Solar Flares

1. Solar Flares Phillip Chamberlin University of Colorado Laboratory for Atmospheric and Space Physics (LASP) Phil.Chamberlin@lasp.colorado.edu (303)492-9318

2. Outline • Solar Atmosphere • Flux Tubes • Two Ribbon Flare • Cartoons • Movies • Irradiance Measurements of Flares • VUV • White Light • TSI Chamberlin - Solar Flares - REU 2007

3. XUV, EUV, and FUV Solar Spectrum Transition Region From Lean (1997) Chamberlin - Solar Flares - REU 2007

4. Solar Images - Oct. 28, 2003 Chromosphere H-Alpha Corona Photosphere Transition Region (Images courtesy of Big Bear Solar Observatory and SOHO EIT) Chamberlin - Solar Flares - REU 2007

5. Flux Tubes (Schrijver and Zwaan, 2000) Chamberlin - Solar Flares - REU 2007

6. 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) Chamberlin - Solar Flares - REU 2007

7. 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) Chamberlin - Solar Flares - REU 2007

8. Emerging Flux (Title, 2004) Chamberlin - Solar Flares - REU 2007

9. 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 (< 10 keV) X-rays (10-30 keV) Main Phase Hard X-rays (> 30 keV) Impulsive Phase Note: Soft X-rays: 0.1-10 nm, Hard X-rays: 0.001-0.1 nm Precursor Chamberlin - Solar Flares - REU 2007

10. 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) Chamberlin - Solar Flares - REU 2007

11. 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] Energy deposited during the impulsive phase heats the plasma up and rises (chromospheric evaporation) to fill flux tube - Gradual Phase! No enhanced emissions during the impulsive phase in the corona due to its low density. Chamberlin - Solar Flares - REU 2007

12. Two-Ribbon Flare Impulsive Phases for Each Loop Post-Flare Loops (Somov, 1992) Chamberlin - Solar Flares - REU 2007

13. X28 Flare, Nov 4, 2003 Chamberlin - Solar Flares - REU 2007

14. Hinode SOT Observes Flare Chamberlin - Solar Flares - REU 2007

15. SOHO (UV) and SORCE XPS (XUV) Observations Chamberlin - Solar Flares - REU 2007

16. 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 (< 10 keV) X-rays (10-30 keV) Main Phase Hard X-rays (> 30 keV) Impulsive Phase Note: Soft X-rays: 0.1-10 nm, Hard X-rays: 0.001-0.1 nm Precursor Chamberlin - Solar Flares - REU 2007

17. 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 Chamberlin - Solar Flares - REU 2007

18. 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 Chamberlin - Solar Flares - REU 2007

19. 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 since then • Two-Ribbon flare Chamberlin - Solar Flares - REU 2007

20. White Light vs UV (170 nm) Flare White Light TRACE 170 nm From Hudson et al., AGU/SPD 2005: http://sprg.ssl.berkeley.edu:80/~hhudson/presentations/spd_wl.050527/ Chamberlin - Solar Flares - REU 2007

21. First detection of flare in TSI record (G. Kopp, 2003) X17 flare observed in TSI Figures from G. Kopp, arranged by T. Woods Chamberlin - Solar Flares - REU 2007

22. Conclusions • Multiple images and spectral measurements are key to understanding energetic of flares • New measurements (Hinode, 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 Chamberlin - Solar Flares - REU 2007

23. Extra Slides Chamberlin - Solar Flares - REU 2007

24. 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) Chamberlin - Solar Flares - REU 2007

25. Flares drive waves in the photosphere Chamberlin - Solar Flares - REU 2007

26. Hinode SOT Movie #2 Chamberlin - Solar Flares - REU 2007

27. 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] Chamberlin - Solar Flares - REU 2007

28. 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 Chamberlin - Solar Flares - REU 2007