Physics – Plasma Physics
Scientific paper
Oct 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008jgra..11310101l&link_type=abstract
Journal of Geophysical Research, Volume 113, Issue A10, CiteID A10101
Physics
Plasma Physics
5
Solar Physics, Astrophysics, And Astronomy: Radio Emissions, Space Plasma Physics: Mathematical And Numerical Techniques (0500, 3200), Solar Physics, Astrophysics, And Astronomy: Corona, Radio Science: Radio Wave Propagation, Space Plasma Physics: Wave/Wave Interactions
Scientific paper
Quasilinear-based simulations are presented of bidirectional type III bursts that originate in the corona and are observed at Earth, assuming plasma emission. By extending a recent simulation model to more realistic three-dimensional source structures and including Langmuir collisional damping, dynamic spectra of both the normal-drifting (normal) and the reverse-slope-drifting (RS) bursts are simulated and studied in detail for realistic electron-release and coronal parameters. The radio flux, brightness temperature, frequency drift rate, and time duration of the bursts agree semiquantitatively with typical observations. The flux of 2f p emission is significantly higher than that of f p emission, which is below the noise thresholds of typical radio instruments. This is mainly because the f p emission is strongly free-free absorbed and further damped by scattering off density fluctuations. The 2f p emission is asymmetric between the normal and RS bursts, with the normal burst stronger and lasting longer than the RS burst, consistent with observations. This occurs primarily because of the downgoing beam being weaker, not faster, and narrower in velocity space than the upgoing beam, and because of stronger free-free absorption for the RS burst than for the normal burst, consistent with a semiquantitative theory. Furthermore, the RS burst terminates at frequencies lower than the maximum simulated, and the normal burst extends to lower frequencies not simulated because of computational limitations. Collisional damping reduces the Langmuir wave levels and consequently suppresses the flux levels and washes out the dynamic spectral structures associated with successive wave-wave interactions when the damping is switched off.
Cairns Iver H.
Li Bo
Robinson Peter A.
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