Ablation in meteors

A comparison of theoretical calculations with the results of radar meteor observations shows that the theory of radio meteors satisfactorily represents observational data. Radar meteor observations are incompatible with the idea of low density for small meteoroids in the ablation process. The main mechanism of ablation is evaporation. During intensive evaporation, small meteoroids have a density close to that of usual stone meteorites

On the mechanism behind the fragmentation of tiny meteor bodies in the atmosphere

Fragmentation mechanism of small meteors during atmospheric entr

Meteoric phenomena in the earth's atmosphere. Investigations of meteors, no. 2

Meteoritic radiance and ionization observations in earth atmospher

The role of fragmentation in interaction of meteoroids with the Earth's atmosphere

As a rule, when analyzing the mechanism of quasi continuous fragmentation (QCF) it is assumed that fragments separated from the parent meteoroid (PM) are of equal initial mass. In reality, this may not be so. A major difficulty is the lack of observational data on the function of the fragment initial mass distribution and so one must resort to theoretical modeling. A discrete distribution is considered which excluded to a certain extent some mathematical difficulties. The calculation results are given and discussed

Mass Loss Due to Sputtering and Thermal Processes in Meteoroid Ablation

Conventional meteoroid theory assumes that the dominant mode of ablation is by evaporation following intense heating during atmospheric flight. In this paper we consider the question of whether sputtering may provide an alternative disintegration process of some importance.For meteoroids in the mass range from 10^-3 to 10^-13 kg and covering a meteor velocity range from 11 to 71 km/s, we numerically modeled both thermal ablation and sputtering ablation during atmospheric flight. We considered three meteoroid models believed to be representative of asteroidal (3300 kg m^-3 mass density), cometary (1000 kg m^-3) and porous cometary (300 kg m^-3) meteoroid structures. Atmospheric profiles which considered the molecular compositions at different heights were used in the sputtering calculations. We find that while in many cases (particularly at low velocities and for relatively large meteoroid masses) sputtering contributes only a small amount of mass loss during atmospheric flight, in some cases sputtering is very important. For example, a 10^-10 kg porous meteoroid at 40 km/s will lose nearly 51% of its mass by sputtering, while a 10^-13 kg asteroidal meteoroid at 60 km/s will lose nearly 83% of its mass by sputtering. We argue that sputtering may explain the light production observed at very great heights in some Leonid meteors. The impact of this work will be most dramatic for very small meteoroids such as those observed with large aperture radars.Comment: in pdf form, 48 pgs incl figures and table

Strong E region ionization caused by the 1767 trail during the 2002 Leonids

Intensive E region ionization extending up to 140 km altitude and lasting for several hours was observed with the European Incoherent Scatter (EISCAT) UHF radar during the 2002 Leonids meteor shower maximum. The level of global geomagnetic disturbance as well as the local geomagnetic and auroral activity in northern Scandinavia were low during the event. Thus, the ionization cannot be explained by intensive precipitation. The layer was 30–40 km thick, so it cannot be classified as a sporadic E layer which are typically just a few kilometers wide. Incoherent scatter radars have not to date reported any notable meteor shower-related increases in the average background ionization. The 2002 Leonids storm flux, however, was so high that it might have been able to induce such an event. The Chemical Ablation Model is used to estimate deposition rates of individual meteors. The resulting electron production, arising from hyperthermal collisions of ablated atoms with atmospheric molecules, is related to the predicted Leonid flux values and observed ionization on 19 November 2002. The EISCAT Svalbard Radar (ESR) located at some 1000 km north of the UHF site did not observe any excess ionization during the same period. The high-latitude electrodynamic conditions recorded by the SuperDARN radar network show that the ESR was within a strongly drifting convection cell continuously fed by fresh plasma while the UHF radar was outside the polar convection region maintaining the ionization

Effect of paracetamol and celecoxib on the state of hemocoagulation in the most acute period of heat injury in rats

Acute heat injury (AHI) occurs due to exposure to high environmental temperatures and is considered a dangerous condition that requires effective prevention and treatment. This underscores the importance of searching for and thoroughly studying thermoprotective agents. Previous studies on a rat model of AHI have shown that the highly selective cyclooxygenase-2 (COX-2) inhibitor celecoxib and the analgesic-antipyretic paracetamol effectively prevent hyperthermia, but celecoxib, unlike paracetamol, improves the functional state of the central nervous system during the recovery period. Since AHI induces blood coagulation disturbances, it is important to determine the effects of these thermoprotective agents on hemostasis. The aim of this study was to investigate the effects of paracetamol and celecoxib as effective thermoprotectors on coagulation parameters during the acute phase of heat trauma in rats. The AHI model was reproduced оn adult white male rats through a 30-minute exposure to +55°C. The animals were divided into four groups of 7-8 rats each: intact control, pathological control, celecoxib group (8.4 mg/kg intragastrically 50-60 minutes before heat exposure), and paracetamol group (125 mg/kg in the same regimen). Rectal temperature was monitored, and in rat plasma, fibrinogen, prothrombin time (PT), thrombin time (TT), activated partial thromboplastin time (APTT) were determined, while D-dimer was measured in serum. The results showed that during the acute phase of AHI in the pathological control group, when body temperature increased by an average of 4.33±0.33°C (p<0.01 compared to baseline), fibrinogen, PT, TT, and APTT levels remained unchanged, but the D-dimer level in serum increased by 2.2 times, indicating enhanced thrombogenesis. Both celecoxib and paracetamol exhibited a statistically significant thermoprotective effect (temperature rise of 3.16±0.40°C and 3.21±0.12°C, respectively, p<0.01 compared to untreated animals), had no effect on fibrinogen, PT, TT, or APTT levels, but normalized the D-dimer level, indicating an antithrombotic effect. The results justify the use of COX inhibitors, particularly celecoxib, in AH

DESIGN OF AN INFORMATION SYSTEM FOR MONITORING AND ANALYZING THE RADIATION SITUATION AT THE PHRO OF THE SVERDLOVSK BRANCH OF THE UTO BRANCH OF THE FED

A comparison of the available software and justification of the choice of structure and software for the rapid assessment of the radiation situation at PRO of the Sverdlovsk branch of the branch "Urals territorial district" of the FSUE RosRAO based on the analysis of mon-itoring results

Orbit, emission spectrum, and photometric analysis of two flickering sporadic fireballs

We present the observations of two fireballs that exhibit fast and quasi-periodic brightness variations along their atmospheric path. This phenomenon, which is known as “flickering”, is associated to the entry of spinning non-spherical meteoroids into the atmosphere. Both bolides were imaged in the framework of the continuous fireball monitoring and meteor spectroscopy campaigns organized by the SPanish Meteor Network (SPMN) in 2012. Their atmospheric trajectory, radiant, and orbit were calculated. The preatmospheric mass and tensile strength of the parent meteoroids were also estimated, and the rotation of these bodies analyzed on the basis of the photometric behavior of the bolides. Although small (less than 80 grams), a non-zero terminal mass was determined for both events. The emission spectra produced during the ablation of the meteoroids in the atmosphere are also discussed