Measurement of solar wind electron density and temperature in the shocked region of Venus and the density and temperature of photoelectrons within the ionosphere of Venus

Knudsen, W. C.; Jones, D. E.; Peterson, Bryan G.; Knadler, Charles E.

doi:10.1002/2016ja022526

Cited by 13 publications

(15 citation statements)

References 9 publications

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Section: Observationssupporting

confidence: 88%

“…Wave power is strongest and spans the most bandwidth at the bow shock crossings. The magnetic field and particle data from these bow shock crossings are similar to those reported previously (e.g., Fränz et al, 2017;Knudsen et al, 2016;Martinecz et al, 2009) Figures 1h and 1i show the geometry of the encounter in the x-y Venus Solar Orbital coordinates (VSO) plane. The red curve shows a notional bow shock, modeled as a conic where r = L∕(1 + cos( )).…”

Section: Data and Processingsupporting

confidence: 79%

“…The plasma double layers and associated kinetic-scale electric field structures are observed just planetward of the bow shock magnetic ramp, a narrow spatial region where solar wind particles are undergo deceleration, deflection and heating. A study by Knudsen et al (2016) explored this region with data from Pioneer Venus, inferring that " … non-Maxwellian … electron velocity distributions colocated with the magnetic field ramp occur in a continuous but convoluted layer of the order of 100 to 200 km thick". The current observations of kinetic plasma structures within the shock ramp are entirely consistent with this, and double layers naturally explain the presence of non-Maxwellian electron velocity distributions.…”

Section: Discussionmentioning

confidence: 99%

“…At Earth, it is ∼12 Earth radii. Knudsen et al (2016) found that, at Venus, transformation of a significant portion of incident solar wind kinetic energy into ion and electron thermal energy was localized to a thin (100–200 km) layer, colocated with observations of non‐Maxwellian electron distributions and the bow shock magnetic ramp. Pressure from heated sheath electrons, combined with the convective electric field, are important for defining the altitude of the ion composition boundary which separates the solar wind from the planetary plasma (Martinecz et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

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Plasma Double Layers at the Boundary Between Venus and the Solar Wind

Malaspina

Goodrich

Livi

et al. 2020

Geophysical Research Letters

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The solar wind is slowed, deflected, and heated as it encounters Venus's induced magnetosphere. The importance of kinetic plasma processes to these interactions has not been examined in detail, due to a lack of constraining observations. In this study, kinetic-scale electric field structures are identified in the Venusian magnetosheath, including plasma double layers. The double layers may be driven by currents or mixing of inhomogeneous plasmas near the edge of the magnetosheath. Estimated double-layer spatial scales are consistent with those reported at Earth. Estimated potential drops are similar to electron temperature gradients across the bow shock. Many double layers are found in few high cadence data captures, suggesting that their amplitudes are high relative to other magnetosheath plasma waves. These are the first direct observations of plasma double layers beyond near-Earth space, supporting the idea that kinetic plasma processes are active in many space plasma environments. Plain Language Summary Venus has no internally generated magnetic field, yet electric currents running through its ionized upper atmosphere create magnetic fields that push back against the flow of the solar wind. These induced fields cause the solar wind to slow and heat as the flow is deflected around Venus. This work reports observations of very small plasma structures that accelerate particles, identifiable by their characteristic electric field signatures, at the boundary where the solar wind starts to be deflected. These small plasma structures observed at Venus have been studied in near-Earth space for decades but have never before been found near another planet. These structures are known to be important to the physics of strong electrical currents in space plasmas and the blending of dissimilar plasmas. Their identification at Venus is a strong demonstration that these small plasma structures are a universal plasma phenomena, at work in many plasma environments.

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Section: Observationssupporting

confidence: 88%

Section: Data and Processingsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Plasma Double Layers at the Boundary Between Venus and the Solar Wind

Malaspina

Goodrich

Livi

et al. 2020

Geophysical Research Letters

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“…30 Flat top electron distributions have also been reported around the magnetic reconnection region 31 and in the ramp of the Venus bow shock. 32 It has been earlier pointed out that the Freja observations of density-depletion structures associated with electric fields were surmised to be electrostatic in nature and a new distribution, later termed as Cairns distribution, successfully explained the observations. We have shown here that for flat top distribution functions, that correspond to the positive values of the spectral index r, ion acoustic waves admit rarefactive solitary structures and therefore this is an alternative way to explicate the observed cavitons by Freja and Viking satellites.…”

Section: -8mentioning

confidence: 99%

An alternative explanation for the density depletions observed by Freja and Viking satellites

et al. 2018

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In this paper, we have studied the linear and nonlinear propagation of ion acoustic waves in the presence of electrons that follow the generalized (r,q) distribution. It has been shown that for positive values of r, which correspond to a flat-topped electron velocity distribution, the nonlinear ion acoustic waves admit rarefactive solitary structures or density depletions. It has been shown that the generalized (r,q) distribution function provides another way to explicate the density depletions observed by Freja and Viking satellites previously explained by proposing Cairns distribution function.

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Plasma Double Layers at the Boundary between Venus and the Solar Wind

Malaspina

Goodrich

Livi

et al. 2020

Preprint

View full text Add to dashboard Cite

The solar wind is slowed, deflected, and heated as it encounters Venus's induced magnetosphere. The importance of kinetic plasma processes to these interactions has not been examined in detail, due to a lack of constraining observations. In this study, kinetic-scale electric field structures are identified in the Venusian magnetosheath, including plasma double layers. The double layers may be driven by currents or mixing of inhomogeneous plasmas near the edge of the magnetosheath. Estimated double-layer spatial scales are consistent with those reported at Earth. Estimated potential drops are similar to electron temperature gradients across the bow shock. Many double layers are found in few high cadence data captures, suggesting that their amplitudes are high relative to other magnetosheath plasma waves. These are the first direct observations of plasma double layers beyond near-Earth space, supporting the idea that kinetic plasma processes are active in many space plasma environments. Plain Language SummaryVenus has no internally generated magnetic field, yet electric currents running through its ionized upper atmosphere create magnetic fields that push back against the flow of the solar wind. These induced fields cause the solar wind to slow and heat as the flow is deflected around Venus. This work reports observations of very small plasma structures that accelerate particles, identifiable by their characteristic electric field signatures, at the boundary where the solar wind starts to be deflected. These small plasma structures observed at Venus have been studied in near-Earth space for decades but have never before been found near another planet. These structures are known to be important to the physics of strong electrical currents in space plasmas and the blending of dissimilar plasmas. Their identification at Venus is a strong demonstration that these small plasma structures are a universal plasma phenomena, at work in many plasma environments.

show abstract

Measurement of solar wind electron density and temperature in the shocked region of Venus and the density and temperature of photoelectrons within the ionosphere of Venus

Cited by 13 publications

References 9 publications

Plasma Double Layers at the Boundary Between Venus and the Solar Wind

Plasma Double Layers at the Boundary Between Venus and the Solar Wind

An alternative explanation for the density depletions observed by Freja and Viking satellites

Plasma Double Layers at the Boundary between Venus and the Solar Wind

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