In this work a wavelet spectral study of a time series of brightest fireballs is presented. The wavelet analysis shows that are two solar periodicities around 27 and 13.5 days. These periodicities ...have been associated to Carrington rotation and lunar motions and indicate that both Solar and Lunar rotations could have an influence on the brightest fireballs fall on Earth. A third periodicity around 2.5 days was also identified in almost all spectra but it could be a harmonic of those periods.
We have extended our earlier model (Mendis et al., 2005) for the study of the dynamical, thermal and charging history of micrometeoroids entering the earth's atmosphere, by taking into account the ...role of sputtering, which is important for high‐speed ones. As before we confine ourselves to motion in the night side of the earth. In this short note we will not discuss these, but will confine our attention to the limited, yet important, effect of electron production in the atmosphere, by three different classes of micrometeoroids (fast—“cometary,” average—“cometary,” and slow—“asteroidal”). It is seen that the altitude profiles of the electron production, which lead to the radar signatures of these bodies, are different, not just quantitatively but also qualitatively. This is due to the different relative importance of the three processes responsible for electron production, namely the ones associated with ablation and sputtering of the infalling micrometeoroid and thermionic electron emission from it. It is seen that sputtering‐associated electron production is the dominant process, particularly at higher altitudes, for the fast micrometeoroid (initial entry speed 60 km/s), ablation‐associated electron production is the dominant process for the average one (initial entry speed 30 km/s), while thermionic electron emission is the dominant process for the slow one (initial entry speed 12.5 km/s).
A NEW PROPOSAL OF THE TERM METEOROID Cordero-Tercero, G.; Maravilla, D.; Covarrubias-Saavedra, M.
Revista mexicana de astronomía y astrofísica,
10/2023, Letnik:
59, Številka:
2
Journal Article
Recenzirano
Odprti dostop
In this document we briefly review the evolution of the term meteoroid and we make several proposals for a definition, emphasizing the importance of the criteria used for it. Finally, we propose a ...definition based on observations rather than on the instrument of observation.
In 1992 the Ulysses spacecraft discovered periodic dust streams escaping from the Jovian system. In 2000, M. Horanyi proposed that the escaping dust streams are not a particular feature of the Jovian ...system and predicted streams of dust particles escaping from Saturn as well. In this work we apply an analytical model, already applied to Jupiter (Maravilla et al., 1995), in order to analyze two possible and different sources: On the one hand the satellites Dione, Helene, Rhea and Enceladus; on the second, the A‐ring outer boundary. Additionally, some general properties of the dust particles that compose these Saturnian streams, such as their radii and escaping speeds, are drawn.
Minimum extreme temperature series from several meteorological stations of the Gulf of Mexico are spectrally analyzed using the Maximum Entropy Method.
We obtained significant periodicities similar ...to those found in meteorological and solar activity phenomena. This indicates that probably the solar activity signals are present in the minimum extreme temperature records of this Mexican region.
Micrometeoroids entering the terrestrial atmosphere lead to two important related electrical effects. One is the electrification of the upper atmosphere along their paths and the other is the ...electrical charging of the micrometeoroids themselves. In this brief note we will emphasize the central role of the initial encounter speed of the incoming micrometeoroid, showing how it changes the altitude profiles of electron production and electrical charging, not just quantitatively but also qualitatively. We will discuss the underlying reasons for this, as well as their importance in meteor studies.
The motion of charged circumplanetary dust particles under the combined influence of gravitational and electrodynamic forces of comparable magnitude (“gravito-electrodynamics”) was first discussed by ...Mendis and Axford (1974) over 25 years ago. This area got a major boost in the early eighties with the Voyager spacecraft observation of peculiar dust features in Saturn's rings (e.g. the so called “spokes”) which could not be explained by gravitational forces alone but could be easily explained by the inclusion of electrodynamic forces on the fine dust grains which were necessarily electrically charged. Since then the progress in the field has been steady with applications also to the dust tails of comets. More recently the role of gravito-electrodynamics in the solar system was underscored by the Ulysses and Galileo observation of periodic, collimated beams of high speed grains emanating from Jupiter. In this brief review I will discuss these as well as the possible role of electrical charging on the transport of dust (Al
2O
3 spherules) injected in large quantities into the terrestrial magnetosphere during solid rocket propellant burns. I will conclude with some comments on the role of gravitoelectrodynamic effects on the fine dust forming a circum-solar ring around 4 solar radii.
A two-dimensional model is analyzed in order to study the dynamical behavior of dust particles which are localized near the Sun, in particular at 4 solar radii. The equation of motion which describes ...the dynamics includes several forces; gravitational, Lorentz and radiation pressure. Also sublimation and gas drags are taken into account. Electrostatic charge is not constant in this model and both collisional and Coulomb drags are included in the equation of motion. It has been assumed that the solar magnetic field is radial outside the source surface. Some numerical results of the equation of motion are presented.
Dust escape mechanism from Io Flandes, A.; Maravilla, D.
Advances in space research,
2004, 2004-00-00, 20040101, Letnik:
34, Številka:
11
Journal Article
Recenzirano
The analysis done of the data obtained by Ulysses and Galileo spacecrafts throughout the Jovian system has confirmed that dust that escapes from Jupiter in collimated streams proceeds from volcanic ...ejections produced in Io. The volcanoes eject a mixture of dust and gases of sulfur and oxygen. Although the speeds of the ejections are just near a half of the escape velocity, the volcanic material escapes. It has been inferred that electromagnetic forces might play an important role in order to understand the physical mechanism that allows some dust particles (grains) to escape from Io.
Dust escape from Io must accomplish at least three different conditions: first of all, grains must have a micrometer size, grains must acquire a minimum electrostatic charge and third, they must get a high enough altitude to be in contact with the surrounding Jovian plasma and being dragged. In this investigation we obtain three results: the maximum and minimum ejection velocities of 15 Ionian known plumes, the maximum escape radii for grains emitted in those plumes and the maximum time of permanence for such dust particles before they escape from the Jovian environment considering a single particle model.
Three data series from different meteorological stations in northern Mexico are spectrally analyzed in order to look for solar activity signals. The series cover a period from January 1929 to ...December 1974. From the spectral analysis a periodicity of around 5 years is present in all the series, which can be considered as a harmonic of the sunspot number. Other periodicities can be related either to some solar phenomena like cosmic ray fluxes, storm sudden commencements, solar magnetic flux emergence and geomagnetic activity, or to meteorological phenomena like the quasi-biennial oscillation.
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