Search Publications
Reducing heliospheric magnetic flux from coronal mass ejections without disconnection
Crooker, N. U.; Gosling, J. T.; Kahler, S. W.
Until 1995, disconnection at the Sun was thought to be the only solution to the problem of balancing the magnetic flux coronal mass ejections (CMEs) added to the heliosphere, in spite of the fact that the expected solar wind signature of disconnection was rare. Disconnection was pictured as merging between open field lines to create completely dis…
Detection of a Supernova Signature Associated with GRB 011121
Piro, L.; Axelrod, T. S.; Frontera, F. +20 more
Using observations from an extensive monitoring campaign with the Hubble Space Telescope, we present the detection of an intermediate-time flux excess that is redder in color relative to the afterglow of GRB 011121, currently distinguished as the gamma-ray burst with the lowest known redshift. The red ``bump,'' which exhibits a spectral rollover a…
The solar wind composition throughout the solar cycle: A continuum of dynamic states
Zurbuchen, T. H.; Gloeckler, G.; Fisk, L. A. +1 more
Variations in the speed and elemental and ionic charge composition of the solar wind are reported throughout the solar cycle, as observed by the SWICS instrument on Ulysses. The apparent bimodal nature of the solar wind during the solar minimum does not persist throughout the solar cycle. Rather, with increasing solar activity, a continuum of sola…
Sources of the solar wind at solar activity maximum
Smith, E. J.; Neugebauer, M.; Zurbuchen, T. H. +2 more
The photospheric sources of solar wind observed by the Ulysses and ACE spacecraft from 1998 to early 2001 are determined through a two-step mapping process. Solar wind speed measured at the spacecraft is used in a ballistic model to determine a foot point on a source surface at a solar distance of 2.5 solar radii. A potential-field source-surface …
The Faint Optical Afterglow and Host Galaxy of GRB 020124: Implications for the Nature of Dark Gamma-Ray Bursts
Piro, L.; Axelrod, T. S.; Frontera, F. +24 more
We present ground-based optical observations of GRB 020124 starting 1.6 hr after the burst, as well as subsequent Very Large Array and Hubble Space Telescope (HST) observations. The optical afterglow of GRB 020124 is one of the faintest afterglows detected to date, and it exhibits a relatively rapid decay, Fν~t-1.60+/-0.04, f…
GRB 011121: A Massive Star Progenitor
Wieringa, M. H.; Axelrod, T. S.; Frontera, F. +29 more
Of the cosmological gamma-ray bursts, GRB 011121 has the lowest redshift, z=0.36. More importantly, the multicolor excess in the afterglow detected in the Hubble Space Telescope (HST) light curves is compelling observational evidence of an underlying supernova. Here we present near-infrared and radio observations of the afterglow, and from our com…
Ulysses' second fast-latitude scan: Complexity near solar maximum and the reformation of polar coronal holes
Balogh, A.; Reisenfeld, D. B.; McComas, D. J. +5 more
Ulysses' second fast latitude scan, near solar maximum, comprises a complicated mixture of solar wind flows from a variety of sources at high southern as well as low heliolatitudes. In contrast, observations northward of ~40° N show the reformation of relatively steady fast solar wind flows, which are virtually indistinguishable from the polar cor…
Phase-steepened Alfvén waves, proton perpendicular energization and the creation of magnetic holes and magnetic decreases: The ponderomotive force
Lakhina, G. S.; Tsurutani, B. T.; Goldstein, B. E. +6 more
Solar wind protons detected within Magnetic Holes (MHs) and Magnetic Decreases (MDs) are found to be preferentially heated perpendicular to B0. The MHs/MDs are associated with the phase-steepened edges of nonlinear Alfvén waves. The proton anisotropies can lead to the proton cyclotron and mirror mode plasma instabilities. We examine the…
Modeling the heliospheric current sheet: Solar cycle variations
Riley, Pete; Linker, J. A.; Mikić, Z.
In this report we employ an empirically driven, three-dimensional MHD model to explore the evolution of the heliospheric current sheet (HCS) during the course of the solar cycle. We compare our results with a simpler ``constant-speed'' approach for mapping the HCS outward into the solar wind to demonstrate that dynamic effects can substantially de…
On electron acceleration at CIR related shock waves
Mann, G.; Keppler, E.; Roelof, E. C. +1 more
The interaction of fast and slow speed solar wind streams leads to the formation of so-called corotating interaction regions (CIRs) in the heliosphere. These CIRs are often associated with shock waves, at which electrons are accelerated as observed by the Ulysses spacecraft. A correlation between the ratio of energetic electron fluxes at the cross…