Väitös (fysiikka): MSc Ghulam Ume Farwa

MSc Ghulam Ume Farwa esittää väitöskirjansa ”Multi-spacecraft observations of large solar energetic particle events with an inner-heliospheric spacecraft fleet” julkisesti tarkastettavaksi Turun yliopistossa maanantaina 20.4.2026 klo 12.00 (Turun yliopisto, Quantum, XVII-luentosali, Vesilinnantie 3, Turku).

Vastaväittäjänä toimii tohtori Norma B. Crosby (Belgian kuninkaallinen aeronomian tutkimuslaitos, Belgia) ja kustoksena professori Rami Vainio (Turun yliopisto). Tilaisuus on englanninkielinen. Väitöksen alana on fysiikka.

Tiivistelmä väitöstutkimuksesta:

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.