On 10 March 2001 the active region NOAA 9368 produced an unusually impulsive solar flare in close proximity to the solar limb. This flare has previously been studied in great detail, with observations classifying it as a type 1 white-light flare with a very hard spectrum in hard X-rays. The flare was also associated with a type II radio burst and coronal mass ejection. The flare emission characteristics appeared to closely correspond with previous instances of seismic emission from acoustically active flares. Using standard local helioseismic methods, we identified the seismic signatures produced by the flare that, to date, is the least energetic (in soft X-rays) of the flares known to have generated a detectable acoustic transient. Holographic analysis of the flare shows a compact acoustic source strongly correlated with the impulsive hard X-ray, visible continuum, and radio emission. Time-distance diagrams of the seismic waves emanating from the flare region also show faint signatures, mainly in the eastern sector of the active region. The strong spatial coincidence between the seismic source and the impulsive visible continuum emission reinforces the theory that a substantial component of the seismic emission seen is a result of sudden heating of the low photosphere associated with the observed visible continuum emission. Furthermore, the low-altitude magnetic loop structure inferred from potential--field extrapolations in the flaring region suggests that there is a significant inverse correlation between the seismicity of a flare and the height of the magnetic loops that conduct the particle beams from the corona.
Multi-wavelength observations of an unusual impulsive flare associated with CME
对2001年3月10日发生在NOAA AR 9368(N27 W 42)上的一次强脉冲太阳耀斑1B/M6.7的多波长观测结果进行了详细的分析。观测结果表明,耀斑是一个非常强的脉冲,在HXR中有非常硬的光谱,显示非热辐射占主导地位。另一方面,该耀斑还产生了II型射电爆发和日冕物质抛射(CME),这不是脉冲耀斑的一般特征。在H $α$中,我们观察到亮质量喷出物(BME),然后是暗质量喷出物(DME)。基于BME和CME的爆发时间和方向的一致性,我们认为这两种现象是密切相关的。据推测,能量积累发生由于光球重连接之间出现的正寄生极性和占主导地位的负极性,这导致作为一个后果的通量抵消。由于正寄生极性的进一步出现,导致通量的强烈增强的抵消,剪切增加到$>80^o$。看来,这种增强的磁通量抵消在一个强烈的剪切区触发了脉冲耀斑。
Spectroscopic observations of a solar limb flare recorded by SUMER on SOHO reveal, for the first time, hot fast magnetic reconnection outflows in the corona. As the reconnection site rises across the SUMER spectrometer slit, significant blue- and red-shift signatures are observed in sequence in the Fe XIX line, reflecting upflows and downflows of hot plasma jets, respectively. With the projection effect corrected, the measured outflow speed is between 900-3500 km/s, consistent with theoretical predictions of the Alfvenic outflows in magnetic reconnection region in solar impulsive events. Based…