Observation of Periodic Rising and Falling Tone ECH Waves at Saturn

Teng, Shang‐Hua; Wu, Yifan; Guo, Ruilong; Yao, Zhen‐Xing; Tao, X.

doi:10.1029/2021gl094559

Cited by 5 publications

(4 citation statements)

References 48 publications

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“…Such frequency chirping has also been observed in several other wave modes, including whistler mode chorus waves (Tsurutani & Smith, 1974), magnetosonic waves (Boardsen et al, 2014;Fu et al, 2014), electron cyclotron harmonic waves (S. Liu et al, 2023;Shen et al, 2021;Teng et al, 2021) in the magnetosphere and Alfvén waves (Heidbrink, 2008;Heidbrink & Sadler, 1994;McGuire et al, 1983) in fusion plasmas. These chirping waves generally consist of discrete packets that are narrowband and quasi-coherent (Tsurutani et al, 2009).…”

mentioning

confidence: 71%

“…Although the linear instability of EMIC waves is well understood and typically related to temperature anisotropy in the inner magnetosphere (Gary et al., 1996; Gendrin et al., 1984), some EMIC waves exhibit nonlinear frequency chirping, in the form of spontaneous rising‐tone emissions (Mursula et al., 1994; Pickett et al., 2010). Such frequency chirping has also been observed in several other wave modes, including whistler mode chorus waves (Tsurutani & Smith, 1974), magnetosonic waves (Boardsen et al., 2014; Fu et al., 2014), electron cyclotron harmonic waves (S. Liu et al., 2023; Shen et al., 2021; Teng et al., 2021) in the magnetosphere and Alfvén waves (Heidbrink, 2008; Heidbrink & Sadler, 1994; McGuire et al., 1983) in fusion plasmas. These chirping waves generally consist of discrete packets that are narrowband and quasi‐coherent (Tsurutani et al., 2009).…”

Section: Introductionmentioning

confidence: 80%

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Frequency Chirping of Electromagnetic Ion Cyclotron Waves in Earth's Magnetosphere

An,

Tao,

Zonca

et al. 2024

Geophysical Research Letters

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Electromagnetic ion cyclotron (EMIC) waves are known to exhibit frequency chirping occasionally, contributing to the rapid acceleration and precipitation of energetic particles in the magnetosphere. However, the chirping mechanism of EMIC waves remains elusive. In this work, a phenomenological model of whistler mode chorus waves named the Trap‐Release‐Amplify (TaRA) model is applied to EMIC waves. Based on the proposed model, we explain how the chirping of EMIC waves occurs, and give predictions on their frequency chirping rates. For the first time, we relate the frequency chirping rate of EMIC waves to both the wave amplitude and the background magnetic field inhomogeneity. Direct observational evidence is provided to validate the model using previously published events of chirping EMIC waves. Our results not only provide a new model for EMIC wave frequency chirping, but more importantly, they indicate the potential wide applicability of the underlying principles of TaRA model.

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confidence: 71%

Section: Introductionmentioning

confidence: 80%

Frequency Chirping of Electromagnetic Ion Cyclotron Waves in Earth's Magnetosphere

An,

Tao,

Zonca

et al. 2024

Geophysical Research Letters

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“…Saturnʼs magnetosphere hosts a variety of plasma waves, e.g., whistler-mode waves (Menietti et al 2013(Menietti et al , 2014Woodfield et al 2022), electron cyclotron harmonic (ECH) waves (Tao et al 2010;Menietti et al 2017;Long et al 2021;Teng et al 2021), and Z-mode waves (Ye et al 2009(Ye et al , 2010Menietti et al 2016;Wu et al 2021). Via resonant wave-particle interactions, these waves are recognized to contribute significantly to the local acceleration and loss of Saturnʼs radiation belt electrons (e.g., Menietti et al 2012;Gu et al 2013;Kollmann et al 2018;Woodfield et al 2018Woodfield et al , 2019Yu et al 2019;Yao et al 2021;Woodfield et al 2022).…”

Section: Introductionmentioning

confidence: 99%

Statistics of Water-group Band Ion Cyclotron Waves in Saturn's Inner Magnetosphere Based on 13 yr of Cassini Measurements

Long

Cao

et al. 2022

ApJ

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Based on Cassini observations from 2004 to 2016, we perform a comprehensive analysis of the statistical distribution of the occurrence rate, averaged amplitude, wave normal angle (WNA), ellipticity, and power spectral intensity of ion cyclotron waves in Saturn's inner magnetosphere. Our results show that ion cyclotron waves mainly occur between the orbits of Enceladus and Dione near the equatorial region (∣λ∣ < 20°), with higher occurrence rates in the northern hemisphere than the southern hemisphere. The averaged wave amplitudes vary between 0.1 and 2 nT with a strong day–night asymmetry and a pronounced minimum at the equator. Saturnian ion cyclotron waves are predominantly left-handed polarized with small WNAs near the equator and become linearly polarized with larger WNAs at higher latitudes. The major wave power occurs frequently at frequencies of 0.5–1.2 f w + , where f w + is the equatorial gyrofrequency of H2O+ ions, with the strongest intensity (>∼10 nT2 Hz−1) at L ∼ 6.5 statistically present in the midnight sector.

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“…In their study, the average duration of the ECH frequency-chirping structures is about 40 s with a chirping rate of about 50 Hz/s, which is very different from the chorus waves. In Saturn's magnetosphere, ECH frequency chirping structures can last several minutes with a chirping rate of ∼Hz/s (Teng et al, 2021). Analysis of burst mode data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) suite (Kletzing et al, 2013) indicates that the duration and chirping rate of ECH rising tones can be comparable with chorus (Gao et al, 2018(Gao et al, , 2020.…”

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confidence: 99%

Statistical Study on Spatial Distribution of Frequency‐Chirping ECH Elements by Van Allen Probes

Liu,

Chen,

Yang

et al. 2023

Geophysical Research Letters

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Electron cyclotron harmonic (ECH) waves can scatter electrons into the atmosphere causing diffuse aurora with diffusion coefficients depending on the wave frequency. Here we report the Van Allen Probe observations of chirping ECH elements, which are fine structures with a frequency‐chirping rate of ∼kHz/s. 1,834 samples are identified in the 51‐month database and over 93 percent of them exhibit a falling tone pattern. ECH elements cover a broad region from 18 Magnetic Local Time (MLT) through dawn to 14 MLT with L = 4 − 7, and mainly occur in the region of 00–07 MLT with L = 5 − 6. More ECH elements are observed with the occurrence region extending to lower L‐shells during the geomagnetic activity period. Chirping ECH elements can propagate to |MLAT| ∼ 20°, but be confined by the contour of magnetic field strength. The statistical results can be applied on the global simulation of ECH‐induced electron penetration.

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Observation of Periodic Rising and Falling Tone ECH Waves at Saturn

Abstract: Rising and falling tone electron cyclotron harmonic (ECH) waves are first reported at Saturn • The discrete elements of falling tone ECH waves last for either several minutes or seconds • The element properties of ECH waves are compared with those observed at Earth

Cited by 5 publications

References 48 publications

Frequency Chirping of Electromagnetic Ion Cyclotron Waves in Earth's Magnetosphere

Frequency Chirping of Electromagnetic Ion Cyclotron Waves in Earth's Magnetosphere

Statistics of Water-group Band Ion Cyclotron Waves in Saturn's Inner Magnetosphere Based on 13 yr of Cassini Measurements

Statistical Study on Spatial Distribution of Frequency‐Chirping ECH Elements by Van Allen Probes

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