White light coronagraph showing prominances and streamers The Coronal Magnetic Field

Coronal expansion with pure dipole magnetic field added (MHD Solution) Fast wind Slow wind Current Sheet Helmet Streamer (Not Flowing)

Solar wind expansion and the heliospheric current sheet.

March 29, 2006 Solar Eclipse Magnetic field lines (MHD Model) Scattered light (MHD Model) Eclipse Images Predictions made two weeks before eclipse using photospheric magnetograms and an MHD Model.

Coronal Mass Ejections (CME’s)

What are they? Huge bubbles of plasma ejected from the Sun. “Coronal” because that is where they are most easily observed. “Mass” because a large amount of solar wind is released at once – not because they contain a lot of mass. They contain strong magnetic fields, usually in the form of a twisted flux rope. Ejection speeds vary from solar than typical solar wind speeds, say 250 km/s, up to 2000 km/s. Fast CME’s create shock waves ahead of them in the solar wind.

CMEs are Part of Streamer Belt Outflow Steady-state Transient

What is the structure of a CME? lHigh degree of variability lSimplest have 3 parts [Bright outer rim [Dark cavity [Bright inner core

Bright Inner Core is Prominence lProminences are dense, cool strands of plasma formed low in solar atmosphere (chromosphere) Viewed best in  line lProminences constitute minor parts of CMEs lPopular media often mistake prominence eruptions for CMEs or flares

Flux Rope Image Depends Upon Point of View

What causes CMEs? lOutstanding question in solar physics lCME formation involves magnetic flux build-up and release, probably through [Emergence of flux from below the photosphere [Shearing of field-line footpoints through photospheric motions [Magnetic reconnection

Magnetic Reconnection lOccurs when antiparallel magnetic field lines break (disconnect) at x point and reconnect with new partners lConverts magnetic energy into kinetic energy lResults in new topological configurations lPlays role in CME release from the Sun

Reconnection in CMEs lAbove CME lRelease mechanism in “breakout” model l~Fast CMEs lBelow CME lForms flux rope in 3D l~Slow CMEs

lTwo sheared loops reconnect to form coil Flux Rope Formation by Reconnection lLoops are part of helmet arcade

lSolar flares are bursts of electromagnetic radiation with peak intensities at X-ray wavelengths. lFlares are ubiquitous and highly variable in strength and duration. lFlares are thought to be evidence of magnetic reconnection everywhere on the Sun. lTwo kinds of flares are associated with CMEs [Intense flares  short in duration  nearly always accompany CMEs  associated with the breakout model [Long-duration flares  wide range of intensities (some so weak that traditionally they would not be classified as a flare)  arcade loop formation  associated with flux-rope formation at CME liftoff Traditional H  flares are chromospheric embers of X ray flares Solar Flares as Evidence of Reconnection

Intense Flare in UV light

lCME model [Forbes] lCME model [Gosling] Model Flare Loops lOld flare model [Pneuman and Kopp] lCusped X-ray Flare Loops