Solar flare emission at X-ray and extreme ultraviolet (EUV) energies can cause substantial enhancements in the electron density in the Earth's lower ionosphere. It is now become clear that flares exhibit quasi-periodic pulsations with timescales of minutes at X-ray energies, but to date, it has not been known if the ionosphere is sensitive to this variability. Here, using a combination of Very Low Frequency (24 kHz) measurement together with space-based X-ray and EUV observations, we report pulsations of the ionospheric D-region, which are synchronized with a set of pulsating flare loops. Modeling of the ionosphere show that the D-region electron density varies by up to an order of magnitude over the timescale of the pulsations (∼20 mins). Our results reveal that the Earth's ionosphere is more sensitive to small-scale changes in solar soft X-ray flux than previously thought, and implies that planetary ionospheres are closely coupled to small-scale changes in solar/stellar activity.
@article{arxiv.1710.01725,
title = {Pulsations in the Earth's Lower Ionosphere Synchronized with Solar Flare Emission},
author = {Laura A. Hayes and Peter T. Gallagher and Joseph McCauley and Brian R. Dennis and Jack Ireland and Andrew Inglis},
journal= {arXiv preprint arXiv:1710.01725},
year = {2017}
}