Exploring the Asymmetry of the Solar Corona Electron Density with Very Long Baseline Interferometry

Aksim, Dan; Melnikov, Alexey; Pavlov, Dmitry; Kurdubov, S.

doi:10.3847/1538-4357/ab499a

Cited by 6 publications

(15 citation statements)

References 30 publications

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“…As in other studies the AWSoM matches well with the astrophysical measurements, however this model is currently too cumbersome to be used effectively by PTAs. Aksim et al (2019) also fit for a variable power spherically symmetric model and find reasonable agreement with their time delay measurements.…”

Section: Solar Electron Density Modelssupporting

confidence: 61%

“…Relaxing the assumption that the electron density around the sun drops off as 1/r 2 , we model the drop off with a more generic power law dependence. These calculations are similar to those in Aksim et al (2019), where the analytical expression for the time delay was calculated directly.…”

Section: General Spherically Symmetric Solar Wind Densitymentioning

confidence: 59%

“…In Aksim et al (2019) the authors compare their measurements of DM using Very Long Baseline Interferometry (VLBI) observations of quasars to both a spherically symmetric model and a numerical integral of the Alfvén Wave Solar Model (AWSoM) (van der Holst et al 2014). As in other studies the AWSoM matches well with the astrophysical measurements, however this model is currently too cumbersome to be used effectively by PTAs.…”

Section: Solar Electron Density Modelsmentioning

confidence: 85%

“…where Γ (x) is the Gamma function. Compare this expression to the time delay equation given in Aksim et al (2019). Equation 11simplifies to Equation 4 when p = 2.…”

Section: General Spherically Symmetric Solar Wind Densitymentioning

confidence: 98%

“…The simplest and most common model for the solar electron density used in pulsar timing software packages like Tempo, Tempo2 and Pint (Nice et al 2015;Hobbs & Edwards 2012;Luo et al 2021) is the spherically-symmetric, time-independent expression n e ( r) = n E (1 au/r) 2 , where n E is the electron density at 1 au, herein Here we have adopted some of the nomenclature of scattering calculations, as in Aksim et al (2019), using b as the impact parameter and defining θ i as the "impact angle", i.e the solar elongation. The vector p points from the Sun to the pulsar, while r ⊕ points from the Sun to the observatory on Earth.…”

Section: Solar Electron Density Modelsmentioning

confidence: 99%

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Bayesian Solar Wind Modeling with Pulsar Timing Arrays

Hazboun,

Simon,

Madison

et al. 2021

Preprint

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Using Bayesian analyses we study the solar electron density with the NANOGrav 11year pulsar timing array (PTA) dataset. Our model of the solar wind is incorporated into a global fit starting from pulse times-of-arrival. We introduce new tools developed for this global fit, including analytic expressions for solar electron column densities and open source models for the solar wind that port into existing PTA software. We perform an ab initio recovery of various solar wind model parameters. We then demonstrate the richness of information about the solar electron density, n E , that can be gleaned from PTA data, including higher order corrections to the simple 1/r 2 model associated with a free-streaming wind (which are informative probes of coronal acceleration physics), quarterly binned measurements of n E and a continuous timevarying model for n E spanning approximately one solar cycle period. Finally, we discuss the importance of our model for chromatic noise mitigation in gravitationalwave analyses of pulsar timing data and the potential of developing synergies between sophisticated PTA solar electron density models and those developed by the solar physics community.

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Section: Solar Electron Density Modelssupporting

confidence: 61%

Section: General Spherically Symmetric Solar Wind Densitymentioning

confidence: 59%

Section: Solar Electron Density Modelsmentioning

confidence: 85%

“…where Γ (x) is the Gamma function. Compare this expression to the time delay equation given in Aksim et al (2019). Equation 11simplifies to Equation 4 when p = 2.…”

Section: General Spherically Symmetric Solar Wind Densitymentioning

confidence: 98%

Section: Solar Electron Density Modelsmentioning

confidence: 99%

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Bayesian Solar Wind Modeling with Pulsar Timing Arrays

Hazboun,

Simon,

Madison

et al. 2021

Preprint

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Fast jet proper motion discovered in a blazar at z=4.72

Zhang

Frey

2020

Science Bulletin

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High-resolution observations of high-redshift (z > 4) radio quasars offer a unique insight into jet kinematics at early cosmological epochs, as well as constraints on cosmological model parameters. Due to the general weakness of extremely distant objects and the apparently slow structural changes caused by cosmological time dilation, only a couple of high-redshift quasars have been studied with parsec-scale resolutions, and with limited number of observing epochs. Here we report on very long baseline interferometry (VLBI) observations of a high-redshift blazar J1430+4204 (z = 4.72) in the 8 GHz frequency band at five different epochs spanning 22 years. The source shows a compact core-jet structure with two jet components being identified within 3 milli-arcsecond (mas) scale. The long time span and multiple-epoch data allow for the kinematic studies of the jet components. That results in a jet proper motion of µ(J1) = 0.017±0.002 mas yr −1 and µ(J2)=0.156±0.015 mas yr −1 , respectively. For the fastestmoving outer jet component J2, the corresponding apparent transverse speed is 19.5 ± 1.9 c. The inferred bulk jet Lorentz factor Γ = 14.6 ± 3.8 and viewing angle θ = 2.2 • ± 1.6 • indicate highly relativistic beaming. The Lorentz factor and apparent proper motion are the highest measured to date among the z > 4 jetted radio sources, while the jet kinematics is still consistent with the cosmological interpretation of quasar redshifts.

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Improving the solar wind density model used in processing of spacecraft ranging observations

Aksim

Pavlov

2022

Monthly Notices of the Royal Astronomical Society

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Solar wind plasma as a cause of radio signal delay plays an important role in solar and planetary science. Early experiments studying the distribution of electrons near the Sun from spacecraft ranging measurements were designed so that the radio signal was passing close to the Sun. At present, processing of spacecraft tracking observations serves a different goal: precise (at metre level) determination of orbits of planets, most importantly Mars. The solar wind adds a time-varying delay to those observations, which is, in this case, unwanted and must be subtracted prior to putting the data into the planetary solution. Present planetary ephemerides calculate the delay assuming a symmetric stationary power-law model for the solar wind density. The present work, based on a custom variant of the EPM lunar–planetary ephemeris, questions the accuracy and correctness of that assumption and examines alternative models based on in situ solar wind density data provided by OMNI and on the ENLIL numerical model of the solar wind.

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Exploring the Asymmetry of the Solar Corona Electron Density with Very Long Baseline Interferometry

Cited by 6 publications

References 30 publications

Bayesian Solar Wind Modeling with Pulsar Timing Arrays

Bayesian Solar Wind Modeling with Pulsar Timing Arrays

Fast jet proper motion discovered in a blazar at z=4.72

Improving the solar wind density model used in processing of spacecraft ranging observations

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