Shock Drift Acceleration and Type II Solar Radio Bursts

1994 ◽  
Vol 11 (1) ◽  
pp. 21-24 ◽  
Author(s):  
Arthur G. Street ◽  
Lewis Ball ◽  
D. B. Melrose
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Shock Front ◽  
Solar Radio ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Type Ii Bursts ◽  
Herringbone Structure ◽  
The Magnetic Field

AbstractShock drift acceleration of the electrons which produce herringbone structure in type II bursts is considered. A non-coplanar component of the magnetic field within the shock front and an electric field across the shock are taken into account. A quantitative difficulty with shock drift acceleration is identified, and possible ways of overcoming the difficulty are outlined.

Band Splitting in Type II Solar Radio Bursts

1967 ◽  
Vol 1 (2) ◽  
pp. 47-49 ◽  
Author(s):  
D. J. McLean
Keyword(s):  
Magnetic Field ◽  
Solar Radio ◽  
The Other ◽  
Spectral Features ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Band Splitting ◽  
Magnetohydrodynamic Shock ◽  
The Magnetic Field

Of the metre-wavelength solar radio bursts which have been recognized, those of type II are characterized by the most complex set of spectral features. Apparently acceptable explanations have now been put forward for most of these features. However, not all these explanations can be considered to be established. In particular the phenomenon of band splitting has been explained in different ways by Sturrock, by Tidman et al., by Zheleznyakov and Zaitsev. However, the theories of Sturrock and Tidman apparently require magnetic fields so strong as to preclude the formation of a magnetohydrodynamic shock wave by a disturbance moving at the velocity (<~ 1000 km/s) attributed to type II bursts. The same problem is encountered in other earlier theories of band splitting involving magnetic effects. The other theory does not involve the magnetic field strength. However, the details of this theory do not appear to have been properly worked out as yet.

scholarly journals Quelques relations entre sursauts radioélectriques solaires sur ondes décimétriques et caractères morphologiques des éruptions chromosphériques associées

1968 ◽  
Vol 35 ◽  
pp. 598-599
Author(s):  
A. Koeckelenbergh
Keyword(s):  
Magnetic Field ◽  
Solar Radio ◽  
Second Phase ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
The Magnetic Field ◽  
Radio Event

This work analyses some correlations or associations between certain features of solar radio bursts at 600 Mc/s and of associated chromospheric flares respectively. Subject of the analysis are 149 radio events observed at the Humain station and 125 associated flares observed at Uccle during the years 1957–61. It is found that the radioelectric energy of the bursts is associated with the eruptive area and the Hα intensity of the flares, whereas the duration of the bursts is associated with the Hα broadening. For bursts connected with a second phase, the eruptive area and the importance of the magnetic field have a bearing on the characteristics of the radio event.

Type II Solar Radio Bursts Observed with the Culgoora Radioheliograph during a Flare on 17 June 1968

1968 ◽  
Vol 1 (4) ◽  
pp. 141-142 ◽  
Author(s):  
K. Kai ◽  
D. J. McLean
Keyword(s):  
Solar Radio ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Flare Event ◽  
Type Iv ◽  
Type Ii Bursts

On 17 June 1968 we observed a flare event with the 80 MHz Culgoora radioheliograph consisting of a sequence of two type II bursts followed by enhanced emission possibly of type IV. In this paper we shall attempt to summarize some ofthe profuse data collected by the radioheliograph during this event and relate it to data from the radiospectrograph and Hα films of the associated flare (the Hα films were kindly made available by the Division of Physics, CSIRO).

scholarly journals Estimation of Shock Thickness from Dynamic Spectra of Type II Bursts

1980 ◽  
Vol 91 ◽  
pp. 257-259
Author(s):  
H. S. Sawant ◽  
S. S. Degaonkar ◽  
S. K. Alurkar ◽  
R. V. Bhonsle
Keyword(s):  
Solar Radio ◽  
Narrow Band ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Fast Electrons ◽  
Dynamic Spectra ◽  
Type Ii Bursts ◽  
Shock Thickness

Twenty type II solar radio bursts were observed during the period 1968 to 1972 by a solar radio spectroscope (240-40 MHz) at Ahmadebad. Intensity variations in type II bursts as a function of frequency and time are sometimes observed in their dynamic spectra. This fine structure enables determination of the shock thickness of the order of a few hundred to a few thousand kilometers. In a few cases, an interaction between streams of fast electrons and propagating shocks is clearly evidenced by simultaneous observations of short duration narrow band structures in type III bursts and type II bursts.

On the Longitudinal Distribution of Solar Type II Bursts

1980 ◽  
Vol 4 (1) ◽  
pp. 59-61 ◽  
Author(s):  
C. S. Wright
Keyword(s):  
Uniform Distribution ◽  
Solar Radio ◽  
Source Mechanism ◽  
Longitudinal Distribution ◽  
Central Meridian ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Solar Type ◽  
Type Ii Bursts

Distributions in longitude of solar radio bursts often are compiled by identifiying the position of the burst with the position of the associated H-Alpha flare. Early work on the longitudinal distribution of type II bursts compiled in this way (eg. Maxwell and Thompson 1962) indicated an approximately uniform distribution. Subsequently Svestka and Fritzova — Svestkova (1974) and Svestka (1976) published a distribution of 244 H-Alpha flares with which type II bursts were associated (hereafter called type II flares) that showed marked deficits near central meridian and the limb (Fig. 1). They suggested that the distribution was a product of propagational selection, being in some way dependant on the nature of the type II source mechanism as well as the manner by which the radiation reached the observer. On this basis they argued that the number of type II bursts that occurred near central meridian and near the limb was underestimated.

scholarly journals Harmonic Structure and Band Splitting of Type II Solar Radio Bursts

1965 ◽  
Vol 18 (5) ◽  
pp. 473 ◽  
Author(s):  
M Krishnamurthi ◽  
G Sivarama Sastry ◽  
T Seshagiri Rao
Keyword(s):  
Solar Radio ◽  
Solar Radius ◽  
Single Frequency ◽  
Radio Bursts ◽  
Type Ii ◽  
Harmonic Structure ◽  
Solar Radio Bursts ◽  
Band Splitting ◽  
Characteristic Features ◽  
The Magnetic Field

An analysis of single-frequency records of type II solar radio bursts at 29 Mc/s has been made. Such characteristic features as harmonic structure and band splitting due to coronal magnetic fields have been identified. Calculations indicate that the shock fronts generating the type II bursts experience a deceleration as they move outwards. Existing theories have been used to estimate the magnetic field strengths, which come out to be of the order of 3-8 G at a height of 0�7 solar radius above the photosphere at the time of occurrence of these bursts.

scholarly journals The Nature and Velocity of the Sources of Type II Solar Radio Bursts

1965 ◽  
Vol 18 (2) ◽  
pp. 167 ◽  
Author(s):  
The Late AA Weiss
Keyword(s):  
Magnetic Field ◽  
Speed Of Sound ◽  
Solar Radio ◽  
Frequency Drift ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Harmonic Emission ◽  
Band Splitting ◽  
Standard Density

Velocities of the sources of type II bursts are derived from rates of frequency drift using standard density models, both statistically for 21 bursts, and individually for 5 bursts extending over wide frequency ranges. The derived velocities exceed the speed of sound in the magnetic-field.free corona: on the average the velocity decreases with increasing height to a minimum of ,....., 750 kmjs at a little below I Ro' and j,hereafter slowly increases with height. The nature of the type II source is discussed in relation to these velocities, and also in relation to detailed measurements of harmonic ratios and band splitting for the five individual bursts. It is suggested that the type II source is either a strong parallel shock (direction of propagation of shock parallel to magnetic field) or a perpendicular shock. Magnetic field strengths of 2-20 G at 0�5 R 0 above the photosphere, decreasing to 1-10 G at 2 Ro, are derived. Finally, it is shown that theories by which fundamental emission arises in front of the shock, whilst harmonic emission originates in the interior of the shock, are untenable.

scholarly journals On the Issue of the Origin of Type II Solar Radio Bursts

2021 ◽  
Vol 922 (1) ◽  
pp. 82
Author(s):  
Gennady Chernov ◽  
Valery Fomichev
Keyword(s):  
Shock Waves ◽  
Radio Emission ◽  
Solar Atmosphere ◽  
Solar Radio ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Type Ii Radio Bursts ◽  
Type Ii Bursts ◽  
The Relationship

Abstract Type II solar radio bursts are among the most powerful events in the solar radio emission in the meter wavelength range. It is generally accepted that the agents generating type II radio bursts are magnetohydrodynamic shock waves. But the relationship between the shock waves and the other manifestations of the large-scale disturbances in the solar atmosphere (coronal mass ejections, Morton waves, EUW waves) remains unclear. To clarify a problem, it is important to determine the conditions of generation of type II radio bursts. Here, the model of the radio source is based on the generation of radio emission within the front of the collisionless shock wave where the Buneman instability of plasma waves is developed. In the frame of this model, the Alfvén magnetic Mach number must exceed the critical value, and there is a strict restriction on the perpendicularity of the front. The model allows us to obtain the information about the parameters of the shock waves and the parameters of the medium by the parameters of type II bursts. The estimates, obtained in this paper for several events with the band splitting of the fundamental and harmonic emission bands of the type II bursts, confirm the necessary conditions of the model. In this case the registration of type II radio bursts is an indication of the propagation of shock waves in the solar atmosphere, and the absence of type II radio bursts is not an indication of the absence of shock waves. Such a situation should be taken into account when investigating the relationship between type II radio bursts and other manifestations of solar activity.

Type II Solar Radio Bursts over Solar Cycle 21

1994 ◽  
Vol 144 ◽  
pp. 283-284
Author(s):  
G. Maris ◽  
E. Tifrea
Keyword(s):  
Solar Radio ◽  
Interplanetary Space ◽  
Impulsive Phase ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Strong Energy ◽  
Mass Ejection ◽  
Geophysical Effect ◽  
Radio Event

The type II solar radio bursts produced by a shock wave passing through the solar corona are one of the most frequently studied solar activity phenomena. The scientific interest in this type of phenomenon is due to the fact that the presence of this radio event in a solar flare is an almost certain indicator of a future geophysical effect. The origin of the shock waves which produce these bursts is not at all simple; besides the shocks which are generated as a result of a strong energy release during the impulsive phase of a flare, there are also the shocks generated by a coronal mass ejection or the shocks which appear in the interplanetary space due to the supplementary acceleration of the solar particles.

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