Bibliography

Observation of equatorial plasma bubbles by the airglow imager on ISS-IMAP

Using 630 nm airglow data observed by an airglow imager on the International Space Station (ISS), the occurrence of equatorial plasma bubbles (EPBs) is studied. In order to examine the physical mechanisms in the boundary region between the Earth and the outer space, an ionosphere, mesosphere, upper atmosphere, and plasmasphere mapping (IMAP) mission had been conducted onboard the ISS since October 2012. The visible light and infrared spectrum imager (VISI) is utilized in the ISS-IMAP mission for nadir-looking observation of the earth\textquoterights atmospheric airglow. In this study, we automatically select EPBs according to the criterion for extracting the tilted dark lines from VISI data. Using the selected events, the dependence of the occurrence rate of EPBs is examined. There is no other report of the occurrence rate of EPBs using downward-looking visible airglow data (630 nm). In this result, the occurrence rate is high at all longitudes in the equinoctial seasons. In the solstice seasons, in contrast, the occurrence rate is very small especially in the Pacific and American sectors. This result is basically consistent with previous studies, e.g., those determined by plasma density data on DMSP satellites.During the June solstice in 2013, EPBs were observed in association with geomagnetic storms that occurred due to a southward turning of the IMF Bz. Using these events, we examined the storm-time features of the occurrence of EPBs in the Pacific-American sectors during the June solstice. In these sectors, where the occurrence rate of EPBs is very small during solstice seasons, some EPBs were observed in the peak and recovery phases of the storms. This result shows that the prompt penetration of electric fields causes the development of EPBs, in the data we analyzed, the geomagnetic storms did not inhibit the generation of EPB in the Pacific\textendashAmerican sectors.

Nakata, Hiroyuki; Takahashi, Akira; Takano, Toshiaki; Saito, Akinori; Sakanoi, Takeshi;

Published by: Progress in Earth and Planetary Science      Published on: 12/2018

YEAR: 2018     DOI: 10.1186/s40645-018-0227-0

Variations of the neutral temperature and sodium density between 80 and 107 km above Troms\o during the winter of 2010-2011 by a new solid-state sodium lidar

A new solid-state sodium lidar installed at Ramfjordmoen, Troms\o (69.6\textdegreeN, 19.2\textdegreeE), started observations of neutral temperature together with sodium density in the mesosphere-lower thermosphere (MLT) region on 1 October 2010. The new lidar provided temperature data with a time resolution of 10 min and with good quality between \~80 and \~105 km from October 2010 to March 2011. This paper aims at introducing the new lidar with its observational results obtained over the first 6 months of observations. We succeeded in obtaining neutral temperature and sodium density data of \~255.5 h in total. In order to evaluate our observations, we compared (1) the sodium density with that published in the literature, (2) average temperature and column sodium density data with those obtained with Arctic Lidar Observatory for Middle Atmosphere Research Weber sodium lidar, and (3) the neutral temperature data with those obtained by Sounding of the Atmosphere with Broadband Emission Radiometry/Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite. For the night of 5 October 2010, we succeeded in conducting simultaneous observations of the new lidar and the European Incoherent Scatter UHF radar with the tristatic Common Program 1 (CP-1) mode. Comparisons of neutral and ion temperatures showed a good agreement at 104 km between 0050 and 0230 UT on 6 October 2010 when the electric field strength was smaller, while significant deviations (up to \~25 K) are found at 107 km. We evaluated contributions of Joule heating and electron-ion heat exchange, but derived values seem to be underestimated.

Nozawa, S.; Kawahara, T.; Saito, N.; Hall, C.; Tsuda, T.; Kawabata, T.; Wada, S.; Brekke, A.; Takahashi, T.; Fujiwara, H.; Ogawa, Y.; Fujii, R.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 01/2014

YEAR: 2014     DOI: 10.1002/2013JA019520

Joule heating; neutral temperature; polar MLT; sodium lidar

Thermospheric tidal effects on the ionospheric midlatitude summer nighttime anomaly using SAMI3 and TIEGCM

This paper is the first study to employ a three-dimensional physics-based ionosphere model, SAMI3, coupled with the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) and Global Scale Wave Model to simulate the mesospheric and lower thermospheric tidal effects on the development of midlatitude summer nighttime anomaly (MSNA). Using this coupled model, the diurnal variation of MSNA electron densities at 300 km altitude is simulated on both June solstice (day of year (DOY) 167) and December solstice (DOY 350) in 2007. Results show successful reproduction of the southern hemisphere MSNA structure including the eastward drift feature of the southern MSNA, which is not reproduced by the default SAMI3 runs using the neutral winds provided by the empirical Horizontal Wind Model 93 neutral wind model. A linear least squares algorithm for extracting tidal components is utilized to examine the major tidal component affecting the variation of southern MSNA. Results show that the standing diurnal oscillation component dominates the vertical neutral wind manifesting as a diurnal eastward wave-1 drift of the southern MSNA in the local time frame. We also find that the stationary planetary wave-1 component of vertical neutral wind can cause diurnal variation of the summer nighttime electron density enhancement around the midlatitude ionosphere.

Chen, C.; Lin, C.; Chang, L.; Huba, J.; Lin, J.; Saito, A.; Liu, J;

Published by: Journal of Geophysical Research: Space Physics      Published on: 06/2013

YEAR: 2013     DOI: 10.1002/jgra.50340

MSNA; SAMI3; tidal effect; TIEGCM

Long-term variations of the nighttime electron density enhancement during the ionospheric midlatitude summer

This study, for the first time, presented the long-term variations of Midlatitude Summer Nighttime Anomaly (MSNA) in the two hemispheres by using 66 ground-based ionosonde observations from 1957 to 2010. MSNA is characterized by the feature of higher nighttime electron density than daytime density in the midlatitude region during local summer months. Observations from 66 ionosonde stations were used to calculate the MSNA index which is defined by the difference between nighttime and noontime NmF2 values. The MSNA occurrence is determined by positive value of the MSNA index. The global distribution map of the MSNA index shows that there are three regions of intense MSNA. Three ionosonde stations in each of active MSNA regions were chosen to study the long-term variation of MSNA covering longer than one solar cycle. One station in the southern hemisphere is AIJ6N (Argentine IS; 65.2\textdegreeS, 64.3\textdegreeW geographic) and two stations in the northern hemisphere are LN047 (Lannion; 48.8\textdegreeN, -3.4\textdegreeE geographic) and MG560 (Magadan; 60.0\textdegreeN, 151.0\textdegreeE geographic). Results show that there is a clear solar activity negative dependence of the MSNA index, high MSNA in the low solar activity condition and low MSNA in the high solar activity condition. The seasonal and solar activity variations of the MSNA index are explained by the combined effects of the vertical plasma drift induced by the neutral wind and photoionization during the nighttime.

Chen, C.; Saito, A.; Lin, C.; Liu, J;

Published by: Journal of Geophysical Research      Published on: 07/2012

YEAR: 2012     DOI: 10.1029/2011JA017138

ionization-uplift effect; midlatitude summer nighttime anomaly; MSNA index

Super-medium-scale traveling ionospheric disturbance observed at midlatitude during the geomagnetic storm on 10 November 2004

Medium-scale traveling ionospheric disturbances (MSTIDs) whose peak-to-peak amplitude was larger than 20 TECU (=1016el/m2) were observed at midlatitude during the geomagnetic storm on 10 November 2004. This amplitude was more than 10 times larger than that of the average MSTID. High-resolution data of the GPS Earth Observation Network (GEONET) clarified the characteristic of the total electron content (TEC) disturbances over Japan on 10 November 2004. The disturbances started around 1000 UT in the central part of Japan. The maximum of TEC temporal change was 7.2 TECU in 30 s. The disturbances had several wave fronts which extended from northwest to southeast and propagated from northeast to southwest. TEC data around Japan revealed that the disturbances were mainly observed from 18°N/S to 34°N/S of the geomagnetic latitude in the both hemispheres. Since those characteristics were similar to those of MSTIDs in spite of the unusual large amplitude, the MSTIDs are referred as “super-MSTIDs” in this paper. TEC variations of the super-MSTIDs were also observed at 460 km altitude by the GRACE satellite. The ion density fluctuations of the super-MSTIDs were observed in situ by the CHAMP and DMSP-F15 satellites, which flew at 360 km and 850 km, respectively. It is found that the plasma density variations of the super-MSTIDs occurred mainly above 360 km altitude. The characteristics that distinguish the event from plasma bubbles are its successive wave fronts, constant northwest-southeast direction along which the wave fronts stretched, and late local time of the occurrence. It is found that the uplift of the ionosphere around sunset excited the super-MSTIDs at midlatitudes. The uplift was attributed to the strong eastward electric field during the geomagnetic storm.

Nishioka, M.; Saito, A.; Tsugawa, T.;

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

YEAR: 2009     DOI: https://doi.org/10.1029/2008JA013581

super-MSTID; Ionosphere

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

Low-latitude total electron content enhancement at low geomagnetic activity observed over Japan

Kutiev, Ivan; Otsuka, Yuichi; Saito, Akinori; Tsugawa, Takuya;

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

YEAR: 2007     DOI:

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: