Research Highlights

Research Highlights

A selection of highlights culled from publications by HAO staff.

A portion of the inner penumbra in the MURaM sunspot simulation by Rempel (2015) with some filaments hosting a counter-Evershed flow (see also Siu-Tapia et al. 2018)

Superstrong photospheric magnetic fields in sunspot penumbrae

Recently, there have been some reports of unusually strong photospheric magnetic fields (which can reach values of over 7 kG) inferred from Hinode SOT/SP sunspot observations within penumbral regions. These superstrong penumbral fields are even larger than the strongest umbral fields in record and appear associated with supersonic downflows.

Maps of the E-region horizontal and radial currents for 18 March 2016 at 11:22 UT

Dipolar elementary current systems for ionospheric current reconstruction at low and middle latitudes

The flow of ionospheric current can be probed by examining magnetic field measurements at the ground and at Low-Earth-Orbit (LEO) altitude. The interpretation of the magnetic field perturbations with respect of ionospheric current flow is complicated by the fact that the perturbations reflect the integrated effect of current flow close-by and far-away.

Polar maps of the simulated electron density at pressure level 2 (~300 km) in the Northern Hemisphere as a function of geographic latitude and local time on 17 March 2013

Formation of Double Tongues of Ionization During the 17 March 2013 Geomagnetic Storm

During geomagnetic disturbances, enhanced high‐latitude convection transports ionospheric F2‐region plasma from the dayside midlatitude region into the polar cap, leading to structures such as tongues of ionization (TOIs) and patches. In this study, we investigate the dynamic evolution of TOIs during the 17 March 2013 storm using a high‐resolution coupled thermosphere‐ionosphere‐electrodynamics model and Defense Meteorological Satellite Program (DMSP) satellite observations.

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

We conduct observational and modeling studies of thermospheric composition responses to weak geomagnetic activity (non-geomagnetic storms).

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)

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

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.

Analysis results for the observation on November 3, 2016 (dataset D2)

Mapping the magnetic field in the solar corona through magnetoseismology

Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona.

White light images (upper panels A and B) from HAO's KCOR instrument are shown with Fe XIII emission line polarization data (HAO's CoMP instrument) acquired one day after the initial flare was released

Dynamics of Late-Stage Reconnection in the 2017 September 10 Solar Flare

In this multi-instrument paper, we search for evidence of sustained magnetic reconnection far beyond the impulsive phase of the X8.2-class solar flare on 2017 September 10.

Height variation of quiet time evening vertical drifts over Jicamarca for moderate solar flux conditions(after Fejer et al., 2014)

Equatorial Ionospheric Electrodynamics

The low latitude ionosphere is one of the dynamic regions of the Earth’s upper atmosphere. The morphology of this region is controlled by radiative and coupled chemical, neutral and plasma transport processes.

H+ band Electromagnetic Ion Cyclotron (EMIC) waves produce loss of relativistic electrons as seen by two Van Allen Probes spacecraft separated along orbit by ~ 1 hour during June 2015 storm (Qin et al., 2019)

Statistical Dependence of EMIC Wave Scattering on Wave and Plasma Parameters

A recent statistical study (Qin et al., 2018) has suggested that not all electromagnetic ion cyclotron (EMIC) waves can scatter relativistic electrons. However, knowledge of the factors that influence the EMIC wave scattering efficiency is still limited in observations.