Solar Activity

While most people are familiar with the layers of the earth’s atmosphere most people are not aware that there is an invisible boundary ~ 60,000 km above the earth called the magnetopause that makes life as we know it possible. The Magnetopause separates particles and magnetic fields connected to the sun from those connected to the Earth. Inside the magnetopause invisible lines of force extend outward from the earth’s north and south magnetic poles. The magnetosphere exists because the Earth is believed to behave like a huge magnet due to its mostly metallic molten interior. As the Earth rotates, the hot core generates strong electric currents that create the magnetosphere. The magnetosphere forms a protective shell around the Earth.

Like our ozone blocking ultra violet radiation from the Earth, the magnetosphere acts as a shield to charged particles that are streaming from the Sun. These particles which make up the solar wind constantly travel outward from the Sun and are deflected around the earth by our magnetosphere. The bow shock is the outermost boundary and serves to slow down and partially deflect the solar wind flow. As these particles slow down they pile up in an area called the magnetosheath. The magnetopause is the upper boundary of the magnetic field lines in the magnetosphere.

Without the magnetosphere these particles could continue toward the Earth’s surface over time stripping away the atmosphere and drastically changing surface conditions on the planet. The magnetosphere does not provide perfect protection from the solar wind. Here gases in the upper atmosphere are ionized producing aurora. In addition the pressure on the magnetosphere due to the solar wind acts to compress the sunward side of the magnetosphere and extend the side away from the sun. Particles along the magnetosphere are energized and may move toward the poles to add to the aurora. During solar storms (flares, CME’s) the magnetosphere can be compressed even further energizing even more particles and creating more intense aurora. Currently scientists are collecting and interpreting satellite data in an attempt to more fully understand the interactions between solar wind and the magnetosphere/upper atmosphere. It has been discovered that at the upper boundary of the magnetosphere the bow shock and magnetopause move as a result of changes in solar wind. The current research is being done to answer a variety of questions.

Scientist at NASA and other istitutions are working to answer these and other questions by using data that has been collected by a number of satellites. Commonly used satellites include: Wind, Geotail, Sampex and a host of others.

WIND Wind was launched on November 1, 1994. WIND is positioned in an orbit outside the magnetosphere where it can monitor the solar wind. WIND provides data for plasma, particles, and magnetic fields between the Sun and the Earth. WIND data allows scientists to study changes in solar wind and magnetic fields associated with solar activity.

GEOTAIL The GEOTAIL satellite was launched on July 24, 1992. The primary purpose of this mission is to study the structure and dynamics of the tail region of the magnetosphere. Scientist are still working to gain a complete understanding of the flow of energetic particles through the tail region. GEOTAIL monitors magnetic fields, plasma and energetic particles.

SAMPEX SAMPEX was launched in July 1992. SAMPEX studies the energy, composition, and charge states of particles from supernova explosions in the distant reaches of the galaxy, from the heart of solar flares, and from the depths of nearby interstellar space. It also monitors closely the magnetospheric particle populations which plunge occasionally into the middle atmosphere of the Earth, thereby ionizing neutral gases and altering the atmospheric chemistry. A key part of SAMPEX is to use the magnetic field of the earth as an essential component of the measurement strategy. The Earth's field is used as a giant magnetic spectrometer to separate different energies and charge states of particles as SAMPEX executes its near polar orbit.

In order to view more detailed information and data visit the homepages for these satellites that are listed below.
WIND (Link to http://www-istp.gsfc.nasa.gov/istp/wind/ )
GEOTAIL (Link to http://www.gtl.isas.ac.jp/ )
SAMPEX (Link to: http://lepsam.gsfc.nasa.gov/www/sampex.html)

The general public is also becoming interested in scientific studies of the solar wind and magnetosphere interactions due to recent satellite and power system failures that may be attributed to solar events. During May 1998, SAMPEX and other satellites monitored solar, solar wind and magnetosphere changes . The Galaxy 4 communications satellite had electronic malfunctions and was lost during early May 1998.