My research interests are concerned with theoretical and computational studies of solar and stellar atmospheres, and fundamental plasma physics processes in laboratory plasmas relevant to astrophysical contexts. In particular, I investigate the heating of stellar atmospheres, the mechanisms responsible for triggering and driving flares, and the heating and acceleration of winds. I use both theoretical and computational tools and work closely with experimentalists and observers to test and constrain my models. As an example, I compare the spectral emission signatures predicted by my solar flare models with hard X-ray spectra observed by space-borne instruments, which allows me to place strong constraints on the properties of the underlying energetic electron spectrum. Additionally, I use analytical methods to gain insights into the basic physical processes that dominate particular phenomena and to make predictions (such as scaling relationships) to be tested against observational measurements.

To facilitate this analysis I have built, from scratch, a state-of-the-art computational model (HYDRAD). As its extensive use by diverse international teams shows, HYDRAD meets the significant challenges associated with capturing the physics of solar and stellar atmospheres. Recent examples of its application include: global active region models; impulsive heating in the chromosphere as a source of the mass and energy flux into the corona; detailed calculations of the ionization state and optically-thin radiative emissions during impulsive coronal heating/cooling and predicting observable signatures of coronal heating; thermal and non-thermal energization mechanisms for compact flares; outflows driven by interchange reconnection at active region boundaries as a component of the slow solar wind; slow shocks and conduction fronts driven by the reconnection of skewed magnetic fields and the magneto-rotational instability; evolution of the energy balance during the solar atmosphere heating/cooling cycle; excitation and damping of standing acoustic waves in coronal loops; and testing diagnostic tools for coronal seismology. HYDRAD is flexible enough to be applied to a broad variety of research problems in solar, astrophysical, and laboratory plasma physics.

HYDRAD has provided deep insights into the physics of mass and energy transport through the solar atmosphere. A Major Science Goal of the present Decadal Survey’s Solar and Heliospheric Physics Panel is to “Determine how the Sun’s magnetism creates its dynamic atmosphere”, with the associated action to “Determine whether chromospheric dynamics is the origin of heat and mass fluxes into the corona and the solar wind.” I have used HYDRAD to show that direct chromospheric heating yields spectral signatures associated with the supply of mass and energy to the corona that are not consistent with current observations, and concluded that the bulk of the corona must be due to in-situ coronal heating.