S.Ibadov1, F.S.Ibodov2, S.S. Grigoryan2
Astrophysics, Dushanbe, Tajikistan
2Moscow State University, Moscow, Russia
Coronagraphic observations by SOLWIND, SMM and SOHO missions indicate the presence of a continuous comet flow passing close to the solar surface or colliding with the Sun. The disintegration of nuclei of sungrazing comets by the solar photospheric thermal radiation leads to insignificant decrease in the cometary nucleus radius, amounting to no more than 20 meters.
Explosive evolution of nuclei of sungrazing comets near the solar surface, which occurs under the conditions of intense interaction between the solar atmosphere and infalling high-velocity cometary nuclei, as well as its relation to the character of solar activity, are analytically considered.
It is found that, due to aerodynamic fragmentation of the infalling body in the solar chromosphere and transversal expansion of the fragmented mass, stopping of the disk-like hypervelocity fragmented mass occurs within a relatively very thin photospheric layer and has, therefore, essentially impulsive and strongly explosive character.
The specific energy release in the explosion zone, erg/g, considerably exceeds the sublimation heat of the body, so that the process is accompanied by generation of a high-temperature plasma.
The energetics of such an explosive process corresponds to that of very large solar flares, for infalling bodies having masses equal to the mass of the nucleus of Comet Halley.
Spectral observations of sungrazing comets by SOHO-like telescopes in a wide spectral range, including X-rays, with a high time resolutions, of the order of 0.1-10 s, are important for revealing solar activity in the form of an impact-generated photospheric flare.