Frequency-dependent polarization characteristics of Pc1 geomagnetic pulsations observed by multipoint ground stations at low latitudes

2011 ◽  
Vol 116 (A1) ◽  
pp. n/a-n/a ◽  
Author(s):  
R. Nomura ◽  
K. Shiokawa ◽  
V. Pilipenko ◽  
B. Shevtsov
Keyword(s):  
Geomagnetic Pulsations ◽  
Frequency Dependent ◽  
Low Latitudes ◽  
Dependent Polarization ◽  
Polarization Characteristics

scholarly journals A fast radio burst with frequency-dependent polarization detected during Breakthrough Listen observations

2019 ◽  
Vol 486 (3) ◽  
pp. 3636-3646 ◽  
Author(s):  
D C Price ◽  
G Foster ◽  
M Geyer ◽  
W van Straten ◽  
V Gajjar ◽  
...  
Keyword(s):  
Radio Burst ◽  
Dynamic Spectrum ◽  
Radio Interference ◽  
Fractional Bandwidth ◽  
Frequency Dependent ◽  
Polarization Voltage ◽  
Geosynchronous Satellite ◽  
Object Based ◽  
Dependent Polarization ◽  
Fast Radio Burst

ABSTRACT Here, we report on the detection and verification of fast radio burst FRB 180301, which occurred on utc 2018 March 1 during the Breakthrough Listen observations with the Parkes telescope. Full-polarization voltage data of the detection were captured – a first for non-repeating FRBs – allowing for coherent de-dispersion and additional verification tests. The coherently de-dispersed dynamic spectrum of FRB 180301 shows complex, polarized frequency structure over a small fractional bandwidth. As FRB 180301 was detected close to the geosynchronous satellite band during a time of known 1–2 GHz satellite transmissions, we consider whether the burst was due to radio interference emitted or reflected from an orbiting object. Based on the pre-ponderance of our verification tests, we cannot conclusively determine FRB 180301 to be either astrophysical or anthropogenic in origin.

Martian Aquifers: Detection by Magnetic Sounding from Surface Magnetometry

2020 ◽  
Author(s):  
Yanan Yu ◽  
Janet Luhmann ◽  
Christopher Russell
Keyword(s):  
Frequency Dependence ◽  
Vertical Component ◽  
Frequency Dependent ◽  
Source Regions ◽  
Magnetic Pulsations ◽  
Dependent Polarization ◽  
Surface Observations

<p>Magnetic pulsations are observed at Mars in the magnetotail and on the surface by the Maven and InSight magnetometers. The surface observations exhibit a frequency-dependent polarization in which the amplitude of the vertical component weakens with increasing frequency. This frequency dependence is not seen in the source regions studied by MAVEN. The source of the frequency dependence must be in the subsurface of Mars. The attenuation is consistent with an aquifer that is 3 km thick, containing water of the conductivity of terrestrial seawater.</p>

scholarly journals Seismic signature of turbulence during the 2017 Oroville Dam spillway erosion crisis

2018 ◽  
Author(s):  
Phillip J. Goodling ◽  
Vedran Lekic ◽  
Karen Prestegaard
Keyword(s):  
Turbulent Flow ◽  
Rayleigh Wave ◽  
Flood Control ◽  
Large Scale ◽  
Source Location ◽  
Scaling Exponent ◽  
Polarization Analysis ◽  
Frequency Dependent ◽  
Turbulent Eddies ◽  
Dependent Polarization

Abstract. Knowing the location of large-scale turbulent eddies during catastrophic flooding events improves predictions of erosive scour. The erosion damage to the Oroville Dam flood control spillway in early 2017 is an example of the erosive power of turbulent flow. During this event, a defect in the simple concrete channel quickly eroded into a chasm 47 meters deep. Erosion by turbulent flow is difficult to evaluate in real time, but near-channel seismic monitoring provides a tool to evaluate flow dynamics from a safe distance. Previous studies have had limited ability to identify source location or the type of surface wave (i.e. Love or Rayleigh wave) excited by different river processes. Here we use a single three-component seismometer method (Frequency-Dependent Polarization Analysis) to characterize the dominant seismic source location and seismic surface waves produced by the Oroville dam flood control spillway, using the abrupt change in spillway geometry as a natural experiment. We find that the scaling exponent between seismic power and release discharge is greater following damage to the spillway, suggesting larger turbulent eddies excite more seismic energy. The mean azimuth in the 5–10 Hz frequency band was used to resolve the location of spillway damage. Observed polarization attributes deviate from those expected for a Rayleigh wave, though numerical modelling indicates these deviations are explained by propagation up the hillside topography. Our results suggest Frequency-Dependent Polarization Analysis is a promising approach for locating areas of increased flow turbulence. This method could be applied to other erosion problems near engineered structures and to understanding energy dissipation, erosion, and channel morphology development in natural rivers, particularly at high discharges.

UBVRI photopolarimetry of BL Lac objects - The connection between frequency-dependent polarization and growing radio shocks

1991 ◽  
Vol 101 ◽  
pp. 78 ◽  
Author(s):  
L. Valtaoja ◽  
A. Sillanpaa ◽  
E. Valtaoja ◽  
N. M. Shakhovskoi ◽  
Iu. S. Efimov
Keyword(s):  
Frequency Dependent ◽  
Bl Lac Objects ◽  
Bl Lac ◽  
Dependent Polarization

scholarly journals Seismic signature of turbulence during the 2017 Oroville Dam spillway erosion crisis

2018 ◽  
Vol 6 (2) ◽  
pp. 351-367 ◽  
Author(s):  
Phillip J. Goodling ◽  
Vedran Lekic ◽  
Karen Prestegaard
Keyword(s):  
Energy Dissipation ◽  
Turbulent Flow ◽  
Rayleigh Wave ◽  
Flood Control ◽  
Large Scale ◽  
Source Location ◽  
Scaling Exponent ◽  
Polarization Analysis ◽  
Frequency Dependent ◽  
Dependent Polarization

Abstract. Knowing the location of large-scale turbulent eddies during catastrophic flooding events improves predictions of erosive scour. The erosion damage to the Oroville Dam flood control spillway in early 2017 is an example of the erosive power of turbulent flow. During this event, a defect in the simple concrete channel quickly eroded into a 47 m deep chasm. Erosion by turbulent flow is difficult to evaluate in real time, but near-channel seismic monitoring provides a tool to evaluate flow dynamics from a safe distance. Previous studies have had limited ability to identify source location or the type of surface wave (i.e., Love or Rayleigh wave) excited by different river processes. Here we use a single three-component seismometer method (frequency-dependent polarization analysis) to characterize the dominant seismic source location and seismic surface waves produced by the Oroville Dam flood control spillway, using the abrupt change in spillway geometry as a natural experiment. We find that the scaling exponent between seismic power and release discharge is greater following damage to the spillway, suggesting additional sources of turbulent energy dissipation excite more seismic energy. The mean azimuth in the 5–10 Hz frequency band was used to resolve the location of spillway damage. Observed polarization attributes deviate from those expected for a Rayleigh wave, though numerical modeling indicates these deviations may be explained by propagation up the uneven hillside topography. Our results suggest frequency-dependent polarization analysis is a promising approach for locating areas of increased flow turbulence. This method could be applied to other erosion problems near engineered structures as well as to understanding energy dissipation, erosion, and channel morphology development in natural rivers, particularly at high discharges.

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