Heliosphere – where the solar wind meets the interstellar medium
Credit: NASA’s GSFC Conceptual Image Lab
The outer space between stars, planets, and other celestial bodies is often referred to as an example of an almost perfect vacuum. While it is a much better vacuum than achievable in laboratories, the rarefied matter in and around the Solar System plays an important role in the development of life on Earth.
The main source of interplanetary medium is the Sun, which continuously blows out a hot plasma from the solar corona with speeds of ~300-800 km/s called the solar wind. As the solar wind expands, the density drops, and eventually, the pressure of the interstellar medium prevents further expansion, enclosing the solar wind within the heliosphere.
The heliosphere expands more than 100 au from the Sun. The solar wind and interstellar plasmas are magnetized, and the electromagnetic forces prevent direct penetration of interstellar charged particles to the heliosphere. The heliosphere therefore shields Earth from the direct impact of most galactic cosmic rays.
In my research, I study the shape and processes in the heliosphere and the neighboring interstellar medium. I use observations of neutral atoms, which travel between collisions on scales exceeding the heliosphere’s size. Consequently, they can be used as messengers from distant regions of the heliosphere and interstellar medium.
Interstellar neutral (ISN) atoms
Interstellar neutral (ISN) atoms originate from the very local interstellar medium around the heliosphere and can be observed with a detector placed on spacecraft located close to Earth. In my research, I use observations of ISN helium atoms from the IBEX mission. Because many of these atoms are only affected by the Sun’s gravity, we use them to study the physical conditions in the interstellar medium.
Select publications:
- Swaczyna, P., Bzowski, M., Heerikhuisen, J., et al., 2023, Interstellar Conditions Deduced from Interstellar Neutral Helium Observed by IBEX and Global Heliosphere Modeling, The Astrophysical Journal, 953, 107, [DOI, ADS].
- Swaczyna, P., Schwadron, N. A., Möbius, E., et al., 2022, Mixing Interstellar Clouds Surrounding the Sun, The Astrophysical Journal Letters, 937, L32, [DOI, ADS].
- Swaczyna, P., Kubiak, M. A., Bzowski, M., et al., 2022, Very Local Interstellar Medium Revealed by a Complete Solar Cycle of Interstellar Neutral Helium Observations with IBEX, The Astrophysical Journal Supplement Series, 259, 42, [DOI, ADS].
- Swaczyna, P., Bzowski, M., Kubiak, M., et al., 2015, Interstellar Neutral Helium in the Heliosphere from IBEX Observations. I. Uncertainties and Backgrounds in the Data and Parameter Determination Method, The Astrophysical Journal Supplement Series, 220, 26, [DOI, ADS].
Energetic neutral atoms (ENAs)
Credit: Swaczyna et al. (2023, ApJS 266:26, Fig. 4).
Imaging the heliosphere using observations of ENA fluxes at 1 au on the IBEX mission allows for tracking the solar-cycle evolution of the heliosphere. The ENA flux maps show two sources having different geometric properties at the energies covered by the IBEX instruments. The globally distributed flux, which extends over the entire sky, originates mostly from the inner heliosheath. The other source forms a narrow, almost circular structure called the IBEX ribbon. This feature was not expected before the IBEX mission launch. In my research, I develop methods to separate these two sources’ signals to enable individual interpretation of these observations. I also study the geometric properties of the ribbon to uncover its origin.
Select publications:
- Swaczyna, P., Dayeh, M. A., & Zirnstein, E. J., 2023, Spherical Harmonic Representation of Energetic Neutral Atom Flux Components Observed by IBEX, The Astrophysical Journal Supplement Series, 266, 26, [DOI, ADS].
- Swaczyna, P., Eddy, T. J., Zirnstein, E. J., et al., 2022, IBEX Ribbon Separation Using Spherical Harmonic Decomposition of the Globally Distributed Flux, The Astrophysical Journal Supplement Series, 258, 6, [DOI, ADS].
- Swaczyna, P., Bzowski, M., & Sokół, J. M., 2016, The Energy-Dependent Position of the IBEX Ribbon Due to the Solar Wind Structure, The Astrophysical Journal, 827, 71, [DOI, ADS]. (Erratum: Swaczyna, P., Bzowski, M., & Sokół, J. M., 2018, The Astrophysical Journal, 854, 186, [DOI, ADS].)
- Swaczyna, P., Bzowski, M., Christian, et al., 2016, Distance to the IBEX Ribbon Source Inferred from Parallax, The Astrophysical Journal, 823, 119, [DOI, ADS].