Space Science by Motoharu Nowada
Papers by Motoharu Nowada
Journal of Geophysical Research: Space Physics
Journal of Geophysical Research: Space Physics
Auroral morphological changes prior to and during auroral spiral appearance in the late substor... more Auroral morphological changes prior to and during auroral spiral appearance in the late substorm recovery phase are investigated. The source region of the auroral spiral in the magnetotail is extensively distributed over 30 RE, from Xgsm ~-40 to-70 RE. Extensive areas of the magnetotail are active enough to cause auroral spirals even during the late substorm recovery phase.
AGU Fall Meeting Abstracts, Dec 14, 2020
Predicting geomagnetic conditions based on in-situ solar wind observations allows us to evade dis... more Predicting geomagnetic conditions based on in-situ solar wind observations allows us to evade disasters caused by large electromagnetic disturbances originating from the Sun to save lives and protect economic activity. In this study, we aimed to examine the relationship between the Kp index, representing global magnetospheric activity level, and solar wind conditions using an interpretable neural network known as potential learning (PL). Data analyses based on neural networks are difficult to interpret; however, PL learns by focusing on the “potentiality of input neurons” and can identify which inputs are significantly utilized by the network. Using the full advantage of PL, we extracted the influential solar wind parameters that disturb the magnetosphere under southward Interplanetary magnetic field (IMF) conditions. The input parameters of PL were the three components of the IMF (Bx, By, -Bz(Bs)), solar wind flow speed (Vx), and proton number density (Np) in geocentric solar eclip...
[1] The magnetopause is the boundary where the reduced solar wind dynamic pressure is equal to th... more [1] The magnetopause is the boundary where the reduced solar wind dynamic pressure is equal to the magnetic pressure of the Earth's outer magnetosphere. With hundreds of magnetopause crossings identified from the THEMIS data, we estimate a ratio ( f ) of the compressed magnetic field just inside the subsolar magnetopause to the purely dipolar magnetic field. Previous theoretical studies reported that the ratio f was nearly independent of the subsolar standoff distance (r 0 ). Here we report that the ratio f is linearly proportional to r 0 for both northward and southward interplanetary magnetic field (IMF). The proportionality constant for southward IMF is larger than that for northward IMF, implying that the compression level of the magnetic field by inward magnetopause for southward IMF is smaller than that for northward IMF.
Japan Geoscience Union, 2017
Journal of Geophysical Research, 2017
The Astrophysical Journal Letters, 2021
The Advanced Small Analyzer for Neutrals (ASAN) on board the Chang’E-4 Yutu-2 rover first detecte... more The Advanced Small Analyzer for Neutrals (ASAN) on board the Chang’E-4 Yutu-2 rover first detected energetic neutral atoms (ENAs) originating from the lunar surface at various lunar local times on the lunar farside. In this work, we examine the ENA energy spectra, obtained in the first 23 lunar days from 2019 January 11 to 2020 October 12, and find a higher ENA differential flux on the lunar dawnside than on the duskside. Combined with Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) data, we analyze the correlation between the ENA differential flux and solar wind parameters, such as flux, density, dynamic pressure, and velocity, for each ASAN energy channel on the dawnside and duskside. The results show that ENA differential flux is positively correlated with solar wind flux, density, and dynamic pressure and relatively lower on the duskside than on the dawnside. To determine the relationship between solar wind energy and E...
Pigeons signify the resourceful class of vertebrates. Their crop is a thin muscular expansion of ... more Pigeons signify the resourceful class of vertebrates. Their crop is a thin muscular expansion of esophagus which temporarily stores food. Traumatic rupture of the filled crop is common because when expanded to skin, even a small concussion can result in its injury. This project was designed to identify the best and reliable technique for crop rupture repair, with least surgical and post-surgical complications. The study was carried out on 30 apparently healthy pigeons weighing between 275 gm to 350 gm. They were divided into three groups i.e. Group A, B and C comprising ten pigeons each and were numbered as A1-A10, B1-B10 and C1-C10. Ingluviotomy techniques were performed group wise as: for group A-Single Layer closure; group B-Double Layer closure and group C-with surgical glue. Clinical parameters were observed at variable intervals from day 1 to day 30 post-surgery. In vital body signs, temperature (P≤0.05) revealed significant difference between groups whereas pulse rate and respiration showed nonsignificant difference (P≥0.05). Liquid, food intake was superior in group B than group A and C; moreover, group C showed better intake than group A. Droppings were initially watery, which gradually converted from semi-solid to normal with passage of time in all groups. Weight gain/loss, (P≤0.05) revealed significant difference between groups; weight gain was highest in group B, moderate in group C and lowest in group A. Wound healing and leakage evaluations, showed excellent healing with least leakage and associated mortality in group B, whereas groups A and C showed variable leakages with greater mortality in group A than C.
Journal of Geophysical Research: Space Physics, 2018
The cold-dense plasma sheet (CDPS) plays an important role in the entry process of the solar wind... more The cold-dense plasma sheet (CDPS) plays an important role in the entry process of the solar wind plasma into the magnetosphere. Investigating the seasonal variation of CDPS occurrences will help us better understand the long-term variation of plasma exchange between the solar wind and magnetosphere, but any seasonal variation of CDPS occurrences has not yet been reported in the literature. In this paper, we investigate the seasonal variation of the occurrence rate of CDPS using Geotail data from 1996 to 2015 and find a semiannual variation of the CDPS occurrences. Given the higher probability of solar wind entry under stronger northward interplanetary magnetic field (IMF) conditions, 20 years of IMF data (1996-2015) are used to investigate the seasonal variation of IMF B z under northward IMF conditions. We find a semiannual variation of IMF B z , which is consistent with the Russell-McPherron (R-M) effect. We therefore suggest that the semiannual variation of CDPS may be related to the R-M effect.
Geophysical Research Letters, 2021
Journal of Geophysical Research: Space Physics, 2018
Kelvin-Helmholtz waves (KHWs), which have been widely observed at the magnetopause in the region ... more Kelvin-Helmholtz waves (KHWs), which have been widely observed at the magnetopause in the region near the Earth, play an essential role in the transport of solar wind plasma and energy into the magnetosphere under dominantly northward interplanetary magnetic field (IMF) conditions. In this study, we present simultaneous observations of KHWs under the northward IMF observed by both the Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) spacecraft in the Earth's magnetotail around the lunar orbit (at X~À50R E , Y~30R E , dusk side) and the Geotail in the near-Earth space (at X~À5R E , Y~À10R E , dawn side). The KHWs are quantitatively characterized by their dominant period, phase velocity, and wavelength, utilizing wavelet analysis and an approximation of their center-of-mass velocity. Our results suggest that the phase velocity and spatial scale of KHWs may increase as they propagate along the boundary layer toward the tail. Alternatively, the differences between the ARTEMIS and Geotail observations may indicate the possibility of dawn-dusk asymmetry in the excited KHWs in this study. Our results strongly evidence the existence of the development of KHWs in terms of their wave frequency and scale size in the magnetotail and provide insight to the time evolution of KHWs along the magnetopause.
Journal of Geophysical Research: Space Physics, 2017
This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as
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Space Science by Motoharu Nowada
Papers by Motoharu Nowada