Solar Flare Effects Upon the Ionospheres of Earth and Mars

Of the many episodic variations associated with the active Sun, perhaps the solar flare is the most spectacular and enigmatic. Because flares emit photons that reach our atmosphere in about 8 minutes, with no intervening heliospheric or magneto spheric interactions, flare effects upon the geospace system have been a somewhat neglected component in Space Weather research. Once flare photons pass the Earth, the orbit of Mars is reached in just 4 additional minutes. Recent analyses of new ionospheric data at Mars revealed electron density enhancements due to flares. On the same days, ionospheric monitoring stations on Earth equipped with University of Lowell ionosondes also recorded ionospheric flare effects. In this paper, we present observations to characterize how flares modify the ionospheres of both planets, and describe how they can be used as comparative experiments to explore how photochemical, dynamical and electro-dynamical processes operate in solar-planetary-systems.