New Type of Short High‐Frequency VLF Patches (“VLF Birds”) Above 4–5 kHz

Manninen, J.; Клейменова, Н. Г.; Turunen, T.; Nikitenko, A. S.; Gromova, L. I.; Fedorenko, Yu. V.

doi:10.1029/2020ja028601

Cited by 6 publications

(23 citation statements)

References 45 publications

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“…These numbers show that VLF bursty-patches are not a rare occurrence and are observed quite frequently at KAN, also supporting recent results by Manninen et al (2021). On the other hand, other studies have reported VLF bursty-patches at other ground stations (e.g., Shiokawa et al 2014;Martinez-Calderon et al 2015) but they are only mentioned as few selected cases.…”

Section: General Occurrence Of Vlf Bursty-patchessupporting

confidence: 90%

“…This seems to be in agreement with the solar cycle 24 whose minimum was also in 2018, suggesting that VLF bursty-patch generation or propagation are affected by the solar cycle. Previous studies also found that VLF bursty-patches are mostly observed during quiet space weather conditions at times of small negative Dst values (Manninen et al 2021). To understand how solar wind condition affect VLF bursty-patches we need to focus on statistics and their relation to solar wind parameters which are outside of the scope and this paper and will be the subject of a separate study.…”

Section: General Occurrence Of Vlf Bursty-patchesmentioning

confidence: 69%

“…In some cases, they are shaped like bullets with sudden stops or show wing-like features, while in other cases, we note gradual frequency increase or showing multiple periodic features (Manninen et al 2016(Manninen et al , 2017. More recently, Manninen et al (2021) described these type of emissions as highfrequency VLF patches or VLF 'birds' and focused on their relationship to temporal and spatial details of waveparticle interactions. They noticed that these waves were only observed at times of no or weak space weather conditions.…”

Section: Introductionmentioning

confidence: 77%

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A review of unusual VLF bursty-patches observed in Northern Finland for Earth, Planets and Space

Martinez-Calderon¹,

Manninen²,

Manninen³

et al. 2021

Earth Planets Space

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Using numerical filtering techniques allowing us to reduce noise from sferics, we are able to clearly study a new type of differently structured very low frequency (VLF) radio waves above f = 4 kHz at the ground station of Kannuslehto in northern Finland (KAN, MLAT = 64.4°N, L = 5.5). These emissions are intriguing, since they are detected at frequencies above half the electron gyrofrequency in the equatorial plane (fce) for the L-shell of Kannuslehto (fce ~ 5–6 kHz). They are commonly observed at Kannuslehto, but have also been infrequently reported at other stations, sometimes under different names. Their possible common origin and manner of propagation is still under investigation. This paper unifies the nomenclature by regrouping all these waves detected at frequencies higher than the local equatorial 0.5 fce at the L-shell of observation under the name of VLF bursty-patches. While these waves have different spectral features, they appeared mostly composed of hiss bursts with durations of a few seconds to several minutes. They also show periodic features with varying periodicity and shape. They are sometimes characterized by single bursts covering very large frequency ranges of several kHz. We also give a review of the different characteristics of VLF bursty-patches observed at Kannuslehto, which at the moment, is the station with the highest observation rate. We present recent observations between 2019 and 2021.

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Section: General Occurrence Of Vlf Bursty-patchessupporting

confidence: 90%

Section: General Occurrence Of Vlf Bursty-patchesmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 77%

See 1 more Smart Citation

A review of unusual VLF bursty-patches observed in Northern Finland for Earth, Planets and Space

Martinez-Calderon¹,

Manninen²,

Manninen³

et al. 2021

Earth Planets Space

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View full text Add to dashboard Cite

show abstract

“…This seems to be in agreement with the solar cycle 24 whose minimum was also in 2018, suggesting that VLF bursty-patch generation or propagation are affected by the solar cycle. Previous studies also found that VLF burstypatches are mostly observed during quiet space weather conditions at times of small negative Dst values (Manninen et al, 2021). To understand how solar wind condition affect VLF bursty-patches we need to focus on statistics and their relation to solar wind parameters which are outside of the scope and this paper and will be the subject of a separate study.…”

Section: General Occurrence Of Vlf Bursty-patchesmentioning

confidence: 99%

“…The approximate timings of observations of these events are indicated by magenta lines at the top of the spectrum. These emissions are characterized by multiple bursts that have spectral features resembling the shape of a cartoon bird seen from the side (e.g., Manninen et al 2017Manninen et al , 2021. Indeed, with a little bit of imagination the VLF bursty-patches from 09:30 to 10:30 UT could even be seen as a peacock.…”

Section: 'Bird' Vlf Bursty-patchesmentioning

confidence: 99%

A Review of Unusual VLF Bursty-Patches Observed in Northern Finland

Martinez-Calderon

Manninen

et al. 2021

Preprint

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Using numerical ﬁltering techniques allowing to reduce noise from sferics, we are able to clearly study a new type of differently structured very low frequency (VLF) waves above f = 4 kHz at the ground station of Kannuslehto in northern Finland (KAN, MLAT=64.4°N, L=5.5). These emissions are intriguing since they are detected above the local equatorial electron gyrofrequency for the L-shell of Kannuslehto (fce ~ 5- 6 kHz). They are commonly observed at Kannuslehto, but have also been infrequently reported at other stations, sometimes under different names. Their possible common origin and manner of propagation is still under investigation. This paper unifies the nomenclature by regrouping all these waves detected at frequencies higher than the local equatorial 0.5 fce at the L-shell of observation under the name of VLF bursty-patches. We also give a review of the different characteristics of VLF bursty-patches observed by Kannuslehto, which at the moment, is the station with the highest observation rate. We will present recent observations between 2019 and 2021. While these waves have different spectral features, they appeared mostly composed of hiss bursts with durations of a few seconds to several minutes. They also show periodic features with varying periodicity and shape. They are sometimes characterized by single bursts covering very large frequency ranges of several kHz.

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Unexpected VLF Bursty-Patches Above 5 kHz: A Review of Long-Duration VLF Series Observed at Kannuslehto, Northern Finland

et al. 2022

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Unexpected short patches of natural VLF emissions at f > 5 kHz have been observed at the ground station of Kannuslehto (KAN, L ~ 5.5) in Northern Finland. In contrast with usual VLF emissions (e.g., chorus, hiss, and quasiperiodic emissions) these high-frequency bursty-patches are observed at frequencies higher than half of the equatorial electron gyro-frequency of the L shell of KAN. Moreover, most of these waves reached frequencies above the local equatorial electron gyrofrequency at L = 5.5. Thus, they cannot be attributed to the classical theory of electron-cyclotron interaction. We present a review of VLF bursty-patches at KAN during winters 2011–2021. These emissions have rarely been observed as they are usually hidden by sferics originating from lightning discharges. Therefore, a special numeric filtering technique was used to reduce noise from sferics. VLF bursty-patches typically occur as sequences of short right-hand polarized bursts separated by a few minutes and lasting several hours. Here, we discuss the spectral structure of long-lasting bursty-patches (6 + hours) and the properties of individual patches. We established two categories: (1) “triggered-like” hiss-like bursts at f ~ 4–7 kHz with a very abrupt onset and detected under quiet geomagnetic conditions, and (2) “dash-like” emissions at f > 6 kHz that resemble narrowband hiss and observed under moderate activity. Even though VLF bursty-patches in winters 2011–2021 were observed under weak or slightly disturbed magnetic activity, their annual cyclical occurrence was similar to variations in solar activity. The nature of these VLF patches has not been established yet, but they appear to be generated at L shells lower than that of KAN. Their exact generation region and propagation behavior remain unknown, with further theoretical and experimental research being required.

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New Type of Short High‐Frequency VLF Patches (“VLF Birds”) Above 4–5 kHz

Cited by 6 publications

References 45 publications

A review of unusual VLF bursty-patches observed in Northern Finland for Earth, Planets and Space

A review of unusual VLF bursty-patches observed in Northern Finland for Earth, Planets and Space

A Review of Unusual VLF Bursty-Patches Observed in Northern Finland

Unexpected VLF Bursty-Patches Above 5 kHz: A Review of Long-Duration VLF Series Observed at Kannuslehto, Northern Finland

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