Shock-wave Radio Probing of Solar Wind Sources in Coronal Magnetic Fields

Abstract The space weather effects in the near-Earth environment as well as in atmospheres of other terrestrial planets arise by corpuscular radiation from the Sun, known as the solar wind. The solar magnetic fields govern the solar corona structure. Magnetic-field strength values in the solar wind sources—key information for modeling and forecasting the space weather climate—are derived from various solar space- and ground-based observations, but so far not accounting for specific types of radio bursts. These are “fractured” type II radio bursts attributed to collisions of shock waves with coronal structures emitting the solar wind. Here, we report on radio observations of two “fractured” type II bursts to demonstrate a novel tool for probing of magnetic-field variations in the solar wind sources. These results have a direct impact on interpretations of this class of bursts and contribute to the current studies of the solar wind emitters.

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Analyzing the propagation of EUV waves and their connection with type II radio bursts by combining numerical simulations and multi-instrument observations

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038699 ◽

2020 ◽

Vol 644 ◽

pp. A90

Author(s):

A. Koukras ◽

C. Marqué ◽

C. Downs ◽

L. Dolla

Keyword(s):

Magnetic Field ◽

Wave Front ◽

Ray Tracing ◽

Radio Burst ◽

Radio Bursts ◽

Type Ii ◽

Fast Mode ◽

Type Ii Radio Bursts ◽

The Magnetic Field ◽

Burst Emission

Context. EUV (EIT) waves are wavelike disturbances of enhanced extreme ultraviolet (EUV) emission that propagate away from an eruptive active region across the solar disk. Recent years have seen much debate over their nature, with three main interpretations: the fast-mode magneto-hydrodynamic (MHD) wave, the apparent wave (reconfiguration of the magnetic field), and the hybrid wave (combination of the previous two). Aims. By studying the kinematics of EUV waves and their connection with type II radio bursts, we aim to examine the capability of the fast-mode interpretation to explain the observations, and to constrain the source locations of the type II radio burst emission. Methods. We propagate a fast-mode MHD wave numerically using a ray-tracing method and the WKB (Wentzel-Kramers-Brillouin) approximation. The wave is propagated in a static corona output by a global 3D MHD Coronal Model, which provides density, temperature, and Alfvén speed in the undisturbed coronal medium (before the eruption). We then compare the propagation of the computed wave front with the observed wave in EUV images (PROBA2/SWAP, SDO/AIA). Lastly, we use the frequency drift of the type II radio bursts to track the propagating shock wave, compare it with the simulated wave front at the same instant, and identify the wave vectors that best match the plasma density deduced from the radio emission. We apply this methodology for two EUV waves observed during SOL2017-04-03T14:20:00 and SOL2017-09-12T07:25:00. Results. The simulated wave front displays a good qualitative match with the observations for both events. Type II radio burst emission sources are tracked on the wave front all along its propagation. The wave vectors at the ray-path points that are characterized as sources of the type II radio burst emission are quasi-perpendicular to the magnetic field. Conclusions. We show that a simple ray-tracing model of the EUV wave is able to reproduce the observations and to provide insight into the physics of such waves. We provide supporting evidence that they are likely fast-mode MHD waves. We also narrow down the source region of the radio burst emission and show that different parts of the wave front are responsible for the type II radio burst emission at different times of the eruptive event.

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On the Possibility of Radio Emission from Quasi-parallel and Quasi-perpendicular Propagation of Shocks

International Astronomical Union Colloquium ◽

10.1017/s0252921100064629 ◽

2000 ◽

Vol 179 ◽

pp. 259-262

Author(s):

A. Shanmugaraju ◽

S. Umapathy

Keyword(s):

Magnetic Field ◽

Radio Emission ◽

Radio Bursts ◽

Type Ii ◽

Simple Analysis ◽

Type Ii Radio Bursts ◽

Solar Type ◽

Type Ii Bursts

AbstractA set of 21 solar type II radio bursts observed using Hiraiso radio spectrograph have been analysed to study the direction of propagation of coronal shocks. A simple analysis is carried out to find the approximate angle between the shock normal and magnetic field by solving the Rankine-Hugoniot MHD relation with assumption of Alfven speed and plasma beta. From this analysis, it is suggested that both quasi-parallel shocks (favourable) and quasi-perpendicular shocks can generate type II bursts depending upon the circumstances of the corona.

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Electron Acceleration at Quasi-Parallel Shocks in The Solar Corona and Its Signature in Solar Type II Radio Bursts

International Astronomical Union Colloquium ◽

10.1017/s0252921100077836 ◽

1994 ◽

Vol 142 ◽

pp. 577-581

Author(s):

G. Mann ◽

H. Lühr

Keyword(s):

Magnetic Field ◽

Solar Corona ◽

Radio Bursts ◽

Type Ii ◽

Radio Radiation ◽

Earth’S Bow Shock ◽

Type Ii Radio Bursts ◽

Solar Type ◽

Field Geometry ◽

The Magnetic Field

AbstractRecently, strong large amplitude magnetic field structures (SLAMS) have been observed as a common phenomenon in the vicinity of the quasi-parallel region of Earth’s bow shock. A quasi-parallel shock transition can be considered as a patchwork of SLAMS. Using the data of the AMPTE/IRM magnetometer the properties of SLAMS are studied. Within SLAMS the magnetic field is strongly deformed and, thus, the magnetic field geometry is locally swung into a quasi-perpendicular regime. Therefore, electrons can locally be accelerated to high energies within SLAMS. Assuming that SLAMS also exist in the vicinity of supercritical, quasi-parallel shocks in the solar corona, they are able to generate radio radiation via the enhanced Langmuir turbulence excited by the accelerated electrons. Since SLAMS are connected with strong density enhancements, the aforementioned mechanism can explain the multiple-lane structure often occurred in solar Type II radio bursts.Subject headings: acceleration of particles — Earth — shock waves — Sun: corona — Sun: radio radiation

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Coronal Magnetic Field Estimation Using Type-II Radio Bursts

Magnetic Coupling between the Interior and Atmosphere of the Sun - Astrophysics and Space Science Proceedings ◽

10.1007/978-3-642-02859-5_62 ◽

2009 ◽

pp. 482-484 ◽

Cited By ~ 1

Author(s):

K. R. Subramanian ◽

E. Ebenezer ◽

K. H. Raveesha

Keyword(s):

Magnetic Field ◽

Coronal Magnetic Field ◽

Radio Bursts ◽

Type Ii ◽

Field Estimation ◽

Type Ii Radio Bursts

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Coronal shocks associated with CMEs and flares and their space weather consequences

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309029093 ◽

2008 ◽

Vol 4 (S257) ◽

pp. 61-63

Author(s):

Marina Laskari ◽

Panagiota Preka-Papadema ◽

Constantine Caroubalos ◽

George Pothitakis ◽

Xenophon Moussas ◽

...

Keyword(s):

Solar Wind ◽

Geomagnetic Activity ◽

Space Weather ◽

Geophysical Data ◽

Radio Bursts ◽

Type Ii ◽

Geomagnetic Indices ◽

Complex Events ◽

Solar Wind Parameters ◽

Solar Energetic Events

AbstractWe study the geoeffectiveness of a sample of complex events; each includes a coronal type II burst, accompanied by a GOES SXR flare and LASCO CME. The radio bursts were recorded by the ARTEMIS-IV radio spectrograph, in the 100-650 MHz range; the GOES SXR flares and SOHO/LASCO CMEs, were obtained from the Solar Geophysical Data (SGD) and the LASCO catalogue respectively. These are compared with changes of solar wind parameters and geomagnetic indices in order to establish a relationship between solar energetic events and their effects on geomagnetic activity.

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