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25 posts · 10,328 views

The Highlights of Solar Radio Physics (science nuggets) are short communications written in the language accessible to a non-expert in the specific area. The nugget is a brief description of a new and interesting scientific result, not as detailed as a scientific article, but rather written in a more discursive ‘news & views’ style.

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  • April 25, 2017
  • 07:02 AM
  • 85 views

The Brightness Temperature of the Quiet Solar Chromosphere at 2.6 mm by Kazumasa Iwai et al

by CESRA in Solar Radio Science

The brightness temperature of the Sun constitutes a basic property of the solar atmosphere. The main emission mechanism of the Sun at millimeter and submillimeter wavelengths is thermal free–free emission from the chromosphere, which is an atmospheric layer with a temperature ranging between 6000 to 20,000 K. The opacity of thermal free–free emission depends on the temperature and density in the emission region. In addition, the Rayleigh– Jeans law is applicable [...]... Read more »

Iwai, K., Shimojo, M., Asayama, S., Minamidani, T., White, S., Bastian, T., & Saito, M. (2017) The Brightness Temperature of the Quiet Solar Chromosphere at 2.6 mm. Solar Physics, 292(1). DOI: 10.1007/s11207-016-1044-5  

  • April 11, 2017
  • 06:34 AM
  • 242 views

How Electron Beams Produce Continuous Coherent Plasma Emission by H. Che, M. Goldstein, P. Diamond, and R. Sagdeev

by CESRA in Solar Radio Science

It is commonly accepted that energetic electron beams can produce drift frequency radio emission or Type III bursts since Ginzburg and Zhelezniakov first proposed the idea in 1958. However, the electron two-stream instability time (see reference 2) in the corona is fraction of a second, while the duration of coronal Type III bursts lasts several orders of magnitude longer. This problem is called the “Sturrock Dilemma” and remains a subject [...]... Read more »

  • March 28, 2017
  • 08:04 AM
  • 204 views

Radio Diagnostics of Electron Acceleration Sites During the Eruption of a Flux Rope in the Solar Corona by Eoin Carley et al.*

by CESRA in Solar Radio Science

Flares and coronal mass ejections (CMEs) are thought to result from magnetic energy release in the solar corona, often involving the destabilisation of a twisted magnetic structure known as a flux rope (Chen et al. 2011, Webb et al. 2012). This activity may be accompanied by the acceleration of electrons (Kahler 2007, Lin et al. 2011). However, there is ongoing debate on exactly where, when and how this particle acceleration occurs [...]... Read more »

  • March 14, 2017
  • 08:05 AM
  • 254 views

Solar Science with the Atacama Large Millimeter/Submillimeter Array — A New View of Our Sun by S. Wedemeyer

by CESRA in Solar Radio Science

The Atacama Large Millimeter/submillimeter Array (ALMA), which consists of 66 antennas placed on the Chajnantor plateau in the Chilean Andes, has already produced impressive results for a large range of astronomical objects. Regular observations of the Sun have been carried out for the first time in December 2016 and exciting results can be expected soon. ALMA combines high spatial, temporal, and spectral resolution with the diagnostic advantages of radiation at [...]... Read more »

Wedemeyer, S., Bastian, T., Brajša, R., Hudson, H., Fleishman, G., Loukitcheva, M., Fleck, B., Kontar, E., De Pontieu, B., Yagoubov, P.... (2015) Solar Science with the Atacama Large Millimeter/Submillimeter Array—A New View of Our Sun. Space Science Reviews, 200(1-4), 1-73. DOI: 10.1007/s11214-015-0229-9  

  • February 28, 2017
  • 07:03 AM
  • 220 views

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

by CESRA in Solar Radio Science

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 [...]... Read more »

Huang, J., Kontar, E., Nakariakov, V., & Gao, G. (2016) QUASI-PERIODIC ACCELERATION OF ELECTRONS IN THE FLARE ON 2012 JULY 19. The Astrophysical Journal, 831(2), 119. DOI: 10.3847/0004-637X/831/2/119  

  • February 14, 2017
  • 07:02 AM
  • 370 views

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

by CESRA in Solar Radio Science

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 [...]... Read more »

  • January 31, 2017
  • 07:06 AM
  • 584 views

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

by CESRA in Solar Radio Science

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 [...]... Read more »

Ziebell, L., Petruzzellis, L., Yoon, P., Gaelzer, R., & Pavan, J. (2016) PLASMA EMISSION BY COUNTER-STREAMING ELECTRON BEAMS. The Astrophysical Journal, 818(1), 61. DOI: 10.3847/0004-637X/818/1/61  

  • January 17, 2017
  • 07:03 AM
  • 375 views

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

by CESRA in Solar Radio Science

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 [...]... Read more »

  • January 3, 2017
  • 07:01 AM
  • 392 views

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

by CESRA in Solar Radio Science

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 & [...]... Read more »

  • December 20, 2016
  • 07:02 AM
  • 459 views

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

by CESRA in Solar Radio Science

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 [...]... Read more »

  • December 13, 2016
  • 08:23 AM
  • 498 views

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

by CESRA in Solar Radio Science

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 [...]... Read more »

  • December 6, 2016
  • 07:08 AM
  • 423 views

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

by CESRA in Solar Radio Science

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, [...]... Read more »

  • November 29, 2016
  • 07:02 AM
  • 460 views

Simultaneous Submillimeter and Hard X-Ray Intermittent Processes during Flares by Guillermo Giménez de Castro et al.*

by CESRA in Solar Radio Science

Intermittency is a disruptive characteristic of a process, which can be associated, in many cases, with a sudden energy release. Intermittency is a key characteristic of flares that should become evident in the flux time evolution at many different wavelengths. We investigate the similarities and differences of the intermittency during [...]... Read more »

  • November 22, 2016
  • 07:03 AM
  • 480 views

Energetic electrons generated during solar flares by Gottfried Mann

by CESRA in Solar Radio Science

The Sun is an active star. It manifests not only in everybody’s well-known Sun spots with the related 11-year cycle. This activity manifests not only as the well-known sun spot phenomenon with a related 11-year cycle, but also in flares, coronal mass ejections (CMEs), and solar energetic particle (SEP) events. Thus, [...]... Read more »

Gottfried Mann. (2016) Energetic electrons generated during solar flares. Journal of Plasma Physics. info:/

  • November 15, 2016
  • 07:05 AM
  • 448 views

Solar Type III Radio Bursts: Directivity Characteristics by G. Thejappa and R. J. MacDowall

by CESRA in Solar Radio Science

Type III radio bursts are a group of fast drifting radio emissions associated with solar flares [see also previous CESRA highlights on type III bursts here and here]. These radio emissions are believed to be excited at the fundamental and second harmonic of the electron plasma frequency, by the electron beam excited Langmuir waves [...]... Read more »

G. Thejappa and R. J. MacDowall. (2015) Solar Type III Radio Bursts: Directivity Characteristics . Journal of Physics: Conference Series. info:/

  • November 1, 2016
  • 09:01 AM
  • 553 views

Multiwavelength study of 20 jets that emanate from the periphery of active regions by Sargam M. Mulay et al.*

by CESRA in Solar Radio Science

Solar jets are transient phenomena observed in the solar atmosphere. They appear as sharp-edged, impulsive, and collimated flows of plasma that move outwards with a bright spot at the footpoint, which forms an ‘inverted-Y’ topology of magnetic field lines. They are observed throughout the atmosphere i.e. in the photosphere (Hα, Ca II K [...]... Read more »

Mulay et al. (2006) Multiwavelength study of 20 jets that emanate from the periphery of active regions. Astronomy . info:/

  • October 18, 2016
  • 09:02 AM
  • 577 views

Decameter type III bursts with changing frequency drift-rate signs by V. Melnik et al.*

by CESRA in Solar Radio Science

We discuss properties of type III bursts that change the sign of their drift rate from negative to positive and vice versa. Moreover, these bursts may change the sign of their drift rates more than once. These particular type III bursts were observed simultaneously by the radio telescopes UTR-2, URAN-2, [...]... Read more »

V. Melnik et al. (2015) Decameter type III bursts with changing frequency drift-rate signs . Solar Physics. info:/

  • October 4, 2016
  • 09:05 AM
  • 575 views

Propagation of Coronal Mass Ejections: Aerodynamic Drag by Nishtha Sachdeva and Prasad Subramanian

by CESRA in Solar Radio Science

Coronal Mass Ejections (CMEs) are hot, massive blobs of plasma and magnetic fields that erupt from the Sun, and are sometimes Earth-directed. Depending on their speed and mass these transients can strongly effect the space weather, causing geomagnetic storms and damage to space bound technologies. It is therefore imperative to [...]... Read more »

Sachdeva, N., Subramanian, P., Colaninno, R., et al.,. (2015) Propagation of Coronal Mass Ejections: Aerodynamic Drag. Astrophysical Journal, 158. info:/

  • September 27, 2016
  • 09:01 AM
  • 363 views

Diagnostics of the acceleration modulation process based on quasi-periodic variations of flare emission by Kupriyanova et al.*

by CESRA in Solar Radio Science

Quasi-periodic pulsations (QPPs) with the characteristic time scales from a few seconds up to tens of minutes are frequently seen in the time profiles of solar and stellar flare emission (Nakariakov et al., 2016 ). Among all the possibilities of QPPs explanation, two reasons are discussed more actively: magnetohydrodynamic (MHD) [...]... Read more »

Kupriyanova et al. (2016) Diagnostics of the acceleration modulation process based on quasi-periodic variations of flare emission. Solar Physics. info:/

  • September 13, 2016
  • 09:02 AM
  • 551 views

An Analysis of Interplanetary Solar Radio Emissions Associated with a Coronal Mass Ejection by V. Krupar et al.*

by CESRA in Solar Radio Science

Type II and type III bursts are generated, via the plasma emission mechanism, when beams of suprathermal electrons interact with the ambient plasma generating radio emissions at the plasma frequency fp (the fundamental emission) or at its second harmonic 2fp (the harmonic emission) [see also previous CESRA highlights here and [...]... Read more »

V. Krupar et al. (2016) An Analysis of Interplanetary Solar Radio Emissions Associated with a Coronal Mass Ejection. Astrophys. J. Lett., 823, L5. info:/

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