Description:    Nature of the photometric phase curves of the regolith like surfaces (like those of the asteroids) are believed to be dependent on the single particle characteristics like particle size, shape, composition etc. and physical characteristics of the surface like porosity and roughness. Most of the phase curves have a rapid surge of intensity at small phase angles (typically below 5 ° ) known as opposition effect, followed by a linear less decreasing trend at larger phase angles. Average intensity of the linear region has been found to be mostly dependent on the average particle size and its composition, in many laboratory observations. Generally, it is difficult to explain the nature of light scattering by an ensemble of irregular shaped inhomogeneous particles with a theoretical model, just by studying the phase curves. In the present work, we have investigated whether the theoretically expected variation of the scattered light intensity (at a given phase angle) with the average particle size of the grains constituting regoliths, for a given material of the particle is in agreement with the experimental results or not? If yes, this can be a simpler but efficient way to study light scattering by regolith like surfaces. For theoretical analysis, Hapke formula has been used with Mie theory for single particle phase function, where we have neglected the influence of porosity and roughness presently. The data are also fitted with an empirical formula. It has been found that this empirical formula may also be used to estimate the unknown average particle size of a real regolith with known composition. Content Type Journal Article Pages 1-9 DOI 10.1007/s11038-011-9384-5 Authors D. Deb, Department of Physics, Assam University, Silchar, 788011 Assam, India A. K. Sen, Department of Physics, Assam University, Silchar, 788011 Assam, India Journal Earth, Moon, and Planets Online ISSN 1573-0794 Print ISSN 0167-9295

Description:    Acoustic radiation is the signal of choice for exploring Earth’s oceans. Its potential application for the oceans of icy moons requires investigation. However acoustic technology needs to be treated with care for extra-terrestrial purposes. Instruments, calibrations, and predictive codes that have served well on Earth may require fundamental redesign for use on other worlds. However when such an assessment is achieved, acoustic signals open up the possibility of exploring volumes exceeding one million cubic kilometres in a few minutes. This paper begins at tutorial level for novice acousticians, illustrating the principles by which acoustics can be used to monitor the environment at great distances from the source, both by projecting out signals and by using natural signals of opportunity. It then progresses to calculations for a generic icy moon (which resembles, but does not model Europa), proceeding from tutorial calculations of ‘flat world’ models to calculate the propagation times for pulses to circumpropagate around the entire moon. Given that a single emitted pulse can produce multiple arrivals from different propagation paths, the paper discusses how the structure of the received time history can be used to monitor changes in the temperature profile in the ocean, position of the water/ice layer and the asphericity of the moon during orbit. Content Type Journal Article Pages 1-26 DOI 10.1007/s11038-012-9399-6 Authors T. G. Leighton, Faculty of Engineering and the Environment, Institute of Sound and Vibration Research, University of Southampton, Highfield, Southampton, SO17 1BJ UK P. R. White, Faculty of Engineering and the Environment, Institute of Sound and Vibration Research, University of Southampton, Highfield, Southampton, SO17 1BJ UK D. C. Finfer, Faculty of Engineering and the Environment, Institute of Sound and Vibration Research, University of Southampton, Highfield, Southampton, SO17 1BJ UK Journal Earth, Moon, and Planets Online ISSN 1573-0794 Print ISSN 0167-9295

Description:    The paper is devoted to calculation of the precessional effect of the orbit of a two-body system in its geodesic motion through the deformed spacetime of a third body assumed non-rotating. The obtained result is generic, in that no specific assumption on the orbit geometry is made Content Type Journal Article Pages 1-5 DOI 10.1007/s11038-012-9402-2 Authors G. Renzetti, Pescara, Italy Journal Earth, Moon, and Planets Online ISSN 1573-0794 Print ISSN 0167-9295

Description: Using the observed attributes of the Hoba meteorite, that it is a single mass which survived impact intact, we investigate the possible conditions leading to its fall. Specifically, we asses the scenario in which the Hoba progenitor is envisioned as encountering Earth’s atmosphere at a shallow angle of entry, with a low velocity and stabilized profile to the oncoming airflow. In order to physically survive impact we find, via the planar impact approximation, that the Hoba meteorite must have landed with a speed smaller than a few hundred meters per second. We find that the envisioned model can satisfy, in its extreme limit of low entry speed, maximum area profile and near horizontal entry angle the required landing conditions. We deduce that the progenitor mass for the Hoba meteorite was likely of order 5 × 10 5  kg, and that a simple impact crater, now eroded, having a diameter of some 20 m and a depth of about 5 m was produced upon impact. We estimate that the typical arrival time interval for such massive, Hoba-like meteorite falls is of order 5 × 10 6  years.

Description: The aim of this paper is studying the relation between the coronal mass ejections (CMEs), and their associated solar flares. I used the CMEs data (obtained from CME catalogue) which observed by SOHO/LASCO, during the Solar Cycle 23rd (1996–2006), during this period I selected 12,433 CME records. Also I used the X-ray flares data which provided geostationary operational environmental satellite (GOES), during the same interval in the 1–8 Å GOES channel, the recorded flare events are 22,688. I filtered these CMEs and solar flare events to select 529 CME-Flare events. I found that there is a moderate relation between the solar flare fluxes and their associated CME energies, where R = 58 %. In addition I found that 61 % of the CME-Flare associated events ejected from the solar surface after the occurrence of the associated flare. Furthermore I found that the CME-Flare relation improved during the period of high solar activity. Finally, I examined the CME association rate as a function of flare longitude and I found that the CME association rate of the total 529 selected CME-Flare events are mostly disk-Flare events.

Description: We present here a detailed explanation of the reduction method that we use to determine the angular diameters of the stars occulted by the dark limb of the moon. This is a main part of the lunar occultation observation program running at King Abdul Aziz University observatory since late 1993. The process is based on the least square model fitting method of analyzing occultation data, first introduced by Nather et al. (Astron. J. 75:963, 1970 ).

Description: Simultaneous, also called electrophonic sounds were widely reported by eye-witnesses to the Chelyabinsk fireball. The available data indicate that such sounds were heard at ranges to at least ~100 km from the fireball’s atmospheric path. We estimate that the fireball may have generated of order 625 W of energy in the form of very low frequency radiation, and we find some tentative evidence to indicate that the acoustic conversion efficiency at a 100 km range was of order 0.1 %. Numerical simulations of the atmospheric flight path indicate that electrophonic sounds should have commenced some 5 s after the fireball first became luminous and would have lasted for some 7.5 s prior to the moment of catastrophic break-up.

Description: We analyzed spectra, trajectories, orbits, light curves, and decelerations of eight Draconid meteors observed from Northern Italy on October 8, 2011. Meteor morphologies of two of the meteors are also presented, one of them obtained with a high resolution camera. Meteor radiants agree with theoretical predictions, with a hint that some meteors may belong to the pre-1900 meteoroid trails. The spectra confirm that Draconids have normal chondritic composition of main elements (Mg, Fe, Na). There are, nevertheless, differences in the temporal evolution of Na line emission. The differences are correlated with the shapes of the light curves and the deceleration rates. Our data confirm that Draconids are porous conglomerates of grains, nevertheless, significant differences in the atmospheric fragmentation of cm-sized Draconids were found. Various textures with various resistance to fragmentation exist among Draconid meteoroids and even within single meteoroids.

Description: On 8 October 2011, the Draconid meteor shower (IAU \(\#8\) , DRA) was predicted to cause two brief outbursts of meteors, visible from locations in Europe. For the first time, a European airborne meteor observation campaign was organized, supported by ground-based observations. Two aircraft were deployed from Kiruna, Sweden, carrying six scientists, 19 cameras and eight crew members. The flight geometry was chosen such that it was possible to obtain double-station observations of many meteors. The instrument setup on the aircraft as well as on the ground is described in full detail. The main peak from 1900-dust ejecta happened at the predicted time and at the predicted rate. The second peak was observed from the earlier flight and from the ground, and was caused most likely by trails ejected in the nineteenth century. A total of 250 meteors were observed, for which light curve data were derived. The trajectory, velocity, deceleration and orbit of 35 double station meteors were measured. The magnitude distribution index was high, as a result of which there was no excess of meteors near the horizon. The light curve proved to be extremely flat on average, which was unexpected. Observations of spectra allowed us to derive the compositional information of the Draconids meteoroids and showed an early release of sodium, usually interpreted as resulting from fragile meteoroids. Lessons learned from this experience are derived for future airborne meteor shower observation campaigns.

Description: Meteoroids are responsible for deposition of thousands of kilograms of annual mass flux in the Earth’s upper atmosphere but the disintegration mechanisms of these bodies, and hence their composition, still remains a subject of debate in the meteor radar community. The role and significance of fragmentation as a meteoroid disintegration mechanism has been of particular interest in the past few years but in contrast to the head echoes, relatively little work has been done to study the effect and extent of fragmentation on trail echoes observed by the high power large aperture radars. Using the 53 MHz Gadanki MST radar, we present examples of radar meteor trails whose evolution cannot be explained with just the aid of classical meteor ablation theory. These examples are analyzed and discussed on a case-by-case basis and it is reported that the evolution of these trails can be explained with the help of fragmentation. This study will form the basis for future modeling efforts of fragmenting meteor trails and has important implications on the form in which the meteoroid mass is deposited in the upper atmosphere.