Dissertation defence (Physics): MSc Ghulam Ume Farwa
MSc Ghulam Ume Farwa defends the dissertation in Physics titled “Multi-spacecraft observations of large solar energetic particle events with an inner-heliospheric spacecraft fleet” at the University of Turku on 20 April 2026 at 12.00 (University of Turku, Quantum, lecture hall XVII, Vesilinnantie 3, Turku).
Opponent: Dr. Norma B. Crosby (Royal Belgian Institute for Space Aeronomy, Belgium)
Custos: Professor Rami Vainio (University of Turku)
Summary of the Doctoral Dissertation:
The Sun is an active star from which bursts of energy are sometimes released, and fast-moving particles are sent into space. These events, known as solar energetic particle events, can be associated with effects on satellites, communication systems, and even human safety in space and at high altitudes. In this research, an aim is set to better understand how these particles are produced, how they travel, and how their effects can be predicted.
It is found that these particle events can spread widely from the source location, consistent with previous studies. By using data from several spacecraft positioned at different locations around the Sun, it is shown that many events cover large regions of space. It is therefore indicated that a single solar eruption can affect multiple areas of the Solar System at the same time.
It is also found that these particles are not created by just one process, in agreement with earlier findings. They can be accelerated by solar flares or by large eruptions that create shock waves in space. It is demonstrated that both processes can contribute together, depending on the situation.
It is further found that the location of the observer plays a major role, consistent with previous understanding. Particles are transported along magnetic field lines, so strong and early signals are detected when a spacecraft is well connected to the source. If it is not well connected, weaker or delayed signals are observed. In this way, it is explained why the same event can appear very different from different locations.
In addition, it is shown that these events follow similar patterns over time, in line with earlier studies. By combining many events, it is found that both electrons and protons behave in a consistent way as the event develops. This makes it possible for an average solar particle storm to be described.
A particularly useful result that supports the earlier findings is that fast electrons are observed to arrive earlier than slower, more harmful particles such as protons. It is therefore suggested that electrons can act as an early warning signal, helping to predict when radiation levels may increase.
New information is provided by this research through the use of multiple spacecraft observations, allowing a more complete view of solar particle events to be obtained. The role of multiple processes and the importance of location in shaping observations are also highlighted.
The impact of this work is both practical and scientific. Improvements in space weather forecasting are supported, which is important for protecting satellites, communication systems, astronauts, and high-altitude flights. At the same time, an improved understanding of how energetic particles behave in space is achieved.
