The biggest halo coronal mass ejection (CME) since the Halloween storm in 2003, which occurred on 2006 December 13, is studied in terms of its solar source and heliospheric consequences. The CME was accompanied by an X3.4 flare, EUV dimmings, and coronal waves. It generated significant space weather effects such as an interplanetary shock, radio bursts, major solar energetic particle (SEP) events, and a magnetic cloud (MC) that were detected by a fleet of spacecraft including STEREO, ACE, WIND, and Ulysses. Reconstruction of the MC with the Grad-Shafranov (GS) method yields an axis orientation oblique to the flare ribbons. Observations of the SEP intensities and anisotropies show that the particles can be trapped, deflected, and reaccelerated by the large-scale transient structures. The CME-driven shock was observed at both the Earth and Ulysses when they were separated by 74 in latitude and 117 in longitude, which is the largest shock extent ever detected. The ejecta seem to have been missed at Ulysses. The shock arrival time at Ulysses is well predicted by an MHD model that can propagate the 1 AU data outward. The CME /shock is tracked remarkably well from the Sun all the way to Ulysses by coronagraph images, type II frequency drift, in situ measurements, and the MHD model. These results reveal a technique that combines MHD propagation of the solar wind and type II emissions to predict the shock arrival time at the Earth, which is a significant advance for space weather forecasting, especially when in situ data become available from the Solar Orbiter and Solar Sentinels.
The Solar Electron and Proton Telescope (SEPT), one of four instruments of the Solar Energetic Particle (SEP) suite for the IMPACT investigation, is designed to provide the three-dimensional distribution of energetic electrons and protons with good energy and time resolution. This knowledge is essential for characterizing the dynamic behaviour of CME associated and solar flare associated events. SEPT consists of two dual double-ended magnet/foil particle telescopes which cleanly separate and measure electrons in the energy range from 30-400 keV and protons from 60-7 000 keV. Anisotropy information on a nonspinning spacecraft is provided by the two separate telescopes: SEPT-E looking in the ecliptic plane along the Parker spiral magnetic field both towards and away from the Sun, and SEPT-NS looking vertical to the ecliptic plane towards North and South. The dual set-up refers to two adjacent sensor apertures for each of the four view directions: one for protons, one for electrons. The double-ended set-up refers to the detector stack with view cones in two opposite directions: one side (electron side) is covered by a thin foil, the other side (proton side) is surrounded by a magnet. The thin foil leaves the electron spectrum essentially unchanged but stops low energy protons. The magnet sweeps away electrons but lets ions pass. The total geometry factor for electrons and protons is 0.52 cm 2 sr and 0.68 cm 2 sr, respectively. This paper describes the design and calibration of SEPT as well as the scientific objectives that the instrument will address.
The basic physical processes that lead to the long‐term modulation of cosmic rays in the heliosphere have been known for many years. However, our knowledge of the relative importance of the various processes is still incomplete. Observations of cosmic rays at high latitudes can be used to improve our understanding of modulation processes. In this paper we present measurements of galactic proton fluxes with energies above 106 MeV made by the Kiel Electron Telescope on board the Ulysses spacecraft during the fast scan from the South polar passage in September 1994 to the North pole in August 1995, under solar minimum conditions. Comparison of proton fluxes at high latitudes and in the ecliptic shows a 20% higher flux in polar regions. The flux increase is not symmetric with respect to the heliographic equator but rather with respect to a surface shifted by 7° South. In such a coordinate system the latitudinal gradient in both hemispheres has a value of (0.33±0.02)%/deg.
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