Very Low Frequency radio signal amplitude from the Indian navigational transmitter VTX received at Kolkata (Calcutta University) from 2019-04-25 to 2019-05-07 during the Extremely Severe Cyclone Fani of May, 2019

The ZIP file contains Very Low Frequency radio signal amplitude at frequency 18.2 kHz received at Kolkata before, during and after the extremely severe cyclone Fani of May 2019 over northeastern part of the Indian Ocean. The Vertical component of VLF electric field is captured using a 3.65 metre E-field whip antenna, which is then amplified by an OP-AMP amplifier circuit before feeding into the sound card of the computer for analog to digital conversion. SpectrumLab V2.9 software is used to record the amplitude of the VLF field at desired frequency at a sampling rate of 5 Hz. The data are helpful to understand the effects of the cyclonic storm on the lower ionosphere. The ZIP file contains 13 days data and details can also be found in each file. Purpose: These data were collected to study the effects of the tropical cyclone on the lower ionosphere. Atmospheric gravity waves from the cyclone can propagate upward up to the ionospheric heights and disturb the electrical conductivity in the ionosphere. Changes in ionospheric conductivity profiles can be extracted from the VLF received signal.本ZIP压缩包包含2019年5月印度洋东北部极强气旋风暴“法尼（Fani）”前后及期间，在加尔各答（Kolkata）接收的18.2kHz甚低频（Very Low Frequency, VLF）无线电信号振幅数据。实验采用3.65米电场鞭状天线采集甚低频电场的垂直分量，信号经运算放大器（OP-AMP）放大电路处理后，输入计算机声卡完成模数转换。使用SpectrumLab V2.9软件以5Hz的采样率记录指定频率下的甚低频场振幅。该数据集可为分析气旋风暴对低电离层的影响提供支撑。 本ZIP压缩包包含13天的观测数据，每份文件中均附带详细说明。 数据集采集目的： 本数据集旨在探究热带气旋对低电离层的影响。气旋激发的大气重力波可向上传播至电离层高度，扰动电离层的电导率。通过分析接收的甚低频信号，可反演得到电离层电导率剖面的变化。