HR: 08:30h
 AN: SP51C-01    [Abstracts]
 TI: Dissertation Talk: High Resolution Observations of Multi-Wavelength Emissions During Two X-Class White-Light Flares
 AU: * Xu, Y
EM: yx2@njit.edu
 AF: Center for Solar-Terrestrial Research, Physics Department, New Jersey Institute of Technology , 323 Martin Luther King Blvd, Newark, NJ 07102 United States
AU: Cao, W
EM: wcao@bbso.njit.edu
 AF: Center for Solar-Terrestrial Research, Physics Department, New Jersey Institute of Technology , 323 Martin Luther King Blvd, Newark, NJ 07102 United States
AU: Cao, W
EM: wcao@bbso.njit.edu
 AF: Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314 United States
AU: Liu, C
EM: cl45@njit.edu
 AF: Center for Solar-Terrestrial Research, Physics Department, New Jersey Institute of Technology , 323 Martin Luther King Blvd, Newark, NJ 07102 United States
AU: Yang, G
EM: gyang@njit.edu
 AF: Center for Solar-Terrestrial Research, Physics Department, New Jersey Institute of Technology , 323 Martin Luther King Blvd, Newark, NJ 07102 United States
AU: Jing, J
EM: jj4@njit.edu
 AF: Center for Solar-Terrestrial Research, Physics Department, New Jersey Institute of Technology , 323 Martin Luther King Blvd, Newark, NJ 07102 United States
AU: Denker, C
EM: carsten.j.denker@njit.edu
 AF: Center for Solar-Terrestrial Research, Physics Department, New Jersey Institute of Technology , 323 Martin Luther King Blvd, Newark, NJ 07102 United States
AU: Denker, C
EM: carsten.j.denker@njit.edu
 AF: Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314 United States
AU: Wang, H
EM: haimin@flare.njit.edu
 AF: Center for Solar-Terrestrial Research, Physics Department, New Jersey Institute of Technology , 323 Martin Luther King Blvd, Newark, NJ 07102 United States
AU: Wang, H
EM: haimin@flare.njit.edu
 AF: Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314 United States
AB: We observed two X-class white-light flares (WLF) on 2003 October~29 (~20:40~UT) and November~2 (~17:16 UT) using the Dunn Solar Telescope (DST) and its High-Order Adaptive Optics (HOAO) system in several wavelengths. The spatial resolution was close to the diffraction limit of DST's 76~cm aperture. The temporal resolution was as high as 2~s. It is the first time that WLFs were observed in the Near Infrared (NIR) wavelength region. We present a detailed study in this presentation by comparing the photospheric continuum observations during these two events with corresponding line-of-sight (LOS) magnetograms of the Michelson Doppler Imager (MDI) and hard X-ray (HXR) data of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Our observations show that:

  1. Significant intensity enhancements were observed in the visible and NIR continua and G-band during the impulsive phase of the flares. The maximum intensity enhancements were 37% of white-light and 25% of the NIR continuum during the first event, and 76% of white-light and 66% of the NIR continuum for the second flare.
  2. The flares were typical two ribbon flares. All ribbons showed a brighter core surrounded by a halo structure. The ribbon separation speeds were about 28~km/s in the first and 24~km/s in the second event based on NIR observations. The derived electric fields in the reconnection current sheet Ec are about 23~V~ cm-1 and 22~V~cm-1, respectively.
  3. The NIR emission and the impulsive HXR emission up to 800~keV were well correlated, not considering a small delay of less than two minutes.
  4. The high resolution and high cadence images gave us the first chance to measure the cooling time of flares close to the photosphere. We found that the cooling process could be characterized by two steps. A quick temperature drop, which is related to the cooling process of the bright cores, and a relative slow decay related to the halo structures. The fine scale is in the order of less than 30~s and a few minutes for these two steps, respectively. Based on these observational results, we discuss several models that provide possible mechanisms to explain these continuum enhancements, especially in the NIR.
    This work is supported by NSF under grants ATM-0313591, ATM-0236945, ATM-0233931 and AST-0307676, by NASA under grants NAG5-10910, NAG5-10212 and NAG5-12733, and by Air Force under grant F49620-02-1-0265 and by NSFC-10103004.
    DE: 7519 Flares
     DE: 7524 Magnetic fields
     DE: 7529 Photosphere
     SC: Solar Physics Division - AAS [SP]
     MN: 2005 Joint Assembly