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Why is the Microstructure of the Main Pulse and Inter Pulse of the Pulsar in Crab so Strikingly Different?
Proceedings of the XXXVI Conference "modern Problems for ExtraGalactic AStronomy", RF, April 21-26 (2019) (in Russian)

V.M. Kontorovich

In the remarkable work of Hankins and Ailek [1] it was discovered (to the surprise of the authors themselves *) the striking difference in the spectra of the MP (main pulse) and of the IP (inter pulse) at microsecond resolution. In particular, a wide frequency range was observed in the MP spectra, forming ?vertical structures?, while in the IP spectra at the same frequencies ?horizontal structures? with selected frequencies resembling the ?zebra structure? of solar radio bursts were observed. We offer a possible answer to this riddle. It consists in, as can be seen from multifrequency measurements (Moffett and Hankins [2]), in the vicinity of the measurement frequency of the microstructure, there is a change in the prevailing mechanisms of radio emission with growing of frequency. The subrelativistic mechanism of radiation with longitudinal acceleration is still valid for the MP (Kontorovich and Flanchik [3]). In this case, a flat in frequency radiation spectrum is formed, which corresponds to"vertical" microstructures and terminates (breaks off) at the inverse time of particle acceleration. Acceleration occurs from thermal to relativistic velocities in the accelerating electric field increasing from zero on the star's surface. For the MP this mechanism has already been turned off and replaced by another (relativistic) curvature radiation mechanism, which in an inclined magnetic field causes an IP shift (Kontorovich and Trofimenko [4]). Therefore, there are no ?vertical? microstructures in it. We do not discuss here the ?zebra structure?, the explanation of which are devoted various physical scenarios (see [5?8]) and whose connection with curvature radiation is not yet clear. 1. Hankins, T. H. & Eilek, J. A. Radio emission signatures in the Crab pulsar. ApJ. 670, 693, 2007. 2. Moffett D. and Hankins T. ApJ.1996. 468, 779. DOI: 10.1086/177734 3. Kontorovich, V. and Flanchik, A., High-frequency cutoff and change of radio emission mechanism in pulsars, Astrophysics and Space Science, 345, ? 1, 169, 2013.\ 4. V. M. Kontorovich and A. B. Flanchik, Correlation of Pulsar Radio Emission Spectrum with Peculiarities of Particle Acceleration in a Polar Gap, JETP, 116, #1, 80, 2013. 5. Kontorovich V. M. and Trofymenko S. V. J. Phys. Sci. Appl.. 7, No. 4, 11, 2017. 6. M. Lyutikov, Mon. Not. R. Astron. Soc. 381, 1190 (2007). 7. H. Ardavan, A. Ardavan, J. Singleton, and M. Perez, MNRAS, 388, 873, 2008. 8. V. V. Zheleznyakov, V. V. Zaitsev, and E. Ya. Zlotnik, Astron. Lett. 38, 589, 2012. 9. V. M. Kontorovich, Quantization of an Electromagnetic Tornado and the Origin of Bands in the Spectrum of Giant Pulses from the Crab Pulsar, Astronomy Letters, 40, No. 12, 793, 2014. ________________________________________ [*) ?In traditional pulsar models? the MP and IP should be the same in their observable quantities (such as spectrum, time signature, or dispersion). We were?and remain?quite surprised that this turns out not to be the case in the Crab pulsar.? From J. Eilek and T. Hankins paper [1].