scholarly journals Extended radio emission associated with a breakout eruption from the back side of the Sun

2020 ◽  
Vol 633 ◽  
pp. A141 ◽  
Author(s):  
D. E. Morosan ◽  
E. Palmerio ◽  
B. J. Lynch ◽  
E. K. J. Kilpua
Keyword(s):  
Radio Emission ◽  
Radio Burst ◽  
Coronal Mass Ejections ◽  
Extreme Ultraviolet ◽  
Particle Accelerators ◽  
Back Side ◽  
The Sun ◽  
Radio Bursts ◽  
Solar Dynamics Observatory ◽  
Extended Radio

Context. Coronal mass ejections (CMEs) on the Sun are the largest explosions in the Solar System that can drive powerful plasma shocks. The eruptions, shocks, and other processes associated to CMEs are efficient particle accelerators and the accelerated electrons in particular can produce radio bursts through the plasma emission mechanism. Aims. Coronal mass ejections and associated radio bursts have been well studied in cases where the CME originates close to the solar limb or within the frontside disc. Here, we study the radio emission associated with a CME eruption on the back side of the Sun on 22 July 2012. Methods. Using radio imaging from the Nançay Radioheliograph, spectroscopic data from the Nançay Decametric Array, and extreme-ultraviolet observations from the Solar Dynamics Observatory and Solar Terrestrial Relations Observatory spacecraft, we determine the nature of the observed radio emission as well as the location and propagation of the CME. Results. We show that the observed low-intensity radio emission corresponds to a type II radio burst or a short-duration type IV radio burst associated with a CME eruption due to breakout reconnection on the back side of the Sun, as suggested by the pre-eruptive magnetic field configuration. The radio emission consists of a large, extended structure, initially located ahead of the CME, that corresponds to various electron acceleration locations. Conclusions. The observations presented here are consistent with the breakout model of CME eruptions. The extended radio emission coincides with the location of the current sheet and quasi-separatrix boundary of the CME flux and the overlying helmet streamer and also with that of a large shock expected to form ahead of the CME in this configuration.

scholarly journals Variable emission mechanism of a Type IV radio burst

2019 ◽  
Vol 623 ◽  
pp. A63 ◽  
Author(s):  
D. E. Morosan ◽  
E. K. J. Kilpua ◽  
E. P. Carley ◽  
C. Monstein
Keyword(s):  
Frequency Band ◽  
Radio Burst ◽  
Extreme Ultraviolet ◽  
Imaging Spectroscopy ◽  
Continuum Emission ◽  
Particle Accelerators ◽  
Radio Bursts ◽  
Emission Mechanism ◽  
Type Iv ◽  
Dynamic Spectra

Context. The Sun is an active star and the source of the largest explosions in the solar system, such as flares and coronal mass ejections (CMEs). Flares and CMEs are powerful particle accelerators that can generate radio emission through various emission mechanisms. Aims. CMEs are often accompanied by Type IV radio bursts that are observed as continuum emission in dynamic spectra at decimetric and metric wavelengths, but their emission mechanism can vary from event to event. Here, we aim to determine the emission mechanism of a complex Type IV burst that accompanied the flare and CME on 22 September 2011. Methods. We used radio imaging from the Nançay Radioheliograph, spectroscopic data from the e-Callisto network, ARTEMIS, Ondrejov, and Phoenix3 spectrometers combined with extreme-ultraviolet observations from NASA’s Solar Dynamic Observatory to analyse the Type IV radio burst and determine its emission mechanism. Results. We show that the emission mechanism of the Type IV radio burst changes over time. We identified two components in the Type IV radio burst: an earlier stationary Type IV showing gyro-synchrotron behaviour, and a later moving Type IV burst covering the same frequency band. This second component has a coherent emission mechanism. Fundamental plasma emission and the electron-cyclotron maser emission are further investigated as possible emission mechanisms for the generation of the moving Type IV burst. Conclusions. Type IV bursts are therefore complex radio bursts, where multiple emission mechanisms can contribute to the generation of the wide-band continuum observed in dynamic spectra. Imaging spectroscopy over a wide frequency band is necessary to determine the emission mechanisms of Type IV bursts that are observed in dynamic spectra.

scholarly journals Observations of radio spectra at 1–2.5 GHz associated with CME start time

2008 ◽  
Vol 4 (S257) ◽  
pp. 317-321
Author(s):  
José R. Cecatto
Keyword(s):  
Radio Emission ◽  
Coronal Mass Ejections ◽  
Solar Radio ◽  
Solar Maximum ◽  
Radio Spectrum ◽  
The Sun ◽  
Radio Bursts ◽  
Start Time ◽  
Trigger Mechanism ◽  
Made In

AbstractWe know Coronal Mass Ejections (CME) and flares are the most energetic phenomena happening on the Sun. Until now the information about origin and trigger mechanism of CMEs remains scarce. Also, there is unconclusive information about the association between them and flares although progress has been made in recent years. Multi-spectral observations suggested that the flare energy release occurs in regions from where the decimetric radio emission originates. In this case, investigations of the solar emission in this wavelength range can give us valuable information about these questions. During last solar maximum the Brazilian Solar Spectroscope (BSS) observed the solar radio spectrum (1–2.5 GHz) with high time (100–20 ms) and frequency (50–100 channels) resolutions on a daily (11–19 UT) basis. A survey during the period 1999–2002, shows that a significant fraction (20% –57 events) of CMEs recorded by LASCO has an association with the spectra of radio bursts recorded by BSS. Analysis of the radio spectrum associated to CME shows there is a dominance of continuum and/or pulsation and that the association becomes stronger when we consider the CME acceleration since its origin on the Sun. A statistics of this association between CME dynamics and the characteristics of decimetric radio bursts recorded by BSS is presented. Emphasis is given to observations of the association with CME start time.

scholarly journals Probability of Solar Flares Turn out to Form a Coronal Mass Ejections Events due to the Characterization of Solar Radio Burst Type II and III

2014 ◽  
Vol 35 ◽  
pp. 1-85 ◽  
Author(s):  
Zety Sharizat Hamidi
Keyword(s):  
Solar Flare ◽  
Energy Release ◽  
Radio Burst ◽  
Coronal Mass Ejections ◽  
Solar Radio ◽  
The Sun ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
The Earth

The solar flare and Coronal Mass Ejections (CMEs) are well known as one of the most massive eruptions which potentially create major disturbances in the interplanetary medium and initiate severe magnetic storms when they collide with the Earth‟s magnetosphere. However, how far the solar flare can contribute to the formation of the CMEs is still not easy to be understood. These phenomena are associated with II and III burst it also divided by sub-type of burst depending on the physical characteristics and different mechanisms. In this work, we used a Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy in Transportable Observatories (CALLISTO) system. The aim of the present study is to reveal dynamical properties of solar burst type II and III due to several mechanisms. Most of the cases of both solar radio bursts can be found in the range less that 400 MHz. Based on solar flare monitoring within 24 hours, the CMEs that has the potential to explode will dominantly be a class of M1 solar flare. Overall, the tendencies of SRBT III burst form the solar radio burst type III at 187 MHz to 449 MHz. Based on solar observations, it is evident that the explosive, short time-scale energy release during flares and the long term, gradual energy release expressed by CMEs can be reasonably understood only if both processes are taken as common and probably not independent signatures of a destabilization of pre-existing coronal magnetic field structures. The configurations of several active regions can be sourced regions of CMEs formation. The study of the formation, acceleration and propagation of CMEs requires advanced and powerful observational tools in different spectral ranges as many „stages‟ as possible between the photosphere of the Sun and magnetosphere of the Sun and magnetosphere of the Earth. In conclusion, this range is a current regime of solar radio bursts during CMEs events.

scholarly journals Hot prominence spicules launched from turbulent cool solar prominences

2019 ◽  
Vol 627 ◽  
pp. L5 ◽  
Author(s):  
L. P. Chitta ◽  
H. Peter ◽  
L. Li
Keyword(s):  
Transition Region ◽  
Extreme Ultraviolet ◽  
The Sun ◽  
Solar Dynamics Observatory ◽  
Solar Prominences ◽  
Solar Filament ◽  
Solar Dynamics ◽  
Ultraviolet Observations ◽  
Hot Corona ◽  
Shed Light

A solar filament is a dense cool condensation that is supported and thermally insulated by magnetic fields in the rarefied hot corona. Its evolution and stability, leading to either an eruption or disappearance, depend on its coupling with the surrounding hot corona through a thin transition region, where the temperature steeply rises. However, the heating and dynamics of this transition region remain elusive. We report extreme-ultraviolet observations of quiescent filaments from the Solar Dynamics Observatory that reveal prominence spicules propagating through the transition region of the filament-corona system. These thin needle-like jet features are generated and heated to at least 0.7 MK by turbulent motions of the material in the filament. We suggest that the prominence spicules continuously channel the heated mass into the corona and aid in the filament evaporation and decay. Our results shed light on the turbulence-driven heating in magnetized condensations that are commonly observed on the Sun and in the interstellar medium.

scholarly journals Electron acceleration and radio emission following the early interaction of two coronal mass ejections

2020 ◽  
Vol 642 ◽  
pp. A151
Author(s):  
D. E. Morosan ◽  
E. Palmerio ◽  
J. E. Räsänen ◽  
E. K. J. Kilpua ◽  
J. Magdalenić ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Coronal Mass Ejections ◽  
Solar Radio ◽  
Electron Beams ◽  
Solar Radio Emission ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Dynamic Spectra

Context. Coronal mass ejections (CMEs) are large eruptions of magnetised plasma from the Sun that are often accompanied by solar radio bursts produced by accelerated electrons. Aims. A powerful source for accelerating electron beams are CME-driven shocks, however, there are other mechanisms capable of accelerating electrons during a CME eruption. So far, studies have relied on the traditional classification of solar radio bursts into five groups (Type I–V) based mainly on their shapes and characteristics in dynamic spectra. Here, we aim to determine the origin of moving radio bursts associated with a CME that do not fit into the present classification of the solar radio emission. Methods. By using radio imaging from the Nançay Radioheliograph, combined with observations from the Solar Dynamics Observatory, Solar and Heliospheric Observatory, and Solar Terrestrial Relations Observatory spacecraft, we investigate the moving radio bursts accompanying two subsequent CMEs on 22 May 2013. We use three-dimensional reconstructions of the two associated CME eruptions to show the possible origin of the observed radio emission. Results. We identified three moving radio bursts at unusually high altitudes in the corona that are located at the northern CME flank and move outwards synchronously with the CME. The radio bursts correspond to fine-structured emission in dynamic spectra with durations of ∼1 s, and they may show forward or reverse frequency drifts. Since the CME expands closely following an earlier CME, a low coronal CME–CME interaction is likely responsible for the observed radio emission. Conclusions. For the first time, we report the existence of new types of short duration bursts, which are signatures of electron beams accelerated at the CME flank. Two subsequent CMEs originating from the same region and propagating in similar directions provide a complex configuration of the ambient magnetic field and favourable conditions for the creation of collapsing magnetic traps. These traps are formed if a CME-driven wave, such as a shock wave, is likely to intersect surrounding magnetic field lines twice. Electrons will thus be further accelerated at the mirror points created at these intersections and eventually escape to produce bursts of plasma emission with forward and reverse drifts.

scholarly journals Radio Emission from the Sun and Stars: New Insights into Energetic Phenomena

2004 ◽  
Vol 219 ◽  
pp. 145-158
Author(s):  
T. S. Bastian
Keyword(s):  
Radio Emission ◽  
Energy Release ◽  
Coronal Mass Ejections ◽  
Magnetic Energy ◽  
Spectroscopic Techniques ◽  
The Sun ◽  
Late Type ◽  
Radio Observations ◽  
Dwarf Stars ◽  
Magnetic Energy Release

Energetic phenomena on the Sun and late-type stars pose a number of fascinating puzzles. These include coronal heating, flares, and coronal mass ejections, all believed to be manifestations of magnetic energy release. Radio radiation is a sensitive tracer of energetic phenomena on both the Sun and stars. Radio observations of the Sun over the past decade have produced new insights into the physics of magnetic energy release in flares and coronal mass ejections. Radio observations of late-type stars have exploited sensitive imaging and spectroscopic techniques to further constrain the nature of the relevant emission mechanisms. A surprise has been the recent discovery of radio emission from brown dwarf stars, implying the existence of substantial magnetic fields and a means of dissipating magnetic energy, neither of which are understood.

scholarly journals Evolution of the Alfvén Mach number associated with a coronal mass ejection shock

2020 ◽  
Vol 633 ◽  
pp. A56 ◽  
Author(s):  
Ciara A. Maguire ◽  
Eoin P. Carley ◽  
Joseph McCauley ◽  
Peter T. Gallagher
Keyword(s):  
Mach Number ◽  
Radio Emission ◽  
Radio Burst ◽  
Large Scale ◽  
Extreme Ultraviolet ◽  
Splitting Method ◽  
Large Angle ◽  
Electron Acceleration ◽  
Phase Evolution ◽  
Type Ii

The Sun regularly produces large-scale eruptive events, such as coronal mass ejections (CMEs) that can drive shock waves through the solar corona. Such shocks can result in electron acceleration and subsequent radio emission in the form of a type II radio burst. However, the early-phase evolution of shock properties and its relationship to type II burst evolution is still subject to investigation. Here we study the evolution of a CME-driven shock by comparing three commonly used methods of calculating the Alfvén Mach number (MA), namely: shock geometry, a comparison of CME speed to a model of the coronal Alfvén speed, and the type II band-splitting method. We applied the three methods to the 2017 September 2 event, focusing on the shock wave observed in extreme ultraviolet by the Solar Ultraviolet Imager on board GOES-16, in white-light by the Large Angle and Spectrometric Coronagraph on board SOHO, and the type II radio burst observed by the Irish Low Frequency Array. We show that the three different methods of estimating shock MA yield consistent results and provide a means of relating shock property evolution to the type II emission duration. The type II radio emission emerged from near the nose of the CME when MA was in the range 1.4–2.4 at a heliocentric distance of ∼1.6 R⊙. The emission ceased when the CME nose reached ∼2.4 R⊙, despite an increasing Alfvén Mach number (up to 4). We suggest the radio emission cessation is due to the lack of quasi-perpendicular geometry at this altitude, which inhibits efficient electron acceleration and subsequent radio emission.

scholarly journals Radio Burst Emission Mechanisms: General Review

1980 ◽  
Vol 86 ◽  
pp. 149-156
Author(s):  
D. B. Melrose
Keyword(s):  
Radio Emission ◽  
Radio Burst ◽  
Radio Bursts ◽  
General Review ◽  
Burst Emission

This paper is a shortened version of a review of radio emission mechanisms for meter-λ radio bursts.

scholarly journals Three-dimensional reconstruction of multiple particle acceleration regions during a coronal mass ejection

2020 ◽  
Vol 635 ◽  
pp. A62 ◽  
Author(s):  
D. E. Morosan ◽  
E. Palmerio ◽  
J. Pomoell ◽  
R. Vainio ◽  
M. Palmroth ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Radio Emission ◽  
Three Dimensional ◽  
Coronal Magnetic Field ◽  
Radio Bursts ◽  
Emission Mechanism ◽  
Solar Dynamics Observatory ◽  
Type Iv ◽  
Dynamic Spectra ◽  
Solar Dynamics

Context. Some of the most prominent sources for particle acceleration in our Solar System are large eruptions of magnetised plasma from the Sun called coronal mass ejections (CMEs). These accelerated particles can generate radio emission through various mechanisms. Aims. CMEs are often accompanied by a variety of solar radio bursts with different shapes and characteristics in dynamic spectra. Radio bursts directly associated with CMEs often show movement in the direction of CME expansion. Here, we aim to determine the emission mechanism of multiple moving radio bursts that accompanied a flare and CME that took place on 14 June 2012. Methods. We used radio imaging from the Nançay Radioheliograph, combined with observations from the Solar Dynamics Observatory and Solar Terrestrial Relations Observatory spacecraft, to analyse these moving radio bursts in order to determine their emission mechanism and three-dimensional (3D) location with respect to the expanding CME. Results. In using a 3D representation of the particle acceleration locations in relation to the overlying coronal magnetic field and the CME propagation, for the first time, we provide evidence that these moving radio bursts originate near the CME flanks and that some are possible signatures of shock-accelerated electrons following the fast CME expansion in the low corona. Conclusions. The moving radio bursts, as well as other stationary bursts observed during the eruption, occur simultaneously with a type IV continuum in dynamic spectra, which is not usually associated with emission at the CME flanks. Our results show that moving radio bursts that could traditionally be classified as moving type IVs can represent shock signatures associated with CME flanks or plasma emission inside the CME behind its flanks, which are closely related to the lateral expansion of the CME in the low corona. In addition, the acceleration of electrons generating this radio emission appears to be favoured at the CME flanks, where the CME encounters coronal streamers and open field regions.

scholarly journals Asymmetric expansion of coronal mass ejections in the low corona

2020 ◽  
Vol 635 ◽  
pp. A100 ◽  
Author(s):  
H. Cremades ◽  
F. A. Iglesias ◽  
L. A. Merenda
Keyword(s):  
Coronal Mass Ejections ◽  
Weather Forecasting ◽  
Extreme Ultraviolet ◽  
Solar Physics ◽  
Flux Rope ◽  
Field Configuration ◽  
Solar Dynamics Observatory ◽  
Orthogonal Direction ◽  
Solar Dynamics ◽  
Vantage Points

Aims. Understanding how magnetic fields are structured within coronal mass ejections (CMEs), and how they evolve from the low corona into the heliosphere, is a major challenge for space weather forecasting and for solar physics. The study of CME morphology is a particularly auspicious approach to this problem, given that it holds a close relationship with the CME magnetic field configuration. Although earlier studies have suggested an asymmetry in the width of CMEs in orthogonal directions, this has not been inspected using multi-viewpoint observations. Methods. The improved spatial, temporal, and spectral resolution, added to the multiple vantage points offered by missions of the Heliophysics System Observatory, constitute a unique opportunity to gain insight into this regard. We inspect the early evolution (below ten solar radii) of the morphology of a dozen CMEs occurring under specific conditions of observing spacecraft location and CME trajectory, favorable to reduce uncertainties typically involved in the 3D reconstruction used here. These events are carefully reconstructed by means of a forward modeling tool using simultaneous observations of the Solar-Terrestrial Relations Observatory (STEREO) Extreme Ultraviolet Imager and the Solar Dynamics Observatory Atmospheric Imaging Assembly as input when originating low in the corona, and followed up in the outer fields of view of the STEREO and the Solar and Heliospheric Observatory coronagraphs. We then examine the height evolution of the morphological parameters arising from the reconstructions. Results. The multi-viewpoint analysis of this set of CMEs revealed that their initial expansion – below three solar radii – is considerably asymmetric and non-self-similar. Both angular widths, namely along the main axes of CMEs (AWL) and in the orthogonal direction (AWD, representative of the flux rope diameter), exhibit much steeper change rates below this height, with the growth rate of AWL found to be larger than that of AWD, also below that height. Angular widths along the main axes of CMEs are on average ≈1.8 times larger than widths in the orthogonal direction AWD. The ratios of the two expansion speeds, namely in the directions of CMEs main axes and in their orthogonal, are nearly constant in time after ∼4 solar radii, with an average ratio ≈1.6. Heights at which the width change rate is defined to stabilize are greater for AWL than for AWD.

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