G.V. Litvinenko, A.A. Konovalenko, H.O. Rucker, Studying of the quasi-similar structures appearing in the solar and Jovian dynamic spectra of decameter emission G.V. Litvinenko, A.A. Konovalenko, H.O. Rucker, V.E. Shaposhnikov, V.V. Zakharenko, V.N. Melnik, M. Panchenko, A.I. Brazhenko, V.V. Dorovskyy, V.V. Vinogradov, and Ph. Zarka

Introduction. The previous attempts for the study of the solar and the Jovian emission mechanism from the common positions were random, the presented work illustrates the possibilities and advantages of the systematic general approach for solving the corresponding problems as by the experimental as well as from theoretical point of view. The study of the Jupiter and the Sun decameter emission showed that in some cases on the dynamic spectra of both objects the structures appear that visually have similar shape. This fact allows assuming that it also could be possible to find some similarities of the plasma processes in the solar corona and in the Jovian magnetosphere. Here the solar features such as S-bursts, «drifting pairs», absorption bursts (“shadow effect”?) and zebra patterns as well as quasi-similar to them types of the Jovian sporadic decameter radiation are considered.

Instrumentation Radio telescope UTR-2, Kharkov, Ukraine antenna’s effective area about 105 m2, frequency range 8 – 32 MHz, one linear polarization. Radio telescope URAN-2, Poltava, Ukraine the antenna effective area is about 28000 m2, frequency range is 9 – 32 MHz, two linear polarizations. The digital receiver (DSP) frequency resolution 4 kHz, digital sampling 66 MHz, the dynamic range 90 dB.

Data processing algorithm for off-line data analysis at the post-processing stage Graphical interface for optimal construction and visualization of the dynamic spectra of the Jovian and solar radiation with the possibility of the further detailed analysis. Flexible control for a number of the dynamic spectra visualization parameters such as time-frequency sample decimation, averaging values, time and frequency resolution, dynamic range of the received signal power, palette, etc. Program unit for the construction of a two-dimensional time-frequency intensity profile along any selected event on the time-frequency plane. Software possibility for connecting several sequential files of raw data to extend the duration of the continuous fragment being analyzed.

Solar S-bursts Solar S-bursts observed on July 09, 2013 with 100 ms time resolution (UTR-2+DSP)

Jovian S-bursts Fragment of the S-burst storm of the Jovian decameter emission observed on February 22, 2015 with 100 ms time resolution, (UTR-2+DSP)

Comparison of the solar and the Jovian S-bursts parameters The solar S-burst Observed in the 30-80 MHz frequency range against a background of other solar radio activity. Have a narrow instantaneous frequency width from 30 to 200 kHz. Mainly have the negative frequency drift rate which varies from 0.5 MHz/s to 2 MHz/s (in rare cases S-bursts have positive drift). 4. The burst duration is 5 to 160 ms at a fixed frequency. 5. The frequency band-width occupied by burst is varied of 1 ÷ 10 MHz. 6. Have a pronounced circular polarization. The Jovian S-burst Observed in the 8-40 MHz frequency range. Have a narrow instantaneous frequency width from 10 to 300 kHz. Mainly have the negative frequency drift from 15 MHz/s to 25 MHz/s (in rare cases S- bursts have positive drift, f-type bursts). The burst duration is 1 to 100 ms at a fixed frequency. The frequency band-width occupied by burst is varied of 1 ÷ 10 MHz. Have a pronounced elliptic polarization.

Models proposed for the solar and the Jovian S-bursts The plasma emission mechanism is usually used for interpretation of the solar S-burst. Langmuir waves are generated at the local electron plasma frequency by fast electrons that penetrate into the solar coronal plasma. The Langmuir waves interacting with plasma particles and/or other plasma waves are transformed into electromagnetic waves. The negative frequency drift is explained by variation in the local plasma frequency when the electron beams move outside from dense to more rarefied layers of the solar corona. It is generally believed that the Jovian decameter S-bursts are generated by an electron cyclotron maser in extraordinary electromagnetic mode at frequencies close to the local electron gyrofrequency. Unlike the solar S-bursts, variations in the frequency of the Jovian S-bursts are caused by variations in the local electron gyrofrequency. As the frequency drift of the solar S-bursts, the negative frequency drift of the Jovian S-bursts is caused by the motion of the source.

It should be mentioned that there is one more species of the Jovian S- burst, which has a similar type in the solar radiation. These are the so- called Jovian narrow-band S-bursts observed by Krausche et al. (1976). The bursts occupy a narrow frequency range not exceeding 1–2 MHz, have an instantaneous frequency width of about 50 kHz, and a negative frequency drift of 27 MHz/s. The bursts can be observed as a train of pulses from several to tens of milliseconds. Barrow et al. (1976) observed a similar structure in the solar radio emission at a frequency of 264 MHz. Using the detected analogy, a plasma model of generation was proposed for both the Jovian and solar narrow-band S-bursts. While in the first case the generation takes place near the electron gyrofrequency, in the second case the generation is near the plasma frequency. The difference is due to specific features of the plasma in the Jovian magnetosphere and in the solar corona. The S-bursts negative drift rate in both cases is explained by the group delay of electromagnetic waves due to their propagation in a plasma with small refractive index.

Drifting pairs Solar linear drifting pairs with negative drift (July 9, 2013, UTR-2+DSP) The events in the Jovian radiation look as solar linear drifting pairs (November 27, 2009, UTR-2+DSP)

Solar and Jovian «drifting pairs» structures are similar only VISUALLY. Both emissions are a combination of two close drifting S-bursts with a constant delay time between the components. Solar «drifting pairs»: These events in the Sun emission as well as solar S-bursts are associated with solar storms of type III bursts. Consist of two radiation bands, such that at the fine-structure level the features in one band are repeated in another. The lifetime and time delay of the components were almost the same. The frequency drift is usually 0.5–2 MHz/s. Jovian «drifting pairs»: The time delay is about a few milliseconds, much shorter then in solar. They have only a negative frequency drift (5–20 MHz/s). Unlike the solar drifting pairs have different internal structures in two close S-bursts.

Melrose [Melrose, D. B. , & Sy, W Melrose [Melrose, D.B., & Sy, W. 1971] suggested that solar «drifting pairs» present a combination of S-bursts. According to his assumption in case there are two rays reflected from a duct wall a «drift pair» is observed. It is considered by the authors that Melrose theory for solar «drifting pairs» can be successfully used for the Jovian emission as Jovian «drifting pairs» evidently consist of DAM S-bursts.

Absorption bursts («shadow effect») Solar absorption burst July 9, 2013, UTR-2+DSP Jovian absorption burst November 11, 2009, UTR-2+DSP

Combination of the L- and S-burst components of the Jovian emission S- bursts S- bursts L- emission L- emission L- emission L- emission A sequence containing a different number of events. The time duration of one absorption burst varies over the frequency (decrease with frequency increase). The average duration of a single event varies from tens to hundreds of microseconds and the frequency band changes from 0.5 to 1 MHz.

Quasi –harmonic narrow-band structure at the fixed frequency

Zebra structures in the solar emission Chen et al., 2011 Decimeter range

Dynamic spectra of kilometric radiation from Jupiter with five distinctive stripes of enhanced brightness (W.S. Kurth, Cassini RPWS Team). 17

Zebra structures in the Jovian emission Jovian zebra-structure in decameter range (January 30, 2014, URAN-2)

Comparative analysis for parameters of the zebra structures in the solar and Jovian emissions shows that both structures show identical properties: a) the structures represent a number of quasi-equidistant stripes of enhanced brightness with parallel drift in time; b) the structures are observed on a minute time scale; c) frequency spacing between the stripes slightly increases with increasing frequency. The deep analogy between the zebra patterns (ZP) from the Sun and Jupiter implies a similarity of mechanisms responsible for the origin of both structures.

Conclusion 1. The presence of some quasi-similar features in radio emission from the Sun and the Jupiter permits to carry out a comparative study of these phenomena using the experience of research in the solar and magnetospheric physics. 2. Analysis of the physical models allows trying to explain the existing analogy for explanation of the solar radiation properties in the researches of the Jovian emission and vice versa. 3. The differences in details can be connected with the peculiarities of the plasma parameters of the Jovian magnetosphere and the solar corona. Despite a large number of theoretical studies in this field of research, the mechanism for many processes occurring in the magnetosphere and ionosphere of the Jupiter and the plasma environment of the Sun is not fully elaborated. A successful use of the marked analogies will enable to improve the existing theories and develop new ones. .