Maria Hamrin

Dipolarization fronts as a consequence of transient reconnection : In situ evidence

Dipolarization fronts (DFs) are frequently detected in the Earths magnetotail from X-GSM=-30 R-E to X-GSM=-7 R-E. How these DFs are formed is still poorly understood. Three possible mechanisms have been suggested in previous simulations: (1) jet braking, (2) transient reconnection, and (3) spontaneous formation. Among these three mechanisms, the first has been verified by using spacecraft observation, while the second and third have not. In this study, we show Cluster observation of DFs inside reconnection diffusion region. This observation provides in situ evidence of the second mechanism: Transient reconnection can produce DFs. We suggest that the DFs detected in the near-Earth region (X-GSM>-10 R-E) are primarily attributed to jet braking, while the DFs detected in the mid- or far-tail region (X-GSM<-15 R-E) are primarily attributed to transient reconnection or spontaneous formation. In the jet-braking mechanism, the high-speed flow pushes the preexisting plasmas to produce the DF so that there is causality between high-speed flow and DF. In the transient-reconnection mechanism, there is no causality between high-speed flow and DF, because the frozen-in condition is violated.

Energy conversion regions as observed by Cluster in the plasma sheet

In this article we present a review of recent studies of observations of localized energy conversion regions (ECRs) observed by Cluster in the plasma sheet at altitudes of 15–20RE. By examining var ...

Auroral electron acceleration by Alfvén waves and electrostatic fields

We present a two-dimensional numerical model for the formation of discrete auroral arcs. This model describes the evolution of shear Alfven waves generated by a growing force near the equatorial pl ...

Plasma penetration of the dayside magnetopause

Data from the Cluster spacecraft during their magnetopause crossing on 25 January 2002 are presented. The magnetopause was in a state of slow non-oscillatory motion during the observational period. ...

Inhomogeneous transverse electric fields and wave generation in the auroral region: A statistical study

We use data from the Freja satellite to investigate the importance of localized transverse DC electric fields for the generation of broadband waves responsible for ion heating in the auroral region ...

The role of the inner tail to midtail plasma sheet in channeling solar wind power to the ionosphere

In this article we use Cluster power density (E . J) data from 2001, 2002, and 2004 to investigate energy conversion and transfer in the plasma sheet. We show that a southward IMF B-z is favorable ...

Magnetic forces associated with bursty bulk flows in Earth's magnetotail

We present the first direct measurements of magnetic forces acting on bursty bulk flow plasma in the magnetotail. The magnetic forces are determined using Cluster multispacecraft measurements. We a ...

A statistical study of wave properties and electron density at 1700 km in the auroral region

We present a comprehensive overview of the electron density and six different wave types in the range similar to1 Hz to similar to1 MHz, and we investigate their occurrence, average wave frequency ...

IMF dependence of the azimuthal direction of earthward magnetotail fast flows

Cluster magnetotail data together with ACE solar wind data from 2001 to 2009 are used to investigate the dependence of the azimuthal flow direction of earthward magnetotail fast flows on the interp ...

Evidence for the braking of flow bursts as they propagate toward the Earth

In this article we use energy conversion arguments to investigate the possible braking of flow bursts as they propagate toward the Earth. By using EJ data (E and J are the electric field and the cu ...