Maoshui Lv

TEMPORAL SPECTRAL SHIFT AND POLARIZATION OF A BAND-SPLITTING SOLAR TYPE II RADIO BURST

In many type II solar radio bursts, the fundamental and/or the harmonic branches of the bursts can split into two almost parallel bands with similar spectral shapes and frequency drifts. However, the mechanisms accounting for this intriguing phenomenon remain elusive. In this study, we report a special band-splitting type II event in which spectral features appear systematically earlier on the upper band (with higher frequencies) than on the lower band (with lower frequencies) by several seconds. Furthermore, the emissions carried by the splitting band are moderately polarized with the left-hand polarized signals stronger than the right-hand ones. The polarization degree varies in a range of –0.3 to –0.6. These novel observational findings provide important constraints on the underlying physical mechanisms of band-splitting of type II radio bursts.

Broad flattop transparent photonic band in truncated photonic crystals composed of the symmetric unit cell

We theoretically show that a one-dimensional finite all-dielectric periodic structure composed of symmetric unit cells can possess a broad flattop transparent photonic band. In contrast to the conventional viewpoint that the thickness of the truncated photonic crystals affects the transmission within the pass band, the transparent photonic band is insensitive to the change of the periodic number since the equivalent refractive indices of our structures can be nearly equal to that of the background in a wide frequency range. With easy fabrication, this broad flattop transparent photonic band will play an important role in the broadband filtering.