Properties of type III and type IIIb bursts in the frequency band of 8 – 80 MHz observed by the radio telescopes Ukrainian Radio Interferometer of NASU-2 (URAN-2) (Poltava) and Giant Ukrainian Radio Telescope (GURT) (Kharkiv) during the Parker Solar Probe (PSP) perihelion in April 2019 are discussed. These correspond to those that were observed by PSP at frequencies <19 MHz. We analyze dependencies of drift rates and durations on frequency for these bursts. We show that drift rate dependencies on frequency agree well with those derived from the Newkirk corona if source velocities are between 0.17 and 0.2 c $c$ for both type IIIb bursts and type III bursts under the assumption that the first ones are fundamentals and the second ones are their harmonics. However, all observational dependencies are flatter in comparison with the dependencies for a Newkirk corona. We assume that this can be related with coronal temperature decreasing at heliocentric distances from 1.35 to 6.5 solar radii. Duration dependencies of type IIIb and type III bursts on frequency in the range of 10 – 70 MHz are also obtained. We note that the durations and drift rates of type III bursts as well as their dependencies on frequency differ essentially from those for type IIIb bursts.

中文翻译：

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2019 年 4 月初 PSP 近日点期间 8 – 80 MHz 频段中 III 型和 IIIb 型突发的特性

NASU-2 乌克兰射电干涉仪（URAN-2）（波尔塔瓦）和乌克兰巨型射电望远镜（GURT）（哈尔科夫）在 8 – 80 MHz 频段内观测到的 III 型和 IIIb 型爆发的特性讨论了 2019 年 4 月的派克太阳探测器 (PSP) 近日点。这些对应于 PSP 在频率 <19 MHz 下观察到的那些。我们分析了这些爆发的漂移率和持续时间对频率的依赖性。我们表明，如果 IIIb 型爆发和 III 型爆发的源速度都在 0.17 和 0.2 c $c$ 之间，假设第一个是基本原理，第二个那些是他们的谐波。然而，与 Newkirk 日冕的依赖关系相比，所有观测依赖关系都更平坦。我们假设这可能与日心距离从 1.35 到 6.5 太阳半径的日冕温度下降有关。还获得了类型 IIIb 和类型 III 突发对 10 – 70 MHz 范围内频率的持续时间依赖性。我们注意到 III 型爆发的持续时间和漂移率以及它们对频率的依赖性与 IIIb 型爆发的本质不同。