Light curves and photometric parameters of the comets C/1999 S4 (LINEAR), C/2001 Q4 (NEAT), C/2002 T7 (LINEAR), C/2002 V1 (NEAT), C2004 Q2 (Machholz), and 153P/2002 C1 (Ikeya-Zhang)

Light curves of six comets, C/1999 S4 (LINEAR), C/2001 Q4 (NEAT), C/2002 T7 (LINEAR), C/2002 V1 (NEAT), C/2004 Q2 (Machholz), and 153P/2002 C1 (Ikeya-Zhang), were built and investigated. The photometric parameters H ₀, H ₁₀, and n were calculated for these comets, and they were found to change both before and after perihelion. The shift of light curve peak with respect to perihelion passage moment was determined for each comet. Our white-light curves are compared to the results of polarimetric and electrophotometric observations of the comets C/2002 T7 (LINEAR) and C/2004 Q2 (Machholz).     

The light curve of the comet 9P/Tempel 1: Temporal evolution from 1867 till 2005

The light curves of the periodic comet 9P/Tempel 1 obtained during its apparitions in 1972, 1983, 1994, and 2005 have been constructed and studied. The values of the photometric parameters H ₀, n, and H ₁₀ have been determined for these apparitions; and secular variations of the comet’s brightness have been studied. The light curve of the comet obtained close to the moment of the artificial impact agrees well with the change in the production rate of water molecules. The presented results are important from the point of the possible change in the photometric parameters induced by the artificial impact and the long-term evolution of the cometary core activity.     

Peculiarities of Cometary Light Curves and Outburst Activity

We give an overview of the main results of our works on the revision of cometary light curves and on the search for new patterns and features in the evolution of the integrated brightness of comets as they move in circumsolar space. These works revealed several new, previously unknown phenomena in the integrated-brightness variations and outburst activity of comets. Our results supplement and expand the body of observational data that provides a basis for constructing a model of the cometary nucleus and developing a theory of the cometary evolution.     

Secular brightness variations of periodic comets as a result of desintegration of their icy-dust nuclei and the solar activity

Results are presented from studies of the features of secular brightness fading for 18 short-period comets. The results by Sekanina are supplemented by new data on periodic-comet apparitions after 1964. Annual and orbital-period variations in the absolute magnitude for each comet, as well as the corresponding average values are determined. A statistically significant effect of the 90-year solar activity cycle on secular variations in the integrated magnitudes of short-period comets is found. The corresponding correlation coefficient is 0.81.     

Light Curves of Selected Comets: Photometric Parameters and Flares

The light curves of four comets were constructed and analyzed. The photometric parameters H _yand nwere determined. The derived values of H _yand nwere compared with those obtained by other authors. The parameter nfor Comet Ikeya–Secchi was found to vary. A list of flares in these comets was compiled.     

Radio Emission of Meteor Bodies in the Extremely Low Frequency Range

Solar System Research - A model for generating electromagnetic fields in the ELF/VLF range accompanying the final stage of the evolution of meteorites in the Earth’s atmosphere is presented....     

High-Frequency Radio Emission from Meteors

A model of the processes that explain the intrinsic radio emission from meteors is proposed. A method for solving a self-similar problem of a strong explosion is used to determine certain parameters of the plasma wake dynamics at the initial expansion stages. Calculations show that this plasma expansion stage is responsible for the incoherent and unpolarized radiation from the meteor in the upper layers of the atmosphere. A theoretical estimate of the spectral density of the radio emission flux is obtained within this model, and it coincides with the experimental values. The radiation maximum is in the high-frequency range and strongly depends on the altitude and parameters of the meteor. For example, for the characteristic properties of the atmosphere at an altitude of about 90 km for a meteor with a mass of ~5 × 10^–2 kg, the spectral flux is ~2000 W/m² Hz at ~100 km from the source and the maximum is at ~40–60 MHz. According to the experiment, the radio emission spectrum drops sharply at higher frequencies.