A new cosmic ray observation at Syowa Station in the antarctic

A set of Cosmic Ray detectors was newly installed in Syowa Station, in the Antarctic, to observe CR neutrons and muons simultaneously at the same location. The observing system has started working in February 2018 and is in stable operation with a high operation rate, >90%. We describe the new systems and show its stability

Small-Scale Dynamic Aurora

Small-scale dynamic auroras have spatial scales of a few km or less, and temporal scales of a few seconds or less, which visualize the complex interplay among charged particles, Alfvén waves, and plasma instabilities working in the magnetosphere-ionosphere coupled regions. We summarize the observed properties of flickering auroras, vortex motions, and filamentary structures. We also summarize the development of fundamental theories, such as dispersive Alfvén waves (DAWs), plasma instabilities in the auroral acceleration region, ionospheric feedback instabilities (IFI), and the ionospheric Alfvén resonator (IAR)

Mesospheric ionization during a substorm: A case study of PANSY and Arase satellite observations

The Tenth Symposium on Polar Science/Ordinary sessions: [OS] Space and upper atmospheric sciences, Wed. 4 Dec. / Institute of Statistics and Mathematics (ISM) Seminar room 2 (D304) (3rd floor

Asymmetrically traveling auroral surges in the northern and southern hemisphere

The Tenth Symposium on Polar Science/Ordinary sessions: [OS] Space and upper atmospheric sciences, Wed. 4 Dec. / Institute of Statistics and Mathematics (ISM) Seminar room 2 (D304) (3rd floor

Current status of Iceland-Syowa conjugate observation in 2019

The Tenth Symposium on Polar Science/Ordinary sessions: [OS] Space and upper atmospheric sciences, Wed. 4 Dec. / Institute of Statistics and Mathematics (ISM) Seminar room 2 (D304) (3rd floor

Modeling of SEP induced auroral emission at Mars: Contribution of precipitating protons and effects of crustal fields

International audienceSolar Energetic Particle (SEP) and the Imaging UltraViolet Spectrograph (IUVS) instruments on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have discovered diffuse aurora that spans across nightside Mars, which resulted from the interaction of Solar Energetic Particles (SEPs) with Martian atmosphere [Schneider et al., 2015]. Previous models showed that 100 keV monoenergetic electron precipitation should have been at the origin of the low altitude (~60 km) peak of the limb emission, however, no models were able to reproduce the observed emission profiles by using the observed electron energy population [e.g. Haider et al., 2019]. Previous auroral emission models did not take into account the contribution of MeV proton precipitation, although MeV proton can penetrate down to ~60 km altitude as well [e.g., Jolitz et al., 2017]. This study aims to model SEP induced diffuse auroral emission by both electrons and protons.We have developed a Monte-Carlo collision and transport model of SEP electrons and protons with magnetic fields on Mars. We calculated limb intensity profile of CO2+ ultraviolet doublet (UVD) due to precipitation of electrons and protons with energy ranging 100eV-100keV and 100eV-5MeV, respectively, during December 2014 SEP event and September 2017 SEP event by using electron and ion fluxes observed by MAVEN/SEP, SWEA and SWIA.The calculated peak limb intensity of CO2+ UVD due to precipitation of protons is 3-5 times larger than that due to precipitation of electrons during both December 2014 and September 2017 SEP events, which suggests that protons can make brighter CO2+ UVD emission than electrons. Peak altitude of limb intensity profiles of CO2+ UVD due to precipitation of electrons and protons are both 10 - 20 km higher than the observation, a discrepancy could be explained by the uncertainty in the electron and proton fluxes that precipitate into the nightside Mars.We have tested an effect of crustal field on the emission of CO2+ UVD. CO2+ UVD emission due to the precipitating electrons are depleted by a factor of 10 in the region of open crustal field and disappeared in the region of closed and parallel crustal field, whereas emission due to the precipitating protons does not change significantly. Further observations of diffuse aurora in the crustal field region should be needed to constrain the origin of diffuse aurora on Mars

Numerical prediction of the effects of solar energetic particle precipitation on the Martian atmospheric chemical composition

International audienceSolar energetic particles (SEPs) are high-energetic particles that consist mainly of electrons and protons with energies from a few tens of keV to GeV ejected associated with solar flares and coronal mass ejections. SEPs can precipitate into planetary atmospheres cause ionization, excitation and dissociation of atmospheric molecules, leading to changes in atmospheric chemical composition via chemical network [e.g. Solomon et al., 1981; Adams et al., 2021].The effect of SEPs on ozone concentration in the Earth’s polar region has been intensively studied for the past decades. For instance, during the enormous solar flare that occurred in late October 2003, NOx and HOx concentrations were enhanced and ozone concentration was depleted by 40% at the polar lower mesosphere [e.g. Jackman et al., 2005]. Increased ionization and dissociation of atmospheric N2 and O2molecules led to the production of NOx and HOx, which catalytically destroyed ozone at the polar mesosphere.Recently, the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft has discovered global diffuse aurora on the nightside of Mars down to few tens km in altitude during SEP events, indicating that a significant amount of energy could be deposited in the atmosphere deeper than previously thought [Schneider et al., 2015; Nakamura et al., 2022]. However, the effects of SEPs on the atmospheric chemistry of present-day Mars have not yet been investigated by observations and/or models.By coupling a Monte Carlo model PTRIP (Nakamura et al., 2022) and a newly developed photochemical model to investigate the effects of SEPs on the atmospheric compositions at Mars, we performed a simulation to track the effects of a large SEP event on the Martian atmospheric composition. We found that HOx increased by a factor of 10 and ozone decreased by a factor of 10 in the altitude range from 20 km to 60 km. This is the very first estimation of the effects of SEPs on the atmospheric neutral compositions at Mars, indicating that similar effects on HOx and ozone could be expected on Mars than on Earth

Modeling of SEP induced auroral emission: Contribution of MeV protons

International audienceSimultaneous observations with the Solar Energetic Particle (SEP) and the Imaging Ultraviolet Spectrograph (IUVS) instruments on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft discovered a new type of Martian aurora, diffuse aurora, that spans across the nightside of Mars due to the interaction of solar energetic particles (SEPs) with the Martian atmosphere [Schneider et al., 2015, 2018]. It is unclear whether the origin of diffuse aurora is electron or proton precipitations. This study aims to model the SEP induced diffuse auroral emission by both electrons and protons to explain the observed diffuse auroral emission profiles. We have developed a Monte Carlo model to calculate the limb intensity profile of the CO2+ ultraviolet doublet (UVD) due to precipitation of energetic electrons and protons with energy ranges from 100 eV to 100 keV and from 100 eV to 5 MeV, respectively, using electron and proton fluxes observed by MAVEN during the December 2014 SEP event and the September 2017 SEP event. Our results showed that proton-induced CO2+ UVD emission is brighter and narrower with respect to the altitude profile and has a lower peak altitude than electron-induced CO2+UVD emission. The calculated peak altitudes of the CO2+ UVD limb profiles are 76 km and 56 km in the SEP events that occurred during December 2014 and September 2017, respectively, which are in good agreement with the IUVS observations. We have succeeded in reproducing the peak altitudes and shapes of the observed CO2+ UVD limb profiles using the SEP fluxes observed by MAVEN. This was possible by taking into account the contribution of protons with energy up to MeV, indicating that both energetic electrons and protons contribute to producing the observed MAVEN/IUVS diffuse aurora

Modeling of SEP induced auroral emission: Contribution of MeV protons

International audienceSimultaneous observations with the Solar Energetic Particle (SEP) and the Imaging Ultraviolet Spectrograph (IUVS) instruments on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft discovered a new type of Martian aurora, diffuse aurora, that spans across the nightside of Mars due to the interaction of solar energetic particles (SEPs) with the Martian atmosphere [Schneider et al., 2015, 2018]. It is unclear whether the origin of diffuse aurora is electron or proton precipitations. This study aims to model the SEP induced diffuse auroral emission by both electrons and protons to explain the observed diffuse auroral emission profiles. We have developed a Monte Carlo model to calculate the limb intensity profile of the CO2+ ultraviolet doublet (UVD) due to precipitation of energetic electrons and protons with energy ranges from 100 eV to 100 keV and from 100 eV to 5 MeV, respectively, using electron and proton fluxes observed by MAVEN during the December 2014 SEP event and the September 2017 SEP event. Our results showed that proton-induced CO2+ UVD emission is brighter and narrower with respect to the altitude profile and has a lower peak altitude than electron-induced CO2+UVD emission. The calculated peak altitudes of the CO2+ UVD limb profiles are 76 km and 56 km in the SEP events that occurred during December 2014 and September 2017, respectively, which are in good agreement with the IUVS observations. We have succeeded in reproducing the peak altitudes and shapes of the observed CO2+ UVD limb profiles using the SEP fluxes observed by MAVEN. This was possible by taking into account the contribution of protons with energy up to MeV, indicating that both energetic electrons and protons contribute to producing the observed MAVEN/IUVS diffuse aurora