scholarly journals A Modeling Study of the Responses of Mesosphere and Lower Thermosphere Winds to Geomagnetic Storms at Middle Latitudes

2019 ◽  
Vol 124 (5) ◽  
pp. 3666-3680 ◽  
Author(s):  
Jingyuan Li ◽  
Wenbin Wang ◽  
Jianyong Lu ◽  
Jia Yue ◽  
Alan G. Burns ◽  
...  
Keyword(s):  
Geomagnetic Storms ◽  
Lower Thermosphere ◽  
Middle Latitudes ◽  
Mesosphere And Lower Thermosphere ◽  
Modeling Study

scholarly journals On the Responses of Mesosphere and Lower Thermosphere Temperatures to Geomagnetic Storms at Low and Middle Latitudes

2018 ◽  
Vol 45 (19) ◽  
pp. 10,128-10,137 ◽  
Author(s):  
Jingyuan Li ◽  
Wenbin Wang ◽  
Jianyong Lu ◽  
Tao Yuan ◽  
Jia Yue ◽  
...  
Keyword(s):  
Geomagnetic Storms ◽  
Lower Thermosphere ◽  
Middle Latitudes ◽  
Mesosphere And Lower Thermosphere

scholarly journals Characteristics of double sodium layer over Haikou, China (20.0° N, 110.1° E)

2019 ◽  
Vol 5 (2) ◽  
pp. 30-34
Author(s):  
Ян Дали ◽  
Yang Dali ◽  
Чжан Теминь ◽  
Zhang Tiemin ◽  
Ван Цзихун ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Dye Laser ◽  
Low Latitude ◽  
Middle Latitudes ◽  
Sodium Layer ◽  
Layer Structures ◽  
Low Latitudes ◽  
Sporadic E Layer ◽  
Mesosphere And Lower Thermosphere ◽  
Sporadic E

We study the property of double sodium layer structures (DSLs) in the mesosphere and lower thermosphere (MLT) by a lidar at the low-latitude location of Haikou (20.0° N, 110.1° E), China. From April 2010 to December 2013, 21 DSLs were observed within a total of 377 observation days. DSLs were recorded at middle latitudes of Beijing and Wuhan, China, but were rarely observed at low latitudes. We analyze and discuss characteristics of DSLs such as time of occurrence, peak altitude, FWHM, duration time, etc. At the same time, the critical frequency foEs and the virtual height h'Es of the sporadic E layer Es were observed by an ionosonde over Danzhou (19.0° N, 109.3° E). We discuss such their characteristics as differences of time, differences of altitude compared to DSLs. We used an Nd:YAG laser pumped dye laser to generate the probing beam. The wavelength of the dye laser was set to 589 nm by a sodium fluorescence cell. The backscattered fluorescence photons from the sodium layer were collected by a telescope with the Φ1000 mm primary mirror.

scholarly journals Observations of lunar tides in the mesosphere and lower thermosphere at Arctic and middle latitudes

2006 ◽  
Vol 6 (12) ◽  
pp. 4117-4127 ◽  
Author(s):  
D. J. Sandford ◽  
H. G. Muller ◽  
N. J. Mitchell
Keyword(s):  
Lower Thermosphere ◽  
Set Covering ◽  
The Arctic ◽  
Lunar Tide ◽  
Data Set ◽  
Height Range ◽  
Middle Latitudes ◽  
Lunar Tides ◽  
Mesosphere And Lower Thermosphere ◽  
The Uk

Abstract. Meteor radars have been used to measure the horizontal winds in the mesosphere and lower thermosphere over Castle Eaton (52° N) in the UK and over Esrange (68° N) in Arctic Sweden. We consider a 16-year data set covering the interval 1988–2004 for the UK and a 6-year data set covering the interval 1999–2005 for the Arctic. The signature of the 12.42-h (M2) lunar tide has been identified at both locations. The lunar tide is observed to reach amplitudes as large as 11 ms−1. The Arctic radar has an interferometer and so allows investigation of the vertical structure of the lunar tide. At both locations the tide has maximum amplitudes in winter with a second autumnal maximum. The amplitude is found to increase with height over the 80–100 km height range observed. Vertical wavelengths are very variable, ranging from about 15 km in summer to more than 60 km in winter. Comparisons with the Vial and Forbes (1994) model reveals generally good agreement, except in the case of the summer vertical wavelengths which are observed to be significantly shorter than predicted.

The Momentum Budget in the Stratosphere, Mesosphere, and Lower Thermosphere. Part I: Contributions of Different Wave Types and In Situ Generation of Rossby Waves

2018 ◽  
Vol 75 (10) ◽  
pp. 3613-3633 ◽  
Author(s):  
Kaoru Sato ◽  
Ryosuke Yasui ◽  
Yasunobu Miyoshi
Keyword(s):  
Rossby Waves ◽  
Baroclinic Instability ◽  
Lower Thermosphere ◽  
Flux Divergence ◽  
Middle Latitudes ◽  
Momentum Budget ◽  
Isentropic Surface ◽  
Mesosphere And Lower Thermosphere ◽  
Coarse Model

A momentum budget is examined in the stratosphere, mesosphere, and lower thermosphere using simulation data over ~11 years from a whole-atmosphere model in terms of the respective contributions of gravity waves (GWs), Rossby waves (RWs), and tides. The GW forcing is dominant in the mesosphere and lower thermosphere (MLT), as indicated in previous studies. However, RWs also cause strong westward forcing, described by Eliassen–Palm flux divergence (EPFD), in all seasons in the MLT and in the winter stratosphere. Despite the relatively coarse model resolution, resolved GWs with large amplitudes appear in the MLT. The EPFD associated with the resolved GWs is eastward (westward) in the summer (winter) hemisphere, similar to the parameterized GW forcing. A pair of positive and negative EPFDs are associated with the RWs and GWs in the MLT. These results suggest that the RWs and resolved GWs are generated in situ in the MLT. Previous studies suggested that a possible mechanism of RW generation in the MLT is the barotropic/baroclinic instability. This study revisits this possibility and examines causes of the instability from a potential vorticity (PV) viewpoint. The instability condition is characterized as the PV maximum at middle latitudes on an isentropic surface. Positive EPFD for RWs is distributed slightly poleward of the PV maximum. Because the EPFD equals the PV flux, this feature indicates that the RW radiation acts to reduce the PV maximum. The PV maximum is climatologically maintained in both the winter and summer mesospheres, which is caused by parameterized GW forcing.

scholarly journals Observations of lunar tides in the mesosphere and lower thermosphere at Arctic and middle latitudes

2006 ◽  
Vol 6 (3) ◽  
pp. 4643-4672 ◽  
Author(s):  
D. J. Sandford ◽  
H. G. Muller ◽  
N. J. Mitchell
Keyword(s):  
Lower Thermosphere ◽  
Set Covering ◽  
The Arctic ◽  
Lunar Tide ◽  
Data Set ◽  
Height Range ◽  
Middle Latitudes ◽  
Lunar Tides ◽  
Mesosphere And Lower Thermosphere ◽  
The Uk

Abstract. Meteor radars have been used to measure the horizontal winds in the mesosphere and lower thermosphere over Castle Eaton (52° N) in the UK and over Esrange (68° N) in Arctic Sweden. We consider a 16-year data set covering the interval 1988–2004 for the UK and a 6-year data set covering the interval 1999–2005 for the Arctic. The signature of the 12.42-h (M2) lunar tide has been identified at both locations. The lunar tide is observed to reach amplitudes as large as 11 ms−1. The Arctic radar has an interferometer and so allows investigation of the vertical structure of the lunar tide. At both locations the tide has maximum amplitudes in winter with a second autumnal maximum. The amplitude is found to increase with height over the 80–100 km height range observed. Vertical wavelengths are very variable, ranging from about 15 km in summer to more than 60 km in winter. Comparisons with the Vial and Forbes, 1994 model reveals generally good agreement, except in the case of the summer vertical wavelengths which are observed to be significantly shorter than predicted.

scholarly journals Characteristics of double sodium layer over Haikou, China (20.0° N, 110.1° E)

2019 ◽  
Vol 5 (2) ◽  
pp. 28-32
Author(s):  
Ян Дали ◽  
Yang Dali ◽  
Чжан Теминь ◽  
Zhang Tiemin ◽  
Ван Цзихун ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Dye Laser ◽  
Low Latitude ◽  
Middle Latitudes ◽  
Sodium Layer ◽  
Layer Structures ◽  
Low Latitudes ◽  
Sporadic E Layer ◽  
Mesosphere And Lower Thermosphere ◽  
Sporadic E

We study the property of double sodium layer structures (DSLs) in the mesosphere and lower thermosphere (MLT) by a lidar at the low-latitude location of Haikou (20.0° N, 110.1° E), China. From April 2010 to December 2013, 21 DSLs were observed within a total of 377 observation days. DSLs were recorded at middle latitudes of Beijing and Wuhan, China, but were rarely observed at low latitudes. We analyze and discuss characteristics of DSLs such as time of occurrence, peak altitude, FWHM, duration time, etc. At the same time, the critical frequency foEs and the virtual height h'Es of the sporadic E layer Es were observed by an ionosonde over Danzhou (19.0° N, 109.3° E). We discuss such their characteristics as differences of time, differences of altitude compared to DSLs. We used an Nd:YAG laser pumped dye laser to generate the probing beam. The wavelength of the dye laser was set to 589 nm by a sodium fluorescence cell. The backscattered fluorescence photons from the sodium layer were collected by a telescope with the Φ1000 mm primary mirror.

scholarly journals Measurement of geomagnetically induced current (GIC) around Tokyo, Japan

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Shinichi Watari ◽  
Satoko Nakamura ◽  
Yusuke Ebihara
Keyword(s):  
Solar Flare ◽  
Geomagnetic Storms ◽  
Power Grids ◽  
Geomagnetic Variation ◽  
Induced Current ◽  
Interplanetary Shocks ◽  
Geomagnetic Disturbances ◽  
Geomagnetically Induced Current ◽  
Middle Latitudes ◽  
Sudden Commencements

AbstractWe need a typical method of directly measuring geomagnetically induced current (GIC) to compare data for estimating a potential risk of power grids caused by GIC. Here, we overview GIC measurement systems that have appeared in published papers, note necessary requirements, report on our equipment, and show several examples of our measurements in substations around Tokyo, Japan. Although they are located at middle latitudes, GICs associated with various geomagnetic disturbances are observed, such as storm sudden commencements (SSCs) or sudden impulses (SIs) caused by interplanetary shocks, geomagnetic storms including a storm caused by abrupt southward turning of strong interplanetary magnetic field (IMF) associated with a magnetic cloud, bay disturbances caused by high-latitude aurora activities, and geomagnetic variation caused by a solar flare called the solar flare effect (SFE). All these results suggest that GIC at middle latitudes is sensitive to the magnetospheric current (the magnetopause current, the ring current, and the field-aligned current) and also the ionospheric current.

scholarly journals Large-Scale Waves in the Mesosphere and Lower Thermosphere Observed by SABER

2005 ◽  
Vol 62 (12) ◽  
pp. 4384-4399 ◽  
Author(s):  
Rolando R. Garcia ◽  
Ruth Lieberman ◽  
James M. Russell ◽  
Martin G. Mlynczak
Keyword(s):  
Large Scale ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Normal Modes ◽  
Zonal Winds ◽  
Broadband Emission ◽  
Summer Hemisphere ◽  
Mean Structure ◽  
Mesosphere And Lower Thermosphere ◽  
The Tropics

Abstract Observations made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board NASA’s Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics (TIMED) satellite have been processed using Salby’s fast Fourier synoptic mapping (FFSM) algorithm. The mapped data provide a first synoptic look at the mean structure and traveling waves of the mesosphere and lower thermosphere (MLT) since the launch of the TIMED satellite in December 2001. The results show the presence of various wave modes in the MLT, which reach largest amplitude above the mesopause and include Kelvin and Rossby–gravity waves, eastward-propagating diurnal oscillations (“non-sun-synchronous tides”), and a set of quasi-normal modes associated with the so-called 2-day wave. The latter exhibits marked seasonal variability, attaining large amplitudes during the solstices and all but disappearing at the equinoxes. SABER data also show a strong quasi-stationary Rossby wave signal throughout the middle atmosphere of the winter hemisphere; the signal extends into the Tropics and even into the summer hemisphere in the MLT, suggesting ducting by westerly background zonal winds. At certain times of the year, the 5-day Rossby normal mode and the 4-day wave associated with instability of the polar night jet are also prominent in SABER data.

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