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.

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.

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.

scholarly journals On the Relative Position and Origin of Harmonics in the Spectra of Solar Radio Bursts of Spectral Types II And III

1962 ◽  
Vol 15 (2) ◽  
pp. 180 ◽  
Author(s):  
SF Smerd ◽  
JP Wild ◽  
KV Sheridan
Keyword(s):  
Solar Atmosphere ◽  
Relative Position ◽  
Solar Radio ◽  
Second Harmonic ◽  
Simple Theory ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Harmonic Emission ◽  
Type Iii

Observational results are given concerning the relative positions on the Sun's disk of the fundamental and second-harmonic emissions of solar radio bursts of spectral types II and III. Contrary to simple theory, the results indicate that it is common for the harmonic emission in type II bursts to arrive from directions corresponding to much lower heights in the solar atmosphere than the fundamental. The results for type III bursts are inconclusive but suggest the same trend.

scholarly journals Solar Radio Bursts of Spectral Type II

1959 ◽  
Vol 12 (4) ◽  
pp. 327 ◽  
Author(s):  
JA Roberts
Keyword(s):  
Spectral Type ◽  
Solar Radio ◽  
Bone Structure ◽  
Second Harmonic ◽  
Radio Bursts ◽  
Type Ii ◽  
Harmonic Structure ◽  
Solar Radio Bursts ◽  
Band Splitting ◽  
Compound Type

The characteristics of bursts of spectral type II are studied in a sample of 65 bursts. Approximately half the bursts show harmonic structure and about half are compound type III-type II events. Band splitting, the doubling of both the fundamental and second harmonic bands, is also relatively common. A rather less common feature is the appearance of herring-bone structure in which the slowly drifting band of the type II burst appears to be a source from which rapidly drifting elements diverge towards lower and higher frequencies.

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.

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.

Higher Harmonic Plasma Radiation in Type II Solar Radio Bursts

1990 ◽  
pp. 517-518
Author(s):  
V. V. Fomichev ◽  
I. M. Chertok ◽  
R. V. Gorgutsa ◽  
A. K. Markeev ◽  
B. Kliem ◽  
...  
Keyword(s):  
Solar Radio ◽  
Plasma Radiation ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Higher Harmonic

scholarly journals The correlation of solar radio bursts by magnetic activity and cosmic rays

1959 ◽  
Vol 9 ◽  
pp. 210-213
Author(s):  
A. R. Thompson
Keyword(s):  
Cosmic Rays ◽  
Radio Astronomy ◽  
Solar Radio ◽  
Magnetic Activity ◽  
Radio Bursts ◽  
Type Ii ◽  
Frequency Range ◽  
Sweep Frequency ◽  
Solar Radio Bursts ◽  
Auroral Particles

The sweep-frequency equipment at the Harvard Radio Astronomy Station, Fort Davis, Texas, has now been running continuously since 1956 September, recording solar radio activity in the frequency range from 100 to 580 Mc/s. The following contribution describes preliminary investigations of the correlation of the radio data with solar corpuscular emissions. This work was initiated to examine the well-known suggestions that the origins of the type II and type III radio bursts are associated with the ejection of auroral particles and cosmic rays respectively.

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