Influence of atmospheric winds and tides on the propagation direction of mesospheric gravity waves observed in OH airglow in the Alpine region

2020 ◽  
Author(s):  
Patrick Hannawald ◽  
Sabine Wüst ◽  
Michael Bittner ◽  
Friederike Lilienthal ◽  
Christoph Jacobi
Keyword(s):  
Gravity Waves ◽  
Lower Thermosphere ◽  
Phase Speed ◽  
Alpine Region ◽  
Propagation Direction ◽  
Atmospheric Tides ◽  
Prevailing Wind ◽  
Atmospheric Gravity Waves ◽  
Energy And Momentum ◽  
Atmospheric Gravity

<p>Atmospheric gravity waves transport energy and momentum trough the different atmospheric layers from the troposphere up to the mesosphere and above. On the one hand this transport has influence on atmospheric circulation patterns and drives for example the meridional circulation in the mesosphere. On the other hand the prevailing wind field selectively influences the vertical propagation conditions of gravity waves of different phase speed and horizontal propagation direction.</p><p>The OH-airglow layer at ca. 86 km altitude (upper mesosphere / lower thermosphere, UMLT) is well-suited for the investigation of atmospheric dynamics, allowing continuous observations of the night-sky throughout the year. Especially, atmospheric gravity waves are prominent features in the data of airglow imaging systems. Furthermore, this altitude region is known to be a region where wave breaking occurs quite often making it particular interesting for quantifying the amount of energy and momentum released due to gravity waves.</p><p>Five years of airglow observations with three FAIM (Fast Airglow Imager) systems in and around the Alpine region are analysed regarding high-frequency gravity waves. Prevailing wind fields and tides from meteor radar wind data and ERA5 data are compared with the propagation direction of these waves and show patterns with high correlation. On seasonal timescales, the gravity waves clearly propagate predominantly to the East in summer and to the West in winter regarding the zonal direction. The meridional direction varies between the different years. On diurnal timescales, we find that atmospheric tides significantly impact the main propagation directions of the gravity waves.</p><p>We further present a case study of a stereoscopic reconstruction using two synchronized airglow-imagers with overlapping field-of-views. This allows deriving the wave amplitude and a 3D visualization of gravity wave patterns within the airglow layer.</p><p>This work received funding from the Bavarian State Ministry of the Environment and Consumer Protection.</p>

Recurrent high-speed solar wind co-rotating interaction region imprint on the ionosphere and atmosphere: GPS TEC variations and atmospheric gravity waves

2020 ◽  
Author(s):  
James M. Weygand ◽  
Paul Prikryl ◽  
Reza Ghoddousi-Fard ◽  
Lidia Nikitina ◽  
Bharat S. R. Kunduri
Keyword(s):  
Solar Wind ◽  
Gravity Waves ◽  
High Latitude ◽  
High Speed ◽  
Geomagnetic Storms ◽  
Coronal Holes ◽  
Lower Thermosphere ◽  
Ionospheric Currents ◽  
Atmospheric Gravity Waves ◽  
Atmospheric Gravity

<p>High-speed streams (HSS) from coronal holes dominate solar wind structure in the absence of coronal mass ejections during solar minimum and the descending branch of solar cycle. Prominent and long-lasting coronal holes produce intense co-rotating interaction regions (CIR) on the leading edge of high-speed plasma streams that cause recurrent ionospheric disturbances and geomagnetic storms. Through solar wind coupling to the magnetosphere-ionosphere-atmosphere (MIA) system they affect the ionosphere and neutral atmosphere at high latitudes, and, at mid to low latitudes, by the transmission of the electric fields [1] and propagation of atmospheric gravity waves from the high-latitude lower thermosphere [2].</p><p>The high-latitude ionospheric structure, caused by precipitation of energetic particles, strong ionospheric currents and convection, results in changes of the GPS total electron content (TEC) and rapid variations of GPS signal amplitude and phase, called scintillation [3]. The GPS phase scintillation is observed in the ionospheric cusp, polar cap and auroral zone, and is particularly intense during geomagnetic storms, substorms and auroral breakups. Phase scintillation index is computed for a sampling rate of 50 Hz by specialized GPS scintillation receivers from the Canadian High Arctic Ionospheric Network (CHAIN). A proxy index of phase variation is obtained from dual frequency measurements of geodetic-quality GPS receivers sampling at 1 Hz, which include globally distributed receivers of the RT-IGS network that are monitored by the Canadian Geodetic Survey in near-real-time [4]. Temporal and spatial changes of TEC and phase variations following the arrivals of HSS/CIRs [5] are investigated in the context of ionospheric convection and equivalent ionospheric currents derived from  a ground magnetometer network using the spherical elementary current system method [6,7].</p><p>The Joule heating and Lorentz forcing in the high-latitude lower thermosphere have long been recognized as sources of internal atmospheric gravity waves (AGWs) [2] that propagate both upward and downward, thus providing vertical coupling between atmospheric layers. In the ionosphere, they are observed as traveling ionospheric disturbances (TIDs) using various techniques, e.g., de-trended GPS TEC maps [8].</p><p>In this paper we examine the influence on the Earth’s ionosphere and atmosphere of a long-lasting HSS/CIRs from recurrent coronal holes at the end of solar cycles 23 and 24. The solar wind MIA coupling, as represented by the coupling function [9], was strongly increased during the arrivals of these HSS/CIRs.</p><p> </p><p>[1] Kikuchi, T. and K. K. Hashimoto, Geosci. Lett. , 3:4, 2016.</p><p>[2] Hocke, K. and K. Schlegel, Ann. Geophys., 14, 917–940, 1996.</p><p>[3] Prikryl, P., et al., J. Geophys. Res. Space Physics, 121, 10448–10465, 2016.</p><p>[4] Ghoddousi-Fard et al., Advances in Space Research, 52(8), 1397-1405, 2013.</p><p>[5] Prikryl et al. Earth, Planets and Space, 66:62, 2014.</p><p>[6] Amm O., and A. Viljanen, Earth Planets Space, 51, 431–440, 1999.</p><p>[7] Weygand J.M., et al., J. Geophys. Res., 116, A03305, 2011.</p><p>[8] Tsugawa T., et al., Geophys. Res. Lett., 34, L22101, 2007.</p><p>[9] Newell P. T., et al., J. Geophys. Res., 112, A01206, 2007.</p>

Rapid intensification of tropical cyclones: Vortex waves seeded by aurorally-generated atmospheric gravity waves?

2020 ◽  
Author(s):  
Lidia Nikitina ◽  
Paul Prikryl ◽  
Shun-Rong Zhang
Keyword(s):  
Solar Wind ◽  
Tropical Cyclones ◽  
Gravity Waves ◽  
Lower Thermosphere ◽  
Lower Atmosphere ◽  
Rapid Intensification ◽  
Mean Flow ◽  
Atmospheric Gravity Waves ◽  
Convective Bursts ◽  
Atmospheric Gravity

<p>Convective bursts have been linked to intensification of tropical cyclones [1]. We consider a possibility of convective bursts being triggered by aurorally-generated atmospheric gravity waves (AGWs) that may play a role in the intensification process of tropical cyclones [2]. A two-dimensional barotropic approximation is used to obtain asymptotic solutions representing propagation of vortex waves [3] launched in tropical cyclones by quasi-periodic convective bursts. The absorption of vortex waves by the mean flow and formation of the secondary eyewall lead to a process of an eyewall replacement cycle that is known to cause changes in tropical cyclone intensity [4]. Rapid intensification of hurricanes and typhoons from 1995-2018 is examined in the context of solar wind coupling to the magnetosphere-ionosphere-atmosphere (MIA) system. In support of recently published results [2] it is shown that rapid intensification of TCs tend to follow arrival of high-speed solar wind when the MIA coupling is strongest. The coupling generates internal gravity waves in the atmosphere that propagate from the high-latitude lower thermosphere both upward and downward. In the lower atmosphere, they can be ducted [5] and reach tropical troposphere. Despite their significantly reduced amplitude, but subject to amplification upon over-reflection in the upper troposphere, these AGWs can trigger/release moist instabilities leading to convection and latent heat release. A possibility of initiation of convective bursts by aurorally generated AGWs is investigated. Cases of rapid intensification of recent tropical cyclones provide further evidence to support the published results [2].</p><p>References</p><p>[1] Steranka et al., Mon. Weather Rev., 114, 1539-1546, 1986.</p><p>[2] Prikryl et al., J. Atmos. Sol.-Terr. Phys., 2019.</p><p>[3] Nikitina L.V., Campbell L.J., Stud. Appl. Math., 135, 377–446, 2015.</p><p>[4] Willoughby H.E., et al., J. Atmos. Sci., 39, 395–411, 1982.</p><p>[5] Mayr H.G., et al., J. Geophys. Res., 89, 10929–10959, 1984.</p>

scholarly journals Observation evidences of atmospheric Gravity Waves induced by seismic activity from analysis of subionospheric LF signal spectra

2007 ◽  
Vol 7 (5) ◽  
pp. 625-628 ◽  
Author(s):  
A. Rozhnoi ◽  
M. Solovieva ◽  
O. Molchanov ◽  
P.-F. Biagi ◽  
M. Hayakawa
Keyword(s):  
Gravity Waves ◽  
Fresnel Zone ◽  
Signal Amplitude ◽  
Magnetic Storms ◽  
Frequency Range ◽  
Atmospheric Gravity Waves ◽  
Period Range ◽  
Before And After ◽  
Atmospheric Gravity ◽  
Large Earthquakes

Abstract. We analyze variations of the LF subionospheric signal amplitude and phase from JJY transmitter in Japan (F=40 kHz) received in Petropavlovsk-Kamchatsky station during seismically quiet and active periods including also periods of magnetic storms. After 20 s averaging, the frequency range of the analysis is 0.28–15 mHz that corresponds to the period range from 1 to 60 min. Changes in spectra of the LF signal perturbations are found several days before and after three large earthquakes, which happened in November 2004 (M=7.1), August 2005 (M=7.2) and November 2006 (M=8.2) inside the Fresnel zone of the Japan-Kamchatka wavepath. Comparing the perturbed and background spectra we have found the evident increase in spectral range 10–25 min that is in the compliance with theoretical estimations on lithosphere-ionosphere coupling by the Atmospheric Gravity Waves (T>6 min). Similar changes are not found for the periods of magnetic storms.

scholarly journals A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes

1997 ◽  
Vol 15 (8) ◽  
pp. 1048-1056 ◽  
Author(s):  
R. L. Balthazor ◽  
R. J. Moffett
Keyword(s):  
Gravity Waves ◽  
Large Scale ◽  
Ionospheric Disturbance ◽  
Magnetic Equator ◽  
Ionospheric Disturbances ◽  
Atmospheric Gravity Waves ◽  
Opposite Hemisphere ◽  
Travelling Ionospheric Disturbances ◽  
F Region ◽  
Atmospheric Gravity

Abstract. A global coupled thermosphere-ionosphere-plasmasphere model is used to simulate a family of large-scale imperfectly ducted atmospheric gravity waves (AGWs) and associated travelling ionospheric disturbances (TIDs) originating at conjugate magnetic latitudes in the north and south auroral zones and subsequently propagating meridionally to equatorial latitudes. A 'fast' dominant mode and two slower modes are identified. We find that, at the magnetic equator, all the clearly identified modes of AGW interfere constructively and pass through to the opposite hemisphere with unchanged velocity. At F-region altitudes the 'fast' AGW has the largest amplitude, and when northward propagating and southward propagating modes interfere at the equator, the TID (as parameterised by the fractional change in the electron density at the F2 peak) increases in magnitude at the equator. The amplitude of the TID at the magnetic equator is increased compared to mid-latitudes in both upper and lower F-regions with a larger increase in the upper F-region. The ionospheric disturbance at the equator persists in the upper F-region for about 1 hour and in the lower F-region for 2.5 hours after the AGWs first interfere, and it is suggested that this is due to enhancements of the TID by slower AGW modes arriving later at the magnetic equator. The complex effects of the interplays of the TIDs generated in the equatorial plasmasphere are analysed by examining neutral and ion winds predicted by the model, and are demonstrated to be consequences of the forcing of the plasmasphere along the magnetic field lines by the neutral air pressure wave.

Search for Atmospheric Gravity Waves induced by the Eclipse of June 30, 1973

Nature ◽  
1973 ◽  
Vol 246 (5433) ◽  
pp. 412-413 ◽  
Author(s):  
J. E. BECKMAN ◽  
J. I. CLUCAS
Keyword(s):  
Gravity Waves ◽  
Atmospheric Gravity Waves ◽  
Atmospheric Gravity
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