scholarly journals Estimation of Magnetic Field Strength from Enhanced Solar Radio Emission

1994 ◽  
Vol 47 (6) ◽  
pp. 811 ◽  
Author(s):  
SBSS Sarma
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Radio Emission ◽  
Solar Radio ◽  
Active Regions ◽  
Shock Velocity ◽  
Solar Radio Emission ◽  
Type I ◽  
Radio Noise ◽  
Coronal Magnetic Fields

The manifestation of solar activity on radio noise records at 28.6 MHz is discussed with special emphasis on Type-I noise storms and the associated coronal magnetic fields above the active regions in time. Magnetic fields are estimated, assuming that the Type-I radio emission at decametre wavelengths is due to shock waves, by making use of the observed shock velocity. The results are comparable with the existing estimates.

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 Structural and Evolutionary Features of Flare-Producing Active Regions During 1988-1990

1993 ◽  
Vol 141 ◽  
pp. 388-390
Author(s):  
A. A. Golovko
Keyword(s):  
Solar Activity ◽  
Radio Emission ◽  
Solar Radio ◽  
Active Regions ◽  
Magnetic Activity ◽  
High Solar Activity ◽  
Solar Radio Emission ◽  
Evolutionary Features ◽  
Siberian Solar Radio Telescope ◽  
Flare Productivity

During the period of high solar activity (1988-1990) the Sayan and Baikal Observatories of the ISTP carried out observations of the chromosphere in the H-alpha line, the photosphere and of sunspot magnetic fields; at the Siberian Solar Radio Telescope, solar radio emission observations at 5.2 cm wavelength were made. Using those observations a study is made of the evolution of “centers of magnetic activity” (Bumba, 1986) in nine active regions with different flare productivity, for which the most complete observations were available. In three cases (NOAA Nos. 5229, 5643 and 5669) they were the targets of the cooperative international Max’91 program.

scholarly journals On the polarization of solar radio emission at 1.5-m wavelength

1959 ◽  
Vol 9 ◽  
pp. 259-262
Author(s):  
U. J. Alekseev ◽  
V. V. Vitkevich
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Solar Radio ◽  
Polarization Ellipse ◽  
Optical Methods ◽  
Solar Radio Emission ◽  
Polarization Measurements ◽  
New Information ◽  
Extensive Information ◽  
The Magnetic Field

1. Solar radio emission is usually characterized only by the intensity, i.e. by a single value at a given frequency.In polarization measurements the radio emission is characterized by four values (for example, by the unpolarized-component intensity and three components of the polarization ellipse).Here we see that observations of solar radio emission with a polarimeter give us considerably more extensive information than the usual observations give. It is a very important fact that the polarization of the radio emission is determined by the strength and direction of the magnetic field of emitting regions. Thus, we connect the polarized radio emission with a magnetic field that is noticeably higher than the field in the region which we can study by optical methods.It should also be noticed that one of the most interesting unsolved problems is establishing the nature of the disturbed solar radio emission. It is clear that new information on the polarization of radio emission will contribute to the solution of this problem; but in spite of its importance and urgency, investigations to solve it are being carried on only in a small number of observatories. The observations in Australia and the work in Japan may be mentioned.

On the fine structures in interplanetary radio emissions

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  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  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  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>

Polarized Solar Radio Emission at mm Wavelengths associated with Sunspot Magnetic Fields

1971 ◽  
Vol 232 (30) ◽  
pp. 82-84 ◽  
Author(s):  
SIDNEY EDELSON ◽  
EARLE B. MAYFIELD ◽  
FRED I. SHIMABUKURO
Keyword(s):  
Magnetic Fields ◽  
Radio Emission ◽  
Solar Radio ◽  
Solar Radio Emission
Sign in / Sign up

Export Citation Format

Share Document