Optical and radio measurements of a 630‐nm airglow enhancement over Japan on 9 September 1999

Abstract

[1] Using a comprehensive data set from optical and radio instruments, we investigate a midnight brightness wave that appeared in 630-nm airglow images over Japan on the night of 9 September 1999. This may be the first such observation of the brightness wave with an all-sky imager in the East-Asian longitudinal sector. The imager at Shigaraki (35.6°N, 136.1°E) tracked a north-northeastward propagation of the wave with an apparent velocity of 500 m s À1 after midnight. Ionosonde observations at five stations in Japan showed that rapid descent of the F 2 layer propagated northward beyond 35°N with decreasing amplitude. Incoherent scatter observations with the MU radar at Shigaraki also revealed that the F 2 peak altitude decreased from 360 to 280 km during the event. During the F 2 layer descent the altitude profile of the electron density became sharp, enhancing the F 2 peak electron density. After the F 2 layer altitude reached 280 km, electron density in the F 2 layer rapidly decreased because of increased neutral density at low altitude. A FabryPerot interferometer (FPI) at Shigaraki observed northward neutral winds of 10-70 m s À1 during the event. A model calculation demonstrates that the meridional winds estimated from the MU radar electron density profiles are fairly consistent with those observed with the FPI. From these results we conclude that the observed northward wind enhancements, probably caused by the midnight temperature maximum, pushed down the plasma in the F 2 layer to lower altitudes along the geomagnetic field to cause the 630-nm airglow intensity enhancement.

Time evolution of high-altitude plasma bubbles imaged at geomagnetic conjugate points

“…The drastic enhancement after 23:30 LT at Sata may correspond to a large-scale atmospheric wave propagating from the midnight temperature maximum in the equator (e.g. Colerico et al, 1996;Otsuka et al, 2003). …”

Tracking F-region plasma depletion bands using GPS-TEC, incoherent scatter radar, and all-sky imaging at Arecibo

“…Recent imaging studies have revealed that the mid-latitude F-region is also active with plasma depletion bands (or so called slabs, MSTIDs), equatorial plumes, the midnight temperature maximum, spread-F, etc. (Mendillo et al, 1997;Garcia et al, 2000;Kelley et al, 2000bKelley et al, , 2002Kelley et al, , 2004Shiokawa et al, 2003a, b;Otsuka et al, 2003;Seker et al, 2007). The use of imager and radar together has been the subject of several recent papers: Pi et al (2000) (imager, ISR, FPI), Kelley et al (2000a) (imager, ISR), Kelley et al (2002) (imager, ISR, GPS), Otsuka et al (2003) (imager, MU radar, FPI).…”

“…(Mendillo et al, 1997;Garcia et al, 2000;Kelley et al, 2000bKelley et al, , 2002Kelley et al, , 2004Shiokawa et al, 2003a, b;Otsuka et al, 2003;Seker et al, 2007). The use of imager and radar together has been the subject of several recent papers: Pi et al (2000) (imager, ISR, FPI), Kelley et al (2000a) (imager, ISR), Kelley et al (2002) (imager, ISR, GPS), Otsuka et al (2003) (imager, MU radar, FPI). However these papers have typically been limited to comparing the radar "image" and the all-sky image by looking at them simultaneously, rather than using the two jointly to infer additional information about the structures being studied.…”

Global Observations of the 630-nm Nightglow and Patterns of Brightness Measured by ISUAL

“…Based upon the early work mentioned in the introduction section, most of the studies on midnight brightness have attempted to associate the effect with in situ temperature and neutral wind measurements (Herrero and Meriwether 1980;Colerico et al 1996Colerico et al , 2002Otsuka et al 2003). Because the brightening moved pole-ward with time from near the geographic equator, forming the MBW, the observation timing was very important.…”

“…Recently, several studies have clarified the general characteristics of latitudinal and seasonal variations of nighttime airglow emissions in the ionosphere using groundbased observations (Otsuka et al 2003;Niranjan et al 2006;Shiokawa et al 2006;Maruyama et al 2008). However, they could only investigate the ionospheric variations within the localized ground-based observational region and provide a dim macroscopic perspective.…”