Bow shocks are dynamic regions in space where the solar wind flow velocity abruptly decreases as it interacts with an obstacle, causing the solar wind particles to accumulate due to the shock compression. These boundaries are common around planets, with Earth's bow shock being the most studied, but they also form around smaller objects such as comets. Unlike Earth's relatively stable plasma environment, comets, with their highly elliptical orbits, present more dynamic conditions, offering opportunities to study bow shocks in all stages of formation---from birth to fully developed. 

The first mission to closely observe a comet was the Rosetta mission, which orbited comet 67P/Churyumov-Gerasimenko (67P) from 2014 to 2016. Despite its extensive observations, Rosetta did not detect a fully developed bow shock through in situ measurements due to trajectory constraints. This means that any potential information about the bow shock would only be attainable through remote detection.

In this project, I explore the possibility of performing remote analysis using cometary ion energy spectra, based on data collected by the Ion Composition Analyser (ICA) onboard Rosetta, to investigate the bow shock around comet 67P. By examining ion energy spectra, certain spectral features can be observed for ions that may have been affected by the bow shock. These spectral features can be characterised by an elbow point, whose location is identified using Python code.

I begin my analysis with 705 days' worth of data, and after the sorting process---where I implement various criteria, separate days according to their slope change around the elbow point, and discard days based on an estimated noise---I end up with 15 days remaining. These remaining days all exhibit spectral features indicative of ions being influenced by a non-uniform electric field far from the comet nucleus, suggesting the presence of a bow shock.

For these days, I then plot and analyse the flow direction, showing where in ICA's field-of-view the particles enter the instrument, and what energies they possess. In four distinct time periods, I detect a discontinuity in the energy transition between the ions associated with the spectral feature and those that are not, which points to the ions originating from different ion populations. This observation is further confirmed by the corresponding energy spectra, where a separation in ion distribution is apparent for all four time periods.

After comparing my findings with simulations from Alho et al. (2021), where similar spectral features were linked to a bow shock, I conclude that it is feasible to remotely detect bow shock effects in ion energy spectra, and that the observed spectral features in my results are likely caused by such effects. Finally, the separation in ion populations further supports this conclusion.