Observations of Solar Flares in Lyman-Alpha Emission

Background

Solar flares are the most energetic explosions in the solar system. Rapid restructuring of the Sun’s coronal magnetic field results in the acceleration of particles to relativistic energies. These energetic electrons collide with the dense, underlying chromosphere, causing it to heat and expand. The resulting increase in EUV and X-ray radiation can significantly impact the upper layers of Earth’s atmosphere, as well as those of other planets. It also allows us to diagnose the plasma conditions within the flaring chromosphere and put constraints on various theoretical flare heating models. The study of solar flares is also important to help us understand flares on other stars, and how they may impact the search for potentially habitable exoplanets.

Project Description

The Lyman-alpha line of neutral hydrogen is the strongest emission line in the solar spectrum and yet observations of solar flares in this fundamental line have been notoriously scarce in recent years. In 2028, the Japanese Space Agency, JAXA, will launch the SOLAR-C mission, which will feature a dedicated Lyman-alpha instrument. SOLAR-C is the next-generation solar-observing satellite which will unravel the formation mechanisms of the hot plasma during solar flares and the Sun's effects on the Earth. The successful candidate will work primarily on the analysis and interpretation of currently available Lyman-alpha observations of solar flares from space-based observatories such as SORCE/SOLSTICE, GOES-R/EXIS, MAVEN/EUM, Solar Orbiter/EUI, ASO-S/LST, and SDO/EVE, in preparation for the launch of Solar-C. They will also collaborate closely with colleagues at Physikalisch-Meteorologisches Observatorium Davos (PMOD) and Fachhochschule Nordwestschweiz (FHNW) in Switzerland who have significant involvement in the Solar-C and Solar Orbiter missions, respectively. Some of the science questions that this project will aim to answer include:

• By what mechanism are increases in Lyman-alpha irradiance generated during solar flares and where in the Sun’s atmosphere does this emission originate?
• Is there a fundamental upper limit to how much flares can contribute to increases in irradiance?
• Can state-of-the-art radiative hydrodynamic flare models reproduce the relative changes in Lyman-alpha emission and elucidate the plasma conditions under which it is formed?

Facilities

Advanced Space-based Solar Observatory (LST), Solar Orbiter (STIX, EUI, SPICE), Solar Dynamics Observatory (EVE, AIA), GOES-R (EXIS), PROBA2/LYRA, and archival data.

Other information

Funding will be provided within the studentship to allow the successful candidate to travel and present their work at national and international conferences and workshops.

QUB staff and external collaborators associated with the project

Dr. Ryan Milligan (QUB), Prof. Mihalis Mathioudakis (QUB).

For more information contact the primary supervisor Dr. Ryan Milligan (r.milligan@qub.ac.uk).