solar flares

Phillip ChamberlinUniversity of Colorado

Laboratory for Atmospheric and Space Physics (LASP)[email protected]

(303)492-9318

mailto:[email protected]

June 10, 2009 Chamberlin - Solar Flares - REU 2009 2

Outline- Solar Atmosphere- Flux Tubes- Two Ribbon Flare

- Cartoons- Movies

- Irradiance Measurements of Flares- VUV- White Light- TSI


XUV, EUV, and FUV Solar Spectrum

Transition Region

From Lean (1997)


Solar Images - Oct. 28, 2003

Photosphere

Transition Region

Chromosphere

H-Alpha

Corona

(Images courtesy of Big Bear Solar Observatory and SOHO EIT)


Flux Tubes

(Schrijver and Zwaan, 2000)


Flux Tubes


Absence of B-field within convection cells due to B-field line reconnection

B-field lines concentrated in strands between convection cells to form Flux Tubes

Initial rotating convection zone with weak vertical B-field lines


Emerging Flux

Solar Atmosphere

Convection Zone

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


Emerging Flux (Title, 2004)

Solar Flares



Phases of Solar Flares

Radio (100-500 MHz) Microwave Radio (~3000 MHz)

H-alpha (656.2 nm)

Broadband EUV (1 - 103 nm)

Soft X-rays (< 10 keV)

X-rays (10-30 keV)

Hard X-rays (> 30 keV)

PrecursorImpulsive Phase

Main Phase

(Adapted from Schrijver and Zwaan, 2000)

Note: Soft X-rays: 0.1-10 nm,

Hard X-rays: 0.001-0.1 nm


Two-Ribbon ReconnectionReconnection after instability accelerates material down loop. Observed Hard X-ray (and EUV?) enhancements at loop top.

No enhanced emissions during the impulsive phase in the corona due to its low density.

[Ashwanden,2004]

Thick-target model produces Bremsstrahlung radiation in the transition region and chromosphere due to their much higher densities - Impulsive Phase!

Energy deposited during the impulsive phase heats the plasma up and rises (chromospheric evaporation) to fill flux tube - Gradual Phase!


Jets Evidence of Small-Scale Reconnection?


Two-Ribbon Flare

(Priest, 1981)

Triggered by Emerging Flux?

Eruption when some critical limit is reached

Continued thermal heating and formation of post-flare loops

“Stretching” of field lines




H-alpha (656.2 nm)



X-rays (10-30 keV)



Main Phase





Two-Ribbon Flare

Post-Flare Loops

Impulsive Phases for Each Loop (Somov, 1992)


Flares drive waves in the photosphere


X28 Flare, Nov 4, 2003


Hinode SOT Observes Flare


SOHO (UV) and SORCE XPS (XUV) Observations




H-alpha (656.2 nm)



X-rays (10-30 keV)



Main Phase





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]


Flare/Pre-Flare Irradiance Ratio

EUV irradiance increased by a factor of 2 during the gradual phase

Transition region emissions increased by up to a factor of 10 during the impulsive phase

Flare Variations were as large or larger than the solar cycle variations for the Oct 28, 2003 flare


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


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


Hinode SOT Observations

Flares in Photosphere

and Chromosphere


X17 flare observed in TSIFirst detection of flare in TSI record (G. Kopp, 2003)

Figures from G. Kopp, arranged by T. Woods


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


Extra Slides


Simple Loop FlareExisting Flux Loop that Brightens

-Most Common Type

-Are these an actual separate type of flare?

-Only Enhanced Internal Motions

(Priest, 1981)

PHOTOSPHERE

CHROMOSPHERE

CORONA TRANSITION REGION


Hinode SOT Movie #2


Flares Cause Sudden Atmospheric Changes

Sudden increase in the dayside density at low latitude regions due to the X17 solar flare on October 28, 2003

(E. Sutton, 2005)

• 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

GRACE daytime density (490 km)

Lat

itud

e (D

eg)

2003 Day of Year

solar flares

Documents

solar flaresjune

solar images

phases of solar flaresradio

flux tubesschrijver

flux tubesinitial

emerging flux title

flux tube gradual phase

convection cells