Ulysses HISCALE Publications and Presentations

 

Particle Anisotropy During the Onset of a Solar Event

 

Authors: G. M. Simnett and S. J. Tappin, University of Birmingham, U.K.; L. J. Lanzerotti, AT&T Bell Laboratories, Murray Hill, NJ; R. E. Gold and E. C. Roelof, Johns Hopkins University Applied Physics Laboratory, Laurel, MD; K. A. Anderson, Space Sciences Laboratory, University of California-Berkeley; T. P. Armstrong, University of Kansas, Lawrence, KS; R. P. Lin, Space Sciences Laboratory, University of California-Berkeley; S. M. Krimigis, Johns Hopkins University Applied Physics Laboratory, Laurel, MD; M. Pick, Observatoire de Paris, Meudon, France; E. T. Sarris, University of Thrace, Xanthi, Greece.

 

Presented at: European Geophysical Society Meeting, Edinburgh, Scotland, April 1992.

Solar Activity around December 1, 1990

 

Notes:

Main active regions around E50 solar longitude.
Region 6387 (S25) and Region 6390 (N33).
No identified optical flare with GOES x-ray flux above C5 since 10:00 UT, November 20.
There was an unidentified M1.2 x-ray flare around 01.05 UT on December 1.
The December 1 particle event at Ulysses was the largest event seen in 1990.

 

Figures:

(Some of the figures were originally in color; these black and white copies are somewhat degraded in quality.)

 

	Figure 1.		Figure 2.
	Figure 3.		Figure 4.
	Figure 5.		Figure 6.
(figure not available)	Figure 7. Anisotropy of P7 - 1060-5000 keV ions		Figure 8.
	Figure 9.		Figure 10.
	Figure 11.		Figure 12.
	Figure 13.

 

 

Conclusions:

 

• The interplanetary medium is populated with ions less than a few MeV which are largely streaming away from the Sun.
• The event is seen earlier at IMP8 than at Ulysses.
• There is evidence that some of the collimated ion fluxes are back-scattered beyond the spacecraft and are reflected back.
• The ions are generally field-aligned.
• The event is consistent with the spacecraft moving through different flux-tubes populated with energetic solar particles which are for the most part streaming outwards.
• This event, while being relatively weak in electrons, nevertheless was accompanied by significant fluxes up to 300 keV.
• There appeared to be no change in the proton/alpha particle ratio when the spacecraft entered a new flux-tube.