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N. Gopalswamy (NASA/GSFC and Catholic U.), T. J. W. Lazio, N. E. Kassim (Naval Research Laboratory), W. C. Erickson (U. Maryland)
Almost all of the transient disturbances in the Sun-Earth connected space are amenable to probing by metric and decametric radio wavelengths (150 MHz down to ionospheric cut-off at 15 MHz). The long wavelength radio imaging with polarization capability is virtually the only way of measuring magnetic fields in the outer corona and hence an important tool in the study of long-term evolution of the Sun as it sheds its magnetic field through coronal mass ejections (CMEs). Shocks generated during the CMEs are detected as type II radio bursts; some of the energetic electrons are detected as type III bursts; ejected plasmoids are observed as type IV bursts.
Ionospheric effects used to pose a major problem for long wavelength imaging. We now know that most of the shortcomings due to ionospheric effects can be virtually eliminated, thanks to the development in image restoration such as self-calibration (Kassim and Erickson, 1998). Low frequency technologies are relatively cheap and well proven. A synergistic combination of a ground based Long Wavelength Array (LWA) and the space-borne coronagraphs such as on board the STEREO mission could prove to be an extremely powerful tool to understand the interplanetary propagation of solar disturbances. Passive imaging of solar emissions can also be combined with radar imaging to increase the scientific return of the LWA (see poster by Lazio et al). The low frequency regime has also the advantage of combining solar physics with non-solar radio astronomy: Sun in the day time and the rest of the universe at night (see poster by Kassim et al).
NG is an NAS/NRC Senior Research Associate at NASA/GSFC on leave from the Catholic University. Basic research in radio astronomy at the Naval Research Laboratory is supported by the Office of Naval Research.
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