The December 2006 SEP Events at High Heliospheric Latitudes: the KET/ Ulysses Observations

1. The December 2006 SEP Events at High Heliospheric Latitudes: the KET/Ulysses Observations A. Struminsky (astrum@iki.rssi.ru), I. Zimovets, Institute of Space Research, Moscow, Russia. B. Heber, R. Mueller-Mellin, R. Gomez-Herrero, A. Klassen Christian-Albrechts-Universität Kiel, Germany.

2. General review • In the upper panel we may distinguish three proton intensity increases within three lower energy channels related to the solar events of December 5, 6 and 13 (arrows). The SEP event of December 14 was observed by GOES but it might be below background at Ulysses. • The count rate of the 200-2000 MeV Ulysses channel was normalized to the 165-500 MeV GOES intensity in May-June 2001, when both spacecraft were at heliocentric distances of ~1 AU. • The enhancements within the 200-2000 MeV channel is not visible in the logariphmic scale, but two humps would be seen in the linear scale (next slide). • Vertical lines shows interplanetary shocks. We do not see any effects of shocks on proton intensity time profiles, excepting the lowest energy channel of 5-25 MeV. The 5-25 MeV protons show some enhancement after the shocks on 345 and 351 days. Black -5-25 MeV; Red 38-80 MeV; Blue 80-125 MeV; Cyan 250-2000 MeV

3. Comparison with observations at 1 AU Red -165-500 MeV GOES Black -250-2000 MeV Ulysses • The largest maximum intensity within 165-500 MeV was registered on December 13, the SEP event accompanied by Ground Level Enhancement (GLE), but the largest event was registered by Ulysses on December 6 • The onset and time profiles of higher energy channels of Ulysses and GOES coinsided in the December 5 event. A convolution of source and propagation function was identical for protons of ~200 MeV observed during several hours in distant points of the heliosphere. This fact ruled a transport of protons within vicinity of the shock front on December 5!!! • A sharp rise of GOES intensity at 20:30 UT (less than two hours after hard X-ray maximum) on December 6 indicates that the Earth has become much better connected to the source than Ulysses. • A time scale of two hours corresponds to shock propagation characteristic time and might be reflect a role of the shock transport of SEP to Earth on December 6. Conditions of particle propagation to Ulysses were not changed significantly.

4. Comparison with July 2000 event • The KET/Ulysses observations of 250-2000 MeV protons • Modulation during the solar cycle of cosmic ray intensities • Nearly the same enhancement above background despite solar maximum in 2000 and solar minimum in 2006

5. Comparison with December 2001 event • The KET/Ulysses observations of 250-2000 MeV protons • Modulation during the solar cycle, • Nearly the same enhancement above background

6. Ulysses observations at high latitudes & STEREO and GOES observations at the Earth • Red – the GOES intensity of 40-80 MeV protons (left log Y-axis) • Black – the STEREO intensity of 40-60 MeV protons (left log Y-axis) • Blue – the Ulysses intensity of 38-125 MeV protons (left log Y-axis) • Cyan – the Ulysses intensity of 250-2000 MeV protons (right linear Y-axis)

7. KET/Ulysses observations in December 2006 and September 2000 September 2000 5-25 MeV – black 38-80 MeV – red 80-125 MeV – blue December 2006 5-25 MeV – grey 38-80 MeV – yellow 80-125 MeV – cyan • The time profiles are shifted to get the same onset time of the 80-125 MeV channel during the compared events. • As a result we see a similar time profiles in this energy band till onset of the December 6 event. • Contrary, lower energies on December 5 show a time delay in comparison with the 2000 September 12 event. Propagation conditions in December 2006 were complicated.

8. KET/Ulysses observations in December 2006 and November 2001 November 2001 5-25 MeV – black 38-80 MeV – red 80-125 MeV – blue December 2006 5-25 MeV – grey 38-80 MeV – yellow 80-125 MeV – cyan • The time profiles are shifted to get the same onset time of the 80-125 MeV channel during the compared events. • As a result we see a similar time profiles in this energy band till onset of the December 6 event. • Contrary, lower energies on December 5 show a time delay in comparison with the 2000 September 12 event. Propagation conditions in December 2006 were complicated.

9. CONCLUSIONS • Comparison of Ulysses and GOES proton time profiles shows that on 2006 December 5 the proton propagation to high latitudes and distant longitudes for 250-2000 MeV was the same. • A propagation of <80 MeV protons was complicated to high latitudes on December 5. This effect has a clear energetic (rigidity?) dependence. • A value of the maximum intensity within 38-125 MeV doesn’t contradict to the upper limit characteristic for the previous Ulysses events. • The reservoir effect is delayed in comparison with previous cases due to complicated transport to high latitudes in December 2006 and a contribution of several sources to the time profiles. The Ulysses/KET project is supported under grant No. 50OC0105 by the German Bundesminister für Wirtschaft through the Deutsches Zentrum für Luft- und Raumfahrt (DLR).