Limits...
Electron densities inferred from plasma wave spectra obtained by the Waves instrument on Van Allen Probes.

Kurth WS, De Pascuale S, Faden JB, Kletzing CA, Hospodarsky GB, Thaller S, Wygant JR - J Geophys Res Space Phys (2015)

Bottom Line: Good progress has been made in developing algorithms to identify f uh and create a data set of electron densities.However, it is often difficult to interpret the plasma wave spectra during active times to identify f uh and accurately determine ne .We describe the expected accuracy of ne and issues in the interpretation of the electrostatic wave spectrum.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, University of Iowa Iowa City, Iowa, USA.

ABSTRACT

The twin Van Allen Probe spacecraft, launched in August 2012, carry identical scientific payloads. The Electric and Magnetic Field Instrument Suite and Integrated Science suite includes a plasma wave instrument (Waves) that measures three magnetic and three electric components of plasma waves in the frequency range of 10 Hz to 12 kHz using triaxial search coils and the Electric Fields and Waves triaxial electric field sensors. The Waves instrument also measures a single electric field component of waves in the frequency range of 10 to 500 kHz. A primary objective of the higher-frequency measurements is the determination of the electron density ne at the spacecraft, primarily inferred from the upper hybrid resonance frequency f uh. Considerable work has gone into developing a process and tools for identifying and digitizing the upper hybrid resonance frequency in order to infer the electron density as an essential parameter for interpreting not only the plasma wave data from the mission but also as input to various magnetospheric models. Good progress has been made in developing algorithms to identify f uh and create a data set of electron densities. However, it is often difficult to interpret the plasma wave spectra during active times to identify f uh and accurately determine ne . In some cases, there is no clear signature of the upper hybrid band, and the low-frequency cutoff of the continuum radiation is used. We describe the expected accuracy of ne and issues in the interpretation of the electrostatic wave spectrum.

No MeSH data available.


A schematic showing how the AURA rule of hysteresis is employed using a Gaussian probability distribution to weight spectral points closer to the seed frequency more than those farther from the seed.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4497465&req=5

fig06: A schematic showing how the AURA rule of hysteresis is employed using a Gaussian probability distribution to weight spectral points closer to the seed frequency more than those farther from the seed.

Mentions: Once a starting fuh coordinate (frequency bin, spectral time) or initial seed frequency bin is determined, AURA proceeds to each successive spectrum to search for a peak in a limited range of bins centered at the seed frequency bin. The logarithm of the amplitudes in this range is normalized by the minimum value and weighted by a central Gaussian profile given by5where , b is the seed bin number, c = 3, and d = 0. Figure6 shows how this is applied. The Gaussian function, g(x), is used as a probability profile when its values are normalized by the central peak. The values of parameters a, b, c, and d are an ad hoc selection such that the power in frequency bins at least 3 away from the seed frequency within individual spectra are weighted by no lower than a factor of 0.5 (Figure6, bottom).


Electron densities inferred from plasma wave spectra obtained by the Waves instrument on Van Allen Probes.

Kurth WS, De Pascuale S, Faden JB, Kletzing CA, Hospodarsky GB, Thaller S, Wygant JR - J Geophys Res Space Phys (2015)

A schematic showing how the AURA rule of hysteresis is employed using a Gaussian probability distribution to weight spectral points closer to the seed frequency more than those farther from the seed.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4497465&req=5

fig06: A schematic showing how the AURA rule of hysteresis is employed using a Gaussian probability distribution to weight spectral points closer to the seed frequency more than those farther from the seed.
Mentions: Once a starting fuh coordinate (frequency bin, spectral time) or initial seed frequency bin is determined, AURA proceeds to each successive spectrum to search for a peak in a limited range of bins centered at the seed frequency bin. The logarithm of the amplitudes in this range is normalized by the minimum value and weighted by a central Gaussian profile given by5where , b is the seed bin number, c = 3, and d = 0. Figure6 shows how this is applied. The Gaussian function, g(x), is used as a probability profile when its values are normalized by the central peak. The values of parameters a, b, c, and d are an ad hoc selection such that the power in frequency bins at least 3 away from the seed frequency within individual spectra are weighted by no lower than a factor of 0.5 (Figure6, bottom).

Bottom Line: Good progress has been made in developing algorithms to identify f uh and create a data set of electron densities.However, it is often difficult to interpret the plasma wave spectra during active times to identify f uh and accurately determine ne .We describe the expected accuracy of ne and issues in the interpretation of the electrostatic wave spectrum.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, University of Iowa Iowa City, Iowa, USA.

ABSTRACT

The twin Van Allen Probe spacecraft, launched in August 2012, carry identical scientific payloads. The Electric and Magnetic Field Instrument Suite and Integrated Science suite includes a plasma wave instrument (Waves) that measures three magnetic and three electric components of plasma waves in the frequency range of 10 Hz to 12 kHz using triaxial search coils and the Electric Fields and Waves triaxial electric field sensors. The Waves instrument also measures a single electric field component of waves in the frequency range of 10 to 500 kHz. A primary objective of the higher-frequency measurements is the determination of the electron density ne at the spacecraft, primarily inferred from the upper hybrid resonance frequency f uh. Considerable work has gone into developing a process and tools for identifying and digitizing the upper hybrid resonance frequency in order to infer the electron density as an essential parameter for interpreting not only the plasma wave data from the mission but also as input to various magnetospheric models. Good progress has been made in developing algorithms to identify f uh and create a data set of electron densities. However, it is often difficult to interpret the plasma wave spectra during active times to identify f uh and accurately determine ne . In some cases, there is no clear signature of the upper hybrid band, and the low-frequency cutoff of the continuum radiation is used. We describe the expected accuracy of ne and issues in the interpretation of the electrostatic wave spectrum.

No MeSH data available.