Bibliography

New Measurement of the Vertical Atmospheric Density Profile From Occultations of the Crab Nebula With X-Ray Astronomy Satellites Suzaku and Hitomi

We present new measurements of the vertical density profile of the Earth s atmosphere at altitudes between 70 and 200 km, based on Earth occultations of the Crab Nebula observed with the X-ray Imaging Spectrometer onboard Suzaku and the hard X-ray Imager onboard Hitomi. X-ray spectral variation due to the atmospheric absorption is used to derive tangential column densities of the absorbing species, that is, N and O including atoms and molecules, along the line of sight. The tangential column densities are then inverted to obtain the atmospheric number density. The data from 219 occultation scans at low latitudes in both hemispheres from September 15, 2005 to March 26, 2016 are analyzed to generate a single, highly averaged (in both space and time) vertical density profile. The density profile is in good agreement with the Naval-Research-Laboratory s-Mass-Spectrometer-Incoherent-Scatter-Radar-Extended (NRLMSISE-00) model, except for the altitude range of 70–110 km, where the measured density is ∼50\% smaller than the model. Such a deviation is consistent with the recent measurement with the SABER aboard the TIMED satellite (Cheng et al., 2020, https://doi.org/10.3390/atmos11040341). Given that the NRLMSISE-00 model was constructed some time ago, the density decline could be due to the radiative cooling/contracting of the upper atmosphere as a result of greenhouse warming in the troposphere. However, we cannot rule out a possibility that the NRL model is simply imperfect in this region. We also present future prospects for the upcoming Japan-US X-ray astronomy satellite, X-Ray Imaging and Spectroscopy Mission (XRISM), which will allow us to measure atmospheric composition with unprecedented spectral resolution of ΔE ∼ 5 eV in 0.3–12 keV.

Katsuda, Satoru; Fujiwara, Hitoshi; Ishisaki, Yoshitaka; Yoshitomo, Maeda; Mori, Koji; Motizuki, Yuko; Sato, Kosuke; Tashiro, Makoto; Terada, Yukikatsu;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2021     DOI: 10.1029/2020JA028886

Crab Nebula; Hitomi; occultation; Suzaku; upper atmosphere; X-rays

Conjugate Observations of the Evolution of Polar Cap Arcs in Both Hemispheres

We report results from the analysis of a case of conjugate polar cap arcs (PCAs) observed on 5 February 2006 in the Northern Hemisphere by the ground-based Yellow River Station all-sky imager (Svalbard) and in both hemispheres by the space-based DMSP/SSUSI and TIMED/GUVI instruments. The PCA\textquoterights motion in dawn-dusk direction shows a clear dependence on the interplanetary magnetic field (IMF) B_y component and presents a clear asymmetry between Southern and Northern Hemispheres, that is, formed on the duskside and moving from dusk to dawn in the Northern Hemisphere and vice versa in the other hemisphere. The already existing PCAs\textquoteright motion is influenced by the changes in the IMF B_y with a time delay of ~70\ min. We also observed strong flow shears/reversals around the PCAs in both hemispheres. The precipitating particles observed in the ionosphere associated with PCAs showed properties of boundary layer plasma. Based on these observations, we might reasonably expect that the topological changes in the magnetotail can produce a strip of closed field lines and local processes would set up conditions for the formation and evolution of PCAs.

Xing, Zanyang; Zhang, Qinghe; Han, Desheng; Zhang, Yongliang; Sato, Natsuo; Zhang, Shunrong; Hu, Zejun; Wang, Yong; Ma, Yuzhang;

Published by: Journal of Geophysical Research: Space Physics      Published on: 02/2018

YEAR: 2018     DOI: 10.1002/2017JA024272

Conjugate observations of the evolution of a long-duration polar cap arc in both hemispheres

Xing, Zan-Yang; Zhang, Qing-He; Zhang, Yongliang; Sato, Natsuo;

Published by:       Published on:

YEAR: 2016     DOI:

Oscillations of the equatorward boundary of the ion auroral oval – radar observations

Three SuperDARN radars in the afternoon-midnight sector of the auroral oval detected a boundary oscillation, originating near ∼1800 MLT sector. Analysis of the phase of the oscillations measured in three meridians indicates that the disturbance has a longitudinally (azimuthally) isolated source and away from which it propagates. The eastward and westward phase speeds are 2.6 and 3.6 km/s respectively and the period is roughly 28 minutes. An examination of the geo-synchronous magnetic field inclination also revealed oscillations similar to the oscillations of the boundary. Solar wind and IMF conditions were steady during the period except for variations of the IMF By component. The IMF By component showed variations similar to the oscillations in the boundary and the geo-synchronous magnetic field inclination. During reduced and negative IMF By, the boundary was moving equatorward, while during increased or positive IMF By it was moving poleward. The variations in the magnetic field inclination measured at geosynchronous orbit by the GOES satellites were consistent with these boundary motions: decreases (more stretched) and increases (more dipolar) in the inclination corresponded to equatorward and poleward moving boundaries, respectively. Polar cap convection also showed changes in the direction of the convection in response to the change in the IMF By component. Observed oscillation of the boundary can be explained by stretching of the tail field lines due to asymmetric merging associated with changes in the By component of the interplanetary magnetic field.

Jayachandran, P.; Sato, N.; Ebihara, Y.; Yukimatu, A.; Kadokura, A.; MacDougall, J.; Donovan, E.; Liou, K.;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2008     DOI: https://doi.org/10.1029/2007JA012870

Boundary oscillation; SuperDARN radars; Convection

Summer-winter hemispheric asymmetry of the sudden increase in ionospheric total electron content and of the O/N ₂ ratio: Solar activity dependence

Tsugawa, T.; Zhang, S.-R.; Coster, A.; Otsuka, Y.; Sato, J.; Saito, A.; Zhang, Y.; Paxton, L.;

Published by: Journal of Geophysical Research      Published on: Jan-01-2007

YEAR: 2007     DOI: 10.1029/2007JA012415

Summer-winter hemispheric asymmetry of the sudden increase in ionospheric total electron content and of the O/N2 ratio: Solar activity dependence

Tsugawa, T; Zhang, S-R; Coster, AJ; Otsuka, Y; Sato, J; Saito, A; Zhang, Y; Paxton, LJ;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2007     DOI:

Summer-Winter Hemispheric Asymmetry of Sudden Increase in Ionospheric Total Electron Content

Tsugawa, T; Zhang, S; Coster, A; Otsuka, Y; Sato, J; Saito, A; Zhang, Y; Paxton, L;

Published by:       Published on:

YEAR: 2006     DOI: