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Youngdae Jung - One of the best experts on this subject based on the ideXlab platform.
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orientation phenomena for direct s p electron ion collisional excitations in weakly coupled plasmas using the screened Hyperbolic Orbit trajectory method
European Physical Journal D, 2000Co-Authors: Youngdae Jung, Jungsik YoonAbstract:Orientation phenomena for direct electron-ion collisional excitations in weakly coupled plasmas ( ) are investigated using the semiclassical curved trajectory method including the close-encounter effects. The results show that the orientation parameters including the close-encounter effects obtained by the Hyperbolic-Orbit trajectory method have maxima and minima for small impact parameter regions.
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antiscreening versus screening excitations for low energy ion ion collisions in dense plasmas using the screened Hyperbolic Orbit trajectory method
Physics of Plasmas, 1999Co-Authors: Jungsik Yoon, Youngdae JungAbstract:Plasma screening effects are investigated on antiscreening and screening channels for excitation of a one-electron target ion by a one-electron projectile ion in dense plasmas. In weakly coupled plasmas, the ion-ion interaction potential is given by the nonspherical Debye-Huckel model. The semiclassical screened Hyperbolic-Orbit trajectory method is applied to the path of the projectile ion in order to investigate the variation of the antiscreening and screening transition probabilities as functions of the impact parameter and collision energy. The results show that the antiscreening transition probability is always greater than the screening transition probability. It is found that the plasma screening effect on the antiscreening transition probability is more effective than that on the screening transition probability. The maximum position of the transition probability is getting closer to the target core with increasing projectile energy. The plasma screening effect on the antiscreening excitation cross section is also found to be stronger than that on the screening excitation cross section.
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bremsstrahlung in electron ion coulomb scattering in strongly coupled plasma using the Hyperbolic Orbit trajectory method
Physical Review E, 1996Co-Authors: Youngdae Jung, Hwandon JeongAbstract:Classical bremsstrahlung in electron-ion Coulomb scattering in strongly coupled plasmas is investigated using the classical curved trajectory method. In strongly coupled plasmas, the electron-ion interaction potential is obtained by the ion-sphere model potential. The modified Hyperbolic-Orbit trajectory method is applied to describe the motion of the projectile electron in order to investigate the variation of the differential bremsstrahlung radiation cross section as a function of the impact parameter and ion-sphere radius. The results show that the scaled doubly differential bremsstrahlung radiation cross sections have minima at the small impact parameter region for soft photon radiation. For hard photon radiation, the minima disappear. The impact parameter corresponding to the minimum position of the bremsstrahlung radiation cross section recedes from the center of the ion core as the ion-sphere radius increases. The radiation cross section is substantially reduced as the radiation energy increases, especially for the large ion-sphere radius. \textcopyright{} 1996 The American Physical Society.
Maria Hajdukova - One of the best experts on this subject based on the ideXlab platform.
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frequency of Hyperbolic and interstellar meteoroids
Meteoritics & Planetary Science, 2014Co-Authors: Maria Hajdukova, Leonard Kornos, Juraj TothAbstract:Hyperbolic meteor Orbits from the catalog of 64,650 meteors observed by the multistation video meteor network located in Japan (SonotaCo 2009) have been investigated with the aim of determining the relation between the frequency of Hyperbolic and interstellar meteors. The proportion of Hyperbolic meteors in the data decreased significantly (from 11.58% to 3.28%) after a selection of quality Orbits, which shows its dependence on the quality of observations. Initially, the Hyperbolic Orbits were searched for meteors unbound due to planetary perturbation. It was determined that 22 meteors from the 7489 Hyperbolic Orbits in the catalog (and 2 from the selection of the Orbits with the highest quality) had had a close encounter with a planet, none of which, however, produced essential changes in their Orbits. Similarly, the fraction of Hyperbolic Orbits in the data, which could be Hyperbolic by reason of a meteor's interstellar origin, was determined to be at most 3.9 × 10−2. From the statistical point of view, the vast majority of Hyperbolic meteors in the database have definitely been caused by inaccuracy in the velocity determination. This fact does not necessarily assume great measurement errors, since, especially near the parabolic limit, a small error in the value of the heliocentric velocity of a meteor can create an artificial Hyperbolic Orbit that does not really exist. The results show that the remaining 96% of meteoroids with apparent Hyperbolic Orbits belong to the solar system meteoroid population. This is also supported by their high abundance (about 50%) among the meteor showers.
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interstellar meteoroids in the japanese tv catalogue
Publications of the Astronomical Society of Japan, 2011Co-Authors: Maria HajdukovaAbstract:The present work is based on an analysis of the 14763 precise determined meteor Orbits collected in the Japanese tv catalogue (SonotaCo 2009), with the aim of determining the real proportion of interstellar meteors in this database. If interstellar meteors are present among the registered meteor Orbits, the distribution of the excesses of their heliocentric velocities should correspond to the distribution of the radial velocities of close stars. For the velocity vi = 20 km s 1 of an interstellar meteor, with respect to the Sun, we obtain a heliocentric velocity of vH = 46.6 km s 1 of an interstellar meteor arriving at Earth. Any error in the determination of vH , especially near the parabolic limit, can create an artificial Hyperbolic Orbit that does not really exist. The analysis of the data did not produce any convincing arguments in favour of the existence of true Hyperbolic meteors in the catalogue. It was shown that the vast majority of the 484 Hyperbolic Orbits has been caused by an overestimation of their velocity, and approximately 50% of them belong to meteor showers. Furthermore, the Hyperbolic excesses of the velocities in all cases are very low, about one order less than the velocity distribution of neighbouring stars suggest. The upper limit of the proportion of possible interstellar meteors to interplanetary ones among all investigated meteor Orbits in the database is 1.3 10 .
P Brown - One of the best experts on this subject based on the ideXlab platform.
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1i 2017 u1 oumuamua is hot imaging spectroscopy and search of meteor activity
The Astrophysical Journal, 2017Co-Authors: Qicheng Zhang, Michael S P Kelley, P BrownAbstract:1I/2017 U1 ('Oumuamua), a recently discovered asteroid in a Hyperbolic Orbit, is likely the first macroscopic object of extrasolar origin identified in the solar system. Here, we present imaging and spectroscopic observations of 'Oumuamua using the Palomar Hale Telescope as well as a search of meteor activity potentially linked to this object using the Canadian Meteor Orbit Radar. We find that 'Oumuamua exhibits a moderate spectral gradient of 10% ± 6% (100 nm)^(-1), a value significantly lower than that of outer solar system bodies, indicative of a formation and/or previous residence in a warmer environment. Imaging observation and spectral line analysis show no evidence that 'Oumuamua is presently active. Negative meteor observation is as expected, since ejection driven by sublimation of commonly known cometary species such as CO requires an extreme ejection speed of ~40 m s^(−1) at ~100 au in order to reach the Earth. No obvious candidate stars are proposed as the point of origin for 'Oumuamua. Given a mean free path of ~10^9 ly in the solar neighborhood, 'Oumuamua has likely spent a very long time in interstellar space before encountering the solar system.
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1i 2017 u1 oumuamua is hot imaging spectroscopy and search of meteor activity
arXiv: Earth and Planetary Astrophysics, 2017Co-Authors: Qicheng Zhang, Michael S P Kelley, P BrownAbstract:1I/2017 U1 (`Oumuamua), a recently discovered asteroid in a Hyperbolic Orbit, is likely the first macroscopic object of extrasolar origin identified in the solar system. Here, we present imaging and spectroscopic observations of \textquoteleft Oumuamua using the Palomar Hale Telescope as well as a search of meteor activity potentially linked to this object using the Canadian Meteor Orbit Radar. We find that \textquoteleft Oumuamua exhibits a moderate spectral gradient of $10\%\pm6\%~(100~\mathrm{nm})^{-1}$, a value significantly lower than that of outer solar system bodies, indicative of a formation and/or previous residence in a warmer environment. Imaging observation and spectral line analysis show no evidence that \textquoteleft Oumuamua is presently active. Negative meteor observation is as expected, since ejection driven by sublimation of commonly-known cometary species such as CO requires an extreme ejection speed of $\sim40$ m s$^{-1}$ at $\sim100$ au in order to reach the Earth. No obvious candidate stars are proposed as the point of origin for \textquoteleft Oumuamua. Given a mean free path of $\sim10^9$ ly in the solar neighborhood, \textquoteleft Oumuamua has likely spent a very long time in the interstellar space before encountering the solar system.
Jungsik Yoon - One of the best experts on this subject based on the ideXlab platform.
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orientation phenomena for direct s p electron ion collisional excitations in weakly coupled plasmas using the screened Hyperbolic Orbit trajectory method
European Physical Journal D, 2000Co-Authors: Youngdae Jung, Jungsik YoonAbstract:Orientation phenomena for direct electron-ion collisional excitations in weakly coupled plasmas ( ) are investigated using the semiclassical curved trajectory method including the close-encounter effects. The results show that the orientation parameters including the close-encounter effects obtained by the Hyperbolic-Orbit trajectory method have maxima and minima for small impact parameter regions.
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antiscreening versus screening excitations for low energy ion ion collisions in dense plasmas using the screened Hyperbolic Orbit trajectory method
Physics of Plasmas, 1999Co-Authors: Jungsik Yoon, Youngdae JungAbstract:Plasma screening effects are investigated on antiscreening and screening channels for excitation of a one-electron target ion by a one-electron projectile ion in dense plasmas. In weakly coupled plasmas, the ion-ion interaction potential is given by the nonspherical Debye-Huckel model. The semiclassical screened Hyperbolic-Orbit trajectory method is applied to the path of the projectile ion in order to investigate the variation of the antiscreening and screening transition probabilities as functions of the impact parameter and collision energy. The results show that the antiscreening transition probability is always greater than the screening transition probability. It is found that the plasma screening effect on the antiscreening transition probability is more effective than that on the screening transition probability. The maximum position of the transition probability is getting closer to the target core with increasing projectile energy. The plasma screening effect on the antiscreening excitation cross section is also found to be stronger than that on the screening excitation cross section.
J J Kavelaars - One of the best experts on this subject based on the ideXlab platform.
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col ossos colors of the interstellar planetesimal 1i oumuamua
The Astrophysical Journal, 2017Co-Authors: Michele T Bannister, Megan E Schwamb, Wesley C Fraser, Michael Marsset, A Fitzsimmons, Susan D Benecchi, Pedro Lacerda, Rosemary E Pike, J J KavelaarsAbstract:The recent discovery by Pan-STARRS1 of 1I/2017 U1 (`Oumuamua), on an unbound and Hyperbolic Orbit, offers a rare opportunity to explore the planetary formation processes of other stars, and the effect of the interstellar environment on a planetesimal surface. 1I/`Oumuamua's close encounter with the inner Solar System in 2017 October was a unique chance to make observations matching those used to characterize the small-body populations of our own Solar System. We present near-simultaneous g$^\prime$, r$^\prime$, and J photometry and colors of 1I/`Oumuamua from the 8.1-m Frederick C. Gillett Gemini North Telescope, and $gri$ photometry from the 4.2 m William Herschel Telescope. Our g$^\prime$r$^\prime$J observations are directly comparable to those from the high-precision Colours of the Outer Solar System Origins Survey (Col-OSSOS), which offer unique diagnostic information for distinguishing between outer Solar System surfaces. The J-band data also provide the highest signal-to-noise measurements made of 1I/`Oumuamua in the near-infrared. Substantial, correlated near-infrared and optical variability is present, with the same trend in both near-infrared and optical. Our observations are consistent with 1I/`Oumuamua rotating with a double-peaked period of $8.10 \pm 0.42$ hours and being a highly elongated body with an axial ratio of at least 5.3:1, implying that it has significant internal cohesion. The color of the first interstellar planetesimal is at the neutral end of the range of Solar System $g-r$ and $r-J$ solar-reflectance colors: it is like that of some dynamically excited objects in the Kuiper belt and the less-red Jupiter Trojans.