Effects of a Solar Flare on the Martian Hot O Corona and Photochemical Escape

Abstract

We examine for the first time the flare‐induced effects on the Martian hot O corona. The rapid ionospheric response to the increase in the soft X‐ray flux (~800%) facilitates more hot O production at altitudes below the main ionospheric peak, but almost all of these atoms are thermalized before escape. In response to the increase in the extreme ultraviolet (EUV) flux (~170%), the overall upper ionospheric and thermospheric densities are enhanced, and the peak thermospheric responses are found ~1.5 hr later. The photochemical escape rate is predicted to increase by ~20% with the increases in the soft X‐ray and EUV fluxes but decrease rapidly by ~13% about 2.5 hr later before recovering the preflare level. Since escaping hot O atoms are mostly produced at high altitudes where ionization by the EUV flux is the greatest, the main contributor to the 20% increase in escape rate is the enhancement in the EUV flux.

Observations and Impacts of the 10 September 2017 Solar Events at Mars: An Overview and Synthesis of the Initial Results

“…They found a noticeable (∼50%) increase in oxygen escape during a single orbit (∼4.5 hr) following the flare. This increase in photochemical escape was also inferred from coupled global simulations by Lee et al () of the Martian exosphere, thermosphere, and plasma environment for time periods encompassing the flare. They found an increase of ∼20% in the escape rate shortly following the flare, and a rapid decrease within ∼2.5 hr followed by a gradual return to nominal escape conditions.…”

“…They found a noticeable (∼50%) increase in oxygen escape during a single orbit (∼4.5 hr) following the flare. This increase in photochemical escape was also inferred from coupled global simulations by Lee et al (2018) rate shortly following the flare, and a rapid decrease within ∼2.5 hr followed by a gradual return to nominal escape conditions. Measurements of planetary ion escape are continuously made by MAVEN and have been evaluated based on the fluxes of heavy ions measured in a spherical shell with thickness of 0.2 R M and centered around Mars at 1.35 R M (∼1,200-km altitudes; Brain et al, 2015).…”

“…Both global plasma models were driven with MAVEN and proxy measurements of the solar EUV photon flux, solar wind, and IMF at Mars. Ma et al () used the MHD model to run both steady‐state and time‐dependent simulations, and showed increases in heavy ion escape of a factor of 10–20, with rates as high as ∼3 × 10 25 s −1 for at least ∼5 hr, in excess of those reported by Lee et al () for photochemical escape using the same model framework. Both models showed good agreement with quantities measured by MAVEN along its orbit, such as magnetic field strength and direction, plasma velocity, and plasma density.…”

The Mars Topside Ionosphere Response to the X8.2 Solar Flare of 10 September 2017

“…Taken together, Figures a and b indicate that the flare shifted the escaping O production significantly upward, yielding a moderate enhancement in (vertically integrated) loss. Although photochemical escape over the dayside hemisphere has minimal dependence on SZA (Lillis et al, ), care should be taken extrapolating these simulation results to global flare‐induced escape rate because solar flare effects are expected to be strongly dependent on SZA (Y. Lee et al, ; Qian et al, ).…”

Role of stellar physics in regulating the critical steps for life

“…A few points should be noted regarding the above formula. First, incorporating the effects of stellar flares and coronal mass ejections (Drake et al, 2013;Cranmer, 2017;Odert et al, 2017;Patsourakos and Georgoulis, 2017;Lee et al, 2018) is expected to decrease this timescale, perhaps by more than one order of magnitude. Second, this formula was derived under the assumption of a constant atmospheric escape rate.…”