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Search Results: 1 - 10 of 219564 matches for " C. Plainaki "
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Solar cosmic rays during the extremely high ground level enhancement on 23 February 1956
A. Belov, E. Eroshenko, H. Mavromichalaki, C. Plainaki,V. Yanke
Annales Geophysicae (ANGEO) , 2005,
Abstract: The 23 February 1956 ground level enhancement of the solar cosmic ray intensity (GLE05) is the most famous among the proton events observed since 1942. But we do not have a great deal of information on this event due to the absence of solar wind and interplanetary magnetic field measurements at that time. Furthermore, there were no X-Ray or gamma observations and the information on the associated flare is limited. Cosmic ray data was obtained exclusively by ground level detectors of small size and in some cases of a non-standard design. In the present work all available data from neutron monitors operating in 1956 were analyzed, in order to develop a model of the solar cosmic ray behavior during the event. The time-dependent characteristics of the cosmic ray energy spectrum, cosmic ray anisotropy, and differential and integral fluxes have been evaluated utilizing different isotropic and anisotropic models. It is shown that the most outstanding features of this proton enhancement were a narrow and extremely intense beam of ultra-relativistic particles arriving at Earth just after the onset and the unusually high maximum solar particle energy. However, the contribution of this beam to the overall solar particle density and fluency was not significant because of its very short duration and small width. Our estimate of the integral flux for particles with energies over 100 MeV places this event above all subsequent. Perhaps the number of accelerated low energy particles was closer to a record value, but these particles passed mainly to the west of Earth. Many features of this GLE are apparently explained by the peculiarity of the particle interplanetary propagation from a remote (near the limb) source. The quality of the available neutron monitor data does not allow us to be certain of some details; these may be cleared up by the incorporation into the analysis of data from muonic telescopes and ionization chambers operating at that time. Keywords. Interplanatary physics (Cosmic rays; Energetic particles) – Solar physics, astrophysics and astronomy (Flares and mass injections) Full Article (PDF, 1072 KB) Citation: Belov, A., Eroshenko, E., Mavromichalaki, H., Plainaki, C., and Yanke, V.: Solar cosmic rays during the extremely high ground level enhancement on 23 February 1956, Ann. Geophys., 23, 2281-2291, doi:10.5194/angeo-23-2281-2005, 2005. Bibtex EndNote Reference Manager XML
Neutral particle release from Europa's surface
C. Plainaki,A. Milillo,A. Mura,S. Orsini,T. Cassidy
Physics , 2009, DOI: 10.1016/j.icarus.2010.06.041
Abstract: In this paper, we look at space weathering processes on the icy surface of Jupiter's moon Europa. The heavy energetic ions of the Jovian plasma (H+, O+, S+, C+) can erode the surface of Europa via ion sputtering (IS), ejecting up to 1000 H2O molecules per ion. UV Photons impinging the Europa's surface can also result in neutral atom release via photon-stimulated desorption (PSD) and chemical change (photolysis). In this work, we study the efficiency of the IS and PSD processes for ejecting water molecules, simulating the resulting neutral H2O density. We also estimate the contribution to the total neutral atom release by the Ion Backscattering (IBS) process. Moreover, we estimate the possibility of detecting the sputtered high energy atoms, in order to distinguish the action of the IS process from other surface release mechanisms. Our main results are: 1) The most significant sputtered-particle flux and the largest contribution to the neutral H2O-density come from the incident S+ ions; 2) The H2O density produced via PSD is lower than that due to sputtering by ~1.5 orders of magnitude; 3) In the energy range below 1 keV, the IBS can be considered negligible for the production of neutrals, whereas in the higher energy range it becomes the dominant neutral emission mechanism; 4) the total sputtering rate for Europa is 2.0\cdot 1027 H2O s-1; 5) the fraction of escaping H2O via IS is 22% of the total sputtered population, while the escape fraction for H2O produced by PSD is 30% of the total PSD population. Since the PSD exosphere is lower than the IS one, the major agent for Europa's surface erosion is IS on both the non-illuminated and illuminated side. Lastly, the exospheric neutral density, estimated from the Galileo electron density measurements appears to be higher than that calculated for H2O alone; this favours the scenario of the presence of O2 produced by radiolysis and photolysis.
Solar activity and the associated ground level enhancements of solar cosmic rays during solar cycle 23
M. Andriopoulou, H. Mavromichalaki, P. Preka-Papadema, C. Plainaki, A. Belov,E. Eroshenko
Astrophysics and Space Sciences Transactions (ASTRA) , 2011, DOI: 10.5194/astra-7-439-2011
Abstract: The solar cycle 23 seems to be of great interest for the researchers due to many peculiarities. A study of the parameters of the sixteen ground level enhancements recorded during the approximately 12-year period of it (1996–2008) together with the associated solar activity, including the main properties of the solar flares, the coronal mass ejections and the radio bursts has been realized, in an effort to understand the connection of these events. All studied cases seem to be connected with very intense flares of long duration, having a mean importance value of X5.9 and a mean duration of 164.5 min, with either halo or partial halo coronal mass ejections with a mean linear velocity of 1876 km/sec, as well as with intense radio bursts. It is also noticed that the ground level enhancements of the 23rd solar cycle occurred after the onset time of the associated solar X-ray flares with a mean time delay of about 38 min, very useful result for their monitoring and prediction.
A new version of the Neutron Monitor Based Anisotropic GLE Model : Application to GLE60
C. Plainaki,H. Mavromichalaki,A. Belov,E. Eroshenko,M. Andriopoulou,V. Yanke
Physics , 2009, DOI: 10.1007/s11207-010-9576-6
Abstract: In this work we present a cosmic ray model that couples primary solar cosmic rays at the top of the Earth's atmosphere with the secondary ones detected at ground level by neutron monitors during Ground Level Enhancements (GLEs). The Neutron Monitor Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) Model constitutes a new version of the already existing NMBANGLE Model, differing in the solar cosmic ray spectrum assumed. The total output of the model is a multi-dimensional GLE picture that reveals part of the characteristics of the big solar proton events recorded at ground level. We apply both versions of the model to the GLE of 15 April 2001 (GLE60) and compare the results.
Space Weathering on Near-Earth Objects investigated by neutral-particle detection
C. Plainaki,A. Milillo,S. Orsini,A. Mura,E. De Angelis,A. M. Di Lellis,E. Dotto,S. Livi,V. Mangano,S. Massetti,M. E. Palumbo
Physics , 2008, DOI: 10.1016/j.pss.2008.12.002
Abstract: 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 proposed
Space Storm Measurements of 17 and 21 April 2002 Forbush Effects from Artemis-IV Solar Radio-Spectrograph, Athens Neutron Monitor Station and Coronas-F Satellite
C. Caroubalos,X. Moussas,P. Preka-Papadema,A. Hillaris,I. Polygiannakis,H. Mavromichalaki,C. Sarlanis,G. Souvatzoglou,M. Gerontidou,C. Plainaki,S. Tatsis,S. N. Kuznetsov,I. N. Myagkova,K. Kudela
Physics , 2010,
Abstract: In this report we present two complex eruptive solar events and the associated Cosmic Ray effects (Forbush decrease). We use combined recordings from a number of Earthbound Receivers, Space Experiments and data archives (such as the ARTEMIS-IV Radio spectrograph, the Athens NEUTRON MONITOR, the LASCO CME Lists, the SONG of the {CORONAS-F} satellite, etc.). The influence of solar transients on the interplanetary medium conditions and the cosmic ray flux is analysed and discussed. The observed time sequence of events of this time period indicates that the initiation of CMEs is closely related to the appearance of type II and IV radio bursts and strong solar flares. Their effects extend from the lower corona to the near Earth vicinity affecting Cosmic Ray measurements and space weather. As regards the Forbush decrease our data indicate significant amplification at the presence of a MHD shock.
Predictions of local ground geomagnetic field fluctuations during the 7-10 November 2004 events studied with solar wind driven models
Mavromichalaki, Souvatzoglou, Sarlanis, Mariatos, Gerontidou, Papaioannou, Plainaki, Tatsis, Belov, Eroshenko,Yanke
Annales Geophysicae (ANGEO) , 2005,
Abstract: The ground-based neutron monitors (NMs) record galactic and solar relativistic cosmic rays which can play a useful key role in space weather forecasting, as a result of their interaction with interplanetary disturbances. The Earth's-based neutron monitor network has been used in order to produce a real-time prediction of space weather phenomena. Therefore, the Athens Neutron Monitor Data Processing Center (ANMODAP) takes advantage of this unique multi-directional device to solve problems concerning the diagnosis and forecasting of space weather. At this moment there has been a multi-sided use of neutron monitors. On the one hand, a preliminary alert for ground level enhancements (GLEs) may be provided due to relativistic solar particles and can be registered around 20 to 30 min before the arrival of the main part of lower energy particles responsible for radiation hazard. To make a more reliable prognosis of these events, real time data from channels of lower energy particles and X-ray intensity from the GOES satellite are involved in the analysis. The other possibility is to search in real time for predictors of geomagnetic storms when they occur simultaneously with Forbush effects, using hourly, on-line accessible neutron monitor data from the worldwide network and applying a special method of processing. This chance of prognosis is only being elaborated and considered here as one of the possible uses of the Neutron Monitor Network for forecasting the arrival of interplanetary disturbance to the Earth. The achievements, the processes and the future results, are discussed in this work.
The Influence of Space Environment on the Evolution of Mercury
Stefano Orsini,Valeria Mangano,Alessandro Mura,Diego Turrini,Stefano Massetti,Anna Milillo,Christina Plainaki
Physics , 2014, DOI: 10.1016/j.icarus.2014.05.031
Abstract: Mercury, due to its close location to the Sun, is surrounded by an environment whose conditions may be considered as "extreme" in the entire Solar System. Both solar wind and radiation are stronger with respect to other Solar System bodies, so that their interactions with the planet cause high emission of material from its surface. Moreover, the meteoritic precipitation plays a significant role in surface emission processes. This emitted material is partially lost in space. Although under the present conditions the surface particles loss rate does not seem to be able to produce significant erosion of the planetary mass and volume, the long-term effects over billions of years should be carefully considered to properly understand the evolution of the planet. In the early stages, under even more extreme conditions, some of these processes were much more effective in removing material from the planet's surface. This study attempts to provide a rough estimation of the material loss rate as a function of time, in order to evaluate whether and how this environmental effect can be applied to understand the Hermean surface evolution. We show that the most potentially effective Sun-induced erosion process in early times is a combination of ion sputtering, photon stimulated desorption and enhanced diffusion, which could have caused the loss of a surface layer down to a depth of 20 m, as well as a relevant Na depletion.
The Comparative Exploration of the Ice Giant Planets with Twin Spacecraft: Unveiling the History of our Solar System
Diego Turrini,Romolo Politi,Roberto Peron,Davide Grassi,Christina Plainaki,Mauro Barbieri,David M. Lucchesi,Gianfranco Magni,Francesca Altieri,Valeria Cottini,Nicolas Gorius,Patrick Gaulme,Fran?ois-Xavier Schmider,Alberto Adriani,Giuseppe Piccioni
Physics , 2014, DOI: 10.1016/j.pss.2014.09.005
Abstract: In the course of the selection of the scientific themes for the second and third L-class missions of the Cosmic Vision 2015-2025 program of the European Space Agency, the exploration of the ice giant planets Uranus and Neptune was defined "a timely milestone, fully appropriate for an L class mission". Among the proposed scientific themes, we presented the scientific case of exploring both planets and their satellites in the framework of a single L-class mission and proposed a mission scenario that could allow to achieve this result. In this work we present an updated and more complete discussion of the scientific rationale and of the mission concept for a comparative exploration of the ice giant planets Uranus and Neptune and of their satellite systems with twin spacecraft. The first goal of comparatively studying these two similar yet extremely different systems is to shed new light on the ancient past of the Solar System and on the processes that shaped its formation and evolution. This, in turn, would reveal whether the Solar System and the very diverse extrasolar systems discovered so far all share a common origin or if different environments and mechanisms were responsible for their formation. A space mission to the ice giants would also open up the possibility to use Uranus and Neptune as templates in the study of one of the most abundant type of extrasolar planets in the galaxy. Finally, such a mission would allow a detailed study of the interplanetary and gravitational environments at a range of distances from the Sun poorly covered by direct exploration, improving the constraints on the fundamental theories of gravitation and on the behaviour of the solar wind and the interplanetary magnetic field.
The ODINUS Mission Concept - The Scientific Case for a Mission to the Ice Giant Planets with Twin Spacecraft to Unveil the History of our Solar System
Diego Turrini,Romolo Politi,Roberto Peron,Davide Grassi,Christina Plainaki,Mauro Barbieri,David M. Lucchesi,Gianfranco Magni,Francesca Altieri,Valeria Cottini,Nicolas Gorius,Patrick Gaulme,Fran?ois-Xavier Schmider,Alberto Adriani,Giuseppe Piccioni
Physics , 2014,
Abstract: The purpose of this document is to discuss the scientific case of a space mission to the ice giants Uranus and Neptune and their satellite systems and its relevance to advance our understanding of the ancient past of the Solar System and, more generally, of how planetary systems form and evolve. As a consequence, the leading theme of this proposal will be the first scientific theme of the Cosmic Vision 2015-2025 program: What are the conditions for planetary formation and the emergence of life? In pursuing its goals, the present proposal will also address the second and third scientific theme of the Cosmic Vision 2015-2025 program, i.e.: How does the Solar System work? What are the fundamental physical laws of the Universe? The mission concept we will illustrate in the following will be referred to through the acronym ODINUS, this acronym being derived from its main fields of scientific investigation: Origins, Dynamics and Interiors of Neptunian and Uranian Systems. As the name suggests, the ODINUS mission is based on the use of two twin spacecraft to perform the exploration of the ice giants and their regular and irregular satellites with the same set of instruments. This will allow to perform a comparative study of these two systems so similar and yet so different and to unveil their histories and that of the Solar System.
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