Space Physics

Artist's view of space physics topics.
Artist’s view of the heliosphere---cavity formed in the local interstellar medium by the solar wind (credit: Jet Propulsion Lab)
A coronal mass ejection observed in white light with coronagraph on SOHO (credit: Large Angle and Spectrometric Coronagraph).
The oxygen, helium, and hydrogen ions gush into space from Earth poles. The green is the Aurora Borealis plasma (credit: NASA).

The fundamental goal of solar and space physics research is to discover, to explore, and ultimately to understand the activity of a star—the Sun—and the often complex effects of that activity on the interplanetary environment, the planets and other solar system bodies, and the interstellar medium. This enterprise involves the study of an exotic and dynamic world of ionized gases (plasmas), magnetic and electric fields, and small- and large-scale electrical currents. It is motivated by the deep-seated human impulse to know and understand the workings of Nature. Its province is that portion of the universe dominated by the Sun’s activity.

Although solar and space physicists focus their inquiry primarily on the behavior of magnetized plasmas in the solar system and on the interactions of these plasmas with each other and with electrically neutral matter, the processes that they seek to understand are fundamental, so that the lessons of solar and space physics are often relevant to our understanding of astrophysical objects lying well beyond the reach of the Sun’s influence.

The domain of solar and space physics is that region of our galaxy known as the heliosphere. The heliosphere is the cavity formed within the warm plasma of the local interstellar medium by the solar wind, the Sun’s ionized, supersonically expanding atmosphere. Situated inside this bubblelike cavity, and immersed in the solar wind flow, are the nine planets of the solar system, the asteroids, the comets, and the icy trans-Neptunian objects of the Kuiper Belt. At its center is the Sun, an ordinary main-sequence star that, with an age of 4.5 billion years, has reached the midpoint of its stellar life. The size and structure of the heliosphere are determined by the relative pressures of the solar wind and the interstellar medium and will change as these pressures vary. At this point in the history of the solar system, most of the changes in the dimensions of the heliosphere probably result from variations in solar wind ram pressure over the course of the 11-year solar cycle and are likely to be comparatively minor (a few percent).

Major Challenges for Space Physics Research

  • Understanding the structure and dynamics of the Sun’s interior, the generation of solar magnetic fields, the origin of the solar cycle, the causes of solar activity, and the structure and dynamics of the corona.
  • Understanding heliospheric structure, the distribution of magnetic fields and matter throughout the solar system, and the interaction of the solar atmosphere with the local interstellar medium.
  • Understanding the space environments of Earth and other solar system bodies and their dynamical response to external and internal influences.
  • Understanding the basic physical principles manifest in processes observed in solar and space plasmas.
  • Developing near-real-time predictive capability for understanding and quantifying the impact on human activities of dynamical processes at the Sun, in the interplanetary medium, and in Earth’s magnetosphere and ionosphere.
  • Understanding the Sun, heliosphere, and planetary magnetospheres and ionospheres as astrophysical objects and in an astrophysical context

Research Areas:

See also the Website of Plasma Physics.

Experiment: 
Theory & Computation: