404 research outputs found
Average thermodynamic and spectral properties of plasma in and around dipolarizing flux bundles
No full textRecent observations have suggested that spatially localized flows of high-temperature, low-density plasma carrying a dipolarized magnetic field (dipolarizing flux bundles, DFBs) play a key role in hot plasma transport toward the inner magnetosphere. What controls plasma heating in DFBs and how do thermodynamic parameters (such as density, temperature, pressure, and specific entropy) and spectral properties of the DFB population depend on ambient plasma sheet properties and geocentric distance R remains unknown. By statistical analysis of 271 DFB events detected by the Time History of Events and Macroscale Interactions during Substorms mission during the 2008-2009 tail seasons, we find that on average, plasma inside DFBs is a factor of 0.6 less dense and a factor of 1.5 to 2 hotter than ambient tail plasma. The radial profiles of average thermodynamic parameters inside and outside DFBs are similar; when fitted by the -function, their energy spectra have similar -exponents, but a factor of 2 larger peak energies inside DFBs. Our analysis suggests that average DFB plasma properties are closely linked to those of the ambient plasma sheet population. Estimations show that on average, adiabatic heating of the ambient plasma in the increased magnetic field is the major factor in DFB plasma heating.NASA [NAS5-02099, NNX13AF81G]; German Ministry for Economy and Technology; German Center for Aviation and Space (DLR) [50 OC 0302]SCI(E)[email protected]
The Magnetosphere of the Earth under Sub-Alfvenic Solar Wind Conditions as Observed on 24 and 25 May 2002
No full text© 2017 the American Geophysical Union. All rights reserved. On 24 and 25 May 2002, the solar wind density was so low (<0.1 cm-3), that the flow became sub-Alfvénic for intervals that lasted as long as 4 h (the Alfvén Mach number was as low as 0.4). The magnetosphere changed dramatically and (according to simulations and theory) became very asymmetric: The bow shock disappeared and two Alfvén wings formed on the flanks of the magnetosphere (the wings were 600 RE long, the deceleration 30% in one wing and 60% in the other). Geotail's data suggest that it crossed one of these wings multiple times. The magnetosphere was geomagnetically extremely quiet, showed no substorm activity and almost no auroral activity. Simulations show that the closed field line region was very symmetric, extending to 20 RE on the dayside and on the nightside. The open field lines became highly asymmetric: The field lines emanating from the Northern Hemisphere all pointed along the dawn Alfvén wing (around 8:00 LT), the field lines from the Southern Hemisphere all pointed along the other wing (around 22:00 LT). Between 28 November 1963 and 27 September 2015, there were 16 recorded sub-Alfvénic solar wind intervals, lasting for more than 1 h and caused by low solar wind density. Considering the uneven data coverage, these events occur, on average, every 2.2 years.status: Publishe
The magnetosphere of the Earth under sub-Alfvénic solar wind conditions
No full textOn 24 and 25 May 2002, the solar wind density was so low (0.1 /cc), that the flow became sub‐Alfvénic for intervals that lasted as long as 4h (the Alfvén Mach number was as low as 0.4). The magnetosphere changed dramatically and (according to simulations and theory) became very asymmetric: the bow shock disappeared and two Alfvén wings formed on the flanks of the magnetosphere (the wings were 600 Re long, the deceleration 30% in one wing and 60% in the other). Geotail’s data suggest that it crossed one of these wings multiple times. The magnetosphere was geomagnetically extremely quiet, showed no substorm activity and almost no auroral activity. Simulations show that the closed field line region was very symmetric, extending to 20 Re on the dayside and on the nightside. The open field lines became highly asymmetric: the field lines emanating from the Northern Hemisphere all pointed along the dawn Alfvén wing (around 8:00 LT), the field lines from
the Southern Hemisphere all pointed along the other wing (around 22:00 LT). Between 28 November 1963 and 27 September 2015, there were 16 recorded sub‐Alfvénic solar wind intervals, lasting for more than 1h and caused by low solar wind density. Considering the uneven data coverage, these events occur, on average, every 2.2 years.edition: 1status: Publishe
3D transport modelling at the tokamak edge with resonant magnetic field perturbations taking into account screening of perturbations by the plasma
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