What is Heliophysics?

Heliophysics is the science that enables understanding the Sun, heliosphere, and planetary environments as a single connected system.

We need to understand the sources of phenomena and how they propagate through interplanetary space, i.e. the path they take and the time scales involved, in order to conduct a scientific search for things that are scientifically interesting in heliophysics. This necessitates the ability to track objects in four dimensions, but the solution allows us to predict which effects will be visible when and where.

Although some are connected shock fronts associated with propagating phenomena, the majority of effects are induced by various types of emission created by solar activity. The nature of the phenomena, the type of emission, and the observer's location all influence whether or not an effect is detected. Photon emission effects necessitate a line-of-sight view of the source, and any delays are due to light travel durations. Because the velocities are lower and the particles follow a curved course, particle-caused effects take significantly longer to manifest; in certain situations, the effects are only felt if the propagating phenomenon passes the observer. What is observed is determined by the observer's position in reference to the source and in connection to a planet; the presence of a magnetic field and/or atmosphere dictates how a planetary environment is influenced.

The effects of photons take about 8 minutes to appear on Earth; the delay for intense particles travelling at near relativistic velocities can take tens of minutes. Plasma's (low energy ionised material) impacts take significantly longer - tens of hours. The consequences take longer to manifest on planets further out in the Solar System, and the spread of delays is greater. Solar wind velocities can range from a few hundred km/sec to up to 2000 km/sec. Coronal Mass Ejections (CME) can travel at speeds of up to 2000 km/sec.

In addition to solar processes, this domain of study includes the interaction of solar plasma and solar radiation with Earth, the other planets, and the galaxy.

By analyzing the connections between the Sun, solar wind, and planetary space environments, the fundamental physical processes that occur throughout the universe are uncovered.

Methods have been developed to see into the internal workings of the Sun and understand how the earth's magnetosphere responds to solar activity.

There are three primary objectives that define the multi-decadal studies needed:

· To understand the changing flow of energy and matter throughout the Sun, Heliosphere, and Planetary Environments.

· To explore the fundamental physical processes of space plasma systems.

· To define the origins and societal impacts of variability in the Earth-Sun System.

A combination of interrelated elements is used to achieve these objectives. They include complementary missions of various sizes, timely development of enabling and enhancing technologies; and acquisition of knowledge through research, analysis, theory, and modelling.

The impact of emissions or spreading phenomena on a planetary environment are dependent on whether or not the planet has a magnetic field and/or an atmosphere. The planet's magnetic field functions as a screen, affecting how and where charged particles can enter the planetary environment; auroras are caused by particles entering near the poles and can be seen on Earth and other planets. As events are traced down into the planetary environment, we need to be able to track them in models and in-situ measurements as they cascade down from Sun-centered coordinates to planet-centered coordinates.