High-cadence Hα imaging of solar flares

The Ha observation is a powerful tool to study the high-energy aspect of solar flares. Spiky brightenings of flare kernels at the Halpha center reflect the rapid fluctuation in particle acceleration; linear polarization of Halpha emission might be evidence of accelerated pro,tons; red-shifts of the Halpha line are caused by the chromospheric evaporation. To study the spiky brightenings of flare kernels with high-cadence imaging at the Halpha center, a high-speed Halpha camera for the Solar Flare Telescope at Mitaka, NAOJ, had been developed and it started the regular observation in 2001 July. However, the polarimetry and the Dopplermetry are also important and they are required to be carried out in parallel with the high-cadence imaging at the Halpha center. Then, we upgraded the original high-speed Halpha camera to a new Halpha camera system for the multi-aspect Halpha observations. which performs all of the high-cadence imaging, the linear polarization measurements, and the off-band imaging for velocity measurements. The new system started the observation in 2002 July. In this paper, the multi-aspect Halpha imaging system is described and sample Halpha images are presented. (C) 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.