Search Publications
Source regions and storm effectiveness of frontside full halo coronal mass ejections
Webb, D. F.; Zhao, X. P.
Full halo coronal mass ejections (CMEs) erupting from the side of the Sun facing Earth, i.e., frontside full halo CMEs, are considered to be a likely cause of major, transient geomagnetic storms. However, this hypothesis has not been tested over a full solar cycle. We compare all frontside full halo CMEs observed during the first half of solar cyc…
Using an MHD simulation to interpret the global context of a coronal mass ejection observed by two spacecraft
Lario, D.; Odstrcil, D.; Riley, Pete +4 more
In late February 1999 the ACE spacecraft observed a coronal mass ejection (CME) at 1 AU, in the ecliptic plane. Thirteen days later, Ulysses observed a CME at 5 AU and 22°S. We present a detailed analysis of the plasma, magnetic field, and composition signatures of these two events. On the basis of this comparison alone, it is not clear that the t…
Observational evidence of new current sheets trailing coronal mass ejections
Webb, D. F.; Riley, P.; Burkepile, J. +1 more
Field line reconnection in the wake of coronal mass ejections (CMEs) is a fundamental aspect of some magnetically driven eruptive flare/CME models, e.g., the standard reconnection model [cf. Svestka and Cliver, 1992]. This model features a growing hot loop arcade beneath a rising X-type neutral point that is connected to the retreating CME. In mod…
Analyses on the geometrical structure of magnetic field in the current sheet based on cluster measurements
Balogh, A.; Baker, D. N.; Wang, X. +5 more
The geometrical structure of the magnetic field is a critical character in the magnetospheric dynamics. Using the magnetic field data measured by the Cluster constellation satellites, the geometrical structure including the curvature radius, directions of curvature, and normal of the osculating planes of the magnetic field lines within the current…
Implications of the observed anticorrelation between solar wind speed and coronal electron temperature
Gloeckler, George; Geiss, Johannes; Zurbuchen, Thomas H.
Electron temperatures at the source of the solar wind are now obtained routinely and continuously from measurements of charge states of solar wind ions with modern solar wind composition spectrometers over a wide range of solar wind speeds. While the general anticorrelation between solar wind speed and electron temperature was previously noted, th…
ULF wave identification in the magnetosheath: The k-filtering technique applied to Cluster II data
Balogh, A.; Belmont, G.; Sahraoui, F. +8 more
The magnetic fluctuations in the magnetosheath are studied, thanks to Cluster II data. The k-filtering technique is applied to explore ULF magnetic fluctuations using STAFF (Spatio-Temporal Analysis of a Field Fluctuations) data. Based on multipoint measurements, the k-filtering technique allows, for the first time, to estimate the Magnetic Field …
A tilted-dipole MHD model of the solar corona and solar wind
Goldstein, M. L.; Usmanov, A. V.
We simulate the three-dimensional structure of the heliosphere during solar activity minimum by specifying boundary conditions at the coronal base. We compare the output of the model with Ulysses observations obtained during the spacecraft's first fast latitude transition in 1994-1995. The polytropic MHD equations are solved for a steady coronal o…
Consequences of proton and alpha anisotropies in the solar wind: Hybrid simulations
Goldstein, Bruce E.; Neugebauer, Marcia; Gary, S. Peter +3 more
Alfvén fluctuations propagating away from the Sun in the solar corona and solar wind transfer energy via cyclotron resonances to ions of successively larger charge-to-mass ratios. This can yield T⟂/T∥ > 1 for each ion species, where the subscripts refer to directions relative to the background magnetic field. If these anis…
A measure from line-of-sight magnetograms for prediction of coronal mass ejections
Falconer, D. A.; Moore, R. L.; Gary, G. A.
From a sample of 17 vector magnetograms of 12 bipolar active regions we have recently found (1) that a measure of the overall nonpotentiality (the overall twist and shear in the magnetic field) of an active region is given by the strong shear length LSS, the length of the portion of the main neutral line on which the observed transverse…
Twenty-three cycles of changing open solar magnetic flux
Lockwood, M.
This paper presents a comparison of various estimates of the open solar flux, deduced from measurements of the interplanetary magnetic field, from the aa geomagnetic index and from photospheric magnetic field observations. The first two of these estimates are made using the Ulysses discovery that the radial heliospheric field is approximately inde…