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

2021 ◽  
Author(s):  
Claudia Martinez-Calderon ◽  
Jyrki K. Manninen ◽  
Jemina T. Manninen ◽  
Tauno Turunen
Keyword(s):  
Low Frequency ◽  
Spectral Features ◽  
Very Low Frequency ◽  
Ground Station ◽  
New Type ◽  
The Moment ◽  
Electron Gyrofrequency ◽  
Different Characteristics ◽  
Vlf Waves ◽  
Large Frequency

Abstract 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.

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

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Claudia Martinez-Calderon ◽  
Jyrki K. Manninen ◽  
Jemina T. Manninen ◽  
Tauno Turunen
Keyword(s):  
Low Frequency ◽  
Spectral Features ◽  
Radio Waves ◽  
Very Low Frequency ◽  
Ground Station ◽  
New Type ◽  
The Moment ◽  
Electron Gyrofrequency ◽  
Different Characteristics ◽  
Large Frequency

AbstractUsing 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.

scholarly journals Investigation of the Sudden Solar Ionospheric Disturbance using Radio Telescope

2020 ◽  
Vol 240 ◽  
pp. 07003
Author(s):  
Adam Aqasha ◽  
Andrien Zheng ◽  
Sneha Athreya ◽  
Hoe Teck Tan
Keyword(s):  
Solar Flares ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Ionospheric Disturbance ◽  
Low Frequency ◽  
The Sun ◽  
Radio Telescopes ◽  
Very Low Frequency ◽  
Set Up ◽  
Vlf Waves

Low-frequency radio telescopes are cheap and useful devices for the investigation of terrestrial and extra-terrestrial emissions. These emissions come either from the Sun and the planet Jupiter to terrestrial emissions. This project aims to investigate the Very Low Frequency (VLF) waves from mid-August to October 2019 using Radio JOVE (20 MHz) and SSID (3-30 kHz) to observe for the occurrence of solar flares and see how if the radio telescopes that the team set up is reliable. This will allow us future students aspiring to learn about astronomy to examine solar flares in detail during the upcoming solar maximum. Not many flares were detected as this period happens to be a solar minimum. However, a series of flares occurred between 30 September 2019 and 1 October 2019, which the telescopes have been able to detect, particularly SSID.

scholarly journals The Influence of Solar Spectral Lines on Electron Concentration in Terrestrial Ionosphere

2011 ◽  
Vol 20 (4) ◽  
Author(s):  
A. Nina ◽  
V. Čadež ◽  
V. A. Srećković ◽  
D. Šulić
Keyword(s):  
Electron Concentration ◽  
Solar Flares ◽  
Low Frequency ◽  
Spectral Lines ◽  
Very Low Frequency ◽  
Phase Variations ◽  
Time Variations ◽  
Vlf Waves

AbstractOne of the methods of detection and analysis of solar flares is observing the time variations of certain solar spectral lines. During solar flares, a raise of electron concentration occurs in Earth’s ionosphere which results in amplitude and phase variations of the recorded very low frequency (VLF) waves. We compared the data obtained by the analysis of recorded VLF signals and line spectra for different solar flares. In this paper we treated the DHO VLF signal transmitted from Germany at the frequency of 23.4 kHz recorded by the AWESOME system in Belgrade (Serbia) during solar flares in the period between 10:40 UT and 13:00 UT on 2011 April 22.

scholarly journals A new type of plasmodium formation inPhysarum polycephalum

1983 ◽  
Vol 42 (3) ◽  
pp. 285-296 ◽  
Author(s):  
Roger W. Anderson ◽  
Christine L. Truitt
Keyword(s):  
Physarum Polycephalum ◽  
Nuclear Fusion ◽  
Low Frequency ◽  
Temperature Sensitive ◽  
Very Low Frequency ◽  
Sequence Of Events ◽  
Mutant Strains ◽  
Clonal Cultures ◽  
New Type

SUMMARYHaploid amoebae ofPhysarum polycephalummay form plasmodia sexually by ‘crossing’, which involves cellular and nuclear fusion, or asexually by ‘selfing’, which occurs without nuclear fusion. In most amoebal strains, selfing is seen in clonal cultures only at very low frequency. In the present study, we have shown that selfing occurs at a similarly low frequency in mixtures of crossing-incompatible amoebae, but is stimulated in crossing-compatible mixtures. In certain compatible mixtures involving mutant strains, where crossing is temperature-sensitive, selfing may be stimulated even at a temperature that largely or wholly abolishes crossing. The extent to which selfing is stimulated appears to be influenced bymatB, a locus which is known to affect the frequency of amoebal fusion. We have failed to detect any filter-transmissible factor that might be responsible for the effects we have observed. We suggest a sequence of events that might bring about ‘stimulated selfing’ as a consequence of abortive crossing.

Daytime observations of chorus emissions at low latitude

1994 ◽  
Vol 72 (1-2) ◽  
pp. 73-79 ◽  
Author(s):  
R. P. Singh ◽  
U. P. Singh ◽  
Ashok Kumar Singh ◽  
D. P. Singh
Keyword(s):  
Low Frequency ◽  
Resonance Interaction ◽  
Whistler Waves ◽  
Low Latitude ◽  
Energetic Electrons ◽  
Very Low Frequency ◽  
Ground Station ◽  
Transverse Resonance

Discrete very-low-frequency chorus emissions observed during the daytime at ground station Gulmarg (geomag. lat. 24°10′N) are reported. The generation of these emissions is explained in terms of transverse resonance interaction between whistler waves and counter-streaming energetic electrons. The theory is tested by evaluating different parameters.

scholarly journals Very low-frequency oscillations from the 11 Hz pulsar in Terzan 5: frame dragging back on the table.

2021 ◽  
Vol 502 (4) ◽  
pp. 5472-5479
Author(s):  
L du Buisson ◽  
S Motta ◽  
R Fender
Keyword(s):  
Low Frequency ◽  
Compact Object ◽  
Compact Objects ◽  
Time Variability ◽  
Fast Time ◽  
Horizontal Branch ◽  
Frame Dragging ◽  
Very Low Frequency ◽  
Low Frequency Oscillations ◽  
Large Frequency

ABSTRACT We present a re-analysis of 47 Rossi X-ray Timing Explorer observations of the 11 Hz accreting pulsar IGR J17480-2446 in Terzan 5 during its 2010 outburst. We studied the fast-time variability properties of the source and searched for quasi-periodic oscillations (QPOs) in a large-frequency range. General relativity predicts that frame dragging occurs in the vicinity of a spinning compact object and induces the precession of matter orbiting said object. The relativistic precession model predicts that this frame dragging can be observed as QPOs with a characteristic frequency in the light curves of accreting compact objects. Such QPOs have historically been classified as horizontal branch oscillations in neutron star (NS) systems, and for a NS spinning at 11 Hz, these oscillations are expected at frequencies below 1 Hz. However, previous studies of IGR J17480-2446 have classified QPOs at 35–50 Hz as horizontal branch oscillations, thus casting doubts on the frame-dragging nature of such QPOs. Here, we report the detection of seven very low-frequency QPOs, previously undetected, with centroid frequencies below 0.3 Hz, and which can be ascribed to frame dragging. We also discuss the possible nature of the QPOs detected at 35–50 Hz in this alternative scenario.

Lightning‐Generated Whistler Amplitudes Measured by the Van Allen Probes

2021 ◽  
Author(s):  
Thomas Farges ◽  
Jean-Francois Ripoll ◽  
David Malaspina ◽  
Erin Lay ◽  
Gregory Cunningham ◽  
...  
Keyword(s):  
World Wide ◽  
Low Frequency ◽  
Whistler Waves ◽  
Mean Power ◽  
Very Low Frequency ◽  
Van Allen Probes ◽  
Whistler Mode Waves ◽  
The Mean ◽  
Vlf Waves ◽  
Field Wave

<p>This talk will show a statistical analysis of both electric and magnetic field wave amplitudes of very low frequency lightning‐generated whistlers (LGWs) based on the equivalent of 11.5 years of observations made by the Van Allen Probes. We complement this analysis with data from the ground‐based World Wide Lightning Location Network (WWLLN) to explore differences between satellite and ground‐based measurements. We will discuss how LGW mean amplitudes were generally found to be low compared with other whistler mode waves even though there exists extreme events (1 out of 5,000) that can reach 100 pT and contribute strongly to the mean power below L = 2. We will reveal a region of low wave amplitude existing below L=2 thanks to the denser dayside ionosphere, which prevents the intense equatorial lightning VLF waves from propagating through it. Below L = 1.5 at all MLT, LGW amplitudes are found to be weak while the ground‐level lightning activity is maximal. This suggests a difficulty of lightning VLF waves to penetrate / propagate / remain at low L‐shells, certainly due at least to the denser ionosphere during daytime. On the contrary, the mean LGW magnetic power (or RMS) remains nearly constant with respect to L‐shell. We will explain that this is due to strong to extreme LGWs that dominate the wave mean power to the point of compensating the decay of LGW occurrence at low L‐shell. Even though extreme LGW were found to be very powerful, particularly at low L and during night, the mean electric/magnetic power remains low compared with other whistler waves. This implies that LGW resonant effects on electrons are consequently long‐term effects that contribute to “age” trapped inner belt electron populations.</p>

Correlations between very low frequency chorus bursts and impulsive magnetic variations at L ~ 4.5

1981 ◽  
Vol 59 (8) ◽  
pp. 1034-1041 ◽  
Author(s):  
S. Kokubun ◽  
K. Hayashi ◽  
T. Oguti ◽  
K. Tsuruda ◽  
S. Machida ◽  
...  
Keyword(s):  
Low Frequency ◽  
Frequency Range ◽  
Conductivity Enhancement ◽  
Very Low Frequency ◽  
Close Relationship ◽  
Magnetic Pulsations ◽  
Whistler Mode Waves ◽  
Short Time ◽  
Vlf Emissions ◽  
Vlf Waves

Coordinated observations of aurora, ULF, and VLF waves were made at 13 stations in Canada in January and February, 1980. The analysis of simultaneous ULF and VLF data obtained at Park Site (L = 4.4) revealed a close relationship between irregular magnetic pulsations and VLF emissions in the frequency range of 1.5–5 kHz. One-to-one correlations were observed between VLF chorus bursts and impulsive magnetic variations, called magnetic impulses, during sub-storms of Kp ≥ 4+ on the local morning-to-noon side. VLF chorus bursts consist of discrete risers of 0.1–0.3 s duration. It is found that magnetic impulses with a rise time of 0.5–1 s and with a duration of ~2 s coincide with the occurrence of VLF riser groups of a similar duration within ~2 s. This short time difference strongly suggests that magnetic impulses are caused by a conductivity enhancement due to electron precipitation induced by whistler mode waves.

scholarly journals The Generation of ULF/ELF/VLF Waves in the Ionosphere by Modulated Heating

Universe ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 29
Author(s):  
Zhe Guo ◽  
Hanxian Fang ◽  
Farideh Honary
Keyword(s):  
High Frequency ◽  
Modulation Frequency ◽  
Source Region ◽  
Low Frequency ◽  
Future Research ◽  
Very Low Frequency ◽  
The Past ◽  
Ionospheric Modification ◽  
Vlf Waves ◽  
Scientific Achievements

One of the most important effects of ionospheric modification by high power, high frequency (HF) waves is the generation of ultra low frequency/extremely low frequency/very low frequency (ULF/ELF/VLF) waves by modulated heating. This paper reviews the scientific achievements of the past five decades regarding the main mechanisms of excitation of ULF/ELF/VLF waves and discusses their characteristics, such as their electrojet dependency, the location of the source region, continuous and discontinuous waves, the number of HF arrays, and the suitable range of the modulation frequency for different proposed mechanisms. Finally, the outlook for future research in this area is presented.

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