Search Publications
Quasistatic electric field structures and field-aligned currents in the polar cusp region
Jacobsen, K. S.; Moen, J. I.; Pedersen, A.
Cluster data have been examined for quasi-stationary electric field structures and field-aligned currents (FACs) in the vicinity of the dayside cusp region. We have related the measurements to the Region 1/Region 2 (R1/R2) current system and the cusp current system. It has been theoretically proposed that the dayside R1 current may be located on o…
Using a global magnetohydrodynamic model to study the start of the substorm recovery phase
Baker, D. N.; Wiltberger, M.; Farr, N. L.
Magnetospheric substorms are a key manifestation of the transfer of energy from the solar wind to the Earth. Substorms consist of a loading of energy from the solar wind via magnetic reconnection and then a rapid release of that energy. One of the results of this energy release is the intense brightening of the aurora observed in the Earth's high-…
Energetic electron response to ULF waves induced by interplanetary shocks in the outer radiation belt
Zong, Q. -G.; Daly, P. W.; Baker, D. N. +7 more
Strong interplanetary shock interactions with the Earth's magnetosphere have great impacts on energetic particle dynamics in the magnetosphere. An interplanetary shock on 7 November 2004 (with the maximum solar wind dynamic pressure of ∼70 nPa) was observed by the Cluster constellation to induce significant ULF waves in the plasmasphere boundary, …
Nonlinear mechanisms of lower-band and upper-band VLF chorus emissions in the magnetosphere
Katoh, Yuto; Omura, Yoshiharu; Hikishima, Mitsuru +2 more
We develop a nonlinear wave growth theory of magnetospheric chorus emissions, taking into account the spatial inhomogeneity of the static magnetic field and the plasma density variation along the magnetic field line. We derive theoretical expressions for the nonlinear growth rate and the amplitude threshold for the generation of self-sustaining ch…
Radial evolution of nonthermal electron populations in the low-latitude solar wind: Helios, Cluster, and Ulysses Observations
Maksimovic, Milan; Štverák, Štěpán; Marsch, Eckart +3 more
We have performed a statistical study of a substantial amount of solar wind electron velocity distribution functions (eVDFs). In our data set, we combine measurements acquired onboard three spacecrafts (Helios, Cluster II, and Ulysses) in the low ecliptic latitudes covering the heliocentric distance from 0.3 up to 4 AU. In this study, we focus on …
Ion heating resulting from pickup in magnetic reconnection exhausts
Lin, R. P.; Phan, T. D.; Lepri, S. T. +6 more
The heating of ions downstream of the x-line during magnetic reconnection is explored using full-particle simulations, test particle simulations, and analytic analysis. Large-scale particle simulations reveal that the ion temperature increases sharply across the boundary layer that separates the upstream plasma from the Alfvénic outflow. This boun…
Response of Jupiter's and Saturn's auroral activity to the solar wind
Crary, F.; Cecconi, B.; Lamy, L. +18 more
While the terrestrial aurorae are known to be driven primarily by the interaction of the Earth's magnetosphere with the solar wind, there is considerable evidence that auroral emissions on Jupiter and Saturn are driven primarily by internal processes, with the main energy source being the planets' rapid rotation. Prior observations have suggested …
CME interactions with coronal holes and their interplanetary consequences
Gopalswamy, N.; Yashiro, S.; Mäkelä, P. +2 more
A significant number of interplanetary shocks (~17%) during cycle 23 were not followed by drivers. The number of such ``driverless'' shocks steadily increased with the solar cycle with 15%, 33%, and 52% occurring in the rise, maximum, and declining phase of the solar cycle. The solar sources of 15% of the driverless shocks were very close the cent…
Oblique propagation of whistler mode waves in the chorus source region
Gurnett, D. A.; Pickett, J. S.; Santolík, O. +2 more
Whistler mode chorus has been shown to play a role in the process of local acceleration of electrons in the outer Van Allen radiation belt. Most of the quasi-linear and nonlinear theoretical studies assume that the waves propagate parallel to the terrestrial magnetic field. We show a case where this assumption is invalid. We use data from the Clus…
Bulk properties of the slow and fast solar wind and interplanetary coronal mass ejections measured by Ulysses: Three polar orbits of observations
McComas, D. J.; Forsyth, R. J.; Gosling, J. T. +2 more
We examined plasma and magnetic field observations from all three Ulysses polar orbits of the Sun to study the properties of the slow and fast solar wind and interplanetary coronal mass ejections (ICMEs). We derived equations to characterize the radial and latitudinal variations for these three types of heliospheric plasma and identify distinguish…