TY - JOUR
T1 - Traces of the dynamic current sheet during a solar flare
AU - Ji, Haisheng
AU - Wang, Haimin
AU - Goode, Philip R.
AU - Jiang, Yunchun
AU - Yurchyshyn, Vasyl
N1 - Funding Information:
The authors feel deeply indebted to the anonymous referee, who pointed out the sinking motion of the HXR source and proposed many other suggestions. We are grateful to the BBSO observing staff for their support. We are also grateful to the RHESSI team for providing RHESSI data and software. The first author would like to thank Edward J. Schmahl for his kind instructions regarding the issue of RHESSI data. This work is supported by NSF under grants ATM-0313591 and ATM-0233931, NASA under grant NAG5-10910, and ONR under grant N00014-03-1-0093. The work of H. J. is also supported by CNSF 10333030.
PY - 2004/5/20
Y1 - 2004/5/20
N2 - High-cadence and high-resolution time sequences of far Hα off-band images provide a unique tool to study the evolution of the fine structure of flare kernels. The fine structure contains important information on flare topology and the triggering mechanism. In this Letter, we concentrate on the rapid changes of the relative positions of two conjugate flare footpoints. In order to carry out this study with the highest physical precision, we use r c = ΣrjIj/ΣIj (I j is the Hα brightness at rj) to compute the centroid of an Hα bright kernel region caused by solar flares. Using this, we probe the fine temporal structures connected to the distance between the centroids of two conjugate kernels of an M2.3 flare. The flare, which occurred on 2002 September 9 in NOAA Active Region 0105, was observed at Big Bear Solar Observatory at the far off-band center wavelength of H α. - 1.3 Å, with a cadence of ∼40 ms. The flare was also observed by RHESSI. The time profile of the separation distance shows an excellent anticorrelation to that of the hard X-ray (HXR) emissions in 25-50 keV, which exhibit a number of separate spikes (the linear Pearson correlation coefficient is found to be ∼-0.83). The separation between the two centroids decreases at the rising periods of four HXR spikes, then it increases after the peak time of the flare to show the expected separation motion. The most obvious decreasing, which occurred during the first HXR peak, was confirmed by corresponding images. This implies that during the impulsive phases, the energy transported from the corona is deposited increasingly inwardly between the two kernels. This new and perhaps surprising tendency for the energy deposition can be explained as being caused by current sheet pinch motions, which, at the same time, enhance the magnetic energy reconnection rate to produce the observed HXR spikes.
AB - High-cadence and high-resolution time sequences of far Hα off-band images provide a unique tool to study the evolution of the fine structure of flare kernels. The fine structure contains important information on flare topology and the triggering mechanism. In this Letter, we concentrate on the rapid changes of the relative positions of two conjugate flare footpoints. In order to carry out this study with the highest physical precision, we use r c = ΣrjIj/ΣIj (I j is the Hα brightness at rj) to compute the centroid of an Hα bright kernel region caused by solar flares. Using this, we probe the fine temporal structures connected to the distance between the centroids of two conjugate kernels of an M2.3 flare. The flare, which occurred on 2002 September 9 in NOAA Active Region 0105, was observed at Big Bear Solar Observatory at the far off-band center wavelength of H α. - 1.3 Å, with a cadence of ∼40 ms. The flare was also observed by RHESSI. The time profile of the separation distance shows an excellent anticorrelation to that of the hard X-ray (HXR) emissions in 25-50 keV, which exhibit a number of separate spikes (the linear Pearson correlation coefficient is found to be ∼-0.83). The separation between the two centroids decreases at the rising periods of four HXR spikes, then it increases after the peak time of the flare to show the expected separation motion. The most obvious decreasing, which occurred during the first HXR peak, was confirmed by corresponding images. This implies that during the impulsive phases, the energy transported from the corona is deposited increasingly inwardly between the two kernels. This new and perhaps surprising tendency for the energy deposition can be explained as being caused by current sheet pinch motions, which, at the same time, enhance the magnetic energy reconnection rate to produce the observed HXR spikes.
KW - Sun: activity
KW - Sun: flares
KW - Sun: magnetic fields
UR - http://www.scopus.com/inward/record.url?scp=3042596568&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=3042596568&partnerID=8YFLogxK
U2 - 10.1086/421550
DO - 10.1086/421550
M3 - Article
AN - SCOPUS:3042596568
SN - 0004-637X
VL - 607
SP - L55-L58
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1 II
ER -