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 3

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

5. 5

6. Solar wind and magnetic field signatures of CIRs
Richardson et al. 1993, after Belcher & Davis 1971 6

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

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

9. Energetic Particle properties and acceleration theories

10. top panel: plastic sw proton speed
middle panel: SIT He, for 189, 384, and 787 keV/nucleon
arrow marks selection threshold
figure shows events 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 = 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.

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

12. 2005 /
Mason et al., ApJ., 678, 1458, 2008

13. Spectra steepen (roll over) above ~7 to 10 times the solar wind speed
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

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

15. 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]

16. Proton spectra during CIR #22
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
0.700

17. two sample CIRs showing two types of spectra: left, fairly hard
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.

18. Challenge for most models:
at high energies, intense CIRs show power law spectral
form, while most models predict exponential roll-overs 18

19. Spectral index shows large range of values at low energies, with steepening above ~1 MeV/nucleon
Mason et al., ApJ., 678, 1458, 2008 19

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

21. 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 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

22. 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

23. Agreement with fast solar wind composition is slightly better
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

24. Ulysses observations of pick up He+:
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.

25. observed routinely in CIRs
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

26. 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

27. CIR maximum intensities &
Comparison of with solar minimum period

28. Peak intensity:
during ACE survey over recent solar maximum, peak He intensities (386 kev/n) did not correlate with the 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 MeV/nucleon for (filled red circles), and (half-filled squares, values in Table 1).

29. event counts:
period: 36
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 (blue filled circles) and ACE ULEIS current survey (green half-filled squares). Orange line: monthly smoothed sunspot number (right axis) points from Mason et al. (1998) with two additional events added for this plot; data from Mason et al. (2008b).

30. Mason et al., Solar Phys, 256, 393, 2009
“STEREO science results at solar min”
Fig Left: histogram of peak event intensities for 10 MeV protons for 225 solar energetic particle events observed by GOES satellites from (from NOAA web site); Right: peak event intensities for keV/nuc He for CIR events observed from (red shading) and 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 subset.

31. Wind SWE proton speed (blue) from kp data; STEP He5/1
Wind SWE proton speed (blue) from kp data; STEP He5/ 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/ , 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: ; Right:

32. Theories of CIR
energetic particle
acceleration

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

34. 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

35. Fisk & Lee 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

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

37. 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

38. 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

39. 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, , 2002)

41. Giacalone et al. CIR spectrum (blue histogram) vs. March 2000 CIR
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.

42. More complex Fisk & Gloeckler model used to fit CIR spectra
where and EC obtained from spectral fit. For 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) 42

43. Preliminary box score on interplanetary acceleration models:43

44. STEREO observations of
short-term variabity

45. 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

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

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

48. 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).

49. July 2009 spectograms (~8 days corotation)
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 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.

50. ?
Ahead
The energetic particle signatures are only loosely correlated with the solar wind speed and peak duration
:13 EIT
Behind 50

52. Stereo-B SECCHI 19.5nm image
Aug 7, :06:32
(day 220)
10 degree heliographic grid overlay as seen from STEREO-B
Central meridian seen from STEREO-B is in blue; green as seen from Earth; red as seen from STEREO-A
Solar Weather Browser image
Stereo A is at 8.98° latitude; B at 3.78°; so the 5.2° difference is about one-half of a grid spacings. The hole at about E45 is probably the one seen by STEREO-B on day , and was probably missed by STEREO-A since it’s trace is about 5°‚ north of B, a size shown by the double headed arrow at E5
Fig. 8 SECCHI-B 19.5 nm image taken on 2008 day 220 showing the coronal hole feature giving rise to the event #32 shown in Fig. 7. Blue longitude line is central meridian (CM) seen from STEREO-B, green is CM seen from ACE, red is CM seen from STEREO-A. Double headed arrow near CM shows the approximate latitude difference between STEREO-A and -B at this time. Grid on image has 10° spacing.

53. Difference between SIT-A and SIT-B spectral index for He vs
Difference between SIT-A and SIT-B spectral index for He vs. heliographic latitude difference between the two spacecraft. The correlation coefficient between the two quantities is 0.62, which has a <0.1% chance of arising from unrelated variables (n=36).
Mason et al., Solar Phys, 256, 393, 2009
“STEREO science results at solar min”
correlation coef = 0.61, prob of accidential ~0.0001; if we remove outlier at diff near 10°,
then corr coef = (prob ~1%); if 2nd outlier removed corr = 0.30, prob ~10%)

54. Example of case where heliolatitude difference is close to 0°, yet STEREO-A signature is absent of very small
(separation angle ~91° or 6.8 days corotation)

55. “Dropout events” --
in several CIRs, particle intensity increases show a decrease at all energies, followed by a recovery that is also independent of energy
these decreases correlate reasonably well with changes in solar wind speed
particle energy spectra are similar before and after the droput, although intensities may change
these features suggest that connection to the acceleration region beyond 1 AU is responsible for the dropouts -- not temporal changes in the CIRs

56. Fig. 13 ACE (a) solar wind speed, (b) 189 keV/n He intensity (particles/s cm2 sr MeV/nuc), (c) 4-hour average suprathermal He spectral slope for intensity bins centered at 193 and 772 keV/n, and (d) ion arrival spectrogram for C and heavier elements, showing CIR “dropout” early on day 44 and at day ~ Brief low energy events (e.g., near day 45.5 or 46.1) are upstream ions from the Earth’s bow shock.

57. Summary --
many fast solar wind streams and CIRs observed in , but not all streams produced CIRs
spectral forms similar to earlier surveys; much lower intensities at ~few MeV/n compared to active period
CIRs observed sequentially from -B to -A, but not always seen; energetic particle intensity pattern did not corotate rigidly, probably due to magnetic connection effects to the CIR beyond 1 AU
for the most intense CIRs were during solar active periods, but cannot pinpoint simple cause for this

58. period had much better defined high speed solar wind streams than prior solar minimum in , and many more CIRs
size distribution of CIRs shows a much sharper cutoff than 10 MeV SEP protons from GOES
about 25% of CIRs show “dropouts” for a day or so apparently when connection to acceleration region beyond 1 AU changes
some of the complex features of the CIRs appear to be due to relatively small coronal hole solar sources, wherein the different heliolatitude traces of STEREO-B, -A, and ACE played a significant role

59. CIR activity update

60. SEPs provided largest increases in 2010 so far
STEREO-A
PLASTIC &
SIT
Although CIR activity declined after 2008 there were still sizable CIRs in late 2008 and in 2009
SEPs provided largest increases in 2010 so far 60