Search

This is the TEC data used in the paper. For each file, the TEC dimension is 96*360*180, 96 stands for the UT time from 0:10 to 23:55 with a 15-min temporal resolution. 360 is the number of longitudes from -180 to 179. 180 is the number of laitudes from -90 to 89

A thermospheric O and N2 column density ratio (ΣO/N2) depletion with long-duration (>16 hr) was observed by the Global-scale Observations of the Limb and Disk at the Atlantic longitudes (75W–20W) and middle latitudes (20N–50N) during the recovery phase of the 8 June 2019 geomagnetic storm. The National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) simulations reproduced the ΣO/N2 depletion patterns with a similar magnitude, and indicated that the composition recovery at middle latitudes began several hours after the beginning of the recovery phase of the geomagnetic storm. The TIEGCM simulations enable quantitative analysis of the physical mechanisms driving the middle-latitude composition changes during the storm recovery phase. This analysis indicates that vertical advection and molecular diffusion dominated the initial recovery of composition perturbations at middle latitudes. Horizontal advection was also a main driver in the initial recovery of composition, but its contribution decreased rapidly. In the late recovery phase, the composition recovery was mainly determined by horizontal advection. In comparison, vertical advection and molecular diffusion played a much less important role.

these files are the superdarn electric potential and ion drift files. UTs are in the name of each files

These are some data derived from the MAGE model of the thermosphere ionosphere. Neutral density and GOLD equivalent temperatures are given here. More descriptions are as below: dimensions: nlats_gold = 52 ; nlons_gold = 46 ; ndays = 2 ; nut_gold = 4 ; n_height_mage = 92 ; variables: float latitude_gold(nlats_gold, nlons_gold) ; latitude_gold:units = "degree_north; -90 to +90" ; float longitude_gold(nlats_gold, nlons_gold) ; longitude_gold:units = "degree_east; -180 to +180" ; float height_MAGE(n_height_mage) ; height_MAGE:units = "km" ; height_MAGE:long_name = "MAGE geometrical heights" ; string dates(ndays) ; dates:long_name = "YYYYMMDD format date; e.g., 20181130 for November 30, 2018" ; byte ut_times(nut_gold) ; ut_times:units = "Universal Time (in hrs) when GOLD measurements were made" ; float MAGE_Teff(nut_gold, nlats_gold, nlons_gold) ; MAGE_Teff:units = "Kelvin" ; MAGE_Teff:long_name = "GOLD equivalent temperature (Teff) from MAGE" ; float MAGE_density(ndays, n_height_mage) ; MAGE_density:units = "gm/cc" ; MAGE_density:long_name = "MAGE Neutral density; during 10 to 19 UT and 60S to 60N " ; // global attributes: :description = "GOLD Equivalent Temperature and from MAGE model and neutral density; missing data: NaN" ; :history = "Created 2022-07-06 23:26:41.538906"

In order to understand the characteristics of long‐lasting “C‐type” structure in the Sodium (Na) lidargram, six cases from different observational locations have been analyzed. The Na lidargram, collected from low‐, middle‐, and high‐latitude sites, show long lifetime of the C‐type structures which is believed to be the manifestation of Kelvin‐Helmholtz (KH) billows in the Mesosphere and Lower Thermosphere (MLT) region. In order to explore the characteristics of the long‐lasting C‐type structures, the altitude profile of square of Brunt‐Väisälä frequency in the MLT region has been derived using the temperature profile collected from the Na lidar instruments and the SABER instrument onboard TIMED satellite. It is found to be positive in the C‐type structure region for all the six cases which indicates that the regions are convectively stable. Simultaneous wind measurements, which allowed us to calculate the Richardson numbers and Reynolds numbers for three cases, suggest that the regions where the C‐type structure appeared were dynamically stable and nonturbulent. This paper brings out a hypothesis wherein the low temperature can increase the magnitude of the Prandtl number and convectively stable atmospheric region can cause the magnitude of Reynolds number to decrease. As a consequence, the remnant of previously generated KH billows in nearly “frozen‐in” condition can be advected through this conducive region to a different location by the background wind where they can sustain for a long time without much deformation. These long‐lived KH billows in the MLT region will eventually manifest the long‐lasting C‐type structures in the Na lidargram.

The NASA Global-scale Observations of the Limb and Disk (GOLD) mission has flown an ultraviolet-imaging spectrograph on SES-14, a communications satellite in geostationary orbit at 47.5 degrees W longitude. That instrument observes the Earth's far ultraviolet (FUV) airglow at similar to 134-162 nm using two identical channels. The observations performed include limb scans, stellar occultations, and images of the sunlit and nightside disk from 6:10 to 00:40 universal time each day. Initial analyses reveal interesting and unexpected results as well as the potential for further studies of the Earth's thermosphere-ionosphere system and its responses to solar-geomagnetic forcing and atmospheric dynamics. Thermospheric composition ratios for major constituents, O and N-2, temperatures near 160 km, and exospheric temperatures are retrieved from the daytime observations. Molecular oxygen (O-2) densities are measured using stellar occultations. At night, emission from radiative recombination in the ionosphericFregion is used to quantify ionospheric density variations in the equatorial ionization anomaly (EIA). Regions of depletedFregion electron density are frequently evident, even during the current solar minimum. These depletions are caused by the "plasma fountain effect" and are associated with the instabilities, scintillations, or "spreadF" seen in other types of observations, and GOLD makes unique observations for their study. Plain Language Summary The NASA Global-scale Observations of the Limb and Disk (GOLD) mission has flown a dual-channel, ultraviolet-imaging spectrograph on SES-14, a communications satellite in geostationary orbit at 47.5 degrees W longitude. That instrument observes the Earth's far ultraviolet (FUV) airglow at similar to 134-162 nm. The observations performed include images of the Earth's sunlit and nightside disk, limb scans, and stellar occultations, from 6:10 to 00:40 universal time each day. Initial analyses reveal interesting and unexpected results as well as the potential for further studies of the Earth's thermosphere-ionosphere system and its responses to solar-geomagnetic forcing and atmospheric dynamics. Thermospheric temperatures and composition ratios for major constituents, O and N-2, near 160-km altitude and exospheric temperatures are retrieved from the daytime observations. Molecular oxygen (O-2) densities are measured using stellar occultations. At night, emission from radiative recombination in the ionospheric F region is used to quantify ionospheric density variations in the equatorial ionization anomaly (EIA). Regions of depleted F region electron density are frequently evident in the EIA, even during the current solar minimum. NASANational Aeronautics & Space Administration (NASA) [80GSFC18C0061] The authors thank the hundreds of people who had a role in the GOLD mission, including those at SES, Airbus, Arianespace, ESA, CNES, CSG, NASA HQ, NASA GSFC, CPI, CU/LASP, UCB/SSL, and UCF, and those who served on the many review panels. This research is supported by NASA Contract 80GSFC18C0061 to the University of Colorado.

The unambiguous 2-dimensional (2D) maps of OI 135.6 nm radiance retrieved from the Global Observation of Limb and Disk (GOLD) after sunset are compared with the total electron content (TEC) maps me...

Gravity wave packets excited by a source of finite duration and size possess a broad frequency and wave number spectrum and thus span a range of temporal and spatial scales. Observing at a single location relatively close to the source, the wave components with higher frequency and larger vertical wavelength dominate at earlier times and at higher altitudes, while the lower frequency components, with shorter vertical wavelength, dominate during the latter part of the propagation. Utilizing observations from the Na lidar at Utah State University and the nearby Mesospheric Temperature Mapper at Bear Lake Observatory (41.9°N, 111.4°W), we investigate a unique case of vertical dispersion for a spectrally broad gravity wave packet in the mesopause region over Logan, Utah (41.7°N, 111.8°W), that occurred on 2 September 2011, to study the waves' evolution as it propagates upward. The lidar-observed temperature perturbation was dominated by close to a 1 h modulation at 100 km during the early hours but gradually evolved into a 1.5 h modulation during the second half of the night. The vertical wavelength also decreased simultaneously, while the vertical group and phase velocities of the packet apparently slowed, as it was approaching a critical level during the second half of the night. A two-dimensional numerical model is used to simulate the observed gravity wave processes, finding that the location of the lidar relative to the source can strongly influence which portion of the spectrum can be observed at a particular location relative to a source.

In this paper, we report our findings on the correlation between the neutral temperature (around the mesopause) and thermospheric column density O/N2 ratio, along with their response to geomagnetic storms above midlatitude of North America. A temperature/wind Doppler Na lidar, operating at Fort Collins, CO (41°N, 105°W), and later at Logan, UT (42°N and 112°W), observed significant temperature increases (temperature anomaly) above 95 km (as much as 55 K at 105 km altitude) during four coronal mass ejection-induced geomagnetic storms (April 2002, November 2004, May 2005, and October 2012). Coincident Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Global Ultraviolet Spectrographic Imager observations indicate significant depletion in the thermospheric O/N2 ratio at the lidar locations. These observations suggest that the local mesopause warming seen by the lidar is due to transport of the high-latitude joule and particle heated neutrals at the E and F layers to the midlatitude region.

The Na density variations in the E region have been studied over the past few decades. Although considerable progress in understanding and in modeling the metal layer observations has been made, Na density features above 100 km have yet to be explained. Various studies have linked them to the Na+ variations, a major reservoir for Na in E region. But the lack of comprehensive modeling investigations and of wind and temperature observations prevents further understanding on this important ion-neutral coupling topic. In this study, we conduct a numerical simulation on the summer time Na density behavior in the midlatitude E region, where both the ion density and the neutral atmosphere are modulated by tidal and gravity waves. Simulation results show good agreement with Na lidar measurements and reveal that atmospheric waves can transport Na upward to generate Na layers and variations in E region considerably. The vertical wind component of the large amplitude tidal wave can extend the Na layer above 120 km into the thermosphere. The simulation also demonstrates that the modulation of large amplitude gravity (GW) wave can generate small-scale sporadic Na layers (Nas) in the E region. Finally, eddy diffusion enhancement in the GW saturation process can significantly alter the Nas spatial and temporal structures.

Mesospheric inversion layers (MIL) are well studied in the literature but their relationship to the dynamic feature associated with the breaking of atmospheric waves in the mesosphere/lower thermosphere (MLT) region are not well understood. Two strong MIL events (ΔT ~30 K) were observed above 90 km during a 6 day full diurnal cycle Na lidar campaign conducted from 6 August to 13 August Logan, Utah (42°N, 112°W). Colocated Advanced Mesospheric Temperature Mapper observations provided key information on concurrent gravity wave (GW) events and their characteristics during the nighttime observations. The study found both MILs were well correlated with the development and presence of an unstable region ~2 km above the MIL peak altitudes and a highly stable region below, implicating the strengthening of MIL is likely due to the increase of downward heat flux by the enhanced saturation of gravity wave, when it propagates through a highly stable layer. Each MIL event also exhibited distinct features: one showed a downward progression most likely due to tidal-GW interaction, while the peak height of the other event remained constant. During further investigation of atmospheric stability surrounding the MIL structure, lidar measurements indicate a sharp enhancement of the convective stability below the peak altitude of each MIL. We postulate that the sources of these stable layers were different; one was potentially triggered by concurrent large tidal wave activity and the other during the passage of a strong mesospheric bore.

This paper presents a study of the reconstruction of target motion waveform based on the self-mixing interference (SMI) from the sampling rate of data acquiring card. It has been found that the ratio of sampling rate to motion frequency of target (RSF) is of importance in the sampled SMI waveform. Based on the experimental SMI waveforms and the corresponding sampling rate, a quantitative relationship between RSF and the number of peaks of SMI waveform are given, showing that the lowest RSF is 10 points for the normal waveform in every monotony interval of SMI waveform.

The impacts of gravity wave (GW) on the thermal and dynamic characteristics within the mesosphere/lower thermosphere, especially on the atmospheric instabilities, are still not fully understood. In this paper, we conduct a comprehensive and detailed investigation on one GW breaking event during a collaborative campaign between the Utah State University Na lidar and the Advanced Mesospheric Temperature Mapper (AMTM) on 9 September 2012. The AMTM provides direct evidence of the GW breaking as well as the horizontal parameters of the GWs involved, while the Na lidar's full diurnal cycle observations are utilized to uncover the roles of tide and GWs in generating a dynamical instability layer. By studying the changes of the OH layer peak altitude, we located the wave breaking altitude as well as the significance of a 2 h wave that are essential to this instability formation. By reconstructing the mean fields, tidal and GW variations during the wave breaking event, we find that the large-amplitude GWs significantly changed the Brunt–Vaisala frequency square and the horizontal wind shear when superimposed on the tidal wind, producing a transient dynamic unstable region between 84 km and 87 km around 11:00 UT that caused a subsequent small-scale GW breaking.