III. APPLICATIONS of RECONNECTION Yohkoh Bright Pts Loops Holes A magnetic world T=few MK 1. Coronal Heating Quiet Sun (XRT on Hinode) 30-sec cadence, 12-hour duration How is the Corona Heated ? Reconnection: likely cause of coronal heating (i) Drive Simple Recon. at nulls by phot c. motions --> X-ray bright point (ii) Nanoflares -- Parker Braiding (iii) Modern version: Coronal Tectonics (including magnetic carpet) Supported by TRACE 2. SOLAR FLARES & CMEs SOHO Coronagraph -- Artificial eclipse Discovered huge ejections of plasma Photo- sphere [from SOHO] On October 28, rd largest flare Outer Corona [from SOHO] CME 2000 km/s (5 times faster than normal) Snow -- rel c particles Thurs Aurora in St Andrews 1 Week Later (Nov 4 )- Fireworks Continued the biggest solar flare ever recorded ! Conjuring trick -- plasma appearing by magic ? Close-up of plasma motions N.B. Flare & CME are part of 1 magnetic eruptive process (short MHD connection time) Role of filament/prominence -- indicator of high shear So perhaps eruption is driven more from core, where most energy is stored Difference 2-ribbon flare & CME --- magnetic field strength Overall Picture of Eruption In core - magnetic tube twisted (energy stored in fff) - erupts (catastrophe or breakout) - drives reconnection Reconnection heats loops/ribbons (Priest and Schrijver 1999) Reconnection heats loops Continues: new loops form & evaporate. Old loops cool & drain Feet move apart Examples of prominences Eruptions: Ex of Cusped Loops Rising Example from SOHO Example from TRACE (171 A) 1 MK (Fe IX) + 20 MK (Fe XVI) Before: twisted sigmoid --> energy stored Cause of Eruption ? (i) Magnetic Catastrophe (Priest & Forbes) (ii) Antiochos et al - breakout model for eruption Emergence of flux rope into a potential arcade Eruption due to magnetic catastrophe when twist > 3.4 Yuhong Fan Tibor Torok Similar model for kink instability, with different flux tube/ overlying field 3. CONCLUSIONS Understanding how B interacts with plasma: Key to many solar system phenomena Two main equations: Induction equation -- advection + diffusion Eqn. motion -- magnetic tension + pressure forces Reconnection - different roles in coronal heating, - Solar flares & CMEs