Interplanetary Scintillation Observations Research Articles

Analysis of the Causes of the Magnetic Storm on December 1–2, 2023 Based on Observations of Interplanetary Scintillations at the BSA Radio Telescope of the Lebedev Physical Institute

The results of the analysis of observational data of interplanetary scintillations obtained at the Big Synphasic Antenna radio telescope of the Lebedev Physical Institute (BSA LPI) before, during and after the magnetic storm that occurred on December 1–2, 2023. Observational data were compared with model calculations for corotating and propagating large-scale disturbances. The results of observations of scintillations of radio sources indicate that the magnetic storm that took place was caused by the superposition of two types of large-scale disturbances of the solar wind. On the day before the start of the magnetic storm, signs of interaction of the Earth’s magnetosphere with the corotating region of multi-velocity solar wind flows were observed, whereas later signs of disturbance of the magnetosphere by a coronal mass ejection propagating after the M9.8 flare on November 28, 2023 were observed.

An updated catalog of IPS radio sources observed by MEXART at 140 MHz for space weather studies

The Mexican Array Radio Telescope (MEXART) is an instrument dedicated to performing interplanetary scintillation (IPS) observations at 140 MHz. After the MEXART backend’s digitization, the array’s technical capabilities have improved substantially, and we observe new IPS sources. By analyzing observations recorded from June 2020 to June 2022, we present an updated catalog of radio sources observed with an IPS signature by MEXART. First, we implemented an algorithm to treat the noise presented by some channels in the frequency. Next, we obtained the spectra of the observations to get the frequency of the Fresnel’s knee and determine whether each radio source exhibited IPS. We then estimated the source’s flux at 140 MHz by interpolating flux density data to different frequencies using the NASA/IPAC Extragalactic Database. Finally, we present a list of 38 radio sources showing IPS signatures. The source list presents declination, right ascension, and flux at 140 MHz. This updated catalog will allow studies of solar wind properties in the inner heliosphere using MEXART data.

Resolving Moving Heliospheric Structures Using Interplanetary Scintillation Observations With the Murchison Widefield Array

AbstractWe have conducted a blind search in 49 consecutive days of interplanetary scintillation observations made by the Murchison Widefield Array from mid‐2019, with overlapping daily observations approximately East and South‐East of the Sun at an elongation of ∼30° and a field of view of 30°. These observations detect an unprecedented density of sources. In spite of these observations being taken at sunspot minimum, this search has revealed several interesting transitory features characterized by elevated scintillation levels. One solar wind enhancement is captured in two observations several hours apart, allowing its radial movement away from the Sun to be measured. We present here a methodology for measuring the plane‐of‐sky velocity for the moving heliospheric structure. The plane‐of‐sky velocity was inferred as 0.66 ± 0.147 hr−1, or 480 ± 106 kms−1 assuming a distance of 1AU. After cross‐referencing our observed structure with multiple catalogs of heliospheric events, we propose that the likely source of our observed structure is a stream‐interaction region originating from a low‐latitude coronal hole. This work demonstrates the power of widefield interplanetary scintillation observations to capture detailed features in the heliosphere which are otherwise unresolvable and go undetected.

Interplanetary scintillation observation and space weather modelling

Interplanetary scintillation (IPS) refers to random fluctuations in radio intensity of distant small-diameter celestial object, over time periods of the order of 1 s. The scattering and scintillation of emergent radio waves are ascribed to turbulent density irregularities transported by the ubiquitous solar wind streams. The spatial correlation length of density irregularities and the Fresnel radius of radio diffraction are two key parameters in determining the scintillation pattern. Such a scintillation pattern can be measured and correlated between multi-station radio telescopes on the Earth. Using the “phase-changing screen” scenario based on the Born approximation, the bulk-flow speed and turbulent spectrum of the solar wind streams can be extracted from the single-station power spectra fitting and the multi-station cross-correlation analysis. Moreover, a numerical computer-assisted tomography (CAT) model, iteratively fit to a large number of IPS measurements over one Carrington rotation, can be used to reconstruct the global velocity and density structures in the inner heliosphere for the purpose of space weather modelling and prediction. In this review, we interpret the underlying physics governing the IPS phenomenon caused by the solar wind turbulence, describe the power spectrum and cross correlation of IPS signals, highlight the space weather application of IPS-CAT models, and emphasize the significant benefits from international cooperation within the Worldwide IPS Stations (WIPSS) network.

Coronal Mass Ejections and the Magnetic Storm on February 27, 2023 from Interplanetary Scintillation Observations with the BSA LPI Radio Telescope

Coronal Mass Ejections and the Magnetic Storm on February 27, 2023 from Interplanetary Scintillation Observations with the BSA LPI Radio Telescope

Corotating Disturbances of the Solar Wind in the Monitoring Data of Interplanetary Scintillations: Simulation and Observation

A simple model has been proposed for the leading part of an interaction region between solar wind streams of different speeds. The model describes an increased plasma concentration as a spiral jet with a rectangular cross-section. Using this model, two-dimensional dynamic maps of interplanetary scintillation level distribution were calculated, which were specifically adapted to the configuration of the BSA LPI radio telescope. The model calculations were compared with the data from a series of observations of interplanetary scintillation during four geomagnetic storms in 2022 and 2023, caused by corotating disturbances. The calculations and observational data exhibit a qualitative correspondence. It has been shown that corotating disturbances manifest as scintillation enhancement three days before a geomagnetic storm, occurring at around 15:00–16:00 Moscow time. Over the next two days, the scintillation enhancement zone shifts to a later time, while there is no enhancement in the morning sector. During the actual geomagnetic storm period, there is an increase in night scintillations. This sequence of scintillation enhancement indicates that the disturbance approaches Earth from the eastern side while rotating with the Sun. The qualitative differences between the observational data for corotating and propagating large-scale disturbances are discussed.

Correction to: Interplanetary Scintillation Observations of Solar-Wind Disturbances During Cycles 23 and 24

Correction to: Interplanetary Scintillation Observations of Solar-Wind Disturbances During Cycles 23 and 24

Detection and Characterization of a Coronal Mass Ejection Using Interplanetary Scintillation Measurements From the Murchison Widefield Array

AbstractWe have shown previously that the Murchison Widefield Array (MWA), can detect 100s of Interplanetary Scintillation (IPS) sources simultaneously across a field of view (FoV) ∼30° in extent. To test if we can use this capability to track heliospheric structures, we undertook a search of 88 hr of MWA IPS data, and identified an observation likely to have a significant Coronal Mass Ejection (CME) in the FoV. We demonstrate that in a single 5‐min MWA observation we are able to localize and image a CME ∼33 hr after launch at an elongation of ∼37° from the Sun. We use IPS observables to constrain the kinematics of the CME, and describe how MWA IPS observations can be used in the future to make a unique contribution to heliospheric modeling efforts.

Interplanetary Scintillation Observations of Solar-Wind Disturbances During Cycles 23 and 24

Interplanetary Scintillation Observations of Solar-Wind Disturbances During Cycles 23 and 24

Application of novel interplanetary scintillation visualisations using LOFAR: A case study of merged CMEs from September 2017

Observations of interplanetary scintillation (IPS – the scintillation of compact radio sources due to density variations in the solar wind) enable the velocity of the solar wind to be determined, and its bulk density to be estimated, throughout the inner heliosphere. A series of observations using the Low Frequency Array (LOFAR - a radio telescope centred on the Netherlands with stations across Europe) were undertaken using this technique to observe the passage of an ultra-fast CME which launched from the Sun following the X-class flare of 10 September 2017. LOFAR observed the strong radio source 3C147 at an elongation of 82 degrees from the Sun over a period of more than 30 h and observed a strong increase in speed to 900kms−1 followed two hours later by a strong increase in the level of scintillation, interpreted as a strong increase in density. Both speed and density remained enhanced for a period of more than seven hours, to beyond the period of observation. Further analysis of these data demonstrates a view of magnetic-field rotation due to the passage of the CME, using advanced IPS techniques only available to a unique instrument such as LOFAR.

Linear change and minutes variability of solar wind velocity revealed by FAST

ABSTRACT Observation of Interplanetary Scintillation (IPS) provides an important and effective way to study the solar wind and the space weather. A series of IPS observations were conducted by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The extraordinary sensitivity and the wide frequency coverage make FAST an ideal platform for IPS studies. In this paper, we present some first scientific results from FAST observations of IPS with the L-band receiver. Based on the solar wind velocity fitting values of FAST observations on 2020 September 26–28, we found that the velocity decreases with increasing frequency linearly, which has not yet been reported in literature. And we have also detected a variation of solar wind velocity on a time-scale of 3–5 min, which imply the slow change of the background solar wind, a co-existence of high- and low-speed streams, or a reflect of the quasi-periodic electron-density fluctuations.

Interplanetary scintillation (IPS) analyses during LOFAR campaign mode periods that include the first three Parker Solar Probe close passes of the Sun

The University of California, San Diego (UCSD) time-dependent three-dimensional (3-D) reconstruction technique provides volumetric maps of density, velocity, and solar surface extrapolated magnetic fields by iteratively fitting our kinematic 3-D model to interplanetary scintillation (IPS) observations. While we currently use data from the Institute for Space-Earth Environmental Research (ISEE), Japan, we have also integrated this system adding data from Worldwide IPS Stations (WIPSS) network groups to increase both spatial and temporal coverage when these data are available. Some of these stations, especially the LOw Frequency ARray (LOFAR), centered in the Netherlands, currently operate in “campaign” mode only during periods of interest when the Parker Solar Probe (PSP) makes close passes to the Sun. The UCSD 3-D iterative reconstruction technique is unique in its ability to yield a low-resolution seamless extension of density and velocity parameters measured in situ, going outward into the surrounding interplanetary medium at the resolution of the volumetric data. We here present analyses using archival data sets from both ISEE, LOFAR, and BSA3 (Pushchino, Russia), mostly during PSP close passes of the Sun. These analyses provide the location of all inner planets from Mercury to Mars, and the spacecraft PSP, BepiColombo, and Solar Orbiter in the 3-D reconstructed volumes and can show the heliospheric structures that reach them as in-situ predictions of the structures present and forecasts of these parameters in near real time compared with near-Earth data sets.

Testing the Alfvén-wave Model of the Solar Wind with Interplanetary Scintillation

Abstract Understanding the mechanism(s) of solar wind acceleration is important in astrophysics and geophysics. A promising model of solar wind acceleration is known as the wave/turbulence-driven (WTD) model, in which Alfvén waves feed energy to the solar wind. In this study, we tested the WTD model with global measurements of wind speed from interplanetary scintillation (IPS) observations. For Carrington rotations in minimal and maximal activity phases, we selected field lines calculated by the potential-field source-surface method in high and midlatitudes and compared the simulated and observed wind velocities. The simulation was performed in a self-consistent manner by solving the magnetohydrodynamic equations from the photosphere to the solar wind. In high-latitude regions, the simulated solar wind velocity agrees better with the IPS observation than with the classical Wang–Sheeley empirical estimation, both in maximal and minimal activity phases. In midlatitude regions, the agreement worsens, possibly because of the inaccuracy of the WTD model and/or the magnetic-field extrapolation. Our results indicate that the high-latitude solar wind is likely to be driven by waves and turbulence and that the physics-based prediction of the solar wind velocity is highly feasible with an improved magnetic-field extrapolation.

A Study of an Equatorial Coronal Hole Observed at the First Parker Solar Probe Perihelion

Abstract In this study, we present an observational analysis of a coronal hole (CH) observed on 2018 November 1 and solar wind (SW) that originated from it, using the Solar Dynamics Observatory, the Parker Solar Probe (PSP) observations at 68 solar radii, ACE and WIND data at 1 au, and interplanetary scintillation (IPS) observations from 0.2 to 1 au. The CH-originated SW stream was observed by L1 on 2018 November 4 and by PSP on 2018 November 15. We examined the CH for nine Carrington Rotations (CR) and find that the SW stream to reach L1 varied from one CR to other. We find that the pressure, temperature, and magnetic fields increase as the speed of the SW increases and the density decreases with distance. We noticed suprathermal particle enhancement at and after the stream interaction region in both PSP and L1 observations, but the enhancement lasted longer in PSP compared to measurements made at L1. The multiple-rotation observations of the CH imply that any differences in observations between PSP and spacecraft at L1 are due to the radial evolution of the solar wind stream rather than of the CH or the source plasma itself. In addition, IPS measured the radio signal irregularities driven by the SW. Furthermore, we employed a standard analytical model to extrapolate the magnetic field at larger heights. We find that the extrapolated magnetic field at 68 R ⊙ and 1 au matches well with the magnetic field measured by PSP and OMNI.

First Observations of the New MEXART's Digital System

AbstractThe Mexican Array Radio Telescope (MEXART) is a transit instrument mainly dedicated to performing interplanetary scintillation (IPS) observations with a central operating frequency of 139.65 MHz. The main scientific objective is to perform studies of solar wind properties and space weather effects. MEXART initially operated with an analog beam former (16 × 16 Butler matrix), which produced 16 fixed latitudinal beams. MEXART began operations and reported the first measurements of IPS sources. MEXART's beam forming system had several problems, however. The North‐South beams had poor directivity, with large side lobes, and the instrument did not achieve the expected performance. Therefore, we commissioned the design and construction of a digital back‐end. The digital system solved the problems with the beam forming, increases the bandwidth, and significantly improves the instrument's sensitivity. In this paper, we present the first light of MEXART's digital system. We describe the new technical capabilities of the instrument, and we show some preliminary results: an estimation of the radio telescope's sensitivity (ΔSmin = 2.28 ± 0.23 Jy), the transit of the Galaxy at 140 MHz with the simultaneous tracking of 62 latitudinal beams, and an example of an IPS observation and the single‐station methodology for calculating the solar wind speed. The new technical capabilities of the radio telescope will provide the potential for participating in several scientific studies. These include solar wind properties, space weather forecasting, ionospheric perturbations, and astrophysical aims such as the monitoring of repeating fast radio bursts and pulsars' observations.

Global Distribution of the Solar Wind Speed Reconstructed from Improved Tomographic Analysis of Interplanetary Scintillation Observations between 1985 and 2019

Abstract Computer-assisted tomography (CAT) for interplanetary scintillation (IPS) observations enables the determination of the global distribution of solar wind speed. We compared solar wind speeds derived from the CAT analysis of IPS observations between 1985 and 2019 with in situ observations conducted by the near-Earth and Ulysses spacecraft. From this comparison, we found that solar wind speeds from the IPS observations for 2009–2019 were systematically higher than the in situ observations, whereas those for the period until 2008 were in good agreement with the in situ observations. Further, we found that the discrepancy between IPS and the in situ observations is improved by changing the power index of the empirical relation between the solar wind speed and density fluctuations. The CAT analysis using an optimal value for the power index determined from the comparison between IPS and in situ observations revealed long-term variations in the solar wind speed distribution over three cycles, leading to a better understanding of the time-varying global heliosphere. We found that polar solar winds become highly anisotropic at the Cycle 24/25 minimum, which is a peculiar aspect of this minimum. The IPS observations showed general agreement with the Parker Solar Probe observations around the perihelion of Orbit 1; this supports the reliability of the CAT analysis. The results of this study suggest that the physical properties of solar wind microturbulence may vary with a long-term decline in the solar activity, which provides important implication on the solar wind acceleration.

Geoeffective Disturbances in the Solar Wind near the Solar Activity Minimum according to the Data of a Two-year Series of Observations of Interplanetary Scintillations with the BSA LPI Radio Telescope

Geoeffective Disturbances in the Solar Wind near the Solar Activity Minimum according to the Data of a Two-year Series of Observations of Interplanetary Scintillations with the BSA LPI Radio Telescope

Observations of interplanetary scintillation of the 2005 May 13 coronal mass ejection: numerical models

ABSTRACT The 2005 May 13 eruption was an Earth-directed coronal mass ejection (CME) observed using the Multi-Element Radio-Linked Interferometer Network telescope system in the UK as it traversed the Interplanetary Medium on 2005 May 14. Observations of interplanetary scintillation (IPS) provide information on the solar wind conditions, which include velocities and density. In addition, it is also possible to calculate other parameters related to the turbulence and geometry of density irregularities in the solar wind from observations of IPS. Previous analyses have shown that IPS information can be difficult to interpret when a complex structure is crossing the line of sight since the physical properties of the plasma may change quite drastically with distance from the Sun. In order to compare and relate the internal structure of a CME and its physical changes, with the results from observations of IPS obtained previously, we carried out a numerical simulation of the 2005 May 13 eruptive event as it propagates into the IPM, adapting the geometrical properties derived by IPS analysis. In this work, we give a possible explanation of some signatures of CME sub-structure from the point of view of the IPS technique combined with what the modelling reveals.

A pilot study of interplanetary scintillation with FAST

ABSTRACT Observations of interplanetary scintillation (IPS) are an efficient remote-sensing method to study the solar wind and inner heliosphere. From 2016 to 2018, some distinctive observations of IPS sources like 3C 286 and 3C 279 were accomplished with the Five-hundred-meter Aperture Spherical radio Telescope (FAST), the largest single-dish telescope in the world. Due to the 270–1620 MHz wide frequency coverage of the ultra-wideband (UWB) receiver, one can use both single-frequency and dual-frequency analyses to determine the projected velocity of the solar wind. Moreover, based on the extraordinary sensitivity owing to the large collecting surface area of FAST, we can observe weak IPS signals. With the advantages of both the wider frequency coverage and high sensitivity, and also with our radio frequency interference (RFI) mitigation strategy and an optimized model-fitting method, in this paper we analyse the fitting confidence intervals of the solar wind velocity and present some preliminary results achieved using FAST, which point to the current FAST system being highly capable of carrying out observations of IPS.

Impact of Inner Heliospheric Boundary Conditions on Solar Wind Predictions at Earth

AbstractPredictions of the physical parameters of the solar wind at Earth are at the core of operational space weather forecasts. Such predictions typically use line‐of‐sight observations of the photospheric magnetic field to drive a heliospheric model. The models Wang‐Sheeley‐Arge (WSA) and ENLIL for the transport in the heliosphere are commonly used for these respective tasks. Here we analyze the impact of replacing the potential field coronal boundary conditions from WSA with two alternative approaches. The first approach uses a more realistic nonpotential rather than potential approach, based on the Durham Magneto Frictional Code (DUMFRIC) model. In the second approach the ENLIL inner boundary conditions are based on Inter Planetary Scintillation observations (IPS). We compare predicted solar wind speed, plasma density, and magnetic field magnitude with observations from the WIND spacecraft for two 6‐month intervals in 2014 and 2016. Results show that all models tested produce fairly similar output when compared to the observed time series. This is not only reflected in fairly low correlation coefficients (<0.3) but also large biases. For example, for solar wind speed some models have average biases of more than 150 km/s. On a positive note, the choice of coronal magnetic field model has a clear influence on the model results when compared to the other models in this study. Simulations driven by IPS data have a high success rate with regard to detection of the high speed solar wind. Our results also indicate that model forecasts do not degrade for longer forecast times.