Solar energetic particle interactions with the Venusian atmosphere

Abstract

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.

Revisiting the cosmic-ray induced Venusian radiation dose in the context of habitability

“…Although remarkable efforts revealing the temporal evolution of SEP events can be found in the literature (see, e.g., Belov et al 2005;Bombardieri et al 2007;Plainaki et al 2007;Matthiä et al 2009;Miroshnichenko 2018, and references therein), the model efforts to study the GLE-induced atmospheric effects are often based on a mean energy spectrum. As previously discussed in Nordheim et al (2015), Plainaki et al (2016), and Herbst et al (2019a), the Venusian atmospheric ionization is significantly affected by these strong SEP events. We investigated their influence on the atmospheric absorbed dose rates.…”

Planetary space weather: scientific aspects and future perspectives

“…The transition region around the altitude of~100 km hosts a number of peculiar phenomena such as the variable ozone layer (Montmessin et al 2011) and strong variations in air temperatures (Piccialli et al 2015). Incidentally, we note that this region is subject to high-energy deposition rates due to incoming cosmic rays during strong SEP events, as discussed by and by Plainaki et al (2016). Above the very rough level of 110 km, dissociation of molecules by UV radiation becomes important.…”

“…SEP fluxes reaching Venus and Mars are of special interest because the atmospheres of these planets are poorly protected by the weak magnetic fields. Depending on the solar particle energy and direction, SEP events at Venus may result in increased ionization rates in the atmosphere (see estimations by Plainaki et al 2016). The NASA MAVEN mission will provide feedback on the SEP interactions with Mars' upper atmosphere and on how they have contributed to its evolution over time.…”

“…It has also been suggested that aerosols may form by direct condensation of gaseous sulphuric acid onto ions in the lower atmosphere, thus providing a possible link between cloud formation and cosmic ray ionization in the Venusian atmosphere (Aplin 2006(Aplin , 2013. Atmospheric ionization due to the background flux of GCR particles peaks within the main cloud deck at~63 km and recent modelling by and Plainaki et al (2016) has shown that transient SEP events may enhance ionization rates at this altitude by more than an order of magnitude and by up to five orders of magnitude at higher altitudes (~80-100 km; Plainaki et al 2016). Extreme SEP events may yield even larger enhancements in atmospheric ionization rates, and the impact of ''Carrington-level'' SEP events on the Venusian atmosphere was recently investigated by Dartnell et al (2015).…”

Impacts of Cosmic Dust on Planetary Atmospheres and Surfaces

“…Recent theoretical and experimental studies of H 2 SO 4 -H 2 O particle formation have developed state-of-the-art descriptions of the homogeneous and ion-induced particle formation processes , enabling their application to Venus. Modelling of ionization in Venus' atmosphere indicates a significant level of ionization at the cloud formation altitudes around 70 km (Michael et al 2009;Plainaki et al 2016). Many models have considered heterogeneous nucleation on soluble or insoluble particles (James et al 1997).…”