Research Highlights

Research Highlights

A selection of highlights culled from publications by HAO staff.

Snapshot from a two-dimensional test simulation setup with a 8x8Mm domain reaching from the upper convection zone into the transition region

Efficient numerical treatment of ambipolar and Hall drift as hyperbolic system

Partially ionized plasmas, such as the solar chromosphere, require a generalized Ohm's law including the effects of ambipolar and Hall drift. While both describe transport processes that arise from the multifluid equations and are therefore of hyperbolic nature, they are often incorporated in models as a diffusive, i.e. parabolic process. While the formulation as such is easy to include in standard MHD models, the resulting diffusive time-step constraints do require often a computationally more expensive implicit treatment or super-time-stepping approaches.

ν − z phase diagrams (cuts at constant horizontal wavenumber at approx. 2 and 4 Mm−1 through the stacks of the layer-by-layer two-dimensional k − ω phase difference diagrams) for various MURaM models

Acoustic-gravity wave propagation characteristics in three-dimensional radiation hydrodynamic simulations of the solar atmosphere

There has been tremendous progress in the degree of realism of three-dimensional radiation magneto-hydrodynamic simulations of the solar atmosphere in the past decades.

Control of ionospheric plasma velocities by thermospheric winds

Earth’s equatorial ionosphere exhibits significant and unpredictable day-to-day variations in density and morphology. The NASA Ionospheric Connection Explorer (ICON) makes the first coordinated space-based observations of the wind-driven dynamo and the plasma state to understand the relation of the plasma environment to the thermospheric weather below. 

Periodic variations in solar wind and responses of the magnetosphere and thermosphere in March 2017

TIMED/GUVI observed thermospheric column ∑O/N2 depletion in both hemispheres in March 2017. This long duration O/N2 depletion started with a geomagnetic storm between March 1 and 21, 2017 which was caused by large periodic variations in interplanetary magnetic field (IMF) and a high solar wind speed, thus likely associated with a solar wind co-rotating interaction region (CIR).

The enduring mystery of the solar corona

Physicists have long known that the Sun’s magnetic fields make its corona much hotter than the surface of the star itself. But how – and why – those fields transport and deposit their energy is still a mystery. 

Magnetofrictional Modeling of an Erupting Pseudostreamer

In this study, we present a magnetic conguration of an erupting pseudostreamer observed on April 19, 2015 on the Southwest limb embedding a prominence cavity. The eruption resulted in a relatively wide CME with a round front and prominence core intersected by a sharp plume.

The Impact of Solar Activity on Forecasting the Upper Atmosphere via Assimilation of Electron Density Data

This study presents a comprehensive comparison of the impact of solar activity on forecasting the upper atmosphere through assimilation of radio occultation (RO)-derived electron density (Ne) into a physics-based model (TIE-GCM) using an ensemble Kalman filter.

Characteristics of small-scale gravity waves in the Arctic winter mesosphere

Observational datasets in the polar middle atmosphere are extremely valuable for understanding the polar dynamics and coupling between lower and middle atmosphere. Using the long-term datasets observed with an OH all-sky imager, a Fabry-Perot Interferometer at Resolute Bay observatory, Canada (74.7°N, 94.9°W), and Microwave Limb Sounder and reanalysis data, we study the characteristics of small-scale gravity waves (GWs) with the horizontal wavelength less than 20 km in the Arctic winter mesosphere during 2014-2016.

COSMIC Observation of Stratospheric Gravity Wave and Ionospheric Scintillation Correlation

A correlation study is performed to investigate possible connections between the stratospheric gravity waves and the ionospheric plasma bubble induced GPS signal scintillations.