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Corotating Interaction Regions

Corotating Interaction Regions. Glenn Mason, JHU/APL ACE / SOHO / STEREO/ Wind In-situ Science Symposium Kennebunkport, Maine, June 8-11, 2010. Acknowledgements: R. Bucik M. I. Desai A. B. Galvin G. Gloeckler A. Korth R. A. Leske U. Mall R. A. Mewaldt K. Simunac. Outline:

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Corotating Interaction Regions

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  1. Corotating Interaction Regions Glenn Mason, JHU/APL ACE / SOHO / STEREO/ Wind In-situ Science Symposium Kennebunkport, Maine, June 8-11, 2010

  2. Acknowledgements: R. Bucik M. I. Desai A. B. Galvin G. Gloeckler A. Korth R. A. Leske U. Mall R. A. Mewaldt K. Simunac

  3. Outline: • Introduction • Energetic particle properties and acceleration theories • STEREO observations of short term variability

  4. CIR overview - • see ISSI Space Science Series book - 1999 • solar origins • formation in IP medium • turbulence and acceleration • etc

  5. Solar wind and magnetic field signatures of CIRs Richardson et al. 1993, after Belcher & Davis 1971

  6. STEREO / SECCHI white light difference images of CIRs Sun from SOHO 9/17/2007 23:58 Sheeley et al., ApJ Letters, 674, L109, 2008

  7. Magnetic field and plasma signatures of a CIR -- will be covered in CIR session by Lan Jian’s talk

  8. Energetic Particle properties and acceleration theories

  9. top panel: plastic sw proton speed middle panel: SIT He, for 189, 384, and 787 keV/nucleon arrow marks selection threshold figure shows events 15-21 in Table 1. Note increases starting on days 258, 261,284 and 291 are below the selection threshold and so are not in the table bottom panel: SIT O for 67, 136, and 266 keV/nucleon note high speed streams with no suprathermals around day 305, 315, and 330 note: 650 km/s solar wind speed corresponds to 2.2 keV/nucleon; the speeds for the suprathermals are: 67 keV/n = 3589 km/s or 5.52 x greater than 650 189 keV/n = 6027 km/s, 9.3 x greater than fast sw 787 keV/n = 12294 km/s, or 18.9 x greater than fast sw calculated with xls flight times sheet Mason et al., Solar Phys, 256, 393, 2009 “STEREO science results at solar min” Fig. 1 Hourly average values from STEREO-A over a 100 day period in late 2007; Top panel: solar wind proton speed; Middle panel: suprathermal He intensities for 189, 384, and 787 keV/nucleon; Bottom panel: suprathermal O intensities for 67, 136, and 266 keV/nucleon. Arrow on middle panel shows approximate selection threshold for CIRs in survey.

  10. Energetic Particle Activity During Current Solar Minimum “quiet” periods CIRs plot file: uleis_2007_001_2010_140

  11. 2005 / Mason et al., ApJ., 678, 1458, 2008

  12. CIR spectra are power laws down to the point where they merge with the solar wind peak Spectra steepen (roll over) above ~7 to 10 times the solar wind speed From Chotoo et al. 2000

  13. Particle intensities during 2 CIRs in 2003 ULEIS #21; Jian et al #23 ULEIS #22 s

  14. Proton spectra during CIR #21 Rest frame spectrum consists of a local –5 power law that starts at w ≈ 1.7 and has an exponential roll over with e-folding speed wo ≈ 12 and a remote spectrum that bends down due to transport effects fl(w)=15w –5exp[-(w/100)1.0] fr(w)=2•106exp[-(28/w)1.15]w –5exp[-(w/1.1)1.0]

  15. 319.121 320.496 319.809 707.545 734.242 59.261 1367.440 5.056 0.189 4.830 1771.378 5.284 0.252 3.869 13389.887 6.053 0.433 108.425 0.80000319.121 320.496 319.809 707.545 734.242 59.261 1367.440 5.056 0.189 4.830 1771.378 5.284 0.252 3.869 13389.887 6.053 0.433 108.425 0.80000 Proton spectra during CIR #22 Rest frame spectrum consists of a local–5 power law that starts at w ≈ 1 and has sharp exponential roll over with e-folding speed wo ≈ 18 f(w)=1.3•103w –5exp[-(w/18)2.1] 1.300 3.700 1.000 1.900 7.600 0.900 9.000 100.000 0.700

  16. Mason et al., ApJ., 678, 1458, 2008 two sample CIRs showing two types of spectra: left, fairly hard spectrum below 1 MeV/n, steepening above 1 MeV/n (see STEP paper) right: steep spectrum below 1 MeV/n, with slope comparable to steepened portion of left panel spectrum. Note that spectral shape is actually rounded, rather than power law. left panel: combined ULEIS spectra below ~5 MeV/n; SIS is above ~5 MeV/n. Flattening of the spectra above 10 MeV/nucleon is due to Anomalous Cosmic Rays.

  17. Challenge for most models: at high energies, intense CIRs show power law spectral form, while most models predict exponential roll-overs

  18. Spectral index shows large range of values at low energies, with steepening above ~1 MeV/nucleon Mason et al., ApJ., 678, 1458, 2008

  19. Mason et al., ApJ., 678, 1458, 2008

  20. Ratios of heavy ion abundances show that spectral forms are virtually identical for species with a wide range of Q/M values intensities change by a factor of ~10^8 over range shown Mason et al., ApJ., 678, 1458, 2008 ratios wrt O for two cirs: left: CIR example showing spectral break, notice that the abundances not not change noticeably even though the intensities change by a factor of 10^8 over the range shown; right: CIR with just a steep spectrum, also see no significant changes over a smaller energy range. Compare with Cohen et al. 2005 JGR SEP event energy ranges; offset factors of 10 for various elements are same as in figure with plot of X/O vs Fe/C. INSET BOX: average of all 41 events for Fe/O, shows same small systematic rise from low to higher energies

  21. Evidence for a solar wind source for CIR Fe the CIR Fe/O ratio is significantly correlated with the solar wind Fe/O ratio 2-4 days before passage of the CIR Mason et al., ApJ., 678, 1458, 2008

  22. Average composition of 41 CIRs is close to solar wind except for He and Ne. Agreement with fast solar wind composition is slightly better Mason et al., ApJ., 678, 1458, 2008

  23. Ulysses 4.5 AU • Ulysses observations of pick up He+: • at 4.5 AU He+ more abundant than solar wind He++ (!) • evidence that bulk solar wind is not source of the CIR energetic ions Gloeckler et al., JGR, 99, 17637, 1994.

  24. He+ at 1 AU: • observed routinely in CIRs • lower average abundance than at several AU: He+/He++ = 0.25 • other heavy ions show mostly higher charge states Möbius et al. GRL, 2002

  25. Summary of spectral & compositon properties of CIRs: • spectra are broken power laws; extend to very low energies (merge into solar wind) • major elemental composition is similar to fast solar wind, except He and Ne are high • no significant energy dependence up to ~20 MeV/n • suprathermals also seen in CIRs (3He, He+); He+ often observed at ~25% of He++ • Fe/O in ACE CIRs correlates with Fe/O in solar wind prior to CIR passage

  26. CIR maximum intensities & Comparison of 2007-2008 with 1996-1997 solar minimum period

  27. Peak intensity: • during ACE survey over recent solar maximum, peak He intensities (386 kev/n) did not correlate with the 160-910 keV/n spectral index Mason et al., Solar Phys, 256, 393, 2009 “STEREO science results at solar min” Fig. 4 Peak intensity for 386 keV/nucleon He vs. differential energy power law spectral index over the range 0.16-0.91 MeV/nucleon for 1998-2006 (filled red circles), and2007-2008 (half-filled squares, values in Table 1).

  28. event counts: 2007-08 period: 36 1998-2006 period 34 events (remaining 7 events in ApJ survey are in 2007, and so assigned to STEREO survey) 94-97 data: 12 from STEP/LICA survey; 2 additional ones added for this figure (one in 1996, ond in 1997). Mason et al., Solar Phys, 256, 393, 2009 “STEREO science results at solar min” Fig. 10 CIR peak hourly intensities of 386 keV/nucleon He from Wind/STEP (red diamonds) ACE ULEIS 1998-2006 (blue filled circles) and ACE ULEIS current 2007-2008 survey (green half-filled squares). Orange line: monthly smoothed sunspot number (right axis). 1994-97 points from Mason et al. (1998) with two additional events added for this plot; 1998-2006 data from Mason et al. (2008b).

  29. Mason et al., Solar Phys, 256, 393, 2009 “STEREO science results at solar min” Fig. 11 Left: histogram of peak event intensities for 10 MeV protons for 225 solar energetic particle events observed by GOES satellites from 1976-2006 (from NOAA web site); Right: peak event intensities for 320-450 keV/nuc He for CIR events observed from 1994-2008 (red shading) and 2007-2008 survey subset (blue hatching). Below peak intensities of ~10 (/s cm2 sr MeV/nuc) the CIR histogram is missing events during solar active periods due to SEP background, but this does not affect the 2007-2008 subset.

  30. Wind SWE proton speed (blue) from kp data; STEP He5/1.6 -- division by 1.6 to adjust energy window to correpond approximately (20%) to ACE 386 keV/n channel; Wind data blanked out for R<25Re; for solar activity days 1997/308.0-318.0, and for interplanetary shock event on 1997/326 (ACE disturbance list) Mason et al., Solar Phys, 256, 393, 2009 “STEREO science results at solar min” Fig. 12 Hourly average Wind observations of solar wind protons (top panels) from the SWE instrument, and suprathermal He (lower panels) from the EPACT/STEP instrument. Left: 1996-1997; Right: 2007-2008.

  31. Theories of CIR energetic particle acceleration

  32. Solar wind and magnetic field signatures of CIRs Richardson et al. 1993, after Belcher & Davis 1971

  33. Fisk & Lee acceleration model-- • particles in CIRs accelerated by compression at forward and reverse shocks at several AU: propagate in to 1 AU • adiabatic deceleration in solar wind included • yields distribution function spectra and gradients similar to observations above ~100 keV/n • injection energy > 5 keV required, ie from postulated suprathermal tail of the solar wind • composition similar to source material (assumed to be solar wind suprathermal tail) -- (note: no systematic measurements of solar wind comp. available at that time) L. A. Fisk and M. A. Lee, Astrophys. J., 237, 620, 1980

  34. Fisk & Lee CIR spectral form-- CIR spectral form: where: v = particle speed; r = radius of observer; rs = shock radius; = shock strength; diffusion coefficient V = solar wind speed note: Jones & Ellison (1991) model produces a similar but not identical spectral form without transport (r) term

  35. Ulysses observations at 5 AU show well formed shocks and associated intensity increases of ions to > 10 MeV Desai et al. 1999

  36. Spectral form: • flat below ~1 MeV, steepening at higher energies • dashed = F&L; dotted = J&E • spectral index does not follow prediction based on shock compression ratio in Fisk & Lee model Desai et al. 1999

  37. Fisk & Lee model predicts roll-over of spectra at low energies, since the particles can’t make it back into to 1 AU propagating upstream in the solar wind -- this roll-over is not observed

  38. Giacalone, Jokpii and Kota model: • addressed puzzle of CIR spectral power law down to very low energies • particle energization by compression regions associated with CIRs • compression region widths of ~0.03 AU can accelerate particles up to 10 MeV • spectra similar to observations • (Giaclone et al, ApJ, 573, 845-850, 2002)

  39. is scale of compression region; is mfp Mason et al., ApJ., 678, 1458, 2008 Giacalone et al. CIR spectrum (blue histogram) vs. March 2000 CIR O spectrum.

  40. More complex Fisk & Gloeckler model used to fit CIR spectra • where and EC obtained from spectral fit. For 2007-2008 CIR spectral sum (Vsw > 500 km/s) got = 0.43 and EC = 0.28 MeV/nucleon • gives different spectra for different heavy ions • (Gloeckler et al., Kauai Conf., AIP CP 1039, p 367, 2008)

  41. Preliminary box score on interplanetary acceleration models:

  42. STEREO observations of short-term variabity

  43. Connection to CIRs: • with source of particles beyond 1 AU, region of connection of spacecraft to outer region depends on solar wind speed • simple corotating picture sometimes works, but often is more complex Morris et al., API CP598, 2001

  44. Fig. 5 Geocentric Solar Ecliptic positions of STEREO-Ahead and STEREO-Behind from launch through 2008 day 343. Numbers by each position trace indicate day of 2007 or 2008. The green Archimedes spiral line is for a nominal 650 km/s solar wind speed.

  45. Spectograms from -A and -B in spring 2007...quite similar plot from R. Bucik, MPS

  46. Fig. 7 Hourly average 189 keV/nucleon He intensities from SIT-A (red, top panel), ACE-ULEIS (green, middle panel), and SIT-B (blue, bottom panel). The time axes of the plots have been shifted by the nominal corotation delays such that steady corotating features would line up on the page. The dashed line is to guide the eye for the onset of the CIR starting 2008 day 222 at ACE (event #32 in Table 1).

  47. July 2009 spectograms (~8 days corotation) ... some features shifted as expected, others not seen on both S/C ? plot from R. Bucik, MPS Fig. 6 Spectrograms of ion energy vs. arrival time for SIT-A (upper panel) and SIT-B (lower panel) for August 2008. During this period the angular separation of the two STEREO spacecraft increased from 65.4ｰ to 71.2ｰ, or roughly five days of corotation. Double ended arrows point to nominally associated features, or associations that were observed on one spacecraft by not the other.

  48. ? Ahead The energetic particle signatures are only loosely correlated with the solar wind speed and peak duration 2009-07-23 1:13 EIT Behind

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