GOLD

Investigation of the GOLD Observed Merged Nighttime EIA with WACCM-X Simulations during the Storm of November 3–4, 2021

whawkins — Tue, 27 Jun 2023 20:31:42 +0000

Investigation of the GOLD Observed Merged Nighttime EIA with WACCM-X Simulations during the Storm of November 3–4, 2021 whawkins Tue, 06/27/2023 - 14:31

Author:

whawkins

Jun 27, 2023

Geophysical Research Letters: During the storm on November 3 to 4, 2021, the Global-scale Observations of the Limb and Disk (GOLD) mission observed well separated EIA crests post sunset on Nov 3, but merged EIA on Nov 4. We used the Whole Atmosphere Community Climate Model (WACCM-X) to simulate the EIA structures during the two nights. The simulations show two separated post sunset EIA crests on November 3rd but merged post sunset EIA crests on November 4th, which are qualitatively consistent with the GOLD observations. Numerical simulations and Ionospheric Connection Explorer (ICON) neutral wind observations illustrate that the formation of merged EIA crests was due to several hours of downward E × B drifts before and after sunset. Further diagnostic analysis revealed that it was mainly driven by westward electric fields caused by the disturbance dynamo electric field during the recovery phase of the storm.

Nmax observed by GOLD and NmF2 simulated by WACCM-X at 20:10 UT on November 03-04, 2021. The red dotted lines represent the magnetic equator.

Pronounced suppression and X-pattern merging of equatorial ionization anomalies after the 2022 Tonga volcano eruption

whawkins — Fri, 16 Dec 2022 18:47:19 +0000

Pronounced suppression and X-pattern merging of equatorial ionization anomalies after the 2022 Tonga volcano eruption whawkins Fri, 12/16/2022 - 11:47

Author:

whawkins

Dec 16, 2022

Following the 2022 Tonga Volcano eruption, dramatic suppression and deformation of the equatorial ionization anomaly (EIA) crests occurred in the American sector ∼14,000 km away from the epicenter. The EIA crests variations and associated ionosphere-thermosphere disturbances were investigated using Global Navigation Satellite System (GNSS) total electron content (TEC) data, Global-scale Observations of the Limb and Disk (GOLD) ultraviolet images, Ionospheric Connection Explorer (ICON) wind data, and ionosonde observations. The main results are as follows: (1) Following the eastward passage of expected eruption-induced atmospheric disturbances, daytime EIA crests, especially the southern one, showed severe suppression of more than 10 TECU and collapsed equatorward over 10◦ latitudes, forming a single band of enhanced density near the geomagnetic equator around 15–17 UT, (2) Evening EIA crests experienced a drastic deformation around 22 UT, forming a unique X-pattern in a limited longitudinal area between 20–40◦W. (3) Thermospheric zonal winds showed long-lasting quasi-periodic fluctuations between ±200 m/s for 7–8 hours after the passage of volcano-induced Lamb waves. The EIA suppression and X-pattern merging was consistent with a westward equatorial zonal dynamo electric field induced by the strong zonal wind oscillation with westward reversal.

(a–c) ICON MIGHTI track and corresponding zonal wind and meridional wind profiles between 20:48–21:16 UT on 15 January 2022. The iso-distance circles away from the Tonga eruption epicenter are shown in black lines. The blue circle in (a) is the estimated wavefront location of volcano-induced Lamb waves. (d–l) Combined GNSS TEC and GOLD OI 135.6-nm radiance maps in successive disk scan during 20:40–23:55 UT. The dip equator and meridional field lines are shown in cyan.

The effects of IMF By on the middle thermosphere during a geomagnetically “quiet” period at solar minimum

kolinski — Mon, 11 Jul 2022 21:02:35 +0000

The effects of IMF By on the middle thermosphere during a geomagnetically “quiet” period at solar minimum kolinski Mon, 07/11/2022 - 15:02

Publication: JR Space Physics; Authors: Xuguang Cai, Wenbin Wang, Alan Burns, Liying Qian, Richard W. Eastes

Author:

kolinski

Jul 11, 2022

The polar view of the percentage difference of simulated ∑O/N2 and GOLD observed ∑O/N2 between DOY 111 and 110 at 15:10 UT in 2019. The perimeter latitude is 30°N

Numerical simulations using the National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM) are performed to elucidate the effects of the interplanetary magnetic field (IMF) on the middle thermosphere composition during a “geomagnetically quiet” period from the day of year (DOY) 110-111 in 2019 (when the Auroral electrojet (AE) index never exceeded 300 nT and the Kp never exceeded 2). In particular, this paper aims to examine how the Global-scale Observations of the Limb and Disk (GOLD) mission observed daytime thermospheric O and N2 column density ratio (∑O/N2) depletion at mid-latitudes originated under such a “geomagnetically quiet” condition. A comparison of electric potential, Joule heating rate per unit mass, ion velocity, neutral temperature and winds in the middle thermosphere (∼160 km) between real IMF and without the IMF east-west component (By) indicates that a By dominant condition can enhance their strengths under this “geomagnetically quiet” condition. Consequently, ∑O/N2 depletion with a stronger magnitude (30% compared with ∼8% without By) and larger disturbed area was introduced in the post-midnight sector at high-latitudes due to strong and localized upwelling associated with the enhanced Joule heating rate per unit mass. The ∑O/N2 depletion was transported equatorward and corotated from local post-midnight to early morning, and was observed by GOLD at middle latitudes during daytime.

The Molecular Oxygen Density Structure of the Lower Thermosphere as Seen by GOLD and Models

kolinski — Mon, 11 Jul 2022 20:39:20 +0000

The Molecular Oxygen Density Structure of the Lower Thermosphere as Seen by GOLD and Models kolinski Mon, 07/11/2022 - 14:39

Publication: Geophysics Research Letters; Author's: K. R. Greer, F. Laskar, R. Eastes, J. Lumpe, H.-L. Liu, and N. Pedatella

Author:

kolinski

Jul 11, 2022

Comparisons of local time structure of molecular oxygen at 21°N, 170 km altitude. Red dots are for the longitude of 33°E, while blue dots are for the longitude of 128°W. Panel (a) shows molecular oxygen densities as observed by the GOLD instrument for one star, HD74280, between January 2019 and July 2021. Panel (b) are results from the MSISE-00 empirical model sampled for the same locations and conditions as the GOLD observations. Panel (c) is as panel (b) but for the MSIS2.0 empirical model. Panel (d) shows the SD-WACCM-X model sampled for the GOLD observations. The observations show a distinctly diurnal structure in local time, while all the model results indicate a semidiurnal structure.

This paper compares new observations from the Global-scale Observations of Limb and Disk (GOLD) mission of molecular oxygen (O2) in the lower thermosphere (130 - 200 km in altitude) to widely used models in the aeronomy community. The main finding is that the local time structure of the observed molecular oxygen has a minimum at 6 hours local time and a peak near 18 hours local time while the models all show a structure that has peaks at both 6 and 18 hours local time. This significant difference not only influences the total neutral thermospheric density results from the models, but may ultimately impact the calculated ionospheric plasma density and its temporal variability. Understanding ionospheric plasma densities is vital for the proper modeling of the propagation of communications and navigational signals.

NASA Features Research by HAO Scientist Xuguang Cai

kolinski — Thu, 18 Nov 2021 20:58:13 +0000

NASA Features Research by HAO Scientist Xuguang Cai kolinski Thu, 11/18/2021 - 13:58

Author:

kolinski

Nov 18, 2021

Since 2017, HAO has provided scientific support and analysis for NASA's Global-scale Observations of the Limb and Disk (GOLD). This mission includes a ultraviolet imaging spectrograph that flies on a commercial communications satellite in geostationary orbit taking images of the Earth's thermosphere and ionosphere. NASA's recent featured article discusses the "unexpected behavior" captured by GOLD images. The article quotes Dr.Xuguang Cai, a researcher at HAO: "Since GOLD is on a geostationary satellite, we can capture 2D time evolution of these dynamics." Recently, several of Dr. Cai's research papers have been reported by NASA.gov, and are cited on these pages:

Upper atmosphere radiance data assimilation: A feasibility study for GOLD far ultraviolet observations

kolinski — Thu, 18 Nov 2021 19:25:07 +0000

Upper atmosphere radiance data assimilation: A feasibility study for GOLD far ultraviolet observations kolinski Thu, 11/18/2021 - 12:25

Publication Name: Journal of Geophysical Research Space Physics; First HAO Author's Name: Stanley C. Solomon

Author:

kolinski

Nov 18, 2021

Availability of far ultraviolet observations of Earth’s dayglow by the NASA Global-scale Observations of the Limb and Disk (GOLD) mission presents an unparalleled opportunity for upper atmosphere radiance data assimilation.

Assimilation of the observed dayglow emissions can be formulated in a similar fashion to lower atmosphere radiance data assimilation approaches using the sensitivity of the Lyman-Birge-Hopfield (LBH) band emission to thermospheric temperature. To demonstrate such an approach, this paper presents a proof-of-concept implementation of an ensemble filter measurement update step using ensemble simulation of the thermosphere and LBH emission by the NOAA's Whole Atmosphere Model (WAM) and NCAR’s Global Airglow model.

Accuracy of temperature estimates in the measurement update step for four different assimilated observations.

Testing the approach with observing system simulation experiments has yielded the following findings: (1) Assimilation of GOLD LBH disk emission data can reduce the error in model temperature specification from forecast to analysis by 97% under geomagnetically quiet conditions and 87% under disturbed conditions, (2) The reduction in model uncertainty from forecast to analysis as a result of GOLD assimilation is ~20% in the lower thermosphere and ~25% in the upper thermosphere, and (3) Ingestion of three prominent LBH features, in comparison to the entire LBH spectrum, into the WAM leads to more accurate assimilation analyses. With the help of a radiance data assimilation approach, the utility of GOLD observations can be extended to reveal global, time-dependent, altitude-resolved thermospheric structure, offering the key to addressing a number of outstanding questions such as those relating to the properties of travelling atmospheric disturbances.

Link to paper: Upper atmosphere radiance data assimilation: A feasibility study for GOLD far ultraviolet observations

Thermospheric composition O/N2 response to an altered meridional mean circulation during Sudden Stratospheric Warmings observed by GOLD

kolinski — Thu, 18 Nov 2021 18:50:45 +0000

Thermospheric composition O/N2 response to an altered meridional mean circulation during Sudden Stratospheric Warmings observed by GOLD kolinski Thu, 11/18/2021 - 11:50

Publication Name: Geophysical Research Letters; First HAO Author's Name: Nick Pedatella

Author:

kolinski

Nov 18, 2021

GOLD measurements provide the first observational proof of model predictions that the break up of the stratospheric polar vortex changes the composition of the thermosphere.

(a) GOLD O/N2 ratios for 15 December 2018 (day 349, geomagnetic quiet, SZA< 80, 113W to 19E), averaged over all 30 minute cadence images taken during daytime. (b) Time series of O/N2 daytime means averaged over all observed longitudes as a function of geographic latitude (color contours), along with 10 hPa mean zonal winds in the stratosphere at 60N from MERRA-2 (black line). A SSW occurred around day 370 with onset on day 355. The lower panel shows the 3-hourly Kp index (black) and the F10.7 cm radio flux. © Same as (b) but with mean, annual and semi-annual components removed, using all available Level 2 data (6 Oct 2018 – 13 Aug 2019). Plotted as percent deviation.

The important O/N2 ratio is depleted by ~10% through a rather complex chain of processes that connect global-scale waves from the lower atmosphere, wave dissipation, mean meridional circulation, turbulent eddy transport, and molecular diffusion to produce a global O/N2 reduction in the thermosphere. The observed composition changes will likely impact Earth’s ionospheric plasma environment and imply a substantial impact of the lower and middle atmosphere on space weather.

Global-scale Measurements of the Limb and Disk (GOLD) Mission Implementation: Instrument Design and Early Flight Performance

kolinski — Wed, 17 Nov 2021 20:03:40 +0000

Global-scale Measurements of the Limb and Disk (GOLD) Mission Implementation: Instrument Design and Early Flight Performance kolinski Wed, 11/17/2021 - 13:03

ublication Name: Journal of Geophysical Research Space Physics; First HAO Author's Name: Stan Solomon; Authors: McClintock, W. E., Richard Eastes, Alan Hoskins, Oswald Siegmund, Jason McPhate, Andrey Krywonos, Stanley Solomon, and Alan Burns

Author:

kolinski

Nov 17, 2021

The Global-scale Observations of the Limb and Disk (GOLD) is a NASA mission of opportunity designed to study how the Earth’s ionosphere-thermosphere system responds to geomagnetic storms, solar radiation and upward propagating tides on time scales as short as 30 minutes.

Sectional view of a GOLD spectroscopic imaging channel.

GOLD employs two identical ultraviolet spectrographs that make observations of the Earth’s thermosphere and ionosphere from a commercial communications satellite owned and operated by SES and located in geostationary orbit at 47.5° west longitude (near the mouth of the Amazon River). They make images of atomic oxygen 135.6 nm and N2 LBH radiances of the entire disk that is observable from geostationary orbit and on the near-equatorial limb. They also observe occultations of stars to measure molecular oxygen column densities on the limb. Here we describe the GOLD instrument including its optical system and detector. Its performance was characterized in the lab before launch. We compare measurements of laboratory sources made then to observations of the thermosphere after launch and find good agreement.

Link to paper: Global-scale Measurements of the Limb and Disk (GOLD) Mission Implementation: 1. Instrument Design and Early Flight Performance

Comparison of GOLD nighttime measurements with total electron content: preliminary results

kolinski — Tue, 16 Nov 2021 22:37:36 +0000

Comparison of GOLD nighttime measurements with total electron content: preliminary results kolinski Tue, 11/16/2021 - 15:37

ublication: Journal of Geophysical Research, Space Physics; Authors: Xuguang Cai, Alan G. Burns, Wenbin Wang, Anthea Coster, Liying Qian, Jing Liu, Stanley C. Solomon, Richard W. Eastes, Robert E. Daniell, William E. McClintock

Author:

kolinski

Nov 16, 2021

The National Aeronautics and Space Administration (NASA) Global‐scale Observations of the Limb and Disk (GOLD) has been imaging the thermosphere and ionosphere since October 2018. It provides continuous measurements over a large area from its geostationary orbit. The unambiguous 2-dimensional (2D) maps of OI 135.6 nm radiance retrieved from GOLD after sunset are compared with the total electron content (TEC) maps measured by GPS receivers in the American sector. The OI 135.6 nm radiance observed by GOLD is an indicator of the peak electron density of the ionosphere F2 region, while the TEC is the total electron density in the column.

The comparison between the GOLD map and TEC2 map on DOY 72 in 2019 23:10-23:40 (top) and 23:55-24:25 (bottom). The white part stands for the data unavailability and the pink line is the geomagnetic equator. The black points stand for the location of the peaks of the EIA.

Our comparisons show that the two datasets match each other very well in the equatorial ionization anomaly (EIA) morphology and its seasonal variability. Equatorial plasma bubbles (EPBs) are evident in GOLD nighttime OI 135.6 radiance. Corresponding depletions are shown in TEC maps, but without GOLD data as a reference, it is difficult to discern that the depletions are EPBs. In addition, both GOLD 135.6 radiance and TEC maps observed third peaks of electron density poleward of the southern EIA crests. Furthermore, both show that the ionosphere after sunset is quite dynamic and has strong day-to-day variability. In all, the GOLD and TEC have valuable synergy to allow us to gain a better understanding of the equatorial ionosphere.

Link to paper: Comparison of GOLD Nighttime Measurements With Total Electron Content: Preliminary Results

The 2‐D Evolution of Thermospheric ∑O/N2 Response to Weak Geomagnetic Activity During Solar‐Minimum Observed by GOLD

kolinski — Tue, 16 Nov 2021 22:34:30 +0000

The 2‐D Evolution of Thermospheric ∑O/N2 Response to Weak Geomagnetic Activity During Solar‐Minimum Observed by GOLD kolinski Tue, 11/16/2021 - 15:34

Publication Name: Geophysical Research Letters; First HAO Author's Name: Xuguang Cai; Other Authors: Alan G. Burns, Wenbin Wang, Liying Qian, Stanley C. Solomon Richard W. Eastes, Nicolas Pedatella, Robert E. Daniell, Will

Author:

kolinski

Nov 16, 2021

We conduct observational and modeling studies of thermospheric composition responses to weak geomagnetic activity (non-geomagnetic storms). We found that the thermospheric O and N 2 column density ratio (∑O/N 2 ) in part of the Northern Hemisphere measured by Global-scale Observations of the Limb and Disk (GOLD) exhibited large and long-lived depletions during weak geomagnetic activity in May and June 2019.

(top) The Kp and Dst index of three cases (DOY 145 to 148; DOY 153 to 156; DOY 162 to 165); (middle) latitude-longitude distribution of ∑O/N2 percentage difference between two quiet days in three cases; (bottom) percentage difference of ∑O/N2 between disturbed and quiet days in three cases. Corresponding local time is marked on longitude interval.

The depletions reached 30% of quiet time values, extended equatorward to 10°N, and lasted more than 10 hours. Furthermore, numerical simulation results are similar to these observations and indicate that the ∑O/N 2 depletions were pushed westward by zonal winds. The ∑O/N 2 evolution during weak geomagnetic activity suggests that the formation mechanism of the ∑O/N 2 depletions is similar to that during a geomagnetic storm. The effects of weak geomagnetic activity are often ignored, but, in fact, are important for understanding thermosphere neutral composition variability and hence the state of the thermosphere-ionosphere system.

2020 Cai The two dimensional Evolution

GOLD

Investigation of the GOLD Observed Merged Nighttime EIA with WACCM-X Simulations during the Storm of November 3–4, 2021

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Pronounced suppression and X-pattern merging of equatorial ionization anomalies after the 2022 Tonga volcano eruption

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The effects of IMF By on the middle thermosphere during a geomagnetically “quiet” period at solar minimum

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The Molecular Oxygen Density Structure of the Lower Thermosphere as Seen by GOLD and Models

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NASA Features Research by HAO Scientist Xuguang Cai

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Upper atmosphere radiance data assimilation: A feasibility study for GOLD far ultraviolet observations

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Thermospheric composition O/N2 response to an altered meridional mean circulation during Sudden Stratospheric Warmings observed by GOLD

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Global-scale Measurements of the Limb and Disk (GOLD) Mission Implementation: Instrument Design and Early Flight Performance

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Comparison of GOLD nighttime measurements with total electron content: preliminary results

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The 2‐D Evolution of Thermospheric ∑O/N2 Response to Weak Geomagnetic Activity During Solar‐Minimum Observed by GOLD

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