IMF and SWP Data Description

The interplanetary magnetic field ( IMF) is a part of the Sun's magnetic field that is carried into interplanetary space by the http://pluto.space.swri.edu/IMAGE/glossary/solar_wind.html solar wind. The interplanetary magnetic field lines are said to be "frozen in" to the solar wind plasma. Because of the Sun's rotation, the IMF, like the solar wind, travels outward in a spiral pattern that is often compared to the pattern of water sprayed from a rotating lawn sprinkler. The IMForiginates in regions on the Sun where the magnetic field is "open"--that is, where field lines emerging from one region do not return to a conjugate region but extend virtually indefinitely into space. The direction (polarity, sense) of the field in the Sun's northern hemisphere is opposite that of the field in the southern hemisphere. (The polarities reverse with each solar cycle.)

The IMFis a vector quantity with three directional components, two of which (Bxand By) are oriented parallel to the ecliptic. The third component-- Bz--is perpendicular to the ecliptic and is created by waves and other disturbances in the solar wind. When the '''IMF''' and geomagnetic field lines are oriented opposite or "antiparallel" to each other, they can "merge" or "reconnect," resulting in the transfer of energy, mass, and momentum from the solar wind flow to http://pluto.space.swri.edu/IMAGE/glossary/magnetosphere.html magnetosphere. The strongest coupling --with the most dramatic magnetospheric effects-- occurs when the Bz component is oriented southward.

The IMFis a weak field, varying in strength near the Earth from 1 to 37 nT, with an average value of ~6 nT.

The database contents

The collected heliospheric IMFand SWPdata sets have been provided by Principal Investigator J.H. King (Director, National Space Science Data Center. All parameters have been quality controlled, corrected and, as far as possible, written in a similar format.

The interplanetary field and plasma data were all obtained by spacecraft in geocentric or selenocentric orbit when those spacecraft were outside the Earth's bow shock.

WORD DESCRIPTION	UNITS
Bx, GSE	nT
By, GSM	nT
Bz, GSM	nT
Ion density	Per cm3
Flow speed	Km/s