Search Publications

Energetic particle abundances at CIR shocks

Fränz, M.; Keppler, E.; Mason, G. M. +3 more

The forward and reverse shocks that bound corotating interaction regions (CIRs) travel into different solar wind regimes. In order to test whether the energetic ions associated with the CIR shocks reflect the ambient solar wind, we investigate the elemental composition of 0.1-4.0 MeV/N ions in CIRs observed from 1 to 5 AU with instrumentation on b…

Current sheet control of recurrent particle increases at 4-5 AU

Lario, D.; Balogh, A.; Maksimovic, M. +5 more

We examine the relation between the current sheet as derived from observations of the Sun's neutral line, and recurrent particle increases associated with co-rotating interactions regions (CIR) at 4 to 5 AU radial distance as observed by the Ulysses spacecraft during its first out-of-ecliptic orbit around the Sun. We compare observations during th…

Coronal magnetic field topology and source of fast solar wind

McComas, D.; Guhathakurta, M.; Thompson, B. +2 more

We have developed a steady state, 2D semi-empirical MHD model of the solar corona and the solar wind with many surprising results. This model for the first time shows, that the boundary between the fast and the slow solar wind as observed by Ulysses beyond 1 AU, is established in the low corona. The fastest wind observed by Ulysses (680-780 km/s) …

Correction to “The interplanetary events of January-May, 1997 as inferred from energetic particle data, and their relationship with solar events”

St. Cyr, O. C.; Cane, H. V.; Richardson, I. G.

O-Mode Emission at the Io Torus: A Real or Virtual Source?

MacDowall, R. J.; Farrell, W. M.; Hess, R. A.

We examine the nature of an ordinary (o-mode) emission observed near the Io plasma torus during the 1992 Ulysses encounter with Jupiter. The emission appears to intensify by factors of 10-100 in local torus density depletions. We examine whether these intensifications are due to local generation within the density depletion or reflection of a remo…

SOHO/EIT observations of an Earth-directed coronal mass ejection on May 12, 1997

St. Cyr, O. C.; Plunkett, S. P.; Michels, D. J. +3 more

An earth-directed coronal mass ejection (CME) was observed on May 12, 1997 by the SOHO Extreme ultraviolet Imaging Telescope (EIT). The CME, originating north of the central solar meridian, was later observed by the Large Angle Spectrometric Coronagraph (LASCO) as a “halo” CME: a bright expanding ring centered about the occulting disk. Beginning a…

The Sun's total irradiance: Cycles, trends and related climate change uncertainties since 1976

Fröhlich, Claus; Lean, Judith

A composite record of the Sun's total irradiance compiled from measurements made by five independent space-based radiometers since 1978 exhibits a prominent 11-year cycle with similar levels during 1986 and 1996, the two most recent minimum epochs of solar activity. This finding contradicts recent assertions of a 0.04% irradiance increase from the…

Ulysses' return to the slow solar wind

Forsyth, R.; Balogh, A.; McComas, D. J. +9 more

After ten long years of wandering the uncharted seas, Ulysses returned to his home port of Ithaca. Similarly, after its unprecedented five year odyssey through the previously uncharted regions over the poles of the Sun, the Ulysses spacecraft has returned to the slow, variable solar wind which dominates observations near the ecliptic plane. Solar …

Geomagnetic storms caused by coronal mass ejections (CMEs): March 1996 through June 1997

St. Cyr, O. C.; Paswaters, S. E.; Simnett, G. M. +7 more

(1) All but two geomagnetic storms with Kp ≥ 6 during the operating period (March 1996 through June 1997) of the Large Angle Spectroscopic Coronagraph (LASCO) experiment on the Solar and Heliospheric Observatory (SOHO) spacecraft can be traced to Coronal Mass Ejections (CMEs). (2) These geomagnetic storms are not related to high speed solar wind s…

X-ray coronal changes during Halo CMEs

St. Cyr, O. C.; Webb, D. F.; Lemen, J. R. +2 more

Using the Yohkoh soft X-ray images, we examine the coronal structures associated with “halo” coronal mass ejections (CMEs). These may correspond to events near solar disk center. Starting with a list of eleven confirmed halo CMEs over the time range from December 1996 through May 1997, we find seven with surface features identifiable in soft X-ray…