Inferring Compressible Fluid Dynamics From Vent Discharges During Volcanic Eruptions
Inferring Compressible Fluid Dynamics From Vent Discharges During Volcanic Eruptions
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DOI：
10.1029/2018gl078286
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发表时间：
2018-07-28
影响因子：
5.2
通讯作者：
Thomas, R. J.
中科院分区：
文献类型：
--
作者：
Harper, J. S. Mendez;Cimarelli, C.;Thomas, R. J.
对许多火山的观察表明，火山喷发往往伴随着持续的无线电频率(CRF)发射。然而，到目前为止，这种辐射的来源仍然难以捉摸。通过实验和野外资料的分析，我们发现CRF起源于与个别火山爆发相关的可压缩流体动力学驱动的近端排放。爆炸产生的气流以超音速膨胀，在靠近喷口的地方产生介电强度减弱的区域。当喷发的物质通过碎裂、摩擦或其他带电过程通过这样的区域时，火山碎屑以小颗粒间火花放电或电晕放电的形式从其表面带走电荷。只要排气口保持超压状态，排放就保持不变。除了描述CRF的机理外，我们还证明了通过探测和定位CRF源，可以实时推断排气口超压的大小和超音速射流的结构。
Observations at numerous volcanoes reveal that eruptions are often accompanied by continual radio frequency (CRF) emissions. The source of this radiation, however, has remained elusive until now. Through experiments and the analysis of field data, we show that CRF originates from proximal discharges driven by the compressible fluid dynamics associated with individual volcanic explosions. Blasts produce flows that expand supersonically, generating regions of weakened dielectric strength in close proximity to the vent. As erupted materialcharged through fragmentation, friction, or other electrification processtransits through such a region, pyroclasts remove charge from their surfaces in the form of small interparticle spark discharges or corona discharge. Discharge is maintained as long as overpressured conditions at the vent remain. Beyond describing the mechanism underlying CRF, we demonstrate that the magnitude of the overpressure at the vent as well as the structure of the supersonic jet can be inferred in real time by detecting and locating CRF sources.