Microwave imaging of quasi-periodic pulsations at flare current sheet by Yuankun Kou et al.
Community of European Solar Radio Astronomers
by admin_cesra_editor
1M ago
Quasi-periodic pulsations (QPPs; also known as quasi-periodic oscillations, i.e., QPOs) are phenomena that electromagnetic emissions vary quasi-periodically with time. They appear in celestial transient events with different temporal/spatial scales, such as stellar flares, gamma ray bursts and fast radio bursts, and etc. The Sun is a normal but the closest star from us, where flares with QPPs appear frequently (e.g. Zimovets et al. 2021 as a review). In the standard flare model, magnetic reconnection plays an important role in releasing energy from the coronal magnetic field, ejecting plasmo ..read more
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Zebra Stripes with High Gyro-Harmonic Numbers by Jan Benacek and Marian Karlicky
Community of European Solar Radio Astronomers
by admin_cesra_editor
1M ago
The solar radio zebra patterns, or zebras, provide detailed diagnostics of plasma density and magnetic field in the corona. The zebras appear in radiograms during Type IV solar radio bursts as a series of parallel stripes that are narrow in frequency. The main emission model of radio zebras relies on a double plasma resonance, a resonance between the plasma frequency, gyro-harmonic of the cyclotron frequency, and the frequency of unstable upper-hybrid (UH) electrostatic waves (Zhelezniakov & Zlotnik 1975,Chen et al. 2011).  The driver of the instability are superthermal el ..read more
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Flares detected in ALMA single-dish images by I. Skokic et al
Community of European Solar Radio Astronomers
by admin_cesra_editor
2M ago
The (sub)millimeter radiation of solar flares, explosive events detected as brightenings across the electromagnetic spectrum, is poorly understood (Krucker et al. 2013). The major limit of the previous >100 GHz observations was spatial resolution, impeding the combination with observations at other wavelengths. The Atacama Large Millimeter-submillimeter Array (ALMA) offers sufficient resolution for the first time. Shimizu et al. (2021) reported a microflare observed in interferometric mode. However, used as an interferometer, the ALMA field of view is small, and ALMA cannot observe on dem ..read more
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Third and fourth harmonics of electromagnetic emissions by a weak beam in a solar wind plasma with random density fluctuations by C. Krafft
Community of European Solar Radio Astronomers
by admin_cesra_editor
2M ago
Electromagnetic emissions at the third harmonic of the plasma frequency $\omega _{p}$ have been reported during the occurrence of type II and type III solar radio bursts (e.g. Zlotnik 1978, Zlotnik et al. 1998, Cairns; 1986), even if rarely and sometimes controversially. Recently the Wind spacecraft detected several events exhibiting third harmonic emissions in interplanetary type III bursts observed locally near 1 AU (Reiner and MacDowald; 2019). For the first time, the impact of plasma density fluctuations on the wave coalescence mechanisms responsible for the generation of $\mathcal{H}_{3 ..read more
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Narrowband Spikes Observed During the 13 June 2012 Flare in the 800 – 2000 MHz Range by Marian Karlicky et al
Community of European Solar Radio Astronomers
by admin_cesra_editor
5M ago
The solar radio spikes can provide detailed information about plasma processes in solar flares on kinetic scales. Among them, the decimetric spikes belong to the most interesting ones because they are recorded in some cases close to the starting frequency of Type-III bursts and in relation to hard X-ray emissions. Stepanov et al. (1999) and Bárta and Karlický (2001) presented models where spike frequencies correspond to those of the upper-hybrid waves, and Willes and Robinson (1996) presented the model with spike frequencies corresponding to the Bernstein modes. Luo et al. (2021) proposed th ..read more
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Solar radio bursts associated with in situ detected energetic electrons in solar cycles 23 and 24 by R. Miteva et al.*
Community of European Solar Radio Astronomers
by Eoin Carley
7M ago
We present a short overview on the results from the first association analysis between in situ observed solar energetic electrons at 1 AU using the ACE/EPAM instrument (Samwel and Miteva, 2021) and radio bursts of type II, III and IV. The statistical analysis is performed over the last two solar cycles (SCs), 23 and 24 (1997-2019). All previous research has focused on energetic protons, whereas we aimed to compare in situ electrons and remotely observed electron emission. Over the period of interest, we selected 832 electron events with identified solar origin (solar flare or/and coronal mas ..read more
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Trieste CALLISTO Station Setup and Observations of  Solar Radio Bursts by A. Marassi and C. Monstein
Community of European Solar Radio Astronomers
by Eoin Carley
8M ago
A solar radio burst (SRB) is the intense solar radio emission often related to a solar flare and one of the possibly extreme space weather events which may affect Earth’s ionosphere and signal propagation, wireless communication, power grids and navigation systems. If an SRB occurs with the enhancement in L band radio flux, it could influence the Global Navigation Satellite Systems (GNSS) signals through direct radio wave interferences. The major space weather events like solar flares and coronal mass ejections are usually accompanied by solar radio bursts, which can be used for a real time ..read more
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Density Turbulence and the Angular Broadening of Outer Heliospheric Radio Sources at High Latitudes and in the Ecliptic Plane by S. Tasnim et al.*
Community of European Solar Radio Astronomers
by Eoin Carley
8M ago
We investigate angular broadening of radio wave scattering by density irregularities in the outer heliosphere and the very local interstellar medium (VLISM), incorporating an inner scale, latitudinal, and radial dependencies for the density fluctuation spectra and radiation propagation paths both near and out of the ecliptic plane. Outer Heliospheric Radio Emission Low-frequency radio wave emission was discovered in the distant heliosphere by the Voyager missions. A number of investigations [e.g., Gurnett et al., 1998] demonstrated that these radio emissions are apparently generated close to ..read more
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Langmuir-Slow Extraordinary Mode Magnetic Signature Observations with Parker Solar Probe by A. Larosa et al
Community of European Solar Radio Astronomers
by admin_cesra_editor
9M ago
Langmuir-Slow extraordinary mode (L-SE) waves have been routinely observed in the Solar wind and in Earth’s electron foreshock since the early age of the space exploration. They are intimately connected to the plasma emission mechanism for the type III and type II radio emissions. In fact, the generally accepted scenario is that L-SE waves are mode-converted to freely propagating electromagnetic emission at the plasma frequency. However,  the details of the the mode conversion are debated. A magnetic component for the L-SE was expected from the polarization properties of the electric fi ..read more
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LOFAR size and shape measurements of solar metric radio burst sources by Gordovskyy et al
Community of European Solar Radio Astronomers
by admin_cesra_editor
10M ago
The plasma density and magnetic field in the upper solar corona and inner heliosphere are not sufficient to produce detectable bremsstrahlung hard X-ray or gyrosynchrotron microwave emissions, making metric and decametric coherent radio emissions the only tool for probing energetic electrons in these layers of the solar atmosphere (e.g. McLean & Labrum 1985; Pick & Vilmer 2008 as reviews). This source of information is vital to understanding the underlying mechanisms of energetic electron transport in the corona, and their escape from the corona into the heliosphere. In this study, w ..read more
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