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Scientific Interests in OVSA Expanded Array

Scientific Interests in OVSA Expanded Array. Haimin Wang. Physics of Elementary Bursts. Multi-wavelength Observations: Microwave imaging spectroscopy RHESSI demodulated light curves

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Scientific Interests in OVSA Expanded Array

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  1. Scientific Interests in OVSA Expanded Array Haimin Wang

  2. Physics of Elementary Bursts Multi-wavelength Observations: Microwave imaging spectroscopy RHESSI demodulated light curves 0.1”, 100ms resolution flare observations from NST, IBIS, Yunnan 1-m telescope (it has small time overlap with OVSA, but similar science can be done with Chinese FASR)

  3. Trajectoriesof the brightest pixelsin flare kernels K2(left) and K1 (right).The time lapse ismarked by the colortable. The solid (dotted)contours indicate the positive(negative) longitudinal magnetic field. Comparison of Halpha -1.3 Åintensity (thin lines) and hardX-ray flux (thick lines) forthree flare kernels duringthe time interval 18:03:59 18:04:06UT. For the Halpha emission, both the rawdata and a 10-pointsmoothed curve are plotted.

  4. Comparisonof Halpha -1.3 Å intensity(thin lines) and hard X-rayflux (thick lines) for threeflare kernels during thetime interval 18:04:22 18:04:29 UT.For the H emission,both the raw dataand a 10-point smoothedcurve are plotted.

  5. Power spectraof the fast variationsof the Halpha -1.3 Åemission at the threeflare kernels 18:04:22 to 18:04:29 UT

  6. HXR and Radio Observations of the 2011-Feb-15 Flare

  7. The flare: NOAA 11158 (S21O W21O) Occurred at 01:44 UT, peaked around 01:55 UT GOES class: X2.2 Energetic: White-Light Flare Up to 100 keV HXR No Gamma-ray emission Clear Sunquake (RHESSI NUDGET#148 by Hudson & Fletcher)

  8. White-Light (From HINODE/SOT) Red Continuum 6684 Å 01:51:03 UT Green Continuum 5550 Å Before flare Contract-reversed difference image Unaltered image Flare ribbon (dark feature)

  9. HXR (RHESSI) Overview of HXR (4 sec) and SXR time profiles

  10. HXR (RHESSI) Demodulated HXR light curves More peaks than the low cadence light curves in previous slide

  11. HXR (RHESSI) SHS variation A peak at ~ 01:50:10 is NOT selected, Because the change of attenuator.

  12. RADIO (KSRBL) Radio light curve cadence ~ 2.2 sec

  13. HXR vs. RADIO HXR For electron flux, δx =  + 1 = 5.12 (Silva et al. 2000) RADIO α = 1.29 δr= 1.11*α + 1.36 = 2.79 (Silva et al. 2000) δx - δr = 2.33, Still within the upper limit of 2.7 as in Silva et al. 2000

  14. 3-D magnetic field extrapolation • LFF • NLFF (Large FOV of HMI and Seeing Free) • Chromospheric Field Tracing • STEREO Observations --Microwave Diagnosis

  15. Nonpotentiality of Chromospheric Fibrils Objective: We assume that chromospheric fibrils are magnetic field-aligned. By comparing the orientation of the fibrils with the azimuth of the embedding chromospheric magnetic field extrapolated from a potential field model, the shear angle, a measure of nonpotentiality, along the fibrils is readily deduced. Following this approach, we make a quantitative assessment of the nonpotentiality of fibrils in the active region NOAA 11092.

  16. Data Sets: NOAA 11092, 2010 Aug. 2 Left: H image; Right: LOS magnetogram, overlaid with the potential transverse field. FOV: 254”264”

  17. Method: Segmentation and Modeling of Chromospheric Fibrils 1: the original image after Gaussian smoothing; 2: the difference image between the original image and the smoothed image; 3: the segmented pieces of fibrils after the image thresholding; 4: the segmented pieces are grouped with the union-find algorithm and small groups are removed from the image; 5: the second-degree-polynomial modeling of fibrils (red curves); 6: the orientation of fibrils.

  18. Results: Chromospheric Fibrils vs. Chromospheric Potential Transverse Field Left: The chromospheric azimuth field derived from the potential field model, overlaid with the chromospheric fibrils segmented from the H observations; Right: The chromospheric transverse field vectors derived from the potential field model, overlaid with the chromospheric fibrils segmented from the H observations.

  19. Results: Magnetic Shear  along Fibrils Left: the spatial distribution of the magnetic shear angle ; Right: the histogram of the magnetic shear angle .

  20. Microwave Imaging Spectroscopy vs. NLFF Field Extrapolation Objective: Microwave observations provides unique and quantitative information on coronal magnetic fields, and are complementary to the morphological validation of nonlinear force-free (NLFF) field modeling. We will perform imaging spectroscopy in combination with the principle of gyroresonance to map out magnetic field strength at the base of corona above active regions. The coronal magnetic field obtained using microwave measurements will be compared with that obtained using NLFF field extrapolation to quantitatively examine the discrepancies.

  21. Data Sets: NOAA 10930 Photospheric vector magneogram: the Spectro-Polarimeter (SP)/SOT/Hinode Microwave: OVSA

  22. Hudson, Fisher and Welsch (2008) and Fisher et al. (2010): Fields turn to more horizontal after a flareChange of Lorentz Force:δfz=(BzδBz-BxδBx-ByδBy)/4π

  23. Shuo: Estimation of the strength of Bt using weak field approximation.

  24. Summary: Scientific Questions • 1. Elementary Bursts • 2. 3-D magnetic structure Advanced NLFF Extrapolation Chromospheric Field observation STEREO reconstruction • 3. Magnetic field restructuring after flares may be observable by EOVSA

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