TY - JOUR
T1 - Evaluating mean magnetic field in flare loops
AU - Qiu, Jiong
AU - Gary, Dale
AU - Fleishman, Gregory
N1 - Funding Information:
Acknowledgements We thank Yohkoh, TRACE, and OVSA teams for providing quality observations. JQ is supported by NSF grants ATM-0603789 and ATM-0748428, and NASA grant NNX08AE44G to Montana State University. The OVSA observations are supported by NSF grant AST-0607544 and ATM-0707319 and NASA grant NNG06GJ40G to the New Jersey Institute of Technology. We thank the anonymous referee for constructive comments which help improve the manuscript.
PY - 2009/3
Y1 - 2009/3
N2 - We analyze multiple-wavelength observations of a two-ribbon flare exhibiting apparent expansion motion of the flare ribbons in the lower atmosphere and rising motion of X-ray emission at the top of newly-formed flare loops. We evaluate magnetic reconnection rate in terms of V r B r by measuring the ribbon-expansion velocity (V r) and the chromospheric magnetic field (B r) swept by the ribbons. We also measure the velocity (V t) of the apparent rising motion of the loop-top X-ray source, and estimate the mean magnetic field (B t) at the top of newly-formed flare loops using the relation 〈V t B t〉≈ 〈V r B r〉, namely, conservation of reconnection flux along flare loops. For this flare, B t is found to be 120 and 60 G, respectively, during two emission peaks five minutes apart in the impulsive phase. An estimate of the magnetic field in flare loops is also achieved by analyzing the microwave and hard X-ray spectral observations, yielding B=250 and 120 G at the two emission peaks, respectively. The measured B from the microwave spectrum is an appropriately-weighted value of magnetic field from the loop top to the loop leg. Therefore, the two methods to evaluate coronal magnetic field in flaring loops produce fully-consistent results in this event.
AB - We analyze multiple-wavelength observations of a two-ribbon flare exhibiting apparent expansion motion of the flare ribbons in the lower atmosphere and rising motion of X-ray emission at the top of newly-formed flare loops. We evaluate magnetic reconnection rate in terms of V r B r by measuring the ribbon-expansion velocity (V r) and the chromospheric magnetic field (B r) swept by the ribbons. We also measure the velocity (V t) of the apparent rising motion of the loop-top X-ray source, and estimate the mean magnetic field (B t) at the top of newly-formed flare loops using the relation 〈V t B t〉≈ 〈V r B r〉, namely, conservation of reconnection flux along flare loops. For this flare, B t is found to be 120 and 60 G, respectively, during two emission peaks five minutes apart in the impulsive phase. An estimate of the magnetic field in flare loops is also achieved by analyzing the microwave and hard X-ray spectral observations, yielding B=250 and 120 G at the two emission peaks, respectively. The measured B from the microwave spectrum is an appropriately-weighted value of magnetic field from the loop top to the loop leg. Therefore, the two methods to evaluate coronal magnetic field in flaring loops produce fully-consistent results in this event.
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U2 - 10.1007/s11207-009-9316-y
DO - 10.1007/s11207-009-9316-y
M3 - Article
AN - SCOPUS:60849089889
SN - 0038-0938
VL - 255
SP - 107
EP - 118
JO - Solar Physics
JF - Solar Physics
IS - 1
ER -