# Modeling of VLF network observations due to lower ionospheric perturbation during a solar eclipse

TL;DR: In this paper, the temporal dependences of very low frequency (VLF) electric amplitude perturbation from two Japanese VLF transmitters (JJI (22.2kHz) and JJY (40.0kHz) were analyzed.

Abstract: A large part of the path of the Annular Solar Eclipse of May 20,2012 (magnitude 0.9439) (ASE-2012) was over southern Japan. The D-region ionospheric changes associated with the ASE-2012, led to several degree of observable perturbations of sub-ionospheric very low frequency (VLF) radio signal. The solar eclipse associated signal changes were identified in VLF several receiving stations $(R_{x})$ simultaneously for the VLF signals coming from both Japanese and US VLF transmitters ($T_{x}$). In this work, we have analyzed temporal dependences of VLF electric amplitude perturbation $(\Delta A_{ecl,obs}(t))$ from two Japanese VLF transmitters (JJI (22.2kHz) and JJY (40.0kHz)), and the spatio-temporal characteristics of respective subionospheric perturbations are studied in detail. We consider the 2-parameter D-region ionospheric model with the exponential electron density profile. To model the shadow effect on the D-region ionosphere due to obscuration of solar disk, we assume a generalized space-time dependent 2-Dimensional Elliptical Gaussian distribution Model (2DEGM) for ionospheric parameters, such as, effective reflection height $(h')$ and sharpness factor $(\beta )$. In the vicinity of the eclipse zone, we compute the subionospheric VLF signal propagation for several signal propagation paths. In the simulation, we obtain the perturbation of VLF signal amplitude ($\Delta A_{ecl,LWPC}(t))$ at each station and compare with its observtaional counterpart $(\Delta A_{ecl,obs}(t))$.

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9 citations

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446 citations

### "Modeling of VLF network observation..." refers methods in this paper

...We modeled the [h′,β ]ecl(lon, lat, t) parameters of 2component exponential Wait’s lower ionospheric model [7] according to the elliptical nature of the penumbral shadow of ASE-2012....

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...So, in this case, Wait’s 2-component exponential ionospheric model [7] is capable to represent it, because it is related with ‘Ne’ and ‘νe’....

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81 citations

### "Modeling of VLF network observation..." refers background in this paper

...[3] presented the results of total solar eclipse (TSE) in Europe on 11th Aug 1999....

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...Though for a different eclipse, [3] has shown the same ‘-ve’ anomaly for shorter paths like, GBZ-Cambridge, FTA2-Cambridge etc....

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...But, it was proved at several occasions of short and long propagation path analysis, that 2-component exponential ionospheric model, which is simplified and at the same time approximated, works well [3]....

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...[3] explained them with LWPC analysis....

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76 citations

### "Modeling of VLF network observation..." refers methods in this paper

...We choose the daytime ionosphere according to [4, 8, 1], i....

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36 citations

### "Modeling of VLF network observation..." refers background in this paper

...According to [6], the first level approximation of ‘linear relationship’ between hecl and βecl , and the obscuration effect works well for VLF-ionosphere interaction modeling....

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9 citations