RadioAstron Studies of the Nearby, Turbulent Interstellar Plasma With the Longest Space-Ground Interferometer Baseline

Abstract

RadioAstron space-ground VLBI observations of the pulsar B0950+08, conducted with the 10-m space radio telescope in conjunction with the Arecibo 300-m telescope and Westerbork Synthesis Radio Telescope at a frequency of 324 MHz, were analyzed in order to investigate plasma inhomogeneities in the direction of this nearby pulsar. The observations were conducted at a spacecraft distance of 330,000 km, resulting in a projected baseline of 220,000 km, providing the greatest angular resolution ever achieved at meter wavelengths. Our analysis is based on fundamental behavior of structure and coherence functions. We find that the pulsar shows scintillation on two frequency scales, both much less than the observing frequency; but modulation is less than 100%. We infer that the scattering is weak, but a refracting wedge disperses the scintillation pattern. The refraction angle of this "cosmic prism" is measured as theta_0=1.1 - 4.4 mas, with the refraction direction being approximately perpendicular to the observer velocity. We show that the observed parameters of scintillation effects indicate that two plasma layers lie along the line of sight to the pulsar, at distances of 4.4 - 16.4 pc and 26 - 170 pc, and traveling in different directions relative to the line of sight. Spectra of turbulence for the two layers are found to follow a power law with the indices gamma_1 = gamma_2 = 3.00 +/- 0.08, significantly different from the index expected for a Kolmogorov spectrum of turbulence, gamma=11/3.

52 manuscript pages, 10 figures. Submitted to ApJ

References in corpus (4)

• The Origin of Radio Scintillation In the Local Interstellar Medium
• Interstellar Scintillation of PSR J0437-4715
• Probing cosmic plasma with giant radio pulses
• Interferometric Visibility of a Scintillating Source: Statistics at the Nyquist Limit

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• Revealing compact structures of interstellar plasma in the Galaxy with RadioAstron
• Interstellar scintillations of PSR B1919+21: space-ground interferometry
• Long-term study of extreme giant pulses from PSR B0950+08 with AARTFAAC
• Scintillation of PSR B1508+55 -- the view from a 10,000-km baseline
• Pentad and triangular structures behind the Racah matrices
• Lunar Orbital VLBI Experiment: motivation, scientific purposes and status
• Probing the ionosphere by the pulsar B0950+08 with help of RadioAstron ground-space baselines
• Variations in the Radiation Intensity of Pulsar B0950+08: Nine Years of Monitoring at 110 MHz
• Orbit design for mitigating interstellar scattering effects in Earth-space VLBI observations of Sgr A*
• Interstellar scintillation of sources B0821+394 and B1812+412 as observed by the LPA LPI radio telescope