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.

VLF/LF (Very Low Frequency/Low Frequency) Reflection Properties of the Low Latitude Ionosphere

1988 ◽  
Author(s):  
Wayne I. Klemetti ◽  
Paul A. Kossey ◽  
John E. Rasmussen ◽  
Maria Sueli Da Silveira Macedo Moura
Keyword(s):  
Low Frequency ◽  
Low Latitude ◽  
Very Low Frequency ◽  
Low Latitude Ionosphere

scholarly journals Resonant scattering of energetic electrons in the plasmasphere by monotonic whistler-mode waves artificially generated by ionospheric modification

2014 ◽  
Vol 32 (5) ◽  
pp. 507-518 ◽  
Author(s):  
S. S. Chang ◽  
B. B. Ni ◽  
J. Bortnik ◽  
C. Zhou ◽  
Z. Y. Zhao ◽  
...  
Keyword(s):  
Test Particle ◽  
Pitch Angle ◽  
Low Frequency ◽  
Resonant Scattering ◽  
High Energy ◽  
Whistler Waves ◽  
Energetic Electrons ◽  
High Energy Electrons ◽  
Angle Scattering ◽  
Vlf Waves

Abstract. Modulated high-frequency (HF) heating of the ionosphere provides a feasible means of artificially generating extremely low-frequency (ELF)/very low-frequency (VLF) whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high-energy electrons in the plasmasphere. By ray tracing the magnetospheric propagation of ELF/VLF emissions artificially generated at low-invariant latitudes, we evaluate the relativistic electron resonant energies along the ray paths and show that propagating artificial ELF/VLF waves can resonate with electrons from ~ 100 keV to ~ 10 MeV. We further implement test particle simulations to investigate the effects of resonant scattering of energetic electrons due to triggered monotonic/single-frequency ELF/VLF waves. The results indicate that within the period of a resonance timescale, changes in electron pitch angle and kinetic energy are stochastic, and the overall effect is cumulative, that is, the changes averaged over all test electrons increase monotonically with time. The localized rates of wave-induced pitch-angle scattering and momentum diffusion in the plasmasphere are analyzed in detail for artificially generated ELF/VLF whistlers with an observable in situ amplitude of ~ 10 pT. While the local momentum diffusion of relativistic electrons is small, with a rate of < 10−7 s−1, the local pitch-angle scattering can be intense near the loss cone with a rate of ~ 10−4 s−1. Our investigation further supports the feasibility of artificial triggering of ELF/VLF whistler waves for removal of high-energy electrons at lower L shells within the plasmasphere. Moreover, our test particle simulation results show quantitatively good agreement with quasi-linear diffusion coefficients, confirming the applicability of both methods to evaluate the resonant diffusion effect of artificial generated ELF/VLF whistlers.

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.

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

&lt;p&gt;This talk will show a statistical analysis of both electric and magnetic field wave amplitudes of very low frequency lightning&amp;#8208;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&amp;#8208;based World Wide Lightning Location Network (WWLLN) to explore differences between satellite and ground&amp;#8208;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&amp;#8208;level lightning activity is maximal. This suggests a difficulty of lightning VLF waves to penetrate / propagate / remain at low L&amp;#8208;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&amp;#8208;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&amp;#8208;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&amp;#8208;term effects that contribute to &amp;#8220;age&amp;#8221; trapped inner belt electron populations.&lt;/p&gt;

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 Sub-ionospheric very low frequency perturbations associated with the 12 May 2008 <i>M</i> = 7.9 Wenchuan earthquake

2013 ◽  
Vol 13 (9) ◽  
pp. 2331-2336 ◽  
Author(s):  
A. K. Maurya ◽  
R. Singh ◽  
B. Veenadhari ◽  
S. Kumar ◽  
A. K. Singh
Keyword(s):  
Wenchuan Earthquake ◽  
Southwest China ◽  
Low Frequency ◽  
Amplitude Fluctuation ◽  
Fluctuation Analysis ◽  
Low Latitude ◽  
Amplitude Variation ◽  
Very Low Frequency ◽  
Wave Channel ◽  
Potential Factors

Abstract. The present study reports the VLF (very low frequency) sub-ionospheric perturbations observed on transmitter JJI (22.1 kHz), Japan, received at the Indian low-latitude station, Allahabad ( geographic lat. 25.41° N, long 81.93° E), due to Wenchuan earthquake (EQ) that occurred on 12 May 2008 with the magnitude 7.9 and at the depth of 19 km in Sichuan province of Southwest China, located at 31.0° N, 103.4° E. The nighttime amplitude fluctuation analysis gives a significant increase in fluctuation and dispersion two days before EQ, when it crosses 2σ criterion. However, there was no significant change observed in the amplitude trend. The diurnal amplitude variation shows a significant increase in the amplitude of JJI signal on 11 and 12 May 2008. The gravity wave channel and changes in the electric field associated with this EQ seem to be the potential factors of the observed nighttime amplitude fluctuation, dispersion, and significant increase in the signal strength.

scholarly journals Automated identification of discrete, lightning-generated, multiple-dispersed whistler waves in C/NOFS-VEFI very low frequency observations

Radio Science ◽  
2016 ◽  
Vol 51 (9) ◽  
pp. 1547-1569 ◽  
Author(s):  
Abram R. Jacobson ◽  
Robert H. Holzworth ◽  
Robert Pfaff ◽  
Roderick Heelis
Keyword(s):  
Low Frequency ◽  
Automated Identification ◽  
Whistler Waves ◽  
Very Low Frequency
Sign in / Sign up

Export Citation Format

Share Document