Astrid Maute

Quasi 6-Day Planetary Wave Oscillations in Equatorial Plasma Irregularities

whawkins — Fri, 05 Apr 2024 16:26:35 +0000

Quasi 6-Day Planetary Wave Oscillations in Equatorial Plasma Irregularities whawkins Fri, 04/05/2024 - 10:26

Author:

whawkins

Apr 5, 2024

WACCM-X Rayleigh-Taylor (R-T) instability growth rate during from January to December 2021 for simulations with (a) lower atmosphere and solar/geomagnetic variability (LA+S/G), (b) only lower atmosphere variability (LA Only), and (c) only solar/geomagnetic variability (S/G Only) simulations. (d-f) Same as (a-c) except for the time period of November 2020 to March 2021. The results show that the day-to-day variability in the R-T instability growth rates is driven by both the lower atmosphere and solar/geomagnetic variations. A quasi-periodic variability is seen in early 2021 that is related to the quasi-six day planetary wave.

Journal of Geophysical Research–Space Physics: N. M. Pedatella, E. Aa, and A. Maute explore the influence of atmospheric planetary waves on the occurrence of irregularities in the low latitude ionosphere is investigated using Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) simulations and Global Observations of the Limb and Disk (GOLD) observations. GOLD observations of equatorial plasma bubbles (EPBs) exhibit a ∼6-8 day periodicity during January-February 2021. Analysis of WACCM-X simulations, which are constrained to reproduce realistic weather variability in the lower atmosphere, reveals that this coincides with an amplification of the westward propagating wavenumber-1 quasi-six day wave (Q6DW) in the mesosphere and lower thermosphere (MLT). The WACCM-X simulated Rayleigh-Taylor (R-T) instability growth rate, considered as a proxy of EPB occurrence, is found to exhibit a ∼6-day periodicity that is coincident with the enhanced Q6DW in the MLT. Additional WACCM-X simulations performed with fixed solar and geomagnetic activity demonstrate that the ∼6-day periodicity in the R-T instability growth rate is related to the forcing from the lower atmosphere. The simulations suggest that the Q6DW influences the day-to-day formation of EPBs through interaction with the migrating semidiurnal tide. This leads to periodic oscillations in the zonal winds, resulting in periodic variability in the strength of the prereversal enhancement, which influences the R-T instability growth rate and EPBs. The results demonstrate that atmospheric planetary waves, and their interaction with atmospheric tides, can have a significant impact on the day-to-day variability of EPBs.

Delineating the effect of upward propagating migrating solar tides with the TIEGCM-ICON

whawkins — Wed, 11 Jan 2023 00:09:39 +0000

Delineating the effect of upward propagating migrating solar tides with the TIEGCM-ICON whawkins Tue, 01/10/2023 - 17:09

Author:

whawkins

Jan 10, 2023

Zonal wind [m/s] at 250 km for 12 UT and geographic latitude of 30o for simulations a. with tides at the lower boundary (LB), b. without tides at the LB, c. differences between a. and b. which isolates the effect of the LB tides, indicating the strong changes due to upward propagating tides after DOY 232.

Frontiers in Astronomy and Space Sciences: The vertical coupling of the lower and upper atmosphere via atmospheric solar tides varies on time scales from days, seasons to interannually, and modifies the thermosphere and ionosphere system. The Ionospheric Connection (ICON) explorer is designed to study the vertical coupling. In this study we use ICON data from the 220-270 Day Of Year (DOY), 2020 time period when large changes in the migrating semidiurnal tide (SW2) and the zonal and diurnal mean zonal wind occur within 8 days after DOY 232. We use the thermosphere-ionosphere-electrodynamics general circulation model (TIEGCM) driven by observationally fitted tides via the Hough Mode Extension (HME) method to isolate the effect of the changing upward propagating tides on the dynamics, composition, and plasma distribution . We find that associated with the distinct SW2 changes, the zonal and diurnal mean zonal wind at 250 km undergoes a similar dramatic change in the latitudinal structure. The analysis of SW2 reveals that the antisymmetric HMEs become more prevalent after DOY 232 compared to before. Similar latitudinal and temporal changes to SW2 are also found in the migrating diurnal, terdiurnal and quad-diurnal tides (DW1, TW3, QW4, respectively) at 250 km. Ter- and quad-diurnal tides are not included in the HME lower boundary forcing and are generated internally in the model. Especially, TW3 is strong in the thermosphere (almost 2/3 of SW2) and most likely caused by nonlinear tidal interaction between DW1 and SW2 above 130 km. Surprisingly, the solar in-situ forcing of TW3 and SW2 in the upper thermosphere is not nearly as important as their upward propagating tidal component, which contradicts previous findings during other seasons and solar cycle conditions. The strong dynamical changes during the study period lead to an approximately 15-20\% zonal and diurnal mean NmF2 decrease, which has a major contribution from the roughly 10\% decrease in the $O/N_2$ at 300 km during the same period. These changes are stronger than general seasonal behavior which are eliminated in the reported numbers due to using differences of simulations.

Effect of Vertical Shear in the Zonal 1Wind on Low-Latitude Zonal Currents: An Observational Perspective Using Swarm and ICON Data

whawkins — Tue, 10 Jan 2023 23:59:46 +0000

Effect of Vertical Shear in the Zonal 1Wind on Low-Latitude Zonal Currents: An Observational Perspective Using Swarm and ICON Data whawkins Tue, 01/10/2023 - 16:59

Author:

whawkins

Jan 10, 2023

Journal of Geophysical Research: Space Physics: The winds in the ionosphere push the plasma in the presence of Earth's magnetic field, causing ions and electrons to move in different directions, producing electric current. The low-latitude ionospheric current system consists of an intense eastward current at the magnetic equator and off-equatorial reduced eastward or relative westward currents, which are called dip currents, in both hemispheres. Modelling studies have shown that the altitudinal gradient of the zonal wind is related to the strength of the dip currents. However, observational studies to validate these results have been missing to this date. This study utilizes simultaneous observations from ICON and Swarm satellites to provide insights on the connection between low-latitude winds and currents, which will improve our understanding of the causes of daytime ionospheric variability.

Quasi dipole latitudinal variations of the average Swarm and ICON conjunctions: EEJ from Swarm A (left), zonal wind from ICON/MIGHTI (middle), and the corresponding EEJ from the model (rihgt) showing that with westward turning winds in Pedersen conductivity dominated region (middle) the off-equatorial current dips are strong (left).

The Ionospheric Connection Explorer - Prime Mission Review

whawkins — Fri, 16 Dec 2022 19:00:21 +0000

The Ionospheric Connection Explorer - Prime Mission Review whawkins Fri, 12/16/2022 - 12:00

Author:

whawkins

Dec 16, 2022

The two-year prime mission of the NASA Ionospheric Connection Explorer (ICON) is complete. The baseline operational and scientific objectives have been met and exceeded, as detailed in this report. In October of 2019, ICON was launched into an orbit that provides its instruments the capability to provide near-continuous measurements of the densest plasma in Earth's space environment. Through collection of a key set of in-situ and remote sensing measurements that are, by virtue of a detailed mission design, uniquely comparable, ICON provides for new investigations of the mechanisms that control the behavior of the ionosphere-thermosphere system under both geomagnetically quiet and active conditions. In a two-year period that included a deep solar minimum, ICON has elucidated a number of remarkable effects of influences of the lower and middle atmosphere in the ionosphere. The observatory is now moving into a period of elevated solar activity that will dramatically rebalance the impacts of lower and upper atmospheric drivers on the ionosphere.

TIEGCM vertical ExB drift over the 2 year period at the top with lower atmospheric tidal forcing at the TIEGCM lower boundary based on ICON observations and bottom with no tidal forcing at the lower boundary.

Seasonal Variations of Small-Scale Waves observed by ICON-MIGHTI

whawkins — Tue, 18 Oct 2022 18:09:44 +0000

Seasonal Variations of Small-Scale Waves observed by ICON-MIGHTI whawkins Tue, 10/18/2022 - 12:09

Author:

whawkins

Oct 18, 2022

GRL—C. Y. Cullens, S. England, T. J. Immel, A. Maute, B. J. Harding, C. Triplett, J.J. Makela, et al.

Seasonal variations of monthly-zonal-mean small-scale perturbation amplitudes in (a) zonal-winds at 200 km, (b) temperature at 110 km, (c) zonal winds at 110 km, (d) temperature at 94 km averaged over (black) 0-15°N, (blue) 15-30°N, (red) 30-40°N from January 2020 to December 2021. Error bars represent one sigma.

Our understanding of the neutral wind variations in the lower and upper thermosphere is limited, among other, by the sparsity of observations. However, studies indicate that especially smaller scale wind perturbations might be linked to space weather effects such as the generation of plasma depletions. It motivated the present study to analyze the seasonal variations of small-scale perturbations between 90 km to 250 km using temperature and winds measurements made by the Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) instrument onboard the Ionospheric Connection Explorer (ICON) satellite in the latitude range of 0°-40° N in the year of 2020-2021. Both small-scale perturbations (SSP) in temperature and winds below ~120 km show semi-annual variations, whereas annual variations of SSP for winds become dominant between 160 km to 250 km. The largest wind SPP was observed at ~110-120 km throughout the year. Spatial variations of SSP at 90-250 km do not show clear latitudinal/longitudinal variations in both temperature and wind SSPs. The analysis suggests that seasonal variations of SSP between 90 and 250 km altitudes are influenced by both, sources distribution and background wind changes.

Cullens, C. Y., England, S. L., Immel, T. J., Maute, A., Harding, B. J., Triplett, C. C., et al. (2022). Seasonal variations of medium-scale waves observed by ICON-MIGHTI. Geophysical Research Letters, 49, e2022GL099383. https://doi.org/10.1029/2022GL099383.

Horizontal wind shears in the lower thermosphere observed by ICON

whawkins — Fri, 14 Oct 2022 19:56:04 +0000

Horizontal wind shears in the lower thermosphere observed by ICON whawkins Fri, 10/14/2022 - 13:56

Author:

whawkins

Oct 14, 2022

Geophysical Research Letters—S. L. England, C. R. Englert, B. J. Harding, C. C. Triplett, K. Marr, J.M. Harlander, G.R. Swenson, A. Maute, T. Immel

Example of maximum shear determination in zonal wind from 1 orbit of MIGHTI observations a. daytime zonal wind b. magnitude of maximum wind shear.

The neutral wind in the mesosphere-lower thermosphere region around 90 to 120 km is highly variable. In this region large vertical shears in the horizontal winds have been observed for example by rocket experiments or by lidars. However, these observations are of short duration or spatially fixed. In this study observations from the MIGHTI instrument on board the Ionospheric Connection Explorer are analyzed to determine the maximum wind shear in the 95-120 km region during the day time. The strong shear occurrence, horizontal scale and underlying organization is examined. No preferred wind shear direction is found. The shears that persist for a short horizontal extent are slightly larger in amplitude and more numerous than those that persist across large horizontal scales. The altitude at which the strongest shears occur often shows a downward progression with local time, following the climatological winds.

England, S. L., Englert, C. R., Harding, B. J., Triplett, C. C., Marr, K., Harlander, J. M., et al. (2022). Vertical shears of horizontal winds in the lower thermosphere observed by ICON. Geophysical Research Letters, 49, e2022GL098337. https://doi.org/10.1029/2022GL098337

Magnetosphere-ionosphere coupling via prescribed field-aligned current simulated by the TIEGCM

whawkins — Wed, 12 Oct 2022 19:22:26 +0000

Magnetosphere-ionosphere coupling via prescribed field-aligned current simulated by the TIEGCM whawkins Wed, 10/12/2022 - 13:22

Author:

whawkins

Oct 12, 2022

Hemispherically integrated Joule heating [GW] poleward of 50o magnetic latitude based on simulations with a prescibed empirical electric potential model: Weimer-POT (blue), with prescribed electric potential and auroral particle precipitation based on an assimilative method: AMIE-POT (black), and with prescribed field-aligned current: OIM-FAC (red) cases for the northern hemisphere (top) and southern hemisphere (bottom)

A. Maute, A.D. Richmond, G. Lu, D. Knipp, Y. Shi, B. Anderson assert that the magnetosphere-ionosphere (MI) coupling is crucial in modeling the thermosphere-ionosphere (TI) response to geomagnetic activity. In general circulation models (GCMs) the MI coupling is typically realized by specifying the ion convection and auroral particle precipitation patterns from e.g., empirical or assimilative models. Assimilative models have the advantage that the ion convection and auroral particle precipitation patterns are mutually consistent and based on available observations. However, assimilating a large set of diverse data requires expert knowledge and is time consuming. Empirical models, on the other hand, are convenient to use, but do not capture all the observed spatial and temporal variations. With the availability of AMPERE data, there is an opportunity for employing field-aligned currents (FAC) in numerical models to represent the MI coupling. In this study, we introduce a new method using observed FAC and solve for the interhemispherically asymmetric electric potential distribution. We compared geomagnetic storm simulations using the new approach and two other often-used methods for specifying MI coupling based on empirical and assimilative high latitude electric potentials. The comparison shows general similarities of the thermosphere-ionosphere storm time response and improved temporal variability of the new method compared to using empirical models, but results also illustrate substantial differences due to our uncertain knowledge about the MI coupling process.

Equinoctial Asymmetry in the Upper Ionosphere: Comparison of Satellite Observations and Models

whawkins — Wed, 05 Oct 2022 17:16:46 +0000

Equinoctial Asymmetry in the Upper Ionosphere: Comparison of Satellite Observations and Models whawkins Wed, 10/05/2022 - 11:16

Author:

whawkins

Oct 5, 2022

JGR Space Phyics—L. Lomidze, D. J. Knudsen, M. Shepherd, J. D. Huba, and A. Maute

SAMI3 simulation results for electron density near noon using TIE-GCM neutral atmosphere as a model input, the bottom panel is the corresponding relative (in %) change for Ne. The wind effect on electron density is shown by the black dashed line and the neutral density by the turquoise line.

The terrestrial ionosphere displays significant equinoctial asymmetry despite the upper atmosphere receiving similar levels of solar ionization energy at a given location and local time in spring and fall during similar solar activity conditions. This intriguing feature is not well understood or modelled, particularly in the upper ionosphere, and causes of the asymmetry are not fully established and quantified. Yet, their study is important to provide better insights into the atmosphere-ionosphere coupling processes. Analysis of Langmuir probe data from ESA’s Swarm satellite at ~525 km altitude reveals that the daytime electron density is larger for all latitudes during March than during September, while the electron temperature shows inverted asymmetry except at low latitudes. Simultaneously obtained neutral density data from Swarm GPS accelerations indicate that the thermosphere is denser during the spring. The asymmetry seen by Swarm electron density observations is also present in electron densities obtained using GPS radio occultation measurements from the COSMIC satellites. Simulations were performed using physics-based ionosphere models (SAMI3, WACCM-X, and TIE-GCM) to determine their ability to produce the observed asymmetry, understand the generation mechanism(s), and establish the relative role of physical drivers. Modeling of the asymmetry by SAMI3 driven with the TIE-GCM neutral atmosphere shows that both neutral density and winds play a critical role, but the density has a greater effect.

Cultivating a culture of inclusivity in Heliophysics

whawkins — Thu, 22 Sep 2022 19:26:07 +0000

Cultivating a culture of inclusivity in Heliophysics whawkins Thu, 09/22/2022 - 13:26

Author:

whawkins

Sep 22, 2022

CEDAR participants attending the banquet dinner.

Alexa J. Halford, Michael W. Liemohn, Christopher M. Bard, Astrid Maute, Ryan M. McGranaghan, Lynn B. Wilson III

A large number of heliophysicists from across career levels, institution types, and job titles came together to support the position papers titled ”Cultivating a culture of inclusivity in Heliophysics", ”The Importance of Policies: It’s not just a pipeline problem,” and ”Mentorship within Heliophysics.” While writing these position papers, the number of people who privately shared terrifying stories and experiences of bullying and harassment was insane. The number of people who privately expressed how burned out they are was staggering. The number of people who privately spoke about how they considered leaving the field for their and their family’s health was astounding. And for as much good there is in our community, it is still a toxic environment for many. And if we don’t do something now, our field will continue to suffer. Help us have a way to hold bad actors accountable. Help us find a way to remove the constant anxiety about funding and financial security. Help remove constant deadlines and constant last-minute requests. Help us not end up having a community that is hyper-competitive but instead be more collaborative. Help us develop and apply methods to make our community not just a place where people work to survive but a place where they can thrive as a whole person. Help us not have to give up our entire lives to succeed.

On the variability of total electron content over Europe during the 2009 and 2019 Northern Hemisphere SSWs

whawkins — Fri, 02 Sep 2022 16:51:20 +0000

On the variability of total electron content over Europe during the 2009 and 2019 Northern Hemisphere SSWs whawkins Fri, 09/02/2022 - 10:51

Author:

whawkins

Sep 2, 2022

JGR- Space Physics: T. A. Siddiqui, Y. Yamazaki, C. Stolle, A. Maute, J. Lastovicka , I. K. Edemskiy, Z. Mosna.

Sudden Stratospheric Warming events are a polar winter phenomena which mainly occurs in the northern hemisphere. They are associated with large scale changes in the stratosphere which modify significant the solar and lunar tide with a 12 hr period, coupling into the upper atmosphere. One of the observed changes is in middle and low latitudes total electron content (TEC). In this study the variations of the TEC over Europe is investigated during two northern hemisphere SSWs events in 2009 and 2019. TEC variations can be caused by the vertical coupling to lower atmosphere and by geomagnetic forcing. Delineating the two cause of TEC variability in observations is challenging. We investigated the dominant drivers and their respective contributions to TEC changes during both SSW events. We simulate the SSWs using the Whole Atmosphere Community Climate Model eXtended version (WACCM-X) and compare the SSW effect on the semidiurnal solar and lunar tidal variabilities in the mesosphere-lower thermosphere (MLT) region. Further, in order to assess the mechanisms responsible for the TEC variability during the SSWs, we analyze the difference between simulations with the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIE-GCM) driven by WACCM_X fields at the lower boundary with and without geomagnetic forcing. The TIE-GCM simulations allow us to isolate the geomagnetic and lower atmospheric forcing effects on the TEC. We find that there was a major enhancement in daytime TEC over Europe during the 2019 SSW event, which was predominantly geomagnetically forced (∼80%), while for the 2009 SSW, the major variability in TEC was accounted for by lower atmospheric forcing.

Daily averaged TEC over Europe for TIE-GCM forced at the lower boundary by WACCM-X and (a) S1 with geomagnetic forcing and (b) S2 without geomagnetic forcing, as a function of universal time for the 2019 SSW. The TEC increase attributed to the geomagnetic forcing is illustrated in (c) by the difference of (a) and (b). The filled contour lines in (c) are only plotted when absolute TEC difference exceeds 1 TECU. The dashed black and blue open contour lines mark the contribution of geo- magnetic forcing to the TEC variability at 40 and 80% levels, respectively. The vertical black dashed lines mark the day of PVW.

Astrid Maute

Quasi 6-Day Planetary Wave Oscillations in Equatorial Plasma Irregularities

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Delineating the effect of upward propagating migrating solar tides with the TIEGCM-ICON

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Effect of Vertical Shear in the Zonal 1Wind on Low-Latitude Zonal Currents: An Observational Perspective Using Swarm and ICON Data

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The Ionospheric Connection Explorer - Prime Mission Review

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Seasonal Variations of Small-Scale Waves observed by ICON-MIGHTI

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Horizontal wind shears in the lower thermosphere observed by ICON

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Magnetosphere-ionosphere coupling via prescribed field-aligned current simulated by the TIEGCM

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Equinoctial Asymmetry in the Upper Ionosphere: Comparison of Satellite Observations and Models

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Cultivating a culture of inclusivity in Heliophysics

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On the variability of total electron content over Europe during the 2009 and 2019 Northern Hemisphere SSWs

Recent News