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Crossing the termination shock into the heliosheath: magnetic fields
L F Burlaga1, N F Ness, M H Acuña
1NASA-Goddard Space Flight Center, Greenbelt, MD 20771, USA. Leonard.F.Burlaga@nasa.gov
Science (New York, N.Y.)
|September 24, 2005
Summary
Voyager 1 data reveals crossing the termination shock at 94 AU. Magnetic field strength increased significantly, deviating from predictions and showing a Gaussian distribution in the heliosheath.
Area of Science:
- Space Physics
- Heliophysics
- Planetary Science
Background:
- The heliosphere is the vast region of space dominated by the Sun's magnetic field and solar wind.
- The termination shock marks the boundary where the solar wind abruptly slows down.
- Voyager 1's mission provides in-situ measurements of the heliosphere's outer regions.
Purpose of the Study:
- To analyze magnetic field data from Voyager 1 crossing the heliospheric termination shock.
- To characterize the magnetic field properties in the heliosheath.
- To compare observations with theoretical models like Parker's model.
Main Methods:
- In-situ magnetic field measurements by Voyager 1's onboard instruments.
- Analysis of magnetic field strength compression ratio across the termination shock.
- Statistical analysis of magnetic field data in the heliosheath, including distribution and orientation.
Main Results:
- Voyager 1 crossed the termination shock around December 16, 2004, at 94 AU.
- Observed magnetic field compression ratio across the shock was 3.05 ± 0.04.
- Average heliosheath magnetic field strength was 0.136 ± 0.035 nT, ~4.2 times Parker's model prediction.
- Heliosheath magnetic field generally pointed away from the Sun along the Parker spiral.
- Cosmic ray intensity correlated with increased magnetic field strength in the heliosheath.
Conclusions:
- The heliospheric termination shock significantly compresses the interplanetary magnetic field.
- Voyager 1 data indicate a stronger heliosheath magnetic field than predicted by Parker's model.
- The heliosheath's magnetic field structure and its influence on cosmic rays are complex and require further study.
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