Community of European Solar Radio Astronomers – Page 23

Quasi-periodic acceleration of electrons in the flare on 2012 July 19
by Jing Huang et al.*

2017-02-28

We study the quasi-periodic pulsations (QPPs) of nonthermal emission in an M7.7 class flare on 2012 July 19 with spatially resolved observations at microwave and HXR bands and with spectral observations at decimetric, metric waves. Microwave emission at 17 GHz of two footpoints, HXR emission at 20–50 keV of the north footpoint and loop top, and type III bursts at 0.7–3 GHz show prominent in-phase oscillations at 270$\,$s. Through the […]

Large-scale simulations of Langmuir Wave Distributions Induced by Electron Beams
by H. Reid and E. Kontar

2017-02-14

Langmuir waves that generate type III radio bursts are excited by high-energy electron beams streaming out from the corona through interplanetary space. Despite a smooth temporal distribution of electrons, the Langmuir waves are measured to occur in discrete clumps, commonly attributed to the turbulent nature of the solar wind electron density (e.g. Smith and Sime 1979, Melrose et al 1986). But how do fluctuations in the background plasma shape the […]

Emission of radiation by plasmas with counter-streaming electron beams
by L. F. Ziebell et al.*

2017-01-31

The phenomena of emission of radiation by the Sun, which are known as type II and type III solar radio bursts, have been known and investigated for more than sixty years. The bursts of radiation occur at a frequency corresponding to the plasma frequency at the source region, and harmonics are frequently observed. It is commonly accepted that the radiation is generated by a nonlinear mechanism, proposed by Ginzburg and […]

Simultaneous near-Sun observations of a moving type IV radio burst and the associated white-light CME
by K. Hariharan et al.*

2017-01-17

Quasi-continuum radio emissions of duration ~10-60 min that occur along with flares and coronal mass ejections (CMEs) in the solar atmosphere are termed as type IV bursts. The bursts are non-thermal in nature and can be classified into two categories, i.e. moving type IV (type IVm) bursts and stationary type IV (type IVs) bursts, depending on their time-frequency characteristics in the dynamic spectrum. Amongst the two, the former has a […]

Observation of quasi-periodic solar radio bursts associated with propagating fast-mode waves
by C. R. Goddard et al.*

2017-01-03

Flaring activity on the Sun triggers waves and oscillations in the solar corona. The study of these waves and oscillations allows comparisons to magnetohydrodynamic (MHD) theory and modelling to be made, and seismological inversions based on this comparison allow local plasma parameters to be measured indirectly (e.g. De Moortel & Nakariakov 2012). Simultaneous EUV imaging and radio observations make it possible to study how these waves and oscillations can produce […]

Diagnosing the Source Region of a Solar Burst on 26 September 2011 by Using Microwave Type-III Pairs
by Tan B. L. et al.*

2016-12-20

Accelerated electron beams are believed to be responsible for both hard X-ray (HXR) and strong coherent radio emission during solar flares. However, so far the location of the electron acceleration and its physical parameters are poorly known. The solar microwave Type-III pair burst is possibly the most sensitive signature of the primary energy release and electron accelerations in flares (Aschwanden & Benz, 1997, ApJ). A Type-III pair is composed of […]

Acceleration of electrons in the solar wind by Langmuir waves produced by a decay cascade
by Catherine Krafft and Alexander Volokitin

2016-12-13

It was recently reported that a significant part of the Langmuir waveforms observed by the STEREO satellite (Graham and Cairns, 2013) during type III solar radio bursts are likely consistent with the occurrence of electrostatic decay instabilities, when a Langmuir wave $\mathcal{L}$ resonantly interacts with another Langmuir wave $\mathcal{L}^{\prime}$ and an ion sound wave $\mathcal{S}^{\prime}$ through the decay channel $\mathcal{L} \rightarrow\mathcal{L}^{\prime}+\mathcal{S}^{\prime}$. Usually such wave-wave interactions occur in regions of the […]

Source regions of the type II radio burst observed during a CME–CME interaction on 2013 May 22
by P. Mäkelä et al.*

2016-12-06

Occasionally the Sun ejects a pair of magnetized plasma clouds, called coronal mass ejections (CMEs), roughly into the same propagation direction in closely timed sequence. If the second CME is faster than the first one, the CMEs could either just slip through each other or they could collide and interact, when the following CME catches up the preceding one. The possibility of the CME-CME interaction was first suggested by Gopalswamy […]

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