Maria Hamrin

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We present a comprehensive overview of several potentially relevant causes for the oxygen energization in the auroral region. Data from the Freja satellite near 1700 km altitude are used for an unconditional statistical investigation. The data are obtained in the Northern Hemisphere during 21 months in the declining phase of the solar cycle. The importance(More)
We present a method, GALS (Gradient Analysis by Least Squares) for estimating the gradient of a physical field from multi-spacecraft observations. To obtain the best possible spatial resolution, the gradient is estimated in the frame of reference where structures in the field are essentially locally stationary. The estimates are refined iteratively by a(More)
It is well known that nonzero interplanetary magnetic field By conditions lead to a twisted magnetotail configuration. The plasma sheet is rotated around its axis and tail magnetic field lines are twisted, which causes an azimuthal displacement of their ionospheric footprints. According to the untwisting hypothesis, the untwisting of twisted field lines is(More)
Detection of hypervelocity impacts on a spacecraft body using electric field instruments has been established as a new method for monitoring of dust grains in our solar system. Voyager, WIND, Cassini, and STEREO spacecraft have shown that this technique can be a complementary method to conventional dust detectors. This approach uses fast short time changes(More)
Theoretical considerations, observations, and simulations have shown that the By component of the interplanetary magnetic field (IMF) may cause twisting of the magnetotail. However, the fundamental issues, the temporal and spatial responses of the magnetotail in the twisting process, are still unresolved. We report unique multipoint observations of the(More)
In this article we use energy conversion arguments to investigate the possible braking of flow bursts as they propagate toward the Earth. By using E ⋅ J data (E and J are the electric field and the current density) observed by Cluster in the magnetotail plasma sheet, we find indications of a plasma deceleration in the region −20 RE < X < −15 RE . Our(More)