Solar Second Harmonic Plasma Emission and the Head-on Approximation

1995 ◽  
Vol 12 (2) ◽  
pp. 197-201 ◽  
Author(s):  
A. J. Willes ◽  
P. A. Robinson ◽  
D. B. Melrose
Keyword(s):  
Narrow Band ◽  
Plasma Frequency ◽  
Second Harmonic ◽  
Langmuir Wave ◽  
Radio Bursts ◽  
Type Ii ◽  
Coalescence Process ◽  
Solar Radio Bursts ◽  
Langmuir Waves ◽  
Band Spectra

AbstractThe coalescence of two Langmuir waves, L and L′, produces emission at twice the plasma frequency in type II and type III solar radio bursts. The analysis of the coalescence process is usually simplified by assuming the head-on approximation, where the wavevectors of the coalescing waves satisfy kL′ ≈ −kL, corresponding to the two Langmuir waves meeting head on. However, this is not always a valid approximation, particularly when the peak of the Langmuir spectrum lies at small wavenumbers, for narrow band spectra, and for spectra with broad angular ranges. Realistic Langmuir wave spectra are used to investigate the effects of relaxing the head-on approximation.

A Theory of Type I Solar Radio Bursts

1973 ◽  
Vol 2 (4) ◽  
pp. 215-217 ◽  
Author(s):  
W. N. -C. Sy
Keyword(s):  
Narrow Band ◽  
Plasma Frequency ◽  
Type I ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Circularly Polarized ◽  
Average Decrease ◽  
Brightness Temperatures ◽  
Solar Storm ◽  
The Continuum

Type I radio bursts, as distinct from the continuum component frequently associated with them in a solar storm, are short-lived (0.1-2 s), narrow-band (2-10 MHz) bursts with frequency drift rates from 0 to 20 MHz s−1. They come from coronal regions close to the corresponding plasma levels, i.e. the frequency of radiation ω is close to the local plasma frequency ωp. They occur more frequently at frequencies above ~100 MHz but at times extend to frequencies as low as 20 MHz. Their observed equivalent brightness temperatures are usually about 109 K but they can reach 1011 K or higher. Except for an average decrease in polarization towards the limb and except for initial stages of a storm, type I bursts are strongly circularly polarized (approaching 100 per cent) in the sense of the O-mode.

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 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.

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 The Mechanism Responsible for 'Shadow' Type III Solar Radio Bursts. II. Absorption due to Ion Sound Turbulence

1974 ◽  
Vol 27 (2) ◽  
pp. 271 ◽  
Author(s):  
DB Melrose
Keyword(s):  
Energy Density ◽  
Solar Radio ◽  
Plasma Frequency ◽  
Radio Bursts ◽  
Sound Waves ◽  
Solar Radio Bursts ◽  
Langmuir Waves ◽  
Transverse Waves ◽  
Type Iii ◽  
Ion Plasma

The hypothesis is explored that ion sound turbulence generated by the exciting agency for type III bursts is responsible for shadow type III events. The possible absorption mechanisms are listed: the most favourable are the coalescence of transverse waves and ion sound waves into Langmuir waves or the decay of transverse waves into Langmuir waves and ion sound waves. These mechanisms can operate only if the background source emits at the fundamental plasma frequency and the absorbing region is directly above it (;$ 3 x 104 km). It is found that the event discussed by Kai (1973) can be explained in terms of such absorption with reasonable parameters, e.g. with an energy density in ion sound turbulence W' ~ 10-12 ergcm- 3 at frequencies co' ~ O�3cop! (where cop! is the ion plasma frequency).

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.

scholarly journals Recent Results of Meter-decameter Wave Observations of Solar Flares

1989 ◽  
Vol 104 (2) ◽  
pp. 185-189
Author(s):  
N. Copalswamy ◽  
M. R. Kundu
Keyword(s):  
Solar Flares ◽  
Solar Radio ◽  
Radio Bursts ◽  
Type Ii ◽  
Solar Radio Bursts ◽  
Type Iii ◽  
Type Iv

AbstractWe present recent results from meter-decameter imaging of several classes of solar radio bursts: Preflare activity in the form of type III bursts, correlated type IIIs from distant sources, and type II and moving type IV bursts associated with flares and CMEs.

Sign in / Sign up

Export Citation Format

Share Document