Ratio Between Discrete IAR Frequencies From Observations in the Solar Cycle 24

Potapov, A. S.; Guglielmi, A. V.; Klain, B. I.

doi:10.1109/tgrs.2022.3170473

Cited by 6 publications

(24 citation statements)

References 26 publications

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“…In Section 3, we use non-uniform Alfvén velocity profiles to model the individual harmonics and in Section 4 we demonstrate how the individual harmonics are extracted from the spectrograms. To analyze the results of the model alongside the data, we start by calculating the offset of the fundamental frequency from Δf in Section 5 and then compare the results with the uniform Alfvén velocity profile analysis of Hebden et al (2005) and Potapov et al (2022) in Section 6. We conclude in Section 7.…”

Section: Plain Language Summarymentioning

confidence: 99%

“…They suggested the lower boundary lay between being a node and an antinode-though generally closer to a node-and that further work was needed to determine the relationship between Φ and the conditions at the lower boundary. Potapov et al (2022) have also examined the properties of the lower boundary, by assuming a uniform ionosphere and calculating the ratio between the harmonic frequencies of the IAR, for the first five harmonics. Like Hebden et al (2005), Potapov et al (2022) considered the two uniform cases in Figure 1.…”

Section: Uniform Models Of Iar Alfvén Velocitymentioning

confidence: 99%

“…Potapov et al (2022) have also examined the properties of the lower boundary, by assuming a uniform ionosphere and calculating the ratio between the harmonic frequencies of the IAR, for the first five harmonics. Like Hebden et al (2005), Potapov et al (2022) considered the two uniform cases in Figure 1. They presented the ratios of the frequencies in a triangular matrix, where the first row represents the ratio of the frequencies of the higher harmonics with the fundamental, the second row is the ratio between the higher harmonics and the first harmonic, and so on.…”

Section: Uniform Models Of Iar Alfvén Velocitymentioning

confidence: 99%

“…Using observations from Mondy (mid‐latitude in south‐eastern Russia) for the years 2009–2019, Potapov et al. (2022) selected 12 days of data from each year and found the frequencies of the first five harmonics. Potapov et al.…”

Section: Uniform Models Of Iar Alfvén Velocitymentioning

confidence: 99%

“…Potapov et al. (2022) calculated the matrix T ij and the determinant, ensuring that the fundamental was used. They found that the average determinant calculated from all observations was 8.35, which is closest to 9, suggesting that the lower boundary of the IAR has a node in the electric field (and hence an antinode in the magnetic field).…”

Section: Uniform Models Of Iar Alfvén Velocitymentioning

confidence: 99%

See 4 more Smart Citations

Modeling and Observations of the Effects of the Alfvén Velocity Profile on the Ionospheric Alfvén Resonator

Hodnett,

Yeoman,

Beggan

et al. 2024

JGR Space Physics

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We have modeled the individual harmonic frequencies of the Ionospheric Alfvén Resonator (IAR) at Eskdalemuir by solving a one‐dimensional wave equation and using non‐uniform modeled Alfvén velocity profiles. By comparing the results of the modeling alongside harmonics obtained from the Eskdalemuir, UK, data set from 2013 to 2021, the effects of the non‐uniformity of the Alfvén velocity profile on the IAR are considered. We calculated the offset between the fundamental frequency and the harmonic frequency separation and found that this is not constant. From this parameter, we infer that the lower boundary condition of the electric field of the IAR is closest to a node, which agrees with previous studies. We compare the results of the non‐uniform model with previous uniform models and evaluate their interpretations and the implications for the lower boundary condition.

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Section: Plain Language Summarymentioning

confidence: 99%

Section: Uniform Models Of Iar Alfvén Velocitymentioning

confidence: 99%

Section: Uniform Models Of Iar Alfvén Velocitymentioning

confidence: 99%

Section: Uniform Models Of Iar Alfvén Velocitymentioning

confidence: 99%

Section: Uniform Models Of Iar Alfvén Velocitymentioning

confidence: 99%

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Modeling and Observations of the Effects of the Alfvén Velocity Profile on the Ionospheric Alfvén Resonator

Hodnett,

Yeoman,

Beggan

et al. 2024

JGR Space Physics

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Climatology of the Harmonic Frequency Separation of Ionospheric Alfvén Resonances at Eskdalemuir Observatory, UK

et al. 2023

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We extracted the harmonic frequency separation (Δf) of Ionospheric Alfvén Resonances (IAR) observed in the Eskdalemuir induction coil magnetometer data for the 9 year data set of 2013–2021. To obtain Δf values, we used a machine learning technique that identifies the harmonics and from this we calculated the average separation. To investigate the climatology of the IAR, we have modeled the Δf of the IAR for the data set using a time of flight calculation with model Alfvén velocity profiles. When analyzing Δf from the model and data, we found that in general they follow the same trends. The modeled Δf and Δf from the data both show an inverse correlation with foF2, which confirms that the frequencies of the IAR are controlled by electron density. It follows that Δf is greater around midnight and during the winter months, due to the decrease in plasma mass density. Variability is also reflected when comparing yearly trends in Δf with the sunspot number; higher frequencies are observed and modeled at low sunspot number. It is difficult to examine trends with instantaneous geomagnetic activity as IAR are not visible in spectrograms when geomagnetic activity is high. We find cases where the difference in measured and modeled Δf is significant, suggesting that the model does not capture short term variations in plasma mass density that influence the IAR during these days. We plan to undertake further modeling of Δf on shorter timescales.

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Ultra-low-frequency waves for below threshold and thousand times threshold flux events

Shah

2023

Physics of Plasmas

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A recent study by Shah et al. [Astrophys. Space Sci. 366(2), 22 (2021)] explored the effects of large-scale solar wind structures on relativistic electron fluxes in the slot region and categorized the flux events into four classes, including those with the events of maximum peak fluxes, TTF (thousand times threshold flux), and the events of smallest fluxes, BTF (below threshold flux). This study compares ultra-low-frequency (ULF) waves inside a magnetosphere and at the magnetopause boundary for the BTF and TTF events. It is found that during the TTF event, the electron radial drift velocity peaked very early at the position of an inner Van Allen radiation belt (L = 2–3). The delay between the radial velocity peak and the peak of the toroidal mode electric field was 12 min. For the BTF event, strong ULF waves were absent in the outer Van Allen radiation belt. In contrast, peak powers of ULF waves in the outer radiation belt approached 80 (mV/m)2/Hz for the TTF event, and this peak exceeded the peak power of the toroidal mode electric field at the magnetopause boundary (L = 11) for the BTF event. Our findings are critical for understanding the transport of ULF wave-driven charged particles from the magnetopause boundary to the inner magnetosphere.

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Ratio Between Discrete IAR Frequencies From Observations in the Solar Cycle 24

Cited by 6 publications

References 26 publications

Modeling and Observations of the Effects of the Alfvén Velocity Profile on the Ionospheric Alfvén Resonator

Modeling and Observations of the Effects of the Alfvén Velocity Profile on the Ionospheric Alfvén Resonator

Climatology of the Harmonic Frequency Separation of Ionospheric Alfvén Resonances at Eskdalemuir Observatory, UK

Ultra-low-frequency waves for below threshold and thousand times threshold flux events

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