What is termination shock

Most of the matter in the Universe is in the plasma state. The solar wind plasma gets smooshed together, or compressed like people crowded together in a tiny room.

When it is compressed, it also becomes much hotter, in the same way as a bicycle pump heats up in your hand when you vigorously inflate a tire. Also, the solar wind carries outward some of the Sun's magnetic field A field of force that is generated by electric currents. The Sun's average large-scale magnetic field, like that of the Earth, exhibits a north and a south pole linked by lines of magnetic force.

We have only two direct measurements of the distance to the Termination Shock. These measurements were made by Voyager 1 and Voyager 2. Voyager 1 crossed the termination shock at 94 astronomical units The average distance between the Earth and Sun, about million kilometers 93 million miles.

AU and Voyager 2 crossed at 84 AU. Even though the interstellar medium has a low density The amount of mass or number of particles per unit volume. In cgs units mass density has units of gm cm Number density has units cm -3 particles per cubic centimeter. The solar wind flow also represents a strong outward pressure. Decker, M. Lanzerotti, E. Roelof, Voyager 1 exited the solar wind at a distance of 85 au from the sun. Nature , 45 Lallement, E. Quemerais, J. Bertaux, S.

Pheron, Science , Li, G. Zank, AIP Conf. McDonald, E. Stone, A. Cummings, B. Heikkila, N. Lal, W. Webber, Enhancements of energetic particles near the heliospheric termination shock. Nature , 48 Neugebauer, J. Giacalone, E. Chollet, D. Lario, J. Parker, Astrophys. Ratkiewicz, A. Barnes, G. Molvik, J. Spreiter, S. Stahara, M.

Vinokur, S. Venkataswaran, Astron. ADS Google Scholar. Schwadron, D. McComas, Geophys. Cummings, F. McDonald, B. Webber, Science , Whang, L. The solar wind flow also represents a strong outward pressure. Close to the Sun, the solar wind has a high pressure and can easily push the interstellar medium away from the Sun. Further away from the Sun, the pressure from the Interstellar Medium is strong enough to slow down and eventually stop the flow solar wind from traveling into space.

The place where the speed of the solar wind becomes slower than the speed of sound is called the termination shock.

A similar shock is formed when you run water from a faucet into a sink. When the stream of water hits the sink basin, the flowing water spreads out at a relatively fast speed, forming a disk of shallow water that quickly moves outward, like the solar wind inside the termination shock.

Around the edge of the disk, a shock front or wall of water forms; outside the shock front, the water moves relatively slower, like outside the termination shock. Remember, the water shock is only 2-dimensional or flat. The Boundary of our solar system is 3-dimensional like a sphere.

How does the solar system boundary affect me? This graph depicts the fraction of high energy cosmic rays greater than MeV that pass through the boundary of the solar system. There is a small drop off in the number that make it through to the heliopause. The solar system boundary may be defined as the region where the solar wind slows down and interacts with the Interstellar Medium. If the solar system did not have a boundary, or if the boundary changed size so that it was inside the orbit of the Earth, then there would be at least 4 times the amount of cosmic rays in the solar system.

Luckily the Earth's magnetosphere protects us from some of the cosmic rays that come from outside our solar system. However, if there were a dramatic increase in the number of cosmic rays entering the solar system, it could change the amount of high energy cosmic rays that would be able to reach Earth's surface.

Damage to the Earth's ozone layer could occur and cosmic rays may cause damage and mutation to DNA. What are cosmic rays? These particles could be single protons, nuclei of different atoms or electrons.

Cosmic rays are neither light nor beams of particles, so maybe they should be renamed energetic cosmic particles.

Cosmic rays are often made when a star explodes. This is called a supernova. Some cosmic rays can be produced by the Sun and some can even come from as far away as other galaxies.

These particles are very energetic, but also very small. They rarely directly hit anything as they travel through space, but if they do it can cause nuclear reactions with atoms. These reactions are similar to the activities in particle accelerators.

The Sun's heliosphere protects the planets and other objects in the solar system from some of these dangerous particles. The Earth's magnetosphere and atmosphere protect life on Earth from cosmic rays that make it through the heliosphere.

Studying the heliosphere will help us to prepare adequate shielding during future space travel How do cosmic rays affect DNA? Cosmic rays can seriously damage DNA. If DNA damage cannot be repaired by the cell, the cell could die. If the damage is copied into more cells, then a mutation could occur. Exposure to large amounts of cosmic rays could increase the risks for cancer, cataracts and neurological disorders.

Long term exposure to cosmic rays, or short intense bursts, could affect the evolution of life on Earth. What are energetic neutral atoms? ENAs are formed from particles that are ionized, meaning they have lost electrons. Sometimes, these ions interact with neutral atoms taking the electrons from those neutral atoms and becoming neutral themselves. Since the particle is no longer charged it has equal numbers of protons and electrons it no longer reacts to the magnetic fields, and travels in a straight line from the spot where the interaction occurred.

This interaction is called charge exchange.