Search Publications
Ion cyclotron waves in the high altitude cusp: CLUSTER observations at varying spacecraft separations
Balogh, A.; Dandouras, I.; Lavraud, B. +5 more
We have analysed high-resolution Cluster magnetic field data during three high-altitude cusp crossings in 2001 and 2002. The Cluster separations for these crossings varied between 100 and 600 km and therefore provided an unique opportunity to study wave properties at different length scales. In the cusp Cluster sees frequent intervals of magnetic …
Multi-point electric field measurements of Short Large-Amplitude Magnetic Structures (SLAMS) at the Earth's quasi-parallel bow shock
Eriksson, Anders I.; Vaivads, Andris; André, Mats +4 more
We present the first direct measurements of the electric field and plasma density with high resolution in Short Large-Amplitude Magnetic Structures (SLAMS) at a quasi-parallel shock crossing. Cluster observations at the Earth's bow shock confirm the fast-mode structure of SLAMS. Using the four Cluster spacecraft, we determine the velocity of the S…
Relationship between CME velocity and active region magnetic energy
Venkatakrishnan, P.; Ravindra, B.
We find an empirical relationship between the initial speed of Coronal Mass Ejection (CME) and the potential magnetic field energy of the associated active region (AR) that closely resembles the Sedov relation between the speed of a blast wave and the blast energy. We conclude that it is the magnetic energy of an AR that drives the CME. The restru…
Minimum variance free wave identification: Application to Cluster electric field data in the magnetosheath
Walker, S. N.; Dunlop, M.; Amata, E. +4 more
The electric field measurements provided by the EFW instrument on board Cluster spacecraft are used to identify the mode of plasma waves observed in the magnetosheath. Previous identifications of magnetosheath wave modes have involved either the use of dimensionless transport ratios (DR) calculated using magnetic field and plasma parameters or the…
Properties of fast magnetosonic shocklets at the bow shock
Lavraud, B.; Buchert, S.; Stasiewicz, K. +3 more
We present detailed properties of fast magnetosonic shocklets (1000 km in size and amplitude of 10 times the background B-field values) observed in natural unbounded collisionless plasma by a fleet of four Cluster spacecraft at the quasi-parallel bow shock. We provide for the first time details of the internal structure of shocklets which have mag…
When will Voyager 1 and 2 cross the termination shock?
Gloeckler, George; Izmodenov, Vlad; Malama, Yuri
Our Solar System moves through a warm (~6,500 K), partly ionized local interstellar cloud (LIC) with a relative speed of ~26 km/s. The solar wind interacts with the LIC to form a cavity around the Sun called the heliosphere. The solar wind meets the interstellar charged component at the heliopause, where solar wind pressure balances the pressure o…
Lower hybrid cavities in the inner magnetosphere
André, M.; Eriksson, A. I.; Tjulin, A.
We present observations of lower hybrid cavities from altitudes above 10,000 km, using data from Viking and Cluster satellites. Lower hybrid cavities (LHCs) are narrow (ion gyroradius scale) density depletions with enhanced amplitude of waves in the lower hybrid frequency range, previously reported below 1750 km altitude by the Freja satellite and…
Bow shock motions observed with CLUSTER
André, M.; Maksimovic, M.; Bale, S. D. +1 more
The Cluster mission allows the determination not only of the bow shock crossing position but also, with a simple timing method and a reasonable confidence, the shock normal and the velocity along this normal. We apply this technique to a series of eleven consecutive bow shock crossings which occurred during a time interval of approximatively two a…
Are CME ``interactions'' really important for accelerating major solar energetic particle events?
Szabo, Adam; Richardson, Ian G.; Haggerty, Dennis K. +2 more
Recent studies have proposed that the presence or absence of an ``interaction'' with a preceding coronal mass ejection (CME) or other coronal structure within ~50 Rs of the Sun discriminates large, fast CMEs associated with major solar energetic particle (SEP) events from those that are not. We conclude that there is no compelling evide…
Solar magnetic field reversal as seen at Ulysses
Balogh, André; Smith, Edward J.; Jones, Geraint H.
The rapid motion of the Ulysses spacecraft from high southern to high northern latitudes in 2000-2001 provided an excellent opportunity to make inferences regarding the solar magnetic dipole's behaviour around solar maximum. A simple dipole model is fitted to Ulysses measurements of the polarity of the heliospheric magnetic field mapped back to th…