Broadband very low frequency measurement ofDregion ionospheric perturbations caused by lightning electromagnetic pulses

2007 ◽  
Vol 112 (A6) ◽  
pp. n/a-n/a ◽  
Author(s):  
Zhenggang Cheng ◽  
Steven A. Cummer ◽  
Han-Tzong Su ◽  
Rue-Ron Hsu
Keyword(s):  
Low Frequency ◽  
Frequency Measurement ◽  
Electromagnetic Pulses ◽  
Ionospheric Perturbations ◽  
Very Low Frequency

scholarly journals Possible precursor to the March 11, 2011, Japan earthquake: ionospheric perturbations as seen by subionospheric very low frequency/low frequency propagation

2012 ◽  
Vol 55 (1) ◽  
Author(s):  
Masashi Hayakawa ◽  
Yasuhide Hobara ◽  
Yoshihiro Yasuda ◽  
Hiroki Yamaguchi ◽  
Kenji Ohta ◽  
...  
Keyword(s):  
Low Frequency ◽  
Ionospheric Perturbations ◽  
Very Low Frequency

scholarly journals Multi-Experiment Observations of Ionospheric Disturbances as Precursory Effects of the Indonesian Ms6.9 Earthquake on August 05, 2018

2020 ◽  
Vol 12 (24) ◽  
pp. 4050
Author(s):  
Xuemin Zhang ◽  
Yalu Wang ◽  
Mohammed Boudjada ◽  
Jing Liu ◽  
Werner Magnes ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Electric Field ◽  
Low Frequency ◽  
Ionospheric Disturbances ◽  
Radio Waves ◽  
Ionospheric Perturbations ◽  
Very Low Frequency ◽  
Ion Drift ◽  
Ionospheric Height

Taking the 2018 Ms6.9 Indonesia earthquake as a case study, the ionospheric perturbations in very low frequency (VLF) transmitters recorded by China Seismo-Electromagnetic Satellite (CSES) were mainly investigated, as well as the multi parameters of the plasma and electromagnetic field. The characteristics of electron density (Ne), GPS TEC, ULF electric field, ion drift velocity, and ionosphere height were extracted and compared with the features of the signal-noise ratio (SNR) from VLF transmitters of NWC at the southern hemisphere and JJI at the northern hemisphere. Most disturbances in VLF radio waves occurred along the orbits near the epicenter within 10 days before the earthquake. Along these orbits, we observed simultaneous modulations in the Ne and ULF electric field, as well as the changed ion drifting directions. There was also high spatial correspondence between both SNR and ionospheric height anomalies over the epicentral and its magnetic conjugate regions. Combined with the multi observations, these results suggest that the genesis of perturbations in signals emitted by VLF transmitters on satellite was more likely related to the overlapped electric field in the preparation area of the earthquake.

scholarly journals An excitation mechanism for discrete chorus elements in the magnetosphere

2018 ◽  
Vol 36 (5) ◽  
pp. 1201-1206 ◽  
Author(s):  
Peter Bespalov ◽  
Olga Savina
Keyword(s):  
Growth Rate ◽  
Low Frequency ◽  
Magnetic Equator ◽  
Excitation Mechanism ◽  
Radiation Background ◽  
Electromagnetic Pulses ◽  
Very Low Frequency

Abstract. A beam pulsed amplifier mechanism responsible for effective amplification of short very low frequency (VLF) electromagnetic pulses is proposed. Effective amplification near the magnetic equator outside the plasmasphere is considered. A conditional growth rate of short electromagnetic pulses is calculated. Obtained results can explain some important features of the oblique electromagnetic chorus emissions without hiss-like radiation background.

The Attenuation of Very Low Frequency Brain Oscillations in Transitions from a Rest State to Active Attention

2009 ◽  
Vol 23 (4) ◽  
pp. 191-198 ◽  
Author(s):  
Suzannah K. Helps ◽  
Samantha J. Broyd ◽  
Christopher J. James ◽  
Anke Karl ◽  
Edmund J. S. Sonuga-Barke
Keyword(s):  
Brain Activity ◽  
Sampling Rate ◽  
Low Frequency ◽  
Future Research ◽  
Adhd Symptoms ◽  
Default Mode ◽  
Very Low Frequency ◽  
Wide Range ◽  
Interference Hypothesis ◽  
Mode Interference

Background: The default mode interference hypothesis ( Sonuga-Barke & Castellanos, 2007 ) predicts (1) the attenuation of very low frequency oscillations (VLFO; e.g., .05 Hz) in brain activity within the default mode network during the transition from rest to task, and (2) that failures to attenuate in this way will lead to an increased likelihood of periodic attention lapses that are synchronized to the VLFO pattern. Here, we tested these predictions using DC-EEG recordings within and outside of a previously identified network of electrode locations hypothesized to reflect DMN activity (i.e., S3 network; Helps et al., 2008 ). Method: 24 young adults (mean age 22.3 years; 8 male), sampled to include a wide range of ADHD symptoms, took part in a study of rest to task transitions. Two conditions were compared: 5 min of rest (eyes open) and a 10-min simple 2-choice RT task with a relatively high sampling rate (ISI 1 s). DC-EEG was recorded during both conditions, and the low-frequency spectrum was decomposed and measures of the power within specific bands extracted. Results: Shift from rest to task led to an attenuation of VLFO activity within the S3 network which was inversely associated with ADHD symptoms. RT during task also showed a VLFO signature. During task there was a small but significant degree of synchronization between EEG and RT in the VLFO band. Attenuators showed a lower degree of synchrony than nonattenuators. Discussion: The results provide some initial EEG-based support for the default mode interference hypothesis and suggest that failure to attenuate VLFO in the S3 network is associated with higher synchrony between low-frequency brain activity and RT fluctuations during a simple RT task. Although significant, the effects were small and future research should employ tasks with a higher sampling rate to increase the possibility of extracting robust and stable signals.

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