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Title: STUDY OF TWO SUCCESSIVE THREE-RIBBON SOLAR FLARES ON 2012 JULY 6

Abstract

This Letter reports two rarely observed three-ribbon flares (M1.9 and C9.2) on 2012 July 6 in NOAA AR 11515, which we found using Hα observations of 0.''1 resolution from the New Solar Telescope and Ca II H images from Hinode. The flaring site is characterized by an intriguing ''fish-bone-like'' morphology evidenced by both Hα images and a nonlinear force-free field (NLFFF) extrapolation, where two semi-parallel rows of low-lying, sheared loops connect an elongated, parasitic negative field with the sandwiching positive fields. The NLFFF model also shows that the two rows of loops are asymmetric in height and have opposite twists, and are enveloped by large-scale field lines including open fields. The two flares occurred in succession within half an hour and are located at the two ends of the flaring region. The three ribbons of each flare run parallel to the magnetic polarity inversion line, with the outer two lying in the positive field and the central one in the negative field. Both flares show surge-like flows in Hα apparently toward the remote region, while the C9.2 flare is also accompanied by EUV jets possibly along the open field lines. Interestingly, the 12-25 keV hard X-ray sources of the C9.2 flaremore » first line up with the central ribbon then shift to concentrate on the top of the higher branch of loops. These results are discussed in favor of reconnection along the coronal null line, producing the three flare ribbons and the associated ejections.« less

Authors:
; ; ; ;  [1]; ;  [2]
  1. Space Weather Research Laboratory, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States)
  2. Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314-9672 (United States)
Publication Date:
OSTI Identifier:
22364023
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 781; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMMETRY; CALCIUM IONS; COSMIC X-RAY SOURCES; EXTRAPOLATION; FLARING; GAMMA RADIATION; HARD X RADIATION; IMAGES; JETS; KEV RANGE; MAGNETIC FIELDS; MORPHOLOGY; NONLINEAR PROBLEMS; SHEAR; SOLAR FLARES; SUN; TELESCOPES

Citation Formats

Wang, Haimin, Liu, Chang, Deng, Na, Xu, Yan, Jing, Ju, Zeng, Zhicheng, and Cao, Wenda, E-mail: haimin.wang@njit.edu. STUDY OF TWO SUCCESSIVE THREE-RIBBON SOLAR FLARES ON 2012 JULY 6. United States: N. p., 2014. Web. doi:10.1088/2041-8205/781/1/L23.
Wang, Haimin, Liu, Chang, Deng, Na, Xu, Yan, Jing, Ju, Zeng, Zhicheng, & Cao, Wenda, E-mail: haimin.wang@njit.edu. STUDY OF TWO SUCCESSIVE THREE-RIBBON SOLAR FLARES ON 2012 JULY 6. United States. doi:10.1088/2041-8205/781/1/L23.
Wang, Haimin, Liu, Chang, Deng, Na, Xu, Yan, Jing, Ju, Zeng, Zhicheng, and Cao, Wenda, E-mail: haimin.wang@njit.edu. Mon . "STUDY OF TWO SUCCESSIVE THREE-RIBBON SOLAR FLARES ON 2012 JULY 6". United States. doi:10.1088/2041-8205/781/1/L23.
@article{osti_22364023,
title = {STUDY OF TWO SUCCESSIVE THREE-RIBBON SOLAR FLARES ON 2012 JULY 6},
author = {Wang, Haimin and Liu, Chang and Deng, Na and Xu, Yan and Jing, Ju and Zeng, Zhicheng and Cao, Wenda, E-mail: haimin.wang@njit.edu},
abstractNote = {This Letter reports two rarely observed three-ribbon flares (M1.9 and C9.2) on 2012 July 6 in NOAA AR 11515, which we found using Hα observations of 0.''1 resolution from the New Solar Telescope and Ca II H images from Hinode. The flaring site is characterized by an intriguing ''fish-bone-like'' morphology evidenced by both Hα images and a nonlinear force-free field (NLFFF) extrapolation, where two semi-parallel rows of low-lying, sheared loops connect an elongated, parasitic negative field with the sandwiching positive fields. The NLFFF model also shows that the two rows of loops are asymmetric in height and have opposite twists, and are enveloped by large-scale field lines including open fields. The two flares occurred in succession within half an hour and are located at the two ends of the flaring region. The three ribbons of each flare run parallel to the magnetic polarity inversion line, with the outer two lying in the positive field and the central one in the negative field. Both flares show surge-like flows in Hα apparently toward the remote region, while the C9.2 flare is also accompanied by EUV jets possibly along the open field lines. Interestingly, the 12-25 keV hard X-ray sources of the C9.2 flare first line up with the central ribbon then shift to concentrate on the top of the higher branch of loops. These results are discussed in favor of reconnection along the coronal null line, producing the three flare ribbons and the associated ejections.},
doi = {10.1088/2041-8205/781/1/L23},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 781,
place = {United States},
year = {Mon Jan 20 00:00:00 EST 2014},
month = {Mon Jan 20 00:00:00 EST 2014}
}
  • We studied the background field for 60 two-ribbon flares of M-and-above classes during 2011–2015. These flares are categorized into two groups, i.e., eruptive and confined flares, based on whether a flare is associated with a coronal mass ejection or not. The background field of source active regions is approximated by a potential field extrapolated from the B {sub z} component of vector magnetograms provided by the Helioseismic and Magnetic Imager. We calculated the decay index n of the background field above the flaring polarity inversion line, and defined a critical height h {sub crit} corresponding to the theoretical threshold (more » n {sub crit} = 1.5) of the torus instability. We found that h {sub crit} is approximately half of the distance between the centroids of opposite polarities in active regions and that the distribution of h {sub crit} is bimodal: it is significantly higher for confined flares than for eruptive ones. The decay index increases monotonously with increasing height for 86% (84%) of the eruptive (confined) flares but displays a saddle-like profile for the rest, 14% (16%), which are found exclusively in active regions of multipolar field configuration. Moreover, n at the saddle bottom is significantly smaller in confined flares than that in eruptive ones. These results highlight the critical role of background field in regulating the eruptive behavior of two-ribbon flares.« less
  • Solar wind disturbances caused by six hypothetical flares from the same active region are traced out to about 15 au, using a simple empirical modeling method developed by Hakamada and Akasofu (1982). Our method provides a first order construction, temporal and spatial, of flare-induced shocks and their multiple interactions with each other, as well as with the corotating interaction regions. The results are discussed in connection with recent cosmic ray observations by space probes.
  • We carry out a comprehensive investigation comparing the three-dimensional magnetic field restructuring, flare energy release, and the helioseismic response of two homologous flares, the 2011 September 6 X2.1 (FL1) and September 7 X1.8 (FL2) flares in NOAA AR 11283. In our analysis, (1) a twisted flux rope (FR) collapses onto the surface at a speed of 1.5 km s{sup –1} after a partial eruption in FL1. The FR then gradually grows to reach a higher altitude and collapses again at 3 km s{sup –1} after a fuller eruption in FL2. Also, FL2 shows a larger decrease of the flux-weighted centroidmore » separation of opposite magnetic polarities and a greater change of the horizontal field on the surface. These imply a more violent coronal implosion with corresponding more intense surface signatures in FL2. (2) The FR is inclined northward and together with the ambient fields, it undergoes a southward turning after both events. This agrees with the asymmetric decay of the penumbra observed in the peripheral regions. (3) The amounts of free magnetic energy and nonthermal electron energy released during FL1 are comparable to those of FL2 within the uncertainties of the measurements. (4) No sunquake was detected in FL1; in contrast, FL2 produced two seismic emission sources S1 and S2 both lying in the penumbral regions. Interestingly, S1 and S2 are connected by magnetic loops, and the stronger source S2 has a weaker vertical magnetic field. We discuss these results in relation to the implosion process in the low corona and the sunquake generation.« less
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