transients on the sun
DESCRIPTION
Transients on the Sun. Megan Cartwright UCLA SHINE Student Day June 22, 2008. Image of an erupting prominence from online SOHO gallery. Active Regions (AR). An active region on the sun is an area of very strong magnetic field, often observed as sunspots. - PowerPoint PPT PresentationTRANSCRIPT
Transients on the Sun
Megan Cartwright
UCLA
SHINE Student DayJune 22, 2008
Image of an erupting prominence from online SOHO gallery
Active Regions (AR)
Windows to the Universe original artwork by Randy Russell using an image from NASA's TRACE (Transition Region and Coronal Explorer) spacecraft.
• An active region on the sun is an area of very strong magnetic field, often observed as sunspots.
• Solar flares and CME’s are often associated with active regions.
Solar flares are impulsive, transient releases of magnetic energy that rapidly heat the surrounding plasma
EUV image of one of the largest solar flares observed, erupted in November 2003. Image courtesy of SOHO (NASA & ESA).
Coronal Mass Ejections are large scale magnetic structures which are released into the heliosphere
Figure 1 from Riley et al., (2008)
Prominences
• Suspensions of cool (T~104K), dense (n~1010-1011 cm-3) chromospheric material surrounded by the hot (T~106K) and tenuous (n~107-109 cm-3) corona
Image of a prominence from online SOHO gallery
Prominence Magnetic Fields: Origin of flux ropes?
Image of a prominence from HAO in H-alpha
Sigmoids: Shearing Observed in Soft X-Ray Regime
Persistent sigmoid (Left, Top) ;Transient sigmoid (Left, Bottom);Sigmoid associated with CME (Left, Bottom) -- Image from, DOI: 10.1007/s11214-006-9101-2
How are CMEs Initiated?
Flux Injection Model (Chen, 1989, 1996)
Flux Cancellation Models
The Breakout Model
MacNeice et al., 2004. Lynch et al.
• The interaction can be written in words– Expansion
• (Ambient mass density) X (Rate of expansion)2= Delta Pressure (inside – outside)
– Acceleration• (Mass of CME + Virtual mass) X Acceleration = Force
of gravity + Delta (outside magnetic and particle pressure on lower surface area – outside magnetic and particle pressure on upper surface area) – Drag
• Virtual mass allows us to correct for the force necessary to move all the ambient medium away = volume of cylinder time the mass density of the ambient medium.
– Problem is in turning this into equations.• Standard drag term CDAρ abs (VCME –Vsw) (VCME –Vsw)
where CD is a drag coefficient, and (VCME –Vsw) is relative velocities of CME and solar wind.
• How to do it is controversial.
CME Acceleration and Propagation
CME Propagation Model into Heliosphere: ENLIL (Sumerian God of the Wind)
ENLIL Simulation Run Results
Earth
Where to find ‘Solar Transients’ at SHINE/GEM
• Relevant sessions: 5, 9, 11, 14, 16, 18
Coronal Models: CME must be launched into an ambient solar wind.
SOLAR MODELS:
• PFSS: corona field model from 1.5-3.25Rs.
•MAS: 3D corona field model from 1-30 Rs.
• WSA: (A) Potential field + current sheet (B) WSA inner heliosphere
SWMF (UMich): 3D MHD coronal code & inner heliosphere code.
Images from CCMC website (Above Left is MAS model, Above Right is PFSS, & Bottom is magnetogram inputs