奇台低频射电阵列在18~50 MHz首次探测到Ⅱ型射电暴

Type Ⅱ Radio Burst was Detected for the First Time by Qitai LFRA at 18-50 MHz

Ⅱ型射电暴是日冕物质抛射(Coronal Mass Ejections, CME)的最佳示踪器,当日冕物质抛射的速度超过本地阿尔芬速度时,会产生日冕激波或行星际激波,并对地球的磁层产生十分剧烈的影响,在射电波段观测到Ⅱ型射电暴也就意味着观测到了日冕激波,预测激波到达地球的时间,是空间天气预报的重要内容之一。2021年9月28日06:20 UT左右,奇台低频射电阵列(Qitai Low-Frequency Radio Array, Qitai LFRA)首次探测到一次Ⅱ型射电暴爆发事件,频率覆盖范围为18~50 MHz,持续时间10多分钟。由于在极低频(<40 MHz)频段还没有进行过具有有效空间分辨率的观测,未来在这个频段发现未知现象的可能性极大。观测结果表明,奇台低频射电阵列性能良好(增益典型值6 dBi)、灵敏度高(-78 dBm/125 kHz,动态范围72 dB),可以在25周太阳活动峰年发挥独特作用。

Type Ⅱradio bursts are the best tracers of Coronal Mass Ejections(CME).The coronal or interplanetary shocks are generated along with a dramatic effect on the Earth′s magnetosphere,when CME exceed the local Alfin velocity.The detection of type Ⅱ radio bursts in the radio band manifests the generation of coronal shock waves.The prediction of the arrival time of shock waves to the Earth is essential to the space weather prediction.Type Ⅱ radio burst was detected for the first time by Qitai low frequency(Qitai LFRA)at around 06:20 UT on September 28,2021,with a frequency coverage of 18-50 MHz and a duration of more than 10 minutes.Since virtually no observation with effective spatial resolution have been made at extremely low frequency(<40 MHz)band,there is a great possibility to discover unknown phenomena at this band in future.Our observation shows that Qitai LFRA has good performance(Typical gain:6 dBi)and high sensitivity(-78 dBm/125 kHz,DR:72 dB),and can play a unique role in the 25 th annual solar activity peak.