Paweł Swaczyna Ph.D.

Postdoctoral Research Associate
Email Address: 
swaczyna AT
Office Location: 
007 Peyton Hall
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Ph.D., Physical Sciences, Space Research Centre of the Polish Academy of Sciences, Warsaw, Poland (2018)

M.S., Physics, University of Warsaw, Poland (2013)

B.S., Physics, University of Warsaw, Poland (2011)


Paweł Swaczyna is a research scientist involved in the analysis of the IBEX observations. He received his B.Sc. and M.Sc. in Physics at University of Warsaw, specializing in theory of fundamental particles and interactions. His Ph.D. in Physical Sciences was granted by the Space Research Centre of the Polish Academy of Sciences. In Ph.D. thesis, he developed a model of ENA emission of heavy chemical elements (helium, oxygen, nitrogen, and neon) from the inner heliosheath and the IBEX ribbon under the secondary ENA mechanism. He analyzed observations of the IBEX ribbon that allowed for the determination of its parallax and thus the distance to the source region. He works on the analysis of the interstellar neutral gas observed by the IBEX-Lo instrument.

Research Interests

  • Interstellar neutral atoms penetrating the heliosphere
  • Energetic neutral atoms of elements heavier than hydrogen
  • Evolution of the energetic neutral atom flux during solar cycle

Selected Publications

(See more at Google Scholar)

Interstellar neutral helium in the heliosphere from IBEX observations. V. Observations in IBEX-Lo ESA steps 1, 2, & 3 (2018), Swaczyna et al., ApJ

The figure presents IBEX-Lo observations from three lowest energy steps in form of maps. The maps are very similar to each other but some differences may be noticed.Direct-sampling observations of interstellar neutral (ISN) He by the Interstellar Boundary Explorer (IBEX) provide valuable insight into the physical state of and processes operating in the interstellar medium ahead of the heliosphere. The ISN He atom signals are observed at the four lowest ESA steps of the IBEX-Lo sensor. The observed signal is a mixture of the primary and secondary components of ISN He and H. Previously, only data from one of the ESA steps have been used. Here, we extend the analysis to data collected in the three lowest ESA steps with the strongest ISN He signal, for the observation seasons 2009–2015. The instrument sensitivity is modeled as a linear function of the atom impact speed onto the sensor's conversion surface separately for each ESA step of the instrument. We find that the sensitivity increases from lower to higher ESA steps, but within each of the ESA steps it is a decreasing function of the atom impact speed. This result may be influenced by the hydrogen contribution, which was not included in the adopted model, but seems to exist in the signal. We conclude that the currently accepted temperature of ISN He and velocity of the Sun through the interstellar medium do not need a revision, and we sketch a plan of further data analysis aiming at investigating ISN H and a better understanding of the population of ISN He originating in the outer heliosheath.

Helium Energetic Neutral Atoms from the Heliosphere: Perspectives for Future Observations (2017), Swaczyna et al., ApJ

Maps of expected helium energetic neutral atoms for three energies 1 keV/nuc, 2 keV/nuc, and 10 keV/nucObservations of energetic neutral atoms (ENAs) allow for remote sensing of plasma properties in distant regions of the heliosphere. So far, most of the observations have concerned only hydrogen atoms. In this paper, we present perspectives for observations of helium energetic neutral atoms (He ENAs). We calculated the expected intensities of He ENAs created by the neutralization of helium ions in the inner heliosheath and through the secondary ENA mechanism in the outer heliosheath. We found that the dominant source region for He ENAs is the inner heliosheath. The obtained magnitudes of intensity spectra suggest that He ENAs can be observed with future ENA detectors, as those planned on Interstellar Mapping and Acceleration Probe. Observing He ENAs is most likely for energies from a few to a few tens of keV/nuc. Estimates of the expected count rates show that the ratio of helium to hydrogen atoms registered in the detectors can be as low as 1:104. Consequently, the detectors need to be equipped with an appropriate mass spectrometer capability, allowing for recognition of chemical elements. Due to the long mean free paths of helium ions in the inner heliosheath, He ENAs are produced also in the distant heliospheric tail. This implies that observations of He ENAs can resolve its structure, which seems challenging from observations of hydrogen ENAs since energetic protons are neutralized before they progress deeper in the heliospheric tail.

Distance to the IBEX Ribbon Source Inferred from Parallax (2016), Swaczyna et al., ApJ

Chi-square as function of the parallax angle for the used energy steps and all energy steps together.Maps of energetic neutral atom (ENA) fluxes obtained from observations made by the Interstellar Boundary Explorer (IBEX) revealed a bright structure extending over the sky, subsequently dubbed the IBEX ribbon. The ribbon had not been expected from the existing models and theories prior to IBEX, and a number of mechanisms have since been proposed to explain the observations. In these mechanisms, the observed ENAs emerge from source plasmas located at different distances from the Sun. Since each part of the sky is observed by IBEX twice during the year from opposite sides of the Sun, the apparent position of the ribbon as observed in the sky is shifted due to parallax. To determine the ribbon's parallax, we found the precise location of the maximum signal of the ribbon observed in each orbital arc. The apparent positions obtained were subsequently corrected for the Compton–Getting effect, gravitational deflection, and radiation pressure. Finally, we selected a part of the ribbon where its position is similar in the different IBEX energy passbands. We compared the apparent positions obtained from the viewing locations on the opposite sides of the Sun, and found that they are shifted by a parallax angle of 0.41°±0.15°, which corresponds to a distance of 140+84-38 AU. This finding supports models of the ribbon with the source located just outside the heliopause.