Phillip Chamberlin

1
Solar Flares

• Phillip Chamberlin
• University of Colorado
• Laboratory for Atmospheric and Space Physics
  (LASP)
• Phil.Chamberlin_at_lasp.colorado.edu
• [phone]

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Outline

• Solar Atmosphere
• Flux Tubes
• Two Ribbon Flare
• Cartoons
• Movies
• Irradiance Measurements of Flares
• VUV
• White Light
• TSI

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XUV, EUV, and FUV Solar Spectrum
Transition Region
From Lean (1997)
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Solar Images - Oct. 28, 2003
Chromosphere H-Alpha
Corona
Photosphere
Transition Region
(Images courtesy of Big Bear Solar Observatory
and SOHO EIT)
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Flux Tubes
(Schrijver and Zwaan, 2000)
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Flux Tubes
Initial rotating convection zone with weak
vertical B-field lines
B-field lines concentrated in strands between
convection cells to form Flux Tubes
Absence of B-field within convection cells due to
B-field line reconnection
(Schrijver and Zwaan, 2000)
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Emerging Flux
Solar Atmosphere
Active Regions
Balance between hydrostatic pressure and magnetic
pressure causes the flux tubes to be less dense
due to their stronger magnetic pressure
buoyant flux tubes
Convection Zone
(Schrijver and Zwaan, 2000)
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Emerging Flux (Title, 2004)
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Solar Flares
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Phases of Solar Flares
(Adapted from Schrijver and Zwaan, 2000)
Microwave Radio (3000 MHz)
Radio (100-500 MHz)
H-alpha (656.2 nm)
Broadband EUV (1 - 103 nm)
Soft X-rays (lt 10 keV)
X-rays (10-30 keV)
Main Phase
Hard X-rays (gt 30 keV)
Impulsive Phase
Note Soft X-rays 0.1-10 nm, Hard X-rays
0.001-0.1 nm
Precursor
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Two-Ribbon Reconnection
Thick-target model produces Bremsstrahlung
radiation in the transition region and
chromosphere due to their much higher densities -
Impulsive Phase!
Reconnection after instability accelerates
material down loop. Observed Hard X-ray (and
EUV?) enhancements at loop top.
Ashwanden, 2004
No enhanced emissions during the impulsive phase
in the corona due to its low density.
Energy deposited during the impulsive phase heats
the plasma up and rises (chromospheric
evaporation) to fill flux tube - Gradual Phase!
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Jets Evidence of Small-Scale Reconnection?
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Two-Ribbon Flare
Eruption when some critical limit is reached
Triggered by Emerging Flux?
Continued thermal heating and formation of
post-flare loops
Stretching of field lines
(Priest, 1981)
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Phases of Solar Flares
(Adapted from Schrijver and Zwaan, 2000)
Microwave Radio (3000 MHz)
Radio (100-500 MHz)
H-alpha (656.2 nm)
Broadband EUV (1 - 103 nm)
Soft X-rays (lt 10 keV)
X-rays (10-30 keV)
Main Phase
Hard X-rays (gt 30 keV)
Impulsive Phase
Note Soft X-rays 0.1-10 nm, Hard X-rays
0.001-0.1 nm
Precursor
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Two-Ribbon Flare
Impulsive Phases for Each Loop
Post-Flare Loops
(Somov, 1992)
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Flares drive waves in the photosphere
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X28 Flare, Nov 4, 2003
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Hinode SOT Observes Flare
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SOHO (UV) and SORCE XPS (XUV) Observations
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Phases of Solar Flares
(Adapted from Schrijver and Zwaan, 2000)
Microwave Radio (3000 MHz)
Radio (100-500 MHz)
H-alpha (656.2 nm)
Broadband EUV (1 - 103 nm)
Soft X-rays (lt 10 keV)
X-rays (10-30 keV)
Main Phase
Hard X-rays (gt 30 keV)
Impulsive Phase
Note Soft X-rays 0.1-10 nm, Hard X-rays
0.001-0.1 nm
Precursor
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VUV Irradiance Increases Dominate Flare Variations

• VUV irradiance (0.1-200 nm) accounts for only
  0.007 of quite Sun Total Solar Irradiance (TSI)
• VUV irradiance accounts for 30-70 of the
  increase in the TSI during a flare Woods et al.,
  2006

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Flare/Pre-Flare Irradiance Ratio
Transition region emissions increased by up to a
factor of 10 during the impulsive phase
EUV irradiance increased by a factor of 2 during
the gradual phase
Flare Variations were as large or larger than the
solar cycle variations for the Oct 28, 2003 flare
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X-Ray Classification
Due to the large, order-of-magnitude increases in
the soft X-rays makes for an ideal and sensitive
classifications of the magnitude of flares
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White Light Flare

• Carrington Flare September 1, 1859
• Carrington (M.N.R.A.S, 20, 13, 1860)
• One of the largest flares believed to have
  occurred in the
  past 200 years
• Two-Ribbon
  flare

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Flares in Photosphere and Chromosphere
Hinode SOT Observations
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X17 flare observed in TSI
Figures from G. Kopp, arranged by T. Woods
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Conclusions

• Multiple images and spectral measurements are key
  to understanding energetic of flares
• New measurements (Hinode, Stereo, EVE, AIA, etc.)
  will lead to a much greater understanding of
  these processes
• Biggest mystery still is the trigger
• Another topic to that is not fully understood is
  the relationship of CMEs and Flares

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Extra Slides
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Simple Loop Flare

• Existing Flux Loop that Brightens

TRANSITION REGION
CORONA
CHROMOSPHERE
PHOTOSPHERE
-Most Common Type -Are these an actual separate
type of flare?
-Only Enhanced Internal Motions
(Priest, 1981)
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Hinode SOT Movie 2
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Flares Cause Sudden Atmospheric Changes
GRACE daytime density (490 km)

• Increased neutral particle density in low
  latitude regions on the dayside.
• Sudden Ionospheric Disturbances (SIDs) lead to
  Single Frequency Deviations (SFDs).
• Cause radio communication blackouts
• Cause increased error in GPS accuracy

Latitude (Deg)
2003 Day of Year
(E. Sutton, 2005)
Sudden increase in the dayside density at low
latitude regions due to the X17 solar flare on
October 28, 2003