Mesospheric bores at southern midlatitudes observed by ISS-IMAP/VISI: a first report of an undulating wave front

Abstract

Abstract. Large-scale spatial structures of mesospheric bores were observed by the Visible and near-Infrared Spectral Imager (VISI) of the ISS-IMAP mission (Ionosphere, Mesosphere, upper Atmosphere and Plasmasphere mapping mission from the International Space Station) in the mesospheric O2 airglow at 762 nm wavelength. Two mesospheric bore events in southern midlatitudes are reported in this paper: one event at 48–54∘ S, 10–20∘ E on 9 July 2015 and the other event at 35–43∘ S, 24∘ W–1∘ E on 7 May 2013. For the first event, the temporal evolution of the mesospheric bore was investigated from the difference of two observations in consecutive passes. The estimated eastward speed of the bore is 100 m s−1. The number of trailing waves increased with a rate of 3.5 waves h−1. Anticlockwise rotation with a speed of 20∘ h−1 was also recognized. These parameters are similar to those reported by previous studies based on ground-based measurements, and the similarity supports the validity of VISI observation for mesospheric bores. For the second event, VISI captured a mesospheric bore with a large-scale and undulating wave front. The horizontal extent of the wave front was 2200 km. The long wave front undulated with a wavelength of 1000 km. The undulating wave front is a new feature of mesospheric bores revealed by the wide field of view of VISI. We suggest that nonuniform bore propagating speed due to inhomogeneous background ducting structure might be a cause of the undulation of the wave front. Temperature measurements from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) onboard the Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite indicated that bores of both events were ducted in a temperature inversion layer.

Geographical and Seasonal Variability of Mesospheric Bores Observed from the International Space Station

“…The two constructive pass events are counted as two bores in the current analysis. This event was reported in detail by Hozumi et al (2018).…”

Characterization of gravity waves in the lower ionosphere using very low frequency observations at Comandante Ferraz Brazilian Antarctic Station

“…The ionospheric absorption of the cosmic radio noise is a function of the product of these two parameters, and so the fluctuations produced by the effect of GWs can be detected by imaging riometers. The ionospheric absorption modulations observed with different riometer beams permit one to infer the gravity wave parameters such as the phase velocity, period, and direction of propagation, as demonstrated by Jarvis et al (2003) and Moffat-Griffin et al (2008). They validated this technique comparing mesospheric GW signatures observed by using both a colocated imaging riometer and airglow imager.…”

“…These parameters are similar to the ones obtained for mesospheric fronts or bore-type events, which were understood as a rare type of gravity waves at polar latitudes and were first observed at Halley Station in May 2001 (Nielsen et al, 2006). Nowadays, with more observations, it is clear that the mesospheric fronts or bores are more likely to be observed at middle to high latitudes (even in unexpected places such as the South Pole) as can be noted in the recent studies on this subject (e.g., Pautet et al, 2018;Giongo et al, 2018;Hozumi et al, 2018). The VLF amplitude from NAA transmitter detected at EACF on 10 July 2007 is shown in Fig.…”

Characterization of gravity waves in the lower ionosphere using VLF observations at Comandante Ferraz Brazilian Antarctic Station

“…Nowadays, with more observations, it is clear that the mesospheric fronts or bores are more likely to be observed from middle to high latitude (even at unexpected places as the South Pole) as can be noted in the recent studies on this 10 subject (e.g. : Pautet et al, 2018a, Giongo et al, 2018and Hozumi et al, 2018. The first row shows the images with the star field subtracted and applying the Time Difference (TD) 15 image processing, and at the second row are the same images after correcting for the fish-eye lens format.…”