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Helioseismic Analysis Of CME Source Regions Helioseismic Analysis Of CME Source Regions Sushant Sushant Tripathy Tripathy, , Kiran Kiran Jain, Frank Hill and Richard Clark Jain, Frank Hill and Richard Clark GONG Program, National Solar Observatory, Tucson, AZ, USA GONG Program, National Solar Observatory, Tucson, AZ, USA Acknowledgements: Acknowledgements: This work is supported by NASA Grant NNG 05HL41I. NSO/Kitt Peak magnetograms used here are produced cooperatively by NSF/NOAO; NASA/GSFC, and NOAA/SEL. This work utilizes data obtained by the Global Oscillation Network Group (GONG) Program, managed by the National Solar Observatory, which is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation. The data were acquired by instruments operated by the Big Bear Solar Observatory, High Altitude Observatory, Learmonth Solar Observatory, Udaipur Solar Observatory, Instituto de Astrofísica de Canarias, and Cerro Tololo Interamerican Observatory. SOHO is a project of international cooperation between ESA and NASA. Motivation Motivation The mechanisms of coronal mass ejection (CME) initiation are still a theoretical challenge. One possible process is the cancellation of the photospheric magnetic flux by velocity convergence towards the neutral line. Observational evidence of this has been found in a couple of cases by measuring horizontal velocity from the MDI magnetograms using local correlation tracking method. Local helioseismology technique is a powerful diagnostic tool to study the mode parameters and flow fields beneath the solar surface. Data and Analysis Data and Analysis ●The data consists of GONG++ Dopplergrams for regions approximately 15ºx15º in heliographic longitude and latitude, tracked for 1664 minutes. The onset time of the CME is taken as the middle point for each event. ●We use the GONG ring diagram pipeline to obtain the power spectra and mode parameters of the solar oscillations over the selected region. ●CME events which occurred within ±30º of the disk center are chosen to avoid foreshortening effects. In total, we examine 61 CMEs in a wide variety of source regions, including active regions, filament regions, and trans-equatorial filament regions between September 2001 and December 2003. ● Each CME region is compared to a quiet region located at the same heliographic latitude and within the same Carrington rotation. Summary Summary ●We find that few regions associated with low magnetic flux that produce CMEs have shorter line widths than corresponding quiet regions. ●The shorter line width implies a longer lifetime or slow damping process for the oscillation modes of CMEs. ●This is opposite to the result for active regions, in which line widths are greater than the corresponding quiet regions. ●The temporal evolution of CMEs indicate that the line widths are shorter even one day before the CME event. This characteristic could be useful in modeling CMEs or forecasting regions in which CMEs may occur. ●Since the variation between quite regions is significant, the effect of the quiet region on the mode parameters need to be better understood. Figure 4: Figure 4: The topmost figures represent a snapshot of the magnetic field configurations of the Sun on March 16, 2002 (left panel) and September 23, 2001 (right panel). The red boxes indicate the regions which were chosen for the ring- diagram analysis. The changes in half-width as a ratio between the CME and quiet region for three consecutive days are shown in panels a-c. The CME occurred on March 17, 2002 at N0W10. The changes in half-width corresponding to the active region NOAA 9628 located at S22.5E15 on September 23, 2001 are shown in panels d-f. The magnetograms clearly show that the AR9628 has a complex configuration with a higher value of magnetic field as compared to the location of the CME event. Figure 3: Figure 3: Frequency averaged ratio of half-width for 48 CME regions with respect to a single common quiet region at disk center (left panel) as a function of magnetic flux calculated from Kitt Peak and MDI Synoptic magnetograms by averaging the unsigned magnetic flux over the same regions as the CME. The f-modes are averaged in the frequency range of 2.55-2.75 mHz, and the p-modes in the range of 3.0-3.5 mHz. The right panel shows the same quantity for 61 CMEs with respect to its own quiet region at the CME location. The linear correlation coefficients for f, p1, p2, and p3 modes are of the order of 0.71, 0.76, 0.74, 0.66. and 0.40, 0.47, 0.41, 0.30 respectively for left and right panels. Figure 1: Figure 1: The left panel shows the mean changes in ratio of half-width between 56 quiet regions with respect to a single reference quiet region. The regions which cover 14 Carrington rotations (CR1994—CR2007) are located at S22E25, S22W25, N22E25 and N22W25. The error bars signify one standard deviation of the mean. The right panel shows the same quantity between the CME region of December 19, 2002 (Bav = 97.6 G) and the quiet region of December 12, 2002 (Bav = 2.7 G), both located at N22W12. The error bars represent the standard deviations shown in the left panel. Figure 2: Figure 2: The ratio of line-widths between the CME region of January 7, 2003 located at S22E25 (Bav = 25.3 G) and two different quiet regions (CR Longitude = 28.5 and 62.5) within the same Carrington rotation. The quiet regions used in left and right panels have an average magnetic flux of 5.3 G and 5.5 G respectively. The change in line-width ratio due to the use of different quiet regions is significantly different and indicates the dependency of the mode properties on the quiet regions. f p 1 p 2 p 3 (a) (c) (b) (d) (e) (f)
