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VHM/FGM Instrument Page

Until recently, spacecraft have only been able to measure a limited, two-dimensional section of the heliosphere. This is because spacecraft were confined to stay within the plane of the ecliptic (the plane tilted only 7 degrees from the Sun's equator). Ulysses's unique orbit, achieved with a gravity assist from Jupiter, is 80 degrees inclined to the ecliptic plane which gives the spacecraft a novel vantage point in which to track a 3-dimensional solar heliosphere. One of the fundamental features of the heliosphere is the 3-dimensional structure of the solar magnetic field.

The magnetometer was included on the Ulysses spacecraft to track the spatial and temporal variations of the solar magnetic field. The magnetometer also tracks the polarity of the solar magnetic field. The magnetometer uses two sensors, one a Vector Helium Magnetometer, the other a Fluxgate Magnetometer. Onboard data-processing yields measurements of the magnetic field vector with a time resolution up to 2 vectors/second and a senstivity of .01 - 44,000 nT (nanoTeslas).

Since being turned on in October 1990, the magnetometers have produced a steady stream of observations. Several disturbances in the magnetic field have been tracked, including discontinuities in the field, and shock wave activity. Scientists look forward to even more findings as Ulysses is in its second pass of the Sun. It is during this second pass that solar activity related to the magnetic field will be at its peak.

Last modified October 2, 2000 by Jennifer Bergman.

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