Heating and Acceleration of Protons and Minor Ions by Fast Shocks in the Solar Corona

Details Heating and Acceleration of Protons and Minor Ions by Fast Shocks in the Solar Corona Heating and Acceleration of Protons and Minor Ions by Fast Shocks in the Solar Corona

Jun 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000apj...535.1014l&link_type=abstract

The Astrophysical Journal, Volume 535, Issue 2, pp. 1014-1026.

Astronomy and Astrophysics

Astronomy

50

Magnetic Fields, Plasmas, Shock Waves, Sun: Corona, Sun: Magnetic Fields

Scientific paper

We propose a new mechanism of coronal heating, in which protons and minor ions are heated and accelerated by fast shocks. The interaction between network magnetic fields and emerging intranetwork fields may lead to the formation of thin current sheets, which triggers magnetic reconnection and microflares. The disruption of current sheet leads to fast shocks with an Alfvén Mach number MA<2. In addition, fast shocks that originate in the chromosphere by magnetic reconnection of a smaller scale may produce spicules and then enter the corona. The heating and acceleration by shocks are then examined based on a theoretical model and hybrid simulations. The results show the following: (1) the near nondeflection of ion motion across the shock ramp leads to a large perpendicular thermal velocity (vth⊥), which depends on the mass/charge ratio; (2) for subcritical shocks with 1.1<=MA<=1.5, the shock heating leads to a large temperature anisotropy with T⊥/T||~50 for O5+ ions and a mild anisotropy with T⊥/T||~1.2 for protons; (3) these subcritical shocks can directly drive an outward field-aligned velocity ~0.1VA~240 km s-1 for protons; (4) the large perpendicular thermal velocity of O5+ ions can be converted to the radial outflow velocity (u) in the diverging coronal field lines; and (5) the heating and acceleration by shocks with 1.1<=MA<=1.5 can lead to u(O5+)~vth⊥(O5+)~460 km s-1 for O5+ ions and u(H+)~vth⊥(H+)~240 km s-1 for protons at r=3-4 Rsolar. Our results can explain recent Solar and Heliospheric Observatory observations of the heating and acceleration of protons and minor ions in the solar corona.

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