Scintillation Velocity Research Articles

Scintillation Velocity and Arc Observations of FRB 20201124A

We present the scintillation velocity measurements of FRB 20201124A from the Five-hundred-meter Aperture Spherical radio Telescope observations, which reveal an annual variation. This annual variation is further supported by changes detected in the scintillation arc as observed from the secondary spectrum. We attribute the annual velocity variation to the presence of a moderately anisotropic scattering screen located at a distance of 0.4 ± 0.1 kpc from Earth. Our results prove that the scintillation of this fast radio burst (FRB) is mainly caused by material close to Earth on a Galactic scale. However, scintillation observations of other FRBs may expose their surrounding environment or uncover possible orbital motion if scintillation is caused by materials in their host galaxy.

Correction to: Modelling annual scintillation velocity variations of FRB 20201124A

Correction to: Modelling annual scintillation velocity variations of FRB 20201124A

Modelling annual scintillation velocity variations of FRB 20201124A

ABSTRACT Compact radio sources exhibit scintillation, an interference pattern arising from propagation through inhomogeneous plasma, where scintillation patterns encode the relative distances and velocities of the source, scattering material, and Earth. In previous work, we showed that the scintillation velocity of the repeating fast radio burst (FRB) FRB20201124A could be measured by correlating burst spectrum pairs, with low values of the scintillation velocity and scattering time-scale suggesting scattering nearby the Earth at $\sim$0.4 kpc. In this work, we have measured the scintillation velocity at 10 epochs spanning 1 yr, observing an annual variation that strongly implies the screen is within the Milky Way. Modelling the annual variation with a 1D anisotropic or 2D isotropic screen results in a screen distance $d_{\mathrm{ l}} = 0.40\pm 0.04$ or $0.46\pm 0.06\,$ pc from the Earth, respectively, possibly associated with material outside of the Local Bubble or the edge of the Orion–Eridanus superbubble. Additional measurements particularly at times of low effective velocity will help probe changes in screen properties, and distinguish between screen models. Where scintillation of an FRB originates in its host galaxy or local environment, these techniques could be used to detect orbital motion, and probe the FRB’s local ionized environment.

Scintillation time-scale measurement of the highly active FRB20201124A

ABSTRACT Scintillation of compact radio sources results from the interference between images caused by multipath propagation, and probes the intervening scattering plasma and the velocities of the emitting source and scattering screen. In FRB20201124A, a repeating fast radio burst (FRB) that entered a period of extreme activity, we obtained many burst detections in observations at the upgraded Giant Metrewave Radio Telescope (uGMRT) and the Effelsberg 100-m Radio Telescope. Bursts nearby in time show similar scintillation patterns, and we measure a scintillation time-scale of 14.3 ± 1.2 and 7 ± 2 min at Effelsberg (1370 MHz) and uGMRT (650 MHz), respectively, by correlating burst pair spectra. The scintillation bandwidth scaled to 1 GHz is 0.5 ± 0.1 MHz, and the inferred scintillation velocity at Effelsberg is $V_{\mathrm{ISS}}\approx (59\pm 7) \sqrt{d_{\mathrm{ l}}/2\, \rm {kpc}}~{\rm km~s}^{-1}$, higher than Earth’s velocity for any screen beyond a lens distance of $d_{\mathrm{ l}} \gtrsim 400\,$ pc. From the measured scintillation bandwidth, FRB20201124A has comparatively lower scattering than nearby pulsars, and is underscattered by a factor of ∼30 or ∼1200 compared to the NE2001 and YMW16 model predictions, respectively. This underscattering together with the measured scintillation velocity is consistent with a scattering screen more nearby the Earth at $d_{\mathrm{ l}} \sim 400\,$ pc, rather than at 2 kpc spiral arm that NE2001 predicts to be the dominant source of scattering. With future measurements, the distance, geometry, and velocity of the scattering screen could be obtained through modelling of the annual variation in VISS, or through interstation time delays or interferometric observations. Scintillation/scattering measurements of FRBs could help improve Galactic electron density models, particularly in the Galactic halo or at high Galactic latitudes.

Global Distribution of the Solar Wind Flux and Velocity From SOHO/SWAN During SC‐23 and SC‐24

AbstractWe analyze SOHO (SOlar Heliospheric Observatory)/SWAN (Solar Wind ANisotropy) hydrogen Lyman‐α data collected between 1996 and 2018 to derive the solar wind latitudinal distribution over time. Full‐sky interplanetary Lyman‐α maps are inverted to derive the total hydrogen ionization rate latitude profiles, normalized to proton charge‐exchange and photoionization. Using Interplanetary Scintillation velocities to calculate the velocity‐dependent charge‐exchange cross‐sections, we produce the solar wind flux latitudinal profiles. Finally, we compute solar wind velocity latitude profiles, based on the dynamic pressure and energy flux conservation (calculated from OMNI data) over latitude. SWAN reproduces the Interplanetary Scintillation velocity profiles up to at least ±60°, and also agrees with Ulysses in situ measurements for solar minimum periods in 1996–1997 and 2007. During solar maximum, discrepancies are more frequent because in situ data reflect local solar wind conditions, while SWAN data reflect global conditions in the heliosphere.

Equatorial ionospheric zonal drift by monitoring local GPS reference networks

[1] The propagation of electromagnetic waves through the turbulent ionosphere produces scintillations through diffraction, and understanding the physical nature of scintillations is important for engineers and technologists as well as for scientists. In recent years, the establishment of the Global Positioning System (GPS) provided a new technique that can be used to study ionospheric scintillations. The usual way of doing that is the deployment of GPS receivers closely spaced in east-west magnetic direction and then estimating the zonal drift velocities based on the signal power observations. One of the weaknesses of this method is that high-rate sampling such as 20 Hz is required for close-spaced stations and generally no such data are available for studying ionospheric scintillation in the past years. In this research work, a scintillation monitoring method based on slant TEC (STEC) observations of local GPS Continuously Operating Reference Station (CORS) network is proposed. First, the past research works on the equatorial ionospheric drift velocities are summarized. Then, by comparing the scintillation pattern of the signal power and STEC observations of California local GPS reference network, we find that the STEC is a good choice for estimating the ionospheric zonal drift velocity. Then it is illustrated how to calculate the ionospheric scintillation velocity based on STEC. Finally, the proposed method is applied to Hong Kong GPS reference network and several cases of the calculated ionospheric zonal velocities are given.

Scintillation Velocity of PSR B0329+54

We monitored PSR B0329+54 for one year using the Nanshan 25-m radio telescope, the scintillation velocity V ISS shows evidence of systematic variation with the day of the year. States of interstellar medium (ISM) are discussed.

Emergence and disappearance of microarcsecond structure in the scintillating quasar J1819+3845

Abstract The 4.8-GHz light curves of the scintillating intraday variable quasar J1819+3845 during 2004–2005 exhibit sharp structure, down to a time-scale of 15 min, that was absent from light curves taken prior to this period and from the 2006 light curves. Analysis of the light curve power spectra show that the variations must be due to the emergence of new structure in the source. The power spectra yield a scattering screen distance of 3.8 ± 0.3 pc for a best-fitting vISS= 59 ± 0.5 km s−1 or 2.0 ± 0.3 pc for the scintillation velocity reported by Dennett-Thorpe & de Bruyn. The scattering medium is required to be exceptionally turbulent, with C2N≳ 0.7 ΔL−1pc m−20/3 for scattering material of thickness ΔLpc pc along the ray path. The 2004 power spectrum can be explained in terms of a double source with a component separation 240 ± 15 μas in 2004.

Rapid Interstellar Scintillation of PKS 1257−326: Two‐Station Pattern Time Delays and Constraints on Scattering and Microarcsecond Source Structure

We report measurements of time delays of up to 8 minutes in the centimeter-wavelength variability patterns of the intrahour scintillating quasar PKS 1257-326, as observed between the VLA and the ATCA on three separate epochs. These time delays confirm interstellar scintillation as the mechanism responsible for the rapid variability, at the same time effectively ruling out the coexistence of intrinsic intrahour variability in this source. The time delays are combined with measurements of the annual variation in variability timescale exhibited by this source to determine the characteristic length scale and anisotropy of the quasar's intensity-scintillation pattern, as well as to attempt to fit for the bulk velocity of the scattering plasma responsible for the scintillation. We find evidence for anisotropic scattering and highly elongated scintillation patterns at both 4.9 and 8.5 GHz, with an axial ratio >10 : 1, extended in a northwest direction on the sky. The characteristic scale of the scintillation pattern along its minor axis is well determined, but the high anisotropy leads to degenerate solutions for the scintillation velocity. The decorrelation of the pattern over the baseline gives an estimate of the major-axis length scale of the scintillation pattern. We derive an upper limit on the distance to the scattering plasma of no more than 10 pc.

High-precision timing of PSR J1600−3053

We present the results of a high-precision timing campaign directed at the binary millisecond pulsar J1600-3053. Submicrosecond pulsar timing has long been the domain of bright, low dispersion measure millisecond pulsars or large diameter telescopes. This experiment, conducted using the Parkes radio telescope in New South Wales, Australia, and utilizing the latest baseband recording hardware, has allowed this pulsar, although distant and faint, to present residuals to a model of its spin behaviour of 650 ns over a period of more than 2 yr. We have also constrained the orbital inclination via Shapiro delay to be between 59° and 70° to 95 per cent confidence and obtained a scintillation velocity measurement indicating a transverse velocity less than 84 km s-1. This pulsar is demonstrating remarkable stability comparable to, and in most cases improving upon, the very best long-term pulsar timing experiments. If this stability is maintained, the current limits on the energy density of the stochastic gravitational wave background will be reached in four more years. © 2006 RAS.

Preliminary three‐dimensional analysis of the heliospheric response to the 28 October 2003 CME using SMEI white‐light observations

The Solar Mass Ejection Imager (SMEI) has recorded the inner heliospheric response in white‐light Thomson scattering to the 28 October 2003 coronal mass ejection (CME). This preliminary report shows the evolution of this particular event in SMEI observations, as we track it from a first measurement at approximately 20° elongation (angular distance) from the solar disk until it fades in the antisolar hemisphere in the SMEI 180° field of view. The large angle and spectrometric coronagraph (LASCO) images show a CME and an underlying bright ejection of coronal material that is associated with an erupting prominence. Both of these are seen by SMEI in the interplanetary medium. We employ a three‐dimensional (3‐D) reconstruction technique that derives its perspective views from outward flowing solar wind to reveal the shape and extent of the CME. This is accomplished by iteratively fitting the parameters of a kinematic solar wind density model to both SMEI white‐light observations and Solar‐Terrestrial Environment Laboratory (STELab), interplanetary scintillation (IPS) velocity data. This modeling technique separates the true heliospheric signal in SMEI observations from background noise and reconstructs the 3‐D heliospheric structure as a function of time. These reconstructions allow separation of the 28 October CME from other nearby heliospheric structure and a determination of its mass. The present results are the first utilizing this type of 3‐D reconstruction with the SMEI data. We determine an excess‐over‐ambient mass for the southward moving ejecta associated with the prominence material of 7.1 × 1016 g and a total mass of 8.9 × 1016 g. Preliminary SMEI white‐light calibration indicates that the total mass of this CME including possible associated nearby structures may have been as much as ∼2.0 × 1017 g spread over much of the earthward facing hemisphere.

Long-term scintillation observations of five pulsars at 1540 MHz

From 2001 January to 2002 June, we monitored PSRs B0329+54, B0823+26, B1929+10, B2020+28 and B2021+51 using the Nanshan 25-m radio telescope of Urumqi Observatory to study their diffractive interstellar scintillation (DISS). The average interval between observations was about 9 days and the observation duration ranged between 2 and 6 hours depending on the pulsar. Wide variations in the DISS parameters were observed over the 18-month data span. Despite this, the average scintillation velocities are in excellent agreement with the proper motion velocities. The average two-dimensional autocorrelation function for PSR B0329+54 is well described by a thin-screen Kolmogorov model, at least along the time and frequency axes. Observed modulation indices for the DISS time scale and bandwidth and the pulsar flux density are greater than values predicted for a Kolmogorov spectrum of electron density fluctuations. Correlated variations over times long compared to the nominal refractive scintillation time are observed, suggesting that larger-scale density fluctuations are important. For these pulsars, the scintillation bandwidth as a function of frequency has a power-law index (~3.6) much less than expected for Kolmogorov turbulence (~4.4). Sloping fringes are commonly observed in the dynamic spectra, especially for PSR B0329+54. The detected range of fringe slopes are limited by our observing resolution. Our observations are sensitive to larger-scale fringes and hence smaller refractive angles, corresponding to the central part of the scattering disk.

Modeling radio scattering and scintillation observations of the inner solar wind using oblique Alfvén/ion cyclotron waves

Radio scattering and scintillation observations of the near‐Sun solar wind are shown to be dominated by effects associated with obliquely propagating Alfvén/ion cyclotron waves. We base this on a modeling of structure functions from angular/spectral broadening observations and velocity measurements from interplanetary scintillation (IPS) observations. A simple damped‐WKB model was found inadequate, as Landau damping erodes the spectrum faster than is consistent with the observed inner scale. Invoking a turbulent cascade can counteract this damping and push the spectral cutoff back out to the observed inner scale near the ion inertial scale. Adjusting the spectrum amplitude and cascade rate to match observations gives an estimate of the wave dissipation power associated with electron Landau damping and proton cyclotron damping. The implied power levels are substantial, being comparable with levels typically invoked in extended wave heating models. Both the shape and the amplitude of the observed structure functions can be explained by a composite spectrum made up of a power law component of passive or non‐Alfvénic density fluctuations and a local flattening associated with the enhanced linear Alfvén wave compressibility at small (ion cyclotron) scales. Since IPS is dominated by the enhanced small‐scale density fluctuations, the scintillation velocity field should show a strong wave effect. Our modeling of IPS velocities does, in fact, show that the large parallel velocity spread and upward bias to the mean velocity observed near the Sun are a direct result of the density fluctuations associated with Alfvén waves along an extended line of sight.

Pulsar Kicks and Spin Tilts in the Close Double Neutron Stars PSR J0737−3039, PSR B1534+12, and PSR B1913+16

In view of the recent measurement of the scintillation velocity for PSR J0737-3039, we examine the complete set of constraints imposed on the pulsar B natal kicks (magnitude and orientation) and predict the most favorable pulsar kick velocity and spin tilt for both isotropic and polar kicks. Our analysis takes into account both currently unknown parameters: the orientation of the orbital plane on the sky (Ω) and the radial component of the systemic velocity (Vr). Assuming that the system's peculiar velocity is entirely due to the second supernova explosion, we find that the system may have crossed the Galactic plane multiple times since the birth of the second neutron star and that the postsupernova peculiar velocity could have been as high as 1200 km s-1. We also confirm the absolute lower and upper limits on the physical parameters derived in our earlier study. For specific combinations of the two unknown parameters Ω and Vr, however, we find much tighter constraints on the presupernova binary configuration and natal kicks imparted to pulsar B, as well as on the age of system. Once Ω is measured in the coming year, it will be straightforward to use the results presented here to further constrain the natal kicks and the spin-tilt predictions. We complete our comprehensive study and derive similar constraints and spin-tilt predictions for PSR B1534+12, for which the only free parameter is Vr. Finally, for PSR B1913+16 we update the progenitor and kick constraints using the measured pulsar spin tilt and allowing for Roche lobe overflow from the progenitor of the pulsar companion.

Interstellar Scintillation Velocities of the Relativistic Binary PSR B1534+12 and Three Other Millisecond Pulsars

We present interstellar scintillation (ISS) velocity measurements for four millisecond pulsars, obtained from long-term monitoring observations with the Arecibo radio telescope at 430 MHz. We also derive explicit expressions, valid for a thin scattering screen, that relate the measured scintillation velocity to the effective transverse velocity responsible for the motion of the diffraction pattern for both binary and solitary pulsars. For PSR B1257+12, PSR B1534+12, PSR J1640+2224, and PSR J1713+0747 we derive ISS velocity estimates of 197 ± 57, 192 ± 63, 38 ± 8, and 82 ± 16 km s-1, respectively. These values are in good agreement with proper-motion measurements for the four pulsars. For the relativistic binary pulsar PSR B1534+12, we use the ISS velocity dependence on orbital phase to determine the longitude of the ascending node Ω of the pulsar's orbit and to derive an estimate of the effective scattering screen location. The two possible values of Ω are 70° ± 20° and 290° ± 20°, and the approximate screen location is 630 ± 200 pc, with the assumed pulsar distance of 1.1 kpc.

PSR J1740+1000: A Young Pulsar Well Out of the Galactic Plane

We discuss PSR J1740 + 1000, one of five pulsars recently discovered in a search of 470 deg at 430 MHz during the upgrade of the 305 m Arecibo Telescope. The period P = 154 ms and period derivative P = 2.1 x 10(exp -14) s s(exp -1) imply a spin-down age tau(sub s) = P/2P = 114 kyr that is smaller than 95% of all known pulsars. The youth and proximity of this pulsar make it a good candidate for detection at X-ray and gamma-ray energies. Its high Galactic latitude (b = 20.4 deg) suggests a very high velocity if the pulsar was born in the midplane of the Galaxy and if its kinematic age equals its spin-down age. Interstellar scintillations, however, suggest a much lower velocity. We discuss possible explanations for this discrepancy, taking into account (1) possible birth sites away from the midplane; (2) contributions from the unmeasured radial velocity; (3) a kinematic age different from the spin-down age; and (4) biasing of the scintillation velocity by enhanced scattering from the North Polar Spur.

Scintillation measurements of the millisecond pulsar PSR J0030+0451 and pulsar space velocities

Scintillation observations of the nearby single millisecond pulsar (MSP) PSR J0030+0451 were carried out with the Parkes 64 m radiotelescope at three different epochs in 1999. From analysis of the dynamic spectrum we obtained the amplitude of the electron density power spectrum and a scintillation velocity km s-1 . This result shows that the Shklovskii effect on the spin-down rate is negligible. We also performed a correlation analysis between pulsar proper motions (V pm ) and scintillation velocities (V iss ) using updated measurements for a sample of 77 objects, 17 of which are MSPs. The full sample shows a correlation coefficient at an extremely high significance level, while for the MSP sub-sample (excluding 2 outliers) we obtain .

Global Solar Wind Changes over Solar Cycle 21: A Combination ofHeliosPhotometer, In Situ, and Interplanetary Scintillation Data

We combine Helios spacecraft photometer brightnesses, in situ plasma densities, and interplanetary scintillation (IPS) velocity data to obtain a global description of solar wind changes. We find an increase of solar mass flux at solar maximum from the photometer brightnesses larger than would be expected from the usual assumption of invariant momentum flux over solar cycle 21 (1975-1986). A portion of this excess mass is related to solar mass ejections, which have an occurrence rate that follows the solar activity cycle.

On the Correlation between Proper Motion Velocities and Scintillation Velocities of Radio Pulsars

A comparison of pulsar transverse speeds measured using the techniques of (1) interferometric measurements of angular proper motion and (2) motion of the pattern of interstellar scintillations shows significant correlation. However, recent studies have found that scintillation speeds are systematically lower than those from interferometric measurements by factors of 2 or so. The subsequent improvement of the pulsar distance scale and the recent revision of the scintillation velocity formula significantly influence this comparison. A new comparison of proper motion and scintillation speeds for 59 pulsars is presented here. The two speeds are found to agree quite well, and there is no systematic bias. For some pulsars the difference between the two speeds is found to be more than expected from the typical estimation errors alone. For pulsars with large z-heights, this discrepancy is found to be consistent with a 1 kpc scale height for the scattering material in the local Galactic neighborhood. For many of the low z-height pulsars showing a discrepancy between the two speeds, enhanced scattering from the local Orion arm of the Galaxy is found to be a suitable explanation.

Evolution of the solar wind structure over a solar cycle: Interplanetary scintillation velocity measurements compared with coronal observations

Sixteen years of solar wind observations via the technique of interplanetary scintillation (IPS) are presented. By an ecliptic comparison with in situ spacecraft observations, these data are shown to be valuable estimates of the large‐scale slowly evolving structures in the solar wind speed, but to underestimate the speed in small‐scale or rapidly evolving structures. These IPS observations allow the large structures to be studied over solar latitudes from 60° north to 60° south over more than a solar cycle. The observations are presented as half‐yearly averages in Carrington longitude and latitude. These are compared with plots of coronal density estimated from coronameter observations and radial magnetic field estimated from solar magnetograph observations and the potential field method. In low and declining solar activity, there is the expected relationship between fast wind and low‐density open‐field regions, and between slow wind, dense corona and proximity to the neutral sheet. The dipolar field component wanders up to 30° from the rotation axis and is followed by dipolar distributions of density and velocity. Near solar maximum, average wind speeds are uniformly slow over the entire range of latitudes covered, the coronal density becomes more spherically distributed (though it retains a somewhat lower density over the solar poles), and the neutral sheet ranges over all latitudes and sometimes forms disconnected surfaces. The relationship between wind speed, density and angular separation from the neutral sheet are then broken. The results confirm the controlling influence of the coronal magnetic field in determining the three‐dimensional structure of the solar wind.