Goldstone Apple Valley Radio Telescope Observations of 2012 Solar Eclipse: A Multi-wavelength study of cm-l Gyroresonance Emission from Active Regions

Goldstone Apple Valley Radio Telescope (GAVRT) is a science education partnership among NASA, the Jet Propulsion Laboratory (JPL), and the Lewis Center for Educational Research (LCER), offering unique opportunities for K -12 students and their teachers. The GAVRT program operates a 34-m radio telescope with a wide-band, low noise receiver, which is tunable in four independent dual-polarization bands from 3 to 14 GHz. The annular eclipse of the Sun on 2012 May 20 was observed by GAVRT as part of education outreach. In this paper we present the results of this eclipse data and discuss the multi-wavelength derived strip scan brightness distribution across three active regions. We derive the source brightness temperatures and angular sizes as function frequency and interpret the results in terms of gyroresonance mechanism. We show examples of the increasing brightness and widening of source size (isogauss surface) with wavelength as evidence for gyroresonance absorption layers of diverging magnetic field geometry above solar surface. We present an example how the derived frequency – brightness temperature relationship is translated to a magnetic field – brightness temperature relationship under the frame-work of gyroresonance absorption. Our results demonstrate the usefulness of GAVRT bands as excellent probe to study the layers of the corona above the active regions (sun spots), in particular the prevalence of the gyroresonance mechanism.

戈德斯通-苹果谷射电望远镜（Goldstone Apple Valley Radio Telescope, GAVRT）是美国国家航空航天局（NASA）、喷气推进实验室（Jet Propulsion Laboratory, JPL）与刘易斯教育研究中心（Lewis Center for Educational Research, LCER）联合开展的科学教育合作项目，为K-12阶段学生及教师提供了独特的参与机会。GAVRT项目运营一台口径34米的射电望远镜，配备宽带低噪声接收机，可在3至14 GHz频段内实现四个独立双极化波段的调谐。2012年5月20日的日环食被纳入GAVRT的教育推广观测计划。本文呈现了此次日食观测数据的分析结果，并讨论了通过多波长条带扫描得到的三个太阳活动区的亮度分布。研究推导了源亮温度与角尺寸随频率的变化关系，并从回旋共振机制（gyroresonance mechanism）的角度对结果进行阐释。本文展示了随波长增加，源亮度提升、源尺寸（等高斯面，isogauss surface）扩大的实例，以此作为太阳表面上方发散磁场位形下回旋共振吸收层的佐证。此外还给出一个示例，演示如何在回旋共振吸收的理论框架下，将推导得到的频率-亮温度关系转换为磁场-亮温度关系。本研究结果证明，GAVRT波段是研究太阳活动区（太阳黑子，sun spots）上方日冕（corona）层的绝佳探测手段，尤其验证了回旋共振机制的普遍性。