Atmos. Chem. Phys. Discuss., 13, 6007-6033, 2013
www.atmos-chem-phys-discuss.net/13/6007/2013/
doi:10.5194/acpd-13-6007-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Modeling of the Very Low Frequency (VLF) radio wave signal profile due to solar flares using the GEANT4 Monte Carlo simulation coupled with ionospheric chemistry
S. Palit1, T. Basak2, S. K. Mondal1, S. Pal1, and S. K. Chakrabarti1,2
1Indian Centre for Space Physics, 43-Chalantika, Garia Station Road, Kolkata-700084, India
2S N Bose National Centre for Basic Sciences, JD Block, Salt Lake, Kolkata-700098, India

Abstract. X-ray photons emitted during solar flares cause ionization in the lower ionosphere (~ 60 to 100 km) in excess of what is expected from a quiet sun. Very Low Frequency (VLF) radio wave signals reflected from the D region are affected by this excess ionization. In this paper, we reproduce the deviation in VLF signal strength during solar flares by numerical modeling. We use GEANT4 Monte Carlo simulation code to compute the rate of ionization due to a M-class and a X-class flare. The output of the simulation is then used in a simplified ionospheric chemistry model to calculate the time variation of electron density at different altitudes in the lower ionosphere. The resulting electron density variation profile is then self-consistently used in the LWPC code to obtain the time variation of the VLF signal change. We did the modeling of the VLF signal along the NWC (Australia) to IERC/ICSP (India) propagation path and compared the results with observations. The agreement is found to be very satisfactory.

Citation: Palit, S., Basak, T., Mondal, S. K., Pal, S., and Chakrabarti, S. K.: Modeling of the Very Low Frequency (VLF) radio wave signal profile due to solar flares using the GEANT4 Monte Carlo simulation coupled with ionospheric chemistry, Atmos. Chem. Phys. Discuss., 13, 6007-6033, doi:10.5194/acpd-13-6007-2013, 2013.
 
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