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Mhd modelling of coronal loops: injection of high-speed chromospheric flows
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Orlando, S. Petralia, A. Klimchuk, J. A. Reale, F. |
| Copyright Year | 2014 |
| Description | Context. Observations reveal a correspondence between chromospheric type II spicules and bright upward-moving fronts in the corona observed in the extreme-ultraviolet (EUV) band. However, theoretical considerations suggest that these flows are probably not the main source of heating in coronal magnetic loops. Aims. We investigate the propagation of high-speed chromospheric flows into coronal magnetic flux tubes and the possible production of emission in the EUV band. Methods. We simulated the propagation of a dense 104 K chromospheric jet upward along a coronal loop by means of a 2D cylindrical MHD model that includes gravity, radiative losses, thermal conduction, and magnetic induction. The jet propagates in a complete atmosphere including the chromosphere and a tenuous cool (approximately 0.8 MK) corona, linked through a steep transition region. In our reference model, the jet initial speed is 70 km per second, its initial density is 10(exp 11) per cubic centimeter, and the ambient uniform magnetic field is 10 G. We also explored other values of jet speed and density in 1D and different magnetic field values in 2D, as well as the jet propagation in a hotter (approximately 1.5 MK) background loop. Results. While the initial speed of the jet does not allow it to reach the loop apex, a hot shock-front develops ahead of it and travels to the other extreme of the loop. The shock front compresses the coronal plasma and heats it to about 10(exp 6) K. As a result, a bright moving front becomes visible in the 171 Angstrom channel of the SDO/AIA mission. This result generally applies to all the other explored cases, except for the propagation in the hotter loop. Conclusions. For a cool, low-density initial coronal loop, the post-shock plasma ahead of upward chromospheric flows might explain at least part of the observed correspondence between type II spicules and EUV emission excess. |
| File Size | 1458252 |
| Page Count | 9 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_20150007704 |
| Archival Resource Key | ark:/13960/t2s51nz8v |
| Language | English |
| Publisher Date | 2014-07-14 |
| Access Restriction | Open |
| Subject Keyword | Sun: Chromosphere Sun: Uv Radiation Sun: Corona Magnetohydrodynamics (mhd) Magnetohydrodynamics Chromosphere Coronal Loops Computerized Simulation Rankine-hugoniot Relation Spicules Helioseismology Solar Simulation Plasma Jets Astronomical Models High Speed Magnetohydrodynamic Flow Computational Grids Solar Magnetic Field Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
