Search Publications
Global network of slow solar wind
Crooker, N. U.; Neugebauer, M.; Antiochos, S. K. +1 more
The streamer belt region surrounding the heliospheric current sheet (HCS) is generally treated as the primary or sole source of the slow solar wind. Synoptic maps of solar wind speed predicted by the Wang-Sheeley-Arge model during selected periods of solar cycle 23, however, show many areas of slow wind displaced from the streamer belt. These area…
Dual periodicities in planetary-period magnetic field oscillations in Saturn's tail
Coates, A. J.; Dougherty, M. K.; Jackman, C. M. +5 more
We examine magnetic field data from 10 apoapsis passes of the Cassini spacecraft during 2006 when the spacecraft explored the midnight and dawn sectors of Saturn's magnetotail to down-tail distances of ∼65 RS (Saturn radius, RS, is 60,268 km). Oscillations in the radial component of the field near the ∼11 hour planetary perio…
Cyclic loss of open solar flux since 1868: The link to heliospheric current sheet tilt and implications for the Maunder Minimum
Owens, M. J.; Lockwood, M.
Open solar flux (OSF) variations can be described by the imbalance between source and loss terms. We use spacecraft and geomagnetic observations of OSF from 1868 to present and assume the OSF source, S, varies with the observed sunspot number, R. Computing the required fractional OSF loss, χ, reveals a clear solar cycle variation, in approximate p…
The first in situ observation of Kelvin-Helmholtz waves at high-latitude magnetopause during strongly dawnward interplanetary magnetic field conditions
ViñAs, A. F.; Goldstein, M. L.; Wang, Y. +3 more
We report the first in situ observation of high-latitude magnetopause (near the northern duskward cusp) Kelvin-Helmholtz waves (KHW) by Cluster on January 12, 2003, under strongly dawnward interplanetary magnetic field (IMF) conditions. The fluctuations unstable to Kelvin-Helmholtz instability (KHI) are found to propagate mostly tailward, i.e., al…
Three-dimensional ray tracing of fast magnetosonic waves
Xiao, Fuliang; Zhou, Qinghua; He, Zhaoguo +1 more
A three dimensional ray tracing of fast magnetosonic (MS) waves is first performed by using a global core density model and a field-aligned density model. Simulating results show that MS waves are primarily confined within a few degrees of the geomagnetic equator due to magnetospheric reflection. MS waves originating from different L-shells on the…
A computational and theoretical analysis of falling frequency VLF emissions
Omura, Yoshiharu; Nunn, David
Recently much progress has been made in the simulation and theoretical understanding of rising frequency triggered emissions and rising chorus. Both PIC and Vlasov VHS codes produce risers in the region downstream from the equator toward which the VLF waves are traveling. The VHS code only produces fallers or downward hooks with difficulty due to …
Time-dependent MHD modeling of the global solar corona for year 2007: Driven by daily-updated magnetic field synoptic data
Liu, Yang; Wu, S. T.; Feng, X. S. +3 more
In this paper, we develop a time-dependent MHD model driven by the daily-updated synoptic magnetograms (MHD-DUSM) to study the dynamic evolution of the global corona with the help of the 3D Solar-Interplanetary (SIP) adaptive mesh refinement (AMR) space-time conservation element and solution element (CESE) MHD model (SIP-AMR-CESE MHD Model). To ac…
Saturn's inner magnetospheric convection pattern: Further evidence
Gurnett, D. A.; Thomsen, M. F.; Tokar, R. L. +7 more
Observations of the radial locations of satellite absorption microsignatures in energetic particle data at Saturn have suggested the existence of an average convection pattern, fixed in local time, that is superimposed on the dominant near-corotation of the inner magnetosphere. Such a pattern should have additional observational consequences, and …
Localized density enhancements in the magnetosheath: Three-dimensional morphology and possible importance for impulsive penetration
Nilsson, H.; Karlsson, T.; Trotignon, J. -G. +3 more
We use Cluster multipoint density measurements, using the spacecraft potential, to identify localized density enhancements (>50%) in the magnetosheath, and estimate their three-dimensional morphology and orientation. Typically one dimension of the density enhancements is shorter than others, is directed perpendicular to the background magnetic …
Estimating the capture and loss of cold plasma from ionospheric outflow
Nilsson, H.; André, M.; Eriksson, A. +9 more
An important source of magnetospheric plasma is cold plasma from the terrestrial ionosphere. Low energy ions travel along the magnetic field lines and enter the magnetospheric lobes where they are convected toward the tail plasma sheet. Recent observations indicate that the field aligned ion outflow velocity is sometimes much higher than the conve…