Search Publications
ULF wave electromagnetic energy flux into the ionosphere: Joule heating implications
Angelopoulos, V.; Bonnell, J. W.; Hartinger, M. D. +2 more
Ultralow-frequency (ULF) waves—in particular, Alfvén waves-transfer energy into the Earth's ionosphere via Joule heating, but it is unclear how much they contribute to global and local heating rates relative to other energy sources. In this study we use Time History of Events and Macroscale Interactions during Substorms satellite data to investiga…
Survey of Saturn Z-mode emission
Gurnett, D. A.; Persoon, A. M.; Wahlund, J. -E. +6 more
Because of the role of Z-mode emission in the diffusive scattering and resonant acceleration of electrons, we conduct a survey of intensity in the Saturn inner magnetosphere. Z mode is primarily observed as "5 kHz" narrowband emission in the lower density regions where the ratio of cyclotron to plasma frequency, fc/fp > 1 …
Planetary period oscillations in Saturn's magnetosphere: Examining the relationship between abrupt changes in behavior and solar wind-induced magnetospheric compressions and expansions
Coates, A. J.; Dougherty, M. K.; Cowley, S. W. H. +2 more
We examine planetary period oscillations (PPOs) observed in Saturn's magnetospheric magnetic field data from the time of Saturn's equinox in 2009. In particular, we focus on the time period commencing February 2011, when the oscillations started to display sudden and unexpected changes in behavior at ~100-200 day intervals. These were characterize…
Characterizing the low-altitude magnetic belt at Venus: Complementary observations from the Pioneer Venus Orbiter and Venus Express
Luhmann, J. G.; Russell, C. T.; Wei, H. Y. +4 more
Using Venus Express, Zhang et al. (2012b) identified strong magnetic field enhancements at low altitudes over the north polar region of Venus as giant flux ropes. Strong fields at low altitudes were also observed during the Pioneer Venus Orbiter mission, but at low latitudes near the subsolar and midnight regions. We examine the possibility that t…
Modeling the interaction between convection and nonthermal ion outflows
Wiltberger, M.; Lotko, W.; Varney, R. H.
Initial demonstrations of an ionosphere/polar wind model including a phenomenological treatment of transverse heating by wave particle interactions (WPIs) are presented. Tests with fixed WPI parameters in a designated heating region on the dayside with time-varying convection show that the parameters of the resulting nonthermal ion outflow are str…
Solar zenith angle-dependent asymmetries in Venusian bow shock location revealed by Venus Express
Zhang, Tielong; Rong, Zhaojin; Futaana, Yoshifumi +8 more
It has been long known that the Venusian bow shock (BS) location is asymmetric from the observations of the long-lived Pioneer Venus Orbiter mission. The Venus Express (VEX) mission crossed BS near perpendicularly not only in the terminator region but also in the near-subsolar and tail regions. Taking the advantage of VEX orbit geometry, we examin…
Evidence for a seasonally dependent ring plasma in the region between Saturn's A Ring and Enceladus' orbit
Gurnett, D. A.; Persoon, A. M.; Kurth, W. S. +2 more
Equatorial electron density measurements from the Cassini Radio and Plasma Wave Science experiment are derived from the upper hybrid resonance frequency from Saturn Orbit Insertion (SOI) on 1 July 2004 through 21 May 2013. These densities are used to determine the characteristics of the plasma in the inner magnetosphere of Saturn between the outer…
Deriving plasma densities in tenuous plasma regions, with the spacecraft potential under active control
Andriopoulou, M.; Nakamura, R.; Baumjohann, W. +2 more
Variations of the floating potential on spacecraft are often used to derive plasma densities, complementing the plasma instrument measurements. All spacecraft of the Cluster mission are equipped with Active Spacecraft POtential Control (ASPOC) instruments that control the spacecraft potential. Although the ASPOC operation increases the accuracy of…
Asymmetric ionospheric outflow observed at the dayside magnetopause
Glassmeier, K. -H.; Zhang, H.; Zong, Q. -G. +4 more
An important source of the terrestrial magnetospheric plasma is the Earth's ionospheric outflows from the high-latitude regions of both hemispheres. The ionospheric ion outflows have rarely been observed at the dayside magnetopause. We report Cluster observations of the ionospheric ion outflows observed at the dayside magnetopause. The low-energy …
Internal structure of a coronal mass ejection revealed by Akatsuki radio occultation observations
Isobe, H.; Imamura, T.; Häusler, B. +6 more
A coronal mass ejection (CME) was observed at the heliocentric distance of 12.7 Rυ by radio occultation measurements using the Akatsuki spacecraft. The temporal developments of the bulk velocity and the electron column density along the raypath traversing the CME were obtained, and under the assumption that the irregularities are transp…