Magnetic Breaches
Jan 05, 2009

NASA launched the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission on February 17, 2007. The spacecraft continues to monitor Earth's magnetosphere so that planetary scientists can figure out how intense ion storms are created. It is important to understand these explosive outbursts in our planet's magnetic field, because they disrupt communications, overload electrical transmission lines, and cause radiation emissions that can reach the ground.

According to conventional theory, when the magnetosphere "suddenly releases vast amounts of stored solar wind energy," the aurora becomes widespread, intense, more disturbed, and charged particles (electric currents) flow at higher energies. These so-called "substorms" begin in small regions of the magnetosphere but enlarge within minutes, enveloping an immense area. Full-blown magnetic storms are rare, but smaller substorms in the polar regions are more frequent, sometimes hours apart.

Recently, NASA researchers announced that THEMIS discovered a "breach" in Earth's magnetic field larger than anything seen before. Project scientist David Sibeck said: "At first I didn't believe it. This finding fundamentally alters our understanding of the solar wind-magnetosphere interaction."

A strong magnetic disturbance is usually observed when a bright aurora is seen. The field can be greater than that from a magnetic storm but on a local scale, fading more quickly toward the equator. In 1903, Kristian Birkeland's observations in the Arctic led him to propose that electricity energizing the aurora flowed parallel to the auroral formation. Since electric current flows in a closed circuit, and since the currents and the glow seemed to be caused by processes in distant space, he theorized that they came down from space at one end of the auroral arc and back out to space at the other.

In 1973, the U.S. Navy satellite Triad flew through this electrically charged layer. The onboard magnetometer found two electric currents in gigantic sheets, each carrying a million amperes or more, one descending on the auroral zone's morning side and one ascending on the evening side. Since Birkeland's research had predicted the currents that link Earth with space they were called Birkeland currents.

According to the scientists from THEMIS, the "breach" started when magnetic fields from the solar wind wrapped around the magnetosphere and cracked it open. The "cracking" was induced by "magnetic reconnection."

Space physicist Wenhui Li from the University of New Hampshire was quoted as saying: "The opening was huge—four times wider than Earth itself."

Another New Hampshire researcher, Jimmy Raeder said: "10^27 particles per second were flowing into the magnetosphere—that's a 1 followed by 27 zeros. This kind of influx is an order of magnitude greater than what we thought was possible."

Physical processes require an energy input that then changes from one form to another. Consensus views also suggest that this holds true for geomagnetic substorms. It is no accident, according to scientists, that they take place when the interplanetary magnetic field (IMF) slants to the South. The southern orientation means faster "reconnection" between interplanetary and terrestrial field lines, initiating rapid release of magnetic fields and plasma from Earth's sunlit side.

How this energy is released, as well as what starts the process, are still controversial subjects. Energy in nature cannot be destroyed, as the conservation of energy law states, it changes from one form to another. When electricity powers a motor, it is converted to kinetic energy. When friction stops motion, its kinetic energy converts to heat. Magnetic energy is also thought to reappear in different forms. Some becomes heat, increasing the velocity of plasma ions and electrons. Some of the energy ends up driving electric currents in a circuit linking the plasma sheet with Earth.

Don Scott's commentary about magnetic reconnection should be kept in mind when reading reports from NASA about Earth's interaction with the plasma stream (commonly called the solar wind) and electromagnetic energy radiating from the Sun:

1. Magnetic field lines are only convenient concepts, nothing more. They are not loci or contours of constant magnetic flux density (field strength). They just indicate the field’s direction. In regions where they are close together the field is stronger than where they are widely separated.

2. Therefore, sketching magnetic field lines can help us visualize the shape and strength of magnetic fields. They can help us to sketch the net result (vector sum) if and when two or more fields interact (are superimposed on each other).

3. We can only draw magnetic field lines (in cases not involving permanent ferromagnetic magnets) by considering the electric currents that create those fields.

4. Magnetic lines of force do not actually exist in three-dimensional space anymore than lines of latitude or longitude do.

5. If a field moves from one instant to another, we cannot use "streaming video" to watch a given line move and change shape. This is because we must redraw a complete set of lines at each instant. It isn’t the same line that has moved, it is the field that has changed. The two sets of lines describe the field at those two different times.

6. Magnetic lines of force do not move anymore than lines of longitude do. A determined unwillingness to recognize this fact has led to the idea that lines move toward each other, touch, merge, and then release energy. I have said many times that this last notion, if applied to circles of longitude that come together and "merge" at Earth’s poles, could be proposed as causing gravitational energy releases at those locations.

There is no such process as "magnetic merging" or "reconnection" of magnetic field lines in the real world.

Written by Stephen Smith from an idea submitted by Mark Love