited). In our road map, the AC-S8 prototype is the last step before the development of the CryoAC demonstration model, which will be the detector able to demonstrate the critical technologies expected in the CryoAC development programme.
ATHENA is a large X-ray observatory, planned to be launched by ESA in 2028 towards an L2 orbit. One of the two instruments of the payload is the X-IFU: a cryogenic spectrometer based on a large array ...of TES microcalorimeters, able to perform integral field spectrography in the 0.2–12 keV band (2.5 eV FWHM at 6 keV). The X-IFU sensitivity is highly degraded by the particle background expected in the L2 orbit, which is induced by primary protons of both galactic and solar origin, and mostly by secondary electrons. To reduce the particle background level and enable the mission science goals, the instrument incorporates a Cryogenic AntiCoincidence detector (CryoAC). It is a 4 pixel TES based detector, placed < 1 mm below the main array. In this paper we report a scientific assessment of the CryoAC observational capabilities in the hard X-ray band (E > 10 keV). The aim of the study has been to understand if the present detector design can be improved in order to enlarge the X-IFU scientific capability on an energy band wider than the TES array. This is beyond the CryoAC baseline, being this instrument aimed to operate as anticoincidence particle detector and not conceived to perform X-ray observations.
Terrestrial gamma ray flashes (TGFs) are very short bursts of gamma radiation associated to thunderstorm activity and are the manifestation of the highest‐energy natural particle acceleration ...phenomena occurring on Earth. Photon energies up to several tens of megaelectronvolts are expected, but the actual upper limit and high‐energy spectral shape are still open questions. Results published in 2011 by the AGILE team proposed a high‐energy component in TGF spectra extended up to ≈100 MeV, which is difficult to reconcile with the predictions from the Relativistic Runaway Electron Avalanche (RREA) mechanism at the basis of many TGF production models. Here we present a new set of TGFs detected by the AGILE satellite and associated to lightning measurements capable to solve this controversy. Detailed end‐to‐end Monte Carlo simulations and an improved understanding of the instrument performance under high‐flux conditions show that it is possible to explain the observed high‐energy counts by a standard RREA spectrum at the source, provided that the TGF is sufficiently bright and short. We investigate the possibility that single high‐energy counts may be the signature of a fine‐pulsed time structure of TGFs on time scales ≈4 μs, but we find no clear evidence for this. The presented data set and modeling results allow also for explaining the observed TGF distribution in the (Fluence × duration) parameter space and suggest that the AGILE TGF detection rate can almost be doubled.
Key Points
TGFs detected by AGILE with counts energy larger than 40 MeV are compatible with RREA
Data show no evidence of a fine time structure of TGFs on microsecond time scale.
TGFs simultaneous to lightning suggest that the AGILE TGF sample can be significantly increased
AGILE is a mission of the Italian Space Agency (ASI) Scientific Program dedicated to γ-ray astrophysics, and has operated in a low Earth orbit since 2007 April 23. It is designed to be a very light ...and compact instrument, capable of simultaneously detecting and imaging photons in the 18-60 keV X-ray energy band and in the 30 MeV-50 GeV γ-ray energy range with a good angular resolution ( 1◦ @ 1 GeV). The core of the instrument is the Silicon Tracker, supplemented by a CsI calorimeter and an AntiCoincidence system, which form the Gamma Ray Imaging Detector (GRID). Before launch, the GRID needed on-ground calibration with a tagged γ-ray beam to estimate its performance and validate the Monte Carlo simulation. The GRID was calibrated using a tagged γ-ray beam with energy up to 500 MeV at the Beam Test Facilities at the INFN Laboratori Nazionali di Frascati. These data are used to validate a GEANT 3-based simulation by comparing the data and the Monte Carlo simulation by measuring the angular and energy resolutions. The GRID angular and energy resolutions obtained using the beam agree well with the Monte Carlo simulation. Therefore the simulation, can be used to simulate the same performance on-flight with high reliability.
The mini-calorimeter of the AGILE satellite can observe the high-energy part of gamma-ray bursts with good timing-capability. We present the data of the 85 hard gamma-ray bursts observed by the ...mini-calorimeter since the launch (April 2007) until October 2009. We report the timing data for 84 and spectral data for 21 bursts.
The ATHENA X-IFU development program foresees to build and characterize an instrument Demonstration Model (DM), in order to probe the system critical technologies before the mission adoption. In this ...respect, we are now developing the DM of the X-IFU Cryogenic AntiCoincidence Detector (CryoAC), which will be delivered to the Focal Plane Assembly development team for the integration with the TES array. Before the delivery, we will characterize and test the CryoAC DM in our CryoLab at INAF/IAPS. In this paper, we report the main results of the activities performed to improve our cryogenic test setup, making it suitable for the DM integration. These activities mainly consist in the development of a mechanical setup and a cryogenic magnetic shielding system, whose effectiveness has been assessed by FEM simulations and a measurement at warm. The preliminary performance test has been performed by means of the last CryoAC single-pixel prototype, the AC-S8 pre-DM sample.
We report on a multiwavelength observation of the blazar 3C 454.3 (which we dubbed crazy diamond) carried out on November 2007 by means of the astrophysical satellites AGILE, International Gamma-Ray ...Astrophysics Laboratory (INTEGRAL), Swift, the Whole Earth Blazar Telescope (WEBT) Consortium, and the optical-NIR telescope Rapid Eye Mount (REM). Thanks to the wide field of view of the AGILE satellite and its prompt alert dissemination to other observatories, we obtained a long (three weeks), almost continuous gamma -ray coverage of the blazar 3C 454.3 across 14 decades of energy. This broadband monitoring allows us to study in great detail light curves, correlations, time lags, and spectral energy distributions (SEDs) during different physical states. Gamma-ray data were collected during an AGILE pointing toward the Cygnus Region. Target of Opportunity (ToO) observations were performed to follow up the gamma -ray observations in the soft and hard X-ray energy bands. Optical data were acquired continuously by means of a preplanned WEBT campaign and through an REM ToO repointing. 3C 454.3 is detected at a ~19 sigma level during the three-week observing period, with an average flux above 100 MeV of F E > 100 MeV = (170 ± 13) X 10-8 photons cm-2 s-1. The gamma -ray spectrum can be fitted with a single power law with photon index Gamma GRID = 1.73 ± 0.16 between 100 MeV and 1 GeV. We detect significant day-by-day variability of the gamma -ray emission during our observations, and we can exclude that the fluxes are constant at the 99.6% (~2.9 sigma ) level. The source was detected typically around 40 deg off-axis, and it was substantially off-axis in the field of view of the AGILE hard X-ray imager. However, a five-day long ToO observation by INTEGRAL detected 3C 454.3 at an average flux of about F 20-200 keV = 1.49 X 10-3 photons cm-2 s-1with an average photon index of Gamma IBIS = 1.75 ± 0.24 between 20-200 keV. Swift also detected 3C 454.3 with a flux in the 0.3-10 keV energy band in the range (1.23-1.40) X 10-2 photons cm-2 s-1 and a photon index in the range Gamma XRT = 1.56-1.73. In the optical band, both WEBT and REM show an extremely variable behavior in the R band. A correlation analysis based on the entire data set is consistent with no time lags between the gamma -ray and the optical flux variations. Our simultaneous multifrequency observations strongly indicate that the dominant emission mechanism between 30 MeV and 30 GeV is dominated by inverse Compton scattering of relativistic electrons in the jet on the external photons from the broad line region.
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