Research Highlights

Research Highlights

A selection of highlights culled from publications by HAO staff.

Emission line data from IRIS are shown in the top panel. The lower panel lists an expression for the ratio of the emission lines shown of SI and O, under a minimal number of assumptions which often exceed the number of independent data points

Some thoughts on emission-line spectroscopy

Philip Judge states that the interpretation of emission lines formed in large astrophysical plasmas such as the solar atmosphere faces many challenges. Relatively simple line-ratio estimates of physical parameters, while appealing, are heavily laden with assumptions.

TEC plot

Simulated trends in ionosphere-thermosphere climate due to predicted main magnetic field changes from 2015 to 2065

The strength and structure of the Earth's magnetic field is gradually changing. These changes do not only affect the difference between the geographic and magnetic pole, which we have to consider when we hike in higher latitude regions.

Sectional view of a GOLD spectroscopic imaging channel

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

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.

Radial profiles of continuum intensity (b), magnetic field inclination (c), total magnetic field strength (d), vertical magnetic field strength (e), and horizontal magnetic field strength (f)

A distinct magnetic property of the inner penumbral boundary III. Analysis of simulated sunspots

The analyses of sunspot observations revealed a fundamental magnetic property of the umbral boundary, the invariance of the vertical component of the magnetic field. We aim to analyse the magnetic properties of the umbra-penumbra boundary in simulated sunspots and thus assess their similarity to observed sunspots. 

Plots of magnetic field and TSI with time

On the contribution of quiet Sun magnetism to solar irradiance variations: Constraints on quiet Sun variability and grand minimum scenarios

While the quiet Sun magnetic field shows only little variation with the solar cycle, long-term variations cannot be completely ruled out from first principles.

H+ band Electromagnetic Ion Cyclotron (EMIC) waves

Statistical Dependence of EMIC Wave Scattering on Wave and Plasma Parameters

A recent statistical study 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. In our study, we perform 6 years of analysis of data from 2013 to 2018, with relativistic electron precipitation (REP) observed by POES and EMIC wave observations from Van Allen Probes.

Fully processed image of the corona generated by stacking many co-aligned, calibrated images and applying a radial filter and multi-scale unsharp mask to bring out details at higher altitudes

A new facility for airborne solar astronomy: NASA’s WB-57 at the 2017 total solar eclipse

NASA's WB-57 High Altitude Research Program provides a deployable, mobile, stratospheric platform for scientic research. Airborne platforms are of particular value for making coronal observations during total solar eclipses because of their ability both to follow the Moon's shadow and to get above most of the atmospheric airmass that can interfere with astronomical observations.

Sunspot simulations

Opposite Polarity Magnetic Fields and Convective Downflows in a Simulated Sunspot Penumbra

Recent numerical simulations and observations of sunspots show a significant amount of opposite polarity magnetic fields within the sunspot penumbra. Most of the opposite polarity fields are associated with convective downflows.

Average temperature of 35 cavities (black) and their surrounding streamers (red)

Thermal Properties of Coronal Cavities

We have analyzed 33 cavities observed between 2012 and 2018, from solar activity maximum to minimum. For each cavity we applied a differential emission measure method to obtain both a temperature distribution and a value of the average temperature.