Research Highlights

Research Highlights

A selection of highlights culled from publications by HAO staff.

Profiles of wind shear (S, black) and their mean (magenta) as well as the top 10% (blue) and 1% (red) largest S during January (a, d) and July (b, e) at around 40 N (a, b, c) and the Equator (d, e, f), derived from SABER

Gravity-wave-perturbed wind shears derived from SABER temperature observations

Large wind shears around the mesopause region play an important role in atmospheric neutral dynamics and ionospheric electrodynamics. Based on previous observations using sounding rockets, lidars, radars, and model simulations, large shears are mainly attributed to gravity waves (GWs) and modulated by tides (Liu, 2017).

Daily values of migrating diurnal tidal amplitudes (left panel) and phases (right panel) at 1E-2 hPa (80 km) from the novel multiple satellite analysis method described in this paper (upper panel), NOGAPS-ALPHA (middle panel), and WACCM-X (lower panel)

Day-to-Day Variability of Diurnal Tide in the Mesosphere and Lower Thermosphere Driven From Below

The migrating diurnal tide (DW1) is one of the dominant wave motions in the mesosphere and lower thermosphere. It plays a crucial role in neutral atmosphere and ionosphere coupling. The DW1 can vary over a range of time scales from days to years. While the long-term variability of the DW1 is mainly attributed to the source and background atmosphere variability, the driving mechanism of short-term DW1 variability is still openly debated.

The latitude-longitude distribution of the OI 135.6 nm radiance measured by GOLD Channel B from 22:25 to 23:55 UT (22:25, 22:55, 23:10, 23:25, 23:40 and 23:55) on Nov 19, 2018

Observation of Postsunset OI 135.6 nm radiance Enhancement in South America by the Global-scale Observation of Limb and Disk (GOLD) Mission

The Global-scale Observation of Limb and Disk (GOLD) mission, for the first time, provides synoptic two-dimensional (2D) maps of OI 135.6 nm observations.

Air density in the northern hemisphere on 27 March 2003 when CHAMP passes through the edge of a high-latitude density enhancement

Alfvénic thermospheric upwelling in a global geospace model

First author, William Lotko, reveals that the CHAMP satellite orbiting near 400 km altitude near the magnetic cusp routinely traversed thermospheric density enhancements (up to 50%) that are not predicted by empirical models. The density enhancements are well-correlated with kilometer-scale field-aligned currents interpreted as ionospheric Alfvén resonator modes.

SDO and IRIS full-disk observations from 2016 Feb 22

Detecting the Chromospheric Footpoints of the Solar Wind

Coronal Holes present the source of the fast solar wind. However, the fast solar wind is not unimodal—there are discrete, but subtle, compositional, velocity, and density structures that differentiate different coronal holes as well as wind streams that originate within one coronal hole. In this Letter we exploit full-disk observational “mosaics” performed by the Interface Region Imaging Spectrograph (IRIS) spacecraft to demonstrate that significant spectral contrast exists within the chromospheric plasma of coronal holes.

Comparison of the whole atmosphere temperature profiles from the true state, lower atmosphere only assimilation (LA), and lower-atmosphere plus GOLD assimilation (LA+GOLD) for 14 UT (left column) and 18 UT (right column) at different locations inside the GOLD field of view (top) and for the zonal mean (bottom)

Impact of GOLD Retrieved Thermospheric Temperatures on a Whole Atmosphere Data Assimilation Model

The present investigation evaluates the assimilation of synthetic data which has properties similar to actual Global-scale Observations of the Limb and Disk (GOLD) level-2 (L2) and other conventional lower atmospheric observations. The lower atmospheric and GOLD L2 temperature (Tdisk) are assimilated in the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCMX) using Data Assimilation Research Testbed (DART).

An MHD simulation of the evolution of a prominence-forming twisted coronal flux rope, for which large amplitude longitudinal (LAL) oscillations are excited during the quasi-static rise phase, followed by prominence draining towards the flux rope foot-points and the eventual eruption of the flux rope and the prominence

Simulations of prominence eruption preceded with large amplitude longitudinal oscillations and draining

We present magnetohydrodynamic (MHD) simulations of the evolution from quasi-equilibrium to eruption of a prominence-forming twisted coronal flux rope under a coronal streamer. The prominence condensations form at the dips of the twisted flux rope due to run-away radiative cooling.

Comparison of analytic model magnetic field lines to results of numerical reconstruction

Reconstructing the Coronal Magnetic Field: The Role of Cross-Field Currents in Solution Uniqueness

We present a new 3D magnetohydrostatic (MHS) direct elliptic solver for extrapolating the coronal magnetic field from photospheric boundary conditions in a manner consistent with an assumed plasma distribution.

Observations of ionospheric behavior during the 2009 SSW event

Sudden Stratospheric Warmings

Sudden stratospheric warmings (SSWs) are impressive fluid dynamical events in which large and rapid temperature increases in the winter polar stratosphere (∼10–50km) are associated with a complete reversal of the climatological wintertime westerly winds.