DETERMINATION OF THE HELIOSPHERIC RADIAL MAGNETIC FIELD FROM THE STANDOFF DISTANCE OF A CME-DRIVEN SHOCK OBSERVED BY THE STEREO SPACECRAFT
- NASA GSFC, Greenbelt, MD 20771 (United States)
- Space Science Division, U.S. Naval Research Laboratory, Washington, DC 20375 (United States)
We report on the determination of radial magnetic field strength in the heliocentric distance range from 6 to 120 solar radii (R {sub Sun }) using data from Coronagraph 2 (COR2) and Heliospheric Imager I (HI1) instruments on board the Solar Terrestrial Relations Observatory spacecraft following the standoff-distance method of Gopalswamy and Yashiro. We measured the shock standoff distance of the 2008 April 5 coronal mass ejection (CME) and determined the flux-rope curvature by fitting the three-dimensional shape of the CME using the Graduated Cylindrical Shell model. The radial magnetic field strength is computed from the Alfven speed and the density of the ambient medium. We also compare the derived magnetic field strength with in situ measurements made by the Helios spacecraft, which measured the magnetic field at the heliocentric distance range from 60 to 215 R {sub Sun }. We found that the radial magnetic field strength decreases from 28 mG at 6 R {sub Sun} to 0.17 mG at 120 R {sub Sun }. In addition, we found that the radial profile can be described by a power law.
- OSTI ID:
- 22086498
- Journal Information:
- Astrophysical Journal, Vol. 758, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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