Fact of the Day


Solar Wind

The solar wind is a stream of charged particles (i.e., a plasma) which are ejected from the upper atmosphere of the sun. It consists mostly of high-energy electrons and protons (about 1 keV) that are able to escape the sun's gravity in part because of the high temperature of the corona and the high kinetic energy particles gain through a process that is not well understood at this time.

Many phenomena are directly related to the solar wind, including geomagnetic storms that can knock out power grids on Earth, aurorae (e.g., Northern Lights) and the plasma tail of a comet always pointing away from the sun. While early models of the solar wind used primarily thermal energy to accelerate the material, by the 1960s it was clear that thermal acceleration alone cannot account for the high speed solar wind. Some additional acceleration mechanism is required, but is not currently known, but most likely relates to magnetic fields in the solar atmosphere.

Earth itself is nominally protected from the solar wind by its magnetic field, which deflects charged particles but also serves as an electromagnetic energy transmission line to the Earth's upper atmosphere and ionosphere in the auroral zones. We only notice the solar wind when it is strong enough for this energy to produce phenomena such as the aurora and geomagnetic storms. Bright auroras strongly heat the ionosphere, causing its plasma to expand into the magnetosphere, increasing the size of the plasma geosphere, and causing escape of atmospheric matter into the solar wind. Geomagnetic storms result when the pressure of plasmas contained inside the magnetosphere is sufficiently large to inflate and thereby distort the geomagnetic field.

The solar wind blows a "bubble" in the interstellar medium (the rarefied hydrogen and helium gas that permeates the galaxy). The point where the solar wind's strength is no longer great enough to push back the interstellar medium is known as the heliopause, and is often considered to be the outer "border" of the solar system. The distance to the heliopause is not precisely known, and probably varies widely depending on the current velocity of the solar wind and the local density of the interstellar medium, but it is known to lie far outside the orbit of Pluto. Scientists hope to gain more perspective on the heliopause from data acquired through the Interstellar Boundary Explorer (IBEX) mission, to be launched in 2008.

Comments

Post a Comment

Popular posts from this blog

18 DAYS: THE MAHBHARATA RETOLD (CONCEPT NOTES by GRANT MORRISON)

Image
This new version of the Mahbharata is set in fantastic, mythic time, at the end of the Dwapara Yuga (Copper Age) and the beginning of the fallen, corrupt Kali Yuga, the Age of Iron. Although historically, the epic is generally thought to refer to events occurring as recently as 9 BC and as long ago as 15 BC (depending on which account you favour), I’d like to place the action much further back into a more fantastical Indian past so that we can take full advantage of the possibilities for action and spectacle on a scale rarely scene. This is like a psychedelic The Lord of the Rings with Star Wars technology. BHARAT
Read more

Fact of the Day

Ice Cream People have been eating ice cream for 3000 years, originally as flavored snow or ice. Ice cream evolved from flavored ices that were popular with the Roman nobility in the 4th century BC. The emperor Nero is known to have imported snow from the mountains and topped it with fruit juices and honey. In the 13th century, Marco Polo was reported to have returned from China with recipes for making water and milk ices. Early colonists poured maple syrup over snow. Both Washington and Jefferson owned a "cream machine for making ice" and Dolly Madison's White House dinner parties were talked about for the "large shining dome of pink ice cream" as the centerpiece. Colonists talked about going to ice cream houses since the 1700s, which weren't generally called ice cream parlors or ice cream stands until the late 1870s. The discovery that salt would lower the freezing point of cracked ice led to the first practical method of making ice cream. Making ice cr
Read more

Where did the Universe come from? Part 3: Why the Big Bang was the most precisely planned event in all of history

In your kitchen cabinet, you've probably got a spray bottle with an adjustable nozzle.  If you twist the nozzle one way, it sprays a fine mist into the air.  You twist the nozzle the other way, it squirts a jet of water in a straight line.  You turn that nozzle to the exact position you want so you can wash a mirror, clean up a spill, or whatever.    If the universe had expanded a little faster, the matter would have sprayed out into space like fine mist from a water bottle - so fast that a gazillion particles of dust would speed into infinity and never even form a single star.    If the universe had expanded just a little slower, the material would have dribbled out like big drops of water, then collapsed back where it came from by the force of gravity.    A little too fast, and you get a meaningless spray of fine dust.  A little too slow, and the whole universe collapses back into one
Read more