Comprehensive calculation of the energy per ion pair or &amp;lt;I&amp;gt;W&amp;lt;/I&amp;gt; values for five major planetary upper atmospheres

Wedlund, Cyril Simon; Gronoff, Guillaume; Lilensten, Jean; Menager, H.; Barthélemy, Mathieu

doi:10.5194/angeo-29-187-2011

Cited by 70 publications

(61 citation statements)

References 59 publications

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“…On the other hand, higher-energy electrons (0.1-1 keV) lose preferentially their energies by ionizing the ice molecules through collisions. The mean energy lost in each interaction is about 34 eV for a CO gas, while the energy per ion pair lost by electrons of energy lower than 0.1 keV is even higher (Wedlund et al 2011). A 500 eV electron degrades its energy, producing more than 10 low-energy electrons, which in turn lead to further ionization of the molecular species.…”

Section: Products Of the Irradiationmentioning

confidence: 99%

Chemical Evolution of a Co Ice Induced by Soft X-Rays

Ciaravella

Chen

Cecchi‐Pestellini

et al. 2016

ApJ

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We irradiated a pure carbon monoxide ice with soft X-rays of energies up to 1.2 keV. The experiments were performed using the spherical grating monochromator beamline at the National Synchrotron Radiation Research Center in Taiwan, exploiting both monochromatic (at 0.3 and 0.55 keV) and broader energy (0.25-1.2 keV) fluxes. The infrared spectra of the irradiated ices showed the formation of a number of products such as polycarbon monoand dioxides C n O m , and chains containing up to 10 carbon atoms. While a gentle increase in the energy absorbed by the ice sample is reflected by an increase in the column densities of newly born species, such correlation breaks down at very high fluxes. In this regime the production yield falls down sharply by about a factor of 100. The refractory residue obtained in the broad energy irradiation is a "compromise" between those obtained with proton irradiation of C 3 O 2 and CO ices in previous experiments. Finally, we discuss the possible implications for space chemistry

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Section: Products Of the Irradiationmentioning

confidence: 99%

Chemical Evolution of a Co Ice Induced by Soft X-Rays

Ciaravella

Chen

Cecchi‐Pestellini

et al. 2016

ApJ

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“…These processes are parameterized by the primary and secondary ionization rates, respectively, with the ratio of the latter to the former being frequently termed as ionization efficiency (Richards & Torr 1988). The calculation of the primary ionization rate is straightforward with the aid of the classical Beer-Lambert law, whereas the calculation of the secondary ionization rate, which requires either the implementation of the Monte Carlo algorithm (e.g., Bhardwaj & Jain 2009) or the multi-stream solution to the Boltzmann equation (e.g., Wedlund et al 2011), is far more involved.…”

Section: Introductionmentioning

confidence: 99%

Ionization Efficiency in the Dayside Martian Upper Atmosphere

Cui

et al. 2018

ApJL

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Combining the Mars Atmosphere and Volatile Evolution measurements of neutral atmospheric density, solar EUV/X-ray flux, and differential photoelectron intensity made during 240 nominal orbits, we calculate the ionization efficiency, defined as the ratio of the secondary (photoelectron impact) ionization rate to the primary (photon impact) ionization rate, in the dayside Martian upper atmosphere under a range of solar illumination conditions. Both the CO 2 and O ionization efficiencies tend to be constant from 160km up to 250km, with respective median values of 0.19±0.03 and 0.27±0.04. These values are useful for fast calculation of the ionization rate in the dayside Martian upper atmosphere, without the need to construct photoelectron transport models. No substantial diurnal and solar cycle variations can be identified, except for a marginal trend of reduced ionization efficiency approaching the terminator. These observations are favorably interpreted by a simple scenario with ionization efficiencies, as a first approximation, determined by a comparison between relevant cross sections. Our analysis further reveals a connection between regions with strong crustal magnetic fields and regions with high ionization efficiencies, which are likely indicative of more efficient vertical transport of photoelectrons near magnetic anomalies.

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“…We note, however, that since it is unlikely that all energy is consumed for the ionization of the Venusian atmosphere, the peak electron densities calculated here are probably overestimations. Further simulations, possibly including (a) ionospheric chemistry that may lead to electron densities not proportional to the energy deposition rate and/or (b) secondary electron production by electron impact (Wedlund et al, 2011), are necessary in order to draw firm conclusions for the electron density profile in the Venusian atmosphere. It is worth noting, however, that the SEP flux is in general highly variable (Mason et al, 1999); hence, the results in the current study should be considered as a first-order identification and quantification of changes in the Venusian atmosphere during two representative SEP events.…”

Section: Considerations In the Context Of Planetary Space Weather In mentioning

confidence: 99%

Solar energetic particle interactions with the Venusian atmosphere

et al. 2016

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Abstract. In the context of planetary space weather, we estimate the ion production rates in the Venusian atmosphere due to the interactions of solar energetic particles (SEPs) with gas. The assumed concept for our estimations is based on two cases of SEP events, previously observed in near-Earth space: the event in October 1989 and the event in May 2012. For both cases, we assume that the directional properties of the flux and the interplanetary magnetic field configuration would have allowed the SEPs' arrival at Venus and their penetration to the planet's atmosphere. For the event in May 2012, we consider the solar particle properties (integrated flux and rigidity spectrum) obtained by the Neutron Monitor Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) model (Plainaki et al., 2010) applied previously for the Earth case and scaled to the distance of Venus from the Sun. For the simulation of the actual cascade in the Venusian atmosphere initiated by the incoming particle fluxes, we apply the DYASTIMA code, a Monte Carlo (MC) application based on the Geant4 software (Paschalis et al., 2014). Our predictions are afterwards compared to other estimations derived from previous studies and discussed. Finally, we discuss the differences between the nominal ionization profile due to galactic cosmic-ray-atmosphere interactions and the profile during periods of intense solar activity, and we show the importance of understanding space weather conditions on Venus in the context of future mission preparation and data interpretation.

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Comprehensive calculation of the energy per ion pair or <I>W</I> values for five major planetary upper atmospheres

Cited by 70 publications

References 59 publications

Chemical Evolution of a Co Ice Induced by Soft X-Rays

Chemical Evolution of a Co Ice Induced by Soft X-Rays

Ionization Efficiency in the Dayside Martian Upper Atmosphere

Solar energetic particle interactions with the Venusian atmosphere

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