Zebra pattern in decametric radio emission of Jupiter

¹ Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
e-mail: Mykhaylo.Panchenko@oeaw.ac.at
² Commission for Astronomy, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
³ Institute of Geophysics, Gravimetric Observatory, 36014 Poltava, Ukraine
⁴ LESIA, Observatoire de Paris, CNRS, PSL, 92195 Meudon, France
⁵ Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS, PSL, Univ. Orléans, 18330 Nançay, France
⁶ Institute of Radio Astronomy, 61002 Kharkiv, Ukraine
⁷ Institute of Applied Physics, 603950 Nizhny Novgorod, Russia
⁸ National Research University High School of Economics, 603950 Nizhny Novgorod, Russia

Received: 13 June 2017
Accepted: 6 October 2017

Abstract

We report the systematic analysis of zebra-like fine spectral structures in decametric frequency range of Jovian radio emission. Observations were performed by the large ground-based radio telescope URAN-2 during three observation campaigns between, Sep., 2012, and May, 2015. In total, 51 zebra pattern (ZP) events were detected. These rare fine radio features are observed in frequency range from 12.5 to 29.7 MHz as quasi-harmonically related bands of enhanced brightness. ZPs are strongly polarized radio emission with a duration from 20 s to 290 s and flux densities ~10⁵−10⁶ Jy (normalized to 1 AU), that is, 1–2 orders lower than for Io-decametric radio emission (DAM). Occurrence of the events does not depend on the position of Io satellite but is strongly controlled by the Jovian central meridian longitude (CML). ZPs are mainly detected in two active sectors of Jovian CMLs: 100^∘ to 160^∘ for Northern sources (right-handed polarized) and 300^∘ and 60^∘ (via 360^∘) for the Southern sources (left-handed). The frequency interval between neighboring stripes is from 0.26 to 1.5 MHz and in most cases this interval increases with frequency. We discussed the double plasma resonance with electrons or ions as a possible source of the ZPs. The performed analysis of the observations allows us to conclude that the observed ZPs are a new type of narrow band spectral structures in the Jovian DAM.