Inverse problem in Ionospheric Science: Prediction of solar soft-X-ray spectrum from Very Low Frequency Radiosonde results

摘要

X-rays and gamma-rays from astronomical sources such as solar flares aremostly absorbed by the Earth's atmosphere. Resulting electron-ion productionrate as a function of height depends on the intensity and wavelength of theinjected spectrum and therefore the effects vary from one source to another. Inother words, the ion density vs. altitude profile has the imprint of theincident photon spectrum. In this paper, we investigate whether we can invertthe problem uniquely by deconvolution of the VLF amplitude signal to obtain thedetails of the injected spectrum. We find that it is possible to do this up toa certain accuracy. Our method is useful to carry out a similar exercise toinfer the spectra of more energetic events such as the Gamma Ray Bursts (GRBs),Soft Gamma Ray Repeaters (SGRs) etc. by probing even the lower part of theatmosphere. We thus show that to certain extent, the Earth's atmosphere couldbe used as a gigantic detector of relatively strong events.