Saturn Anomalous Myriametric Radiation, a New Type of Saturn Radio Emission Revealed by Cassini

Abstract

A new radio component namely Saturn Anomalous Myriametric Radiation (SAM) is reported. A total of 193 SAM events have been identified by using all the Cassini Saturn orbital data. SAM emissions are L-O mode radio emission and occasionally accompanied by a first harmonic in R-X mode. SAM's intensities decrease with increasing distance from Saturn, suggesting a source near Saturn. SAM has a typical central frequency near 13 kHz, a bandwidth greater than 8 kHz and usually drifts in frequency over time. SAM's duration can extend to near 11 hr and even longer. These features distinguish SAM from the regular narrowband emissions observed in the nearby frequency range, hence the name anomalous. The high occurrence rate of SAM after low frequency extensions of Saturn Kilometric Radiation and the SAM cases observed during compressions of Saturn's magnetosphere suggest a special connection to solar wind dynamics and magnetospheric conditions at Saturn.

Rotational Modulation of the High Frequency Limit of Saturn Kilometric Radiation

“…Y. Wu et al, 2021), Saturn Anomalous Myriametric radiation (below 30 kHz, S. Y. Wu et al, 2022b), and the O mode SKR (below 100 kHz, , which are superimposed and mixed with the SKR emissions from time to time, we eliminate the data with frequencies below 200 kHz. Because the O mode SKR emissions are only marginally observed with weaker intensity and the occurrence is relatively rare , the possible high frequency O mode SKR emissions are simply ignored.…”

“…Secondly, to mitigate the contamination from low‐frequency O mode emissions, for example, Saturn narrowband emissions (mostly below 70 kHz and mainly near 5 and 20 kHz, Ye et al., 2009; S. Y. Wu et al., 2021), Saturn Anomalous Myriametric radiation (below 30 kHz, S. Y. Wu et al., 2022b), and the O mode SKR (below 100 kHz, Lamy, Zarka, Cecconi, Prangé, et al., 2008), which are superimposed and mixed with the SKR emissions from time to time, we eliminate the data with frequencies below 200 kHz. Because the O mode SKR emissions are only marginally observed with weaker intensity and the occurrence is relatively rare (Lamy, Zarka, Cecconi, Prangé, et al., 2008), the possible high frequency O mode SKR emissions are simply ignored.…”

Time-frequency catalogue: JSON implementation and python library

“…TFCat has already been used in several published data collections (Cecconi et al, 2021b;Fogg et al, 2021;Louis et al, 2021;Taubenschuss et al, 2021;Smith et al, 2022;Wu et al, 2021, Wu et al, 2022b, Wu et al, 2022a. In order to showcase the capabilities of the TFCat format and its python implementation, 3 Jupyter notebook tutorials have been prepared, and are available in Cecconi et al (2022a) The TFCat model and python library are used in the SPectrogram Analysis and Cataloguing Environment (SPACE) Labelling Tool (Louis et al, 2022).…”

“…The TFCat (Time-Frequency Catalogue) specification has been developed with the aim of facilitating the recording, rese and processing of low frequency radio temporal-spectral events. In the past two years, several catalogues have been published using the TFCat format, and tools are now implementing interfaces on top of this specification, for labelling observations, displaying catalogues, or even using the catalogue shapes to select and process observational data (Cecconi et al, 2021a;Fogg et al, 2021;Louis et al, 2021;Taubenschuss et al, 2021;Wu et al, 2021, Wu et al, 2022b, Wu et al, 2022a.…”