scholarly journals A climatology of medium-scale gravity wave activity in the midlatitude/low-latitude daytime upper thermosphere as observed by CHAMP

2014 ◽  
Vol 119 (3) ◽  
pp. 2187-2196 ◽  
Author(s):  
J. Park ◽  
H. Lühr ◽  
C. Lee ◽  
Y. H. Kim ◽  
G. Jee ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Wave Activity ◽  
Low Latitude ◽  
Medium Scale

Numerical Modeling of the Concentric Gravity Wave Seeding of Low-Latitude Nighttime Medium-Scale Traveling Ionospheric Disturbances

2018 ◽  
Vol 45 (13) ◽  
pp. 6390-6399 ◽  
Author(s):  
Min-Yang Chou ◽  
Charles C. H. Lin ◽  
Joseph D. Huba ◽  
Chuan-Ping Lien ◽  
Chia-Hung Chen ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Gravity Wave ◽  
Ionospheric Disturbances ◽  
Low Latitude ◽  
Medium Scale ◽  
Traveling Ionospheric Disturbances

First observational evidence of the modulation of gravity wave activity in the low latitude middle atmosphere by equatorial waves

2002 ◽  
Vol 29 (6) ◽  
pp. 1-1-1-4 ◽  
Author(s):  
K. Parameswaran ◽  
K. Rajeev ◽  
M. N. Sasi ◽  
Geetha Ramkumar ◽  
B. V. Krishna Murthy
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Wave Activity ◽  
Observational Evidence ◽  
Equatorial Waves ◽  
Low Latitude

scholarly journals Medium‐scale gravity wave activity in the thermosphere inferred from GOCE data

2016 ◽  
Vol 121 (8) ◽  
pp. 8089-8102 ◽  
Author(s):  
Raphael F. Garcia ◽  
Sean Bruinsma ◽  
Lotfi Massarweh ◽  
Eelco Doornbos
Keyword(s):  
Gravity Wave ◽  
Wave Activity ◽  
Medium Scale

scholarly journals Medium-scale gravity wave activity in the bottomside F region in tropical regions

2017 ◽  
Vol 44 (14) ◽  
pp. 7099-7105 ◽  
Author(s):  
Huixin Liu ◽  
Nicholas Pedatella ◽  
Klemens Hocke
Keyword(s):  
Gravity Wave ◽  
Wave Activity ◽  
Tropical Regions ◽  
Medium Scale ◽  
F Region

scholarly journals Investigation of Low Latitude Spread-F Triggered by Nighttime Medium-Scale Traveling Ionospheric Disturbance

2021 ◽  
Vol 13 (5) ◽  
pp. 945
Author(s):  
Zhongxin Deng ◽  
Rui Wang ◽  
Yi Liu ◽  
Tong Xu ◽  
Zhuangkai Wang ◽  
...  
Keyword(s):  
Ionospheric Disturbance ◽  
Phase Speed ◽  
Morphological Processing ◽  
Wave Number ◽  
Occurrence Rate ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Medium Scale ◽  
Spread F

In the current study, we investigated the mechanism of medium-scale traveling ionospheric disturbance (MSTID) triggering spread-F in the low latitude ionosphere using ionosonde observation and Global Navigation Satellite System-Total Electron Content (GNSS-TEC) measurement. We use a series of morphological processing techniques applied to ionograms to retrieve the O-wave traces automatically. The maximum entropy method (MEM) was also utilized to obtain the propagation parameters of MSTID. Although it is widely acknowledged that MSTID is normally accompanied by polarization electric fields which can trigger Rayleigh–Taylor (RT) instability and consequently excite spread-F, our statistical analysis of 13 months of MSTID and spread-F occurrence showed that there is an inverse seasonal occurrence rate between MSTID and spread-F. Thus, we assert that only MSTID with certain properties can trigger spread-F occurrence. We also note that the MSTID at night has a high possibility to trigger spread-F. We assume that this tendency is consistent with the fact that the polarization electric field caused by MSTID is generally the main source of post-midnight F-layer instability. Moreover, after thorough investigation over the azimuth, phase speed, main frequency, and wave number over the South America region, we found that the spread-F has a tendency to be triggered by nighttime MSTID, which is generally characterized by larger ΔTEC amplitudes.

scholarly journals Influence of the cloud-level neutral layer on the vertical propagation of topographically generated gravity waves on Venus

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Takeru Yamada ◽  
Takeshi Imamura ◽  
Tetsuya Fukuhara ◽  
Makoto Taguchi
Keyword(s):  
Layer Thickness ◽  
Gravity Wave ◽  
Local Time ◽  
Gravity Waves ◽  
Analytical Approach ◽  
Wave Activity ◽  
Neutral Layer ◽  
Low Latitudes ◽  
Vertical Propagation ◽  
The Waves

AbstractThe reason for stationary gravity waves at Venus’ cloud top to appear mostly at low latitudes in the afternoon is not understood. Since a neutral layer exists in the lower part of the cloud layer, the waves should be affected by the neutral layer before reaching the cloud top. To what extent gravity waves can propagate vertically through the neutral layer has been unclear. To examine the possibility that the variation of the neutral layer thickness is responsible for the dependence of the gravity wave activity on the latitude and the local time, we investigated the sensitivity of the vertical propagation of gravity waves on the neutral layer thickness using a numerical model. The results showed that stationary gravity waves with zonal wavelengths longer than 1000 km can propagate to the cloud-top level without notable attenuation in the neutral layer with realistic thicknesses of 5–15 km. This suggests that the observed latitudinal and local time variation of the gravity wave activity should be attributed to processes below the cloud. An analytical approach also showed that gravity waves with horizontal wavelengths shorter than tens of kilometers would be strongly attenuated in the neutral layer; such waves should originate in the altitude region above the neutral layer.

scholarly journals Statistical study of medium-scale traveling ionospheric disturbances in low-latitude ionosphere using an automatic algorithm

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Pin-Hsuan Cheng ◽  
Charles Lin ◽  
Yuichi Otsuka ◽  
Hanli Liu ◽  
Panthalingal Krishanunni Rajesh ◽  
...  
Keyword(s):  
Climate Model ◽  
Geomagnetic Latitude ◽  
Detection Algorithm ◽  
Support Vector ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Low Latitude ◽  
Total Electron ◽  
Medium Scale ◽  
Traveling Ionospheric Disturbances

AbstractThis study investigates the medium-scale traveling ionospheric disturbances (MSTIDs) statistically at the low-latitude equatorial ionization anomaly (EIA) region in the northern hemisphere. We apply the automatic detection algorithm including the three-dimensional fast Fourier transform (3-D FFT) and support vector machine (SVM) on total electron content (TEC) observations, derived from a network of ground-based global navigation satellite system (GNSS) receivers in Taiwan (14.5° N geomagnetic latitude; 32.5° inclination), to identify MSTID from other waves or irregularity features. The obtained results are analyzed statistically to examine the behavior of low-latitude MSTIDs. Statistical results indicate the following characteristics. First, the southward (equatorward) MSTIDs are observed almost every day during 0800–2100 LT in Spring and Winter. At midnight, southward MSTIDs are more discernible in Summer and majority of them are propagating from Japan to Taiwan. Second, northward (poleward) MSTIDs are more frequently detected during 1200–2100 LT in Spring and Summer with the secondary peak of occurrence between day of year (DOY) 100–140 during 0000–0300 LT. The characteristics of the MSTIDs are interpreted with additional observations from radio occultation (RO) soundings of FORMOSAT-3/COSMIC as well as modeled atmospheric waves from the high-resolution Whole Atmosphere Community Climate Model (WACCM) suggesting that the nighttime MSTIDs in Summer is likely connected to the atmospheric gravity waves (AGWs).

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