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LOFAR observations of fine spectral structure dynamics in type IIIb radio bursts View all abstracts by submitter

Ivan Sharykin   Submitted: 2018-06-05 01:11

Solar radio emission features a large number of fine structures demonstrating great variability in frequency and time. We present spatially resolved spectral radio observations of type IIIb bursts in the 30-80 MHz range made by the Low Frequency Array (LOFAR). The bursts show well-defined fine frequency structuring called "stria" bursts. The spatial characteristics of the stria sources are determined by the propagation effects of radio waves; their movement and expansion speeds are in the range of 0.1-0.6c. Analysis of the dynamic spectra reveals that both the spectral bandwidth and the frequency drift rate of the striae increase with an increase of their central frequency; the striae bandwidths are in the range of ~20-100 kHz and the striae drift rates vary from zero to ~0.3 MHz s^-1. The observed spectral characteristics of the stria bursts are consistent with the model involving modulation of the type III burst emission mechanism by small-amplitude fluctuations of the plasma density along the electron beam path. We estimate that the relative amplitude of the density fluctuations is of dn/n~10-3, their characteristic length scale is less than 1000 km, and the characteristic propagation speed is in the range of 400-800 km s-1. These parameters indicate that the observed fine spectral structures could be produced by propagating magnetohydrodynamic waves.

Authors: I.N. Sharykin, E.P. Kontar, A.A. Kuznetsov
Projects: LOw Frequency ARray (LOFAR)

Publication Status: Revised
Last Modified: 2018-06-06 19:53
Go to main E-Print page  Mini-filament Eruptions Triggering Confined Solar Flares Observed by ONSET and SDO   Critical magnetic field strengths for solar coronal plumes in quiet regions and coronal holes?  Edit Entry  Download Preprint  Delete Entry 

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