CORONAL JETS AS A CAUSE OF MICROWAVE NEGATIVE BURSTS

We have investigated the cause of three “isolated” negative radio bursts recorded one after another at several frequencies in the 1–17 GHz range at the Nobeyama Radio Observatory, Ussuriysk Astrophysical Observatory, and Learmonth Solar Observatory on April 10–11, 2014. The cause of the rarely observed “isolated” negative bursts is the absorption of radio emission from the quiet Sun’s regions or a radio source in the material of a large eruptive filament. Analysis of observations in different spectral ranges using images from the Nobeyama radioheliograph and the Solar Dynamics Observatory/Atmospheric Imaging Assembly has shown that the cause of all the three radio emission depressions was the screening of the limb radio source by the material of recurrent coronal jets. Parameters of the absorbing material were estimated using a previously developed model. These estimates confirmed the absorption of solar radio emission in cold material with a temperature of ~104 K at the bottom of the jets.

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Generation of solar spicules and subsequent atmospheric heating

Science ◽

10.1126/science.aaw2796 ◽

2019 ◽

Vol 366 (6467) ◽

pp. 890-894 ◽

Cited By ~ 24

Author(s):

Tanmoy Samanta ◽

Hui Tian ◽

Vasyl Yurchyshyn ◽

Hardi Peter ◽

Wenda Cao ◽

...

Keyword(s):

Solar Atmosphere ◽

Opposite Polarity ◽

Solar Observatory ◽

Magnetized Plasma ◽

Solar Chromosphere ◽

Solar Dynamics Observatory ◽

Polarity Magnetic Field ◽

Solar Dynamics ◽

Solar Spicules ◽

Lower Solar Atmosphere

Spicules are rapidly evolving fine-scale jets of magnetized plasma in the solar chromosphere. It remains unclear how these prevalent jets originate from the solar surface and what role they play in heating the solar atmosphere. Using the Goode Solar Telescope at the Big Bear Solar Observatory, we observed spicules emerging within minutes of the appearance of opposite-polarity magnetic flux around dominant-polarity magnetic field concentrations. Data from the Solar Dynamics Observatory showed subsequent heating of the adjacent corona. The dynamic interaction of magnetic fields (likely due to magnetic reconnection) in the partially ionized lower solar atmosphere appears to generate these spicules and heat the upper solar atmosphere.

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On the fine structures in interplanetary radio emissions

10.5194/egusphere-egu2020-1025 ◽

2020 ◽

Author(s):

Immanuel Christopher Jebaraj ◽

Jasmina Magdalenic ◽

Stefaan Poedts

Keyword(s):

Magnetic Field ◽

Radio Emission ◽

Radio Source ◽

Solar Radio ◽

Wind Waves ◽

Solar Radio Emission ◽

Radio Bursts ◽

Type Ii ◽

Type Iii ◽

Fine Structures

<p>Solar radio emission is studied for many decades and a large number of studies have been dedicated to metric radio emission originating from the low corona. It is generally accepted that solar radio emission&#160; observed at wavelengths below the metric range is produced by the coherent plasma emission mechanism. Fine structures seem to be an intrinsic part of solar radio emission and they are very important for understanding plasma processes in the solar medium. Extensive reporting and number of studies of the metric range fine structures were performed, but studies of fine structures in the interplanetary domain are quite rare. New and advanced ground-based radio imaging spectroscopic techniques (e.g. LOFAR, MWA, etc.,) and space-based observations (Wind/WAVES, STEREO/WAVES A & B, PSP, and SolO in the future) provide a unique opportunity to study radio fine structures observed&#160; all the way from metric to kilometric range.</p><p>Radio signatures of solar eruptive events, such as flares and CMEs, observed in the interplanetary space are mostly confined to type II (radio signatures of magneto-hydrodynamic shock waves), and type III&#160; bursts(electron beams propagating along open and quasi-open magnetic field lines). In this study, we have identified, and analyzed three types of fine structures present within the interplanetary radio bursts. Namely, the striae-like fine structures within type III bursts, continuum-like emission patches, and very slow drifting narrowband structures within type II radio bursts. Since space-based radio observations are limited to dynamic spectra, we use the novel radio triangulation technique employing direction finding measurements from stereoscopic spacecraft (Wind/WAVES, STEREO/WAVES A & B) to obtain the 3D position of the radio emission. The novelty of the technique is that it is not dependent on a density model and in turn can probe the plasma density in the triangulated radio source positions (Magdalenic et al. 2014). Results of the study show that locating the radio source helps not only to understand the generation mechanism of the fine structures but also the ambient plasma conditions such as e.g. electron density. We found that fine structures are associated with complex CME/shock wave structures which interact with the ambient magnetic field structures. We also discuss the possible relationship between the fine structures, the broadband emission they are part of, and the solar eruptive events they are associated with.</p>

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937133 ◽

2020 ◽

Vol 635 ◽

pp. A62 ◽

Cited By ~ 3

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.

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Dynamic processes in an active region in the initial and impulsive phases of the eruptive flare event on June 7, 2011

Acta Astrophysica Taurica ◽

10.31059/aat.vol1.iss1.pp6-12 ◽

2020 ◽

Vol 1 (1) ◽

pp. 6-12

Author(s):

Artur Babin ◽

Aleksandra Koval'

Keyword(s):

Velocity Field ◽

Internal Structure ◽

Line Of Sight ◽

Physical Parameters ◽

Solar Dynamics Observatory ◽

Filament Eruption ◽

Single Structure ◽

Solar Dynamics ◽

Rise Phase ◽

Eruptive Filament

We present the results of an analysis of Hα monochromatic and spectral observations obtained at the Crimean Astrophysical Observatory for an impressive filament eruption during a flare occurred on June 7, 2011. Our ground-based observations are combined with data acquired by multiple instruments onboard the Solar Dynamics Observatory (SDO/AIA, SDO/HMI). The evolution and dynamics of the eruptive process, the cause of eruption, the structure of the line-of-sight velocity field and fine internal structure of the eruptive filament are studied and a number of physical parameters of the eruptive filament are determined. The results of the analysis have shown that: 1) The evolution of the filament eruption consists of two phases: the slow-rise phase, which began about two hours before the flare onset, and the fast-rise phase, which began almost simultaneously with the flare onset. 2) The eruptive filament had a very complex internal structure and complicated line-of-sight velocity field. The filament does not erupt as a single structure. Several discrete massive absorption fragments are seen with a large number of fine-structure elements inside fragments with different velocities, as well as many plasma blobs that detach from the fragments. 3) The motion of the filament fragments is a combination of rotational motion around the axis of the fragment and a movement as a whole towards the observer. The velocities of such plasma motions are determined. 4) Hα line profiles show a large variety of contrast values, Doppler half-widths and Doppler shifts in eruptive filament elements.

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Well-defined EUV wave associated with a CME-driven shock

Astronomy and Astrophysics ◽

10.1051/0004-6361/201630358 ◽

2018 ◽

Vol 612 ◽

pp. A100 ◽

Cited By ~ 2

Author(s):

R. D. Cunha-Silva ◽

C. L. Selhorst ◽

F. C. R. Fernandes ◽

A. J. Oliveira e Silva

Keyword(s):

Shock Wave ◽

Radio Source ◽

Extreme Ultraviolet ◽

Large Angle ◽

Interplanetary Shock ◽

Density Model ◽

Solar Dynamics Observatory ◽

Wave Fronts ◽

Radio Signature ◽

Solar Dynamics

Aims. We report on a well-defined EUV wave observed by the Extreme Ultraviolet Imager (EUVI) on board the Solar Terrestrial Relations Observatory (STEREO) and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The event was accompanied by a shock wave driven by a halo CME observed by the Large Angle and Spectrometric Coronagraph (LASCO-C2/C3) on board the Solar and Heliospheric Observatory (SOHO), as evidenced by the occurrence of type II bursts in the metric and dekameter-hectometric wavelength ranges. We investigated the kinematics of the EUV wave front and the radio source with the purpose of verifying the association between the EUV wave and the shock wave. Methods. The EUV wave fronts were determined from the SDO/AIA images by means of two appropriate directions (slices). The heights (radial propagation) of the EUV wave observed by STEREO/EUVI and of the radio source associated with the shock wave were compared considering the whole bandwidth of the harmonic lane of the radio emission, whereas the speed of the shock was estimated using the lowest frequencies of the harmonic lane associated with the undisturbed corona, using an appropriate multiple of the Newkirk (1961, ApJ, 133, 983) density model and taking into account the H/F frequency ratio fH∕fF = 2. The speed of the radio source associated with the interplanetary shock was determined using the Mann et al. (1999, A&A, 348, 614) density model. Results. The EUV wave fronts determined from the SDO/AIA images revealed the coexistence of two types of EUV waves, a fast one with a speed of ~560 km s−1, and a slower one with a speed of ~250 km s−1, which corresponds approximately to one-third of the average speed of the radio source (~680 km s−1). The radio signature of the interplanetary shock revealed an almost constant speed of ~930 km s−1, consistent with the linear speed of the halo CME (950 km s−1) and with the values found for the accelerating coronal shock (~535–823 km s−1), taking into account the gap between the radio emissions.

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Observations for the Role of Flux rope Eruption in a Geoeffective Solar Flare

JOURNAL OF ADVANCES IN PHYSICS ◽

10.24297/jap.v4i2.6965 ◽

2014 ◽

Vol 4 (2) ◽

pp. 555-564

Author(s):

A.M Aslam

Keyword(s):

Solar Flare ◽

Flux Rope ◽

Magnetic Configuration ◽

Solar Dynamics Observatory ◽

Multi Wavelength ◽

Solar Dynamics ◽

Halo Coronal Mass Ejection ◽

Mass Ejection ◽

The Waves

On September 24, 2011 a solar flare of M 7.1 class was released from the Sun. The flare was observed by most of the space and ground based observatories in various wavebands. We have carried out a study of this flare to understand its causes on Sun and impact on earth. The flare was released from NOAA active region AR 11302 at 12:33 UT. Although the region had already produced many M class flares and one X- class flare before this flare, the magnetic configuration was not relaxed and still continued to evolve as seen from HMI observations. From the Solar Dynamics Observatory (SDO) multi-wavelength (131 Ã…, 171 Ã…, 304 Ã… and 1600Ã…) observations we identified that a rapidly rising flux rope triggered the flare although HMI observations revealed that magnetic configuration did not undergo a much pronounced change. The flare was associated with a halo Coronal Mass Ejection (CME) as recorded by LASCO/SOHO Observations. The flare associated CME was effective in causing an intense geomagnetic storm with minimum Dst index -103 nT. A radio burst of type II was also recorded by the WAVES/WIND. In the present study attempt is made to study the nature of coupling between solar transients and geospace.

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The Solar and Heliospheric Observatory

International Astronomical Union Colloquium ◽

10.1017/s0252921100085596 ◽

1984 ◽

Vol 86 ◽

pp. 155-158 ◽

Cited By ~ 1

Author(s):

Giancarlo Noci

Keyword(s):

Solar Physics ◽

Grazing Incidence ◽

Spectral Irradiance ◽

The Sun ◽

Solar Dynamics Observatory ◽

Solar Constant ◽

Heliospheric Observatory ◽

Explorer Mission ◽

Solar Dynamics ◽

Euv Spectrum

In the past years several space missions have been proposed for the study of the Sun and of the Heliosphere. These missions were intended to clarify various different aspects of solar physics. For example, the GRIST (Grazing Incidence Solar Telescope) mission was intended as a means to improve our knowledge of the upper transition region and low corona through the detection of the solar EUV spectrum with a spatial resolution larger than in previous missions; the DISCO (Dual Spectral Irradiance and Solar Constant Orbiter) and SDO (Solar Dynamics Observatory) missions were proposed to gat observational data about the solar oscillations better than those obtained from ground based instruments; the SOHO (Solar and Heliospheric Observatory) mission was initially proposed to combine the properties of GRIST with the study of the extended corona (up to several radii of heliocentric distance) by observing the scattered Ly-alpha and OVI radiation, which was also the basis of the SCE (Solar Corona Explorer) mission proposal; the development of the interest about the variability of the Sun, both in itself and for its consequences in the history of the Earth, led to propose observations of the solar constant (included in DISCO).

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