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1、Corotating Interaction RegionsGlenn Mason, JHU/APL ACE / SOHO / STEREO/ Wind In-situ Science SymposiumKennebunkport, Maine, June 8-11, 2010Acknowledgements:R. BucikM. I. DesaiA. B. GalvinG. GloecklerA. KorthR. A. LeskeU. MallR. A. MewaldtK. SimunacOutline: Introduction Energetic particle properties
2、and acceleration theories STEREO observations of short term variabilityCIR overview -see ISSI Space Science Series book - 1999 solar origins formation in IP medium turbulence and acceleration etcRichardson et al. 1993, after Belcher & Davis 1971Solar wind and magnetic field signatures of CIRsSheeley
3、 et al., ApJ Letters, 674, L109, 2008Sun from SOHO9/17/2007 23:58STEREO / SECCHI white light difference images of CIRsMagnetic field and plasma signatures of a CIR -will be covered in CIR session by Lan Jians talkEnergetic Particle properties and acceleration theoriestop panel: plastic sw proton spe
4、edmiddle panel: SIT He, for 189, 384, and 787 keV/nucleonarrow marks selection thresholdfigure 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 tablebottom panel: SIT O for 67, 136, and 266 keV/nucleonnote hig
5、h speed streams with no suprathermals around day 305, 315, and 330note: 650 km/s solar wind speed corresponds to 2.2 keV/nucleon; the speeds for the suprathermalsare: 67 keV/n = 3589 km/s or 5.52 x greater than 650189 keV/n = 6027 km/s, 9.3 x greater than fast sw787 keV/n = 12294 km/s, or 18.9 x gre
6、ater than fast swcalculated with xls flight times sheetFig. 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,
7、 and 266 keV/nucleon. Arrow on middle panel shows approximate selection threshold for CIRs in survey.Mason et al., Solar Phys, 256, 393, 2009“STEREO science results at solar min”Energetic Particle Activity DuringCurrent Solar MinimumCIRs“quiet”periodsplot file: uleis_2007_001_2010_140Mason et al., A
8、pJ., 678, 1458, 20082005 /CIR spectra are power laws down to the point where they merge with the solar wind peakSpectra steepen (roll over) above 7 to 10 times the solar wind speed From Chotoo et al. 2000ULEIS #21; Jian et al #23ULEIS #22sParticle intensities during 2 CIRs in 2003Proton spectra duri
9、ng CIR #21Rest 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 12and a remote spectrum that bends down due to transport effectsfl(w )= 15w 5exp-(w /100)1.0fr(w )= 2106exp-(28/w )1.15w 5exp-(w /1.1)1.01.3003.7001.0001.9007.6
10、000.9009.000100.0000.700319.121320.496319.809707.545734.24259.2611367.4405.0560.1894.8301771.3785.2840.2523.86913389.8876.0530.433108.4250.80000Rest 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 18f(w )=1.3103w 5exp-(w /
11、18)2.1Proton spectra during CIR #22two sample CIRs showing two types of spectra: left, fairly hardspectrum below 1 MeV/n, steepening above 1 MeV/n (see STEP paper)right: steep spectrum below 1 MeV/n, with slope comparable tosteepened portion of left panel spectrum. Note that spectral shape is actual
12、ly rounded, rather than power law. left panel: combined ULEIS spectrabelow 5 MeV/n; SIS is above 5 MeV/n. Flattening of the spectra above10 MeV/nucleon is due to Anomalous Cosmic Rays. Mason et al., ApJ., 678, 1458, 2008Challenge for most models:at high energies, intense CIRs show power law spectral
13、form, while most models predict exponential roll-oversSpectral index shows large range of values at low energies, with steepening above 1 MeV/nucleon Mason et al., ApJ., 678, 1458, 2008Mason et al., ApJ., 678, 1458, 2008ratios wrt O for two cirs: left: CIR example showing spectral break, notice that
14、 the abundances not not change noticeably even though the intensities change bya factor of 108 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
15、 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 smallsystematic rise from low to higher energiesRatios of heavy ion abundances show that spectralforms are virtually identical for species with a widerange of Q/M valuesintensit
16、ies change by a factor of 108 over range shownMason et al., ApJ., 678, 1458, 2008Evidence for a solar wind source for CIR Fethe CIR Fe/O ratio is significantly correlated with the solar windFe/O ratio 2-4 days before passage of the CIRMason et al., ApJ., 678, 1458, 2008Average composition of 41 CIRs
17、 is close to solar wind except for He and Ne.Agreement with fast solar wind composition is slightly betterMason et al., ApJ., 678, 1458, 2008Ulysses 4.5 AUGloeckler et al., JGR, 99, 17637, 1994. Ulysses observations of pick up He+: at 4.5 AU He+ more abundant than solar wind He+ (!) evidence that bu
18、lk solar wind is not source of the CIR energetic ions 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 statesMbius et al. GRL, 2002 Summary of spectral & compositon properties of CIRs: spectra are broken pow
19、er 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 w
20、ith Fe/O in solar wind prior to CIR passageCIR maximum intensities&Comparison of 2007-2008 with 1996-1997 solar minimum periodPeak intensity: during ACE survey over recent solar maximum, peak He intensities (386 kev/n) did not correlate with the 160-910 keV/n spectral indexFig. 4 Peak intensity for
21、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), and 2007-2008 (half-filled squares, values in Table 1).Mason et al., Solar Phys, 256, 393, 2009“STEREO science results at solar min”event counts: 2007-08 perio
22、d: 361998-2006 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). Fig. 10 CIR peak hourly intensities of 386 keV/nucleon He from Wind/STEP (red diamo
23、nds) 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. (2008
24、b). 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
25、/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. Mason et al
26、., Solar Phys, 256, 393, 2009“STEREO science results at solar min”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 5 keV required, ie from postulated suprathermal t
27、ail of the solar windcomposition 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, 1980Fisk & Lee CIR spectral form-CIR spectral form:where: v = par
28、ticle speed; r = radius of observer; rs = shock radius;= shock strength; diffusion coefficientV = solar wind speednote: Jones & Ellison (1991) model produces a similar but not identical spectral form without transport (r) termUlysses observations at 5 AU show well formed shocks and associated intens
29、ity increases of ions to 10 MeVDesai et al. 1999Spectral 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 modelDesai et al. 1999Fisk & Lee model predicts roll-over of spectra at l
30、ow energies, since the particles cant make it back into to 1 AU propagating upstream in the solar wind - this roll-over is not observedGiacalone, Jokpii and Kota model: addressed puzzle of CIR spectral power law down to very low energies particle energization by compression regions associated with C
31、IRs 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)Giacalone et al. CIR spectrum (blue histogram) vs. March 2000 CIRO spectrum. is scale of compression region; is mfpMason et al., ApJ., 678, 1458, 200
32、8More complex Fisk & Gloeckler model used to fit CIR spectrawhere and EC obtained from spectral fit. For 2007-2008 CIR spectral sum (Vsw 500 km/s) got = 0.43 and EC = 0.28 MeV/nucleongives different spectra for different heavy ions(Gloeckler et al., Kauai Conf., AIP CP 1039, p 367, 2008)Preliminary
33、box score on interplanetary acceleration models:STEREO observations of short-term variabityMorris et al., API CP598, 2001Connection 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,
34、 but often is more complexFig. 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. plot from R. Bucik, MPSSp
35、ectograms from -A and -B in spring 2007.quite similarFig. 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 corot
36、ating 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). plot from R. Bucik, MPSJuly 2009 spectograms (8 days corotation) . some features shifted as expected, others not seen on both S/CFig. 6 Spectrog
37、rams 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 to 71.2, or roughly five days of corotation. Double ended arrows point to nominally associated features, or
38、associations that were observed on one spacecraft by not the other. ?2009-07-23 1:13 EITAheadBehindThe energetic particle signatures are only loosely correlated with the solar wind speed and peak durationStereo-B SECCHI 19.5nm imageAug 7, 2007 00:06:32(day 220)10 degree heliographic grid overlay as
39、seen from STEREO-BCentral meridian seen from STEREO-B is in blue; green as seen from Earth; red as seen from STEREO-A Solar Weather Browser imageStereo 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 STER
40、EO-B on day 224-26, and was probably missed by STEREO-A since its 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 centr
41、al 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. correlation coef = 0.61, prob of accidential 0.0001; if we remove ou
42、tlier at diff near 10,then corr coef = 0.44 (prob 1%); if 2nd outlier removed corr = 0.30, prob 10%)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.
43、1% chance of arising from unrelated variables (n=36). Mason et al., Solar Phys, 256, 393, 2009“STEREO science results at solar min”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)“Dropout events”
44、- 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
45、may change these features suggest that connection to the acceleration region beyond 1 AU is responsible for the dropouts - not temporal changes in the CIRsFig. 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
46、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 46.3. Brief low energy events (e.g., near day 45.5 or 46.1) are upstream ions from the Earths bow shock. Summary - many fast solar wind streams a
47、nd CIRs observed in 2007-2008, 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, prob
48、ably due to magnetic connection effects to the CIR beyond 1 AU for 1994-2008 the most intense CIRs were during solar active periods, but cannot pinpoint simple cause for this 2007-2008 period had much better defined high speed solar wind streams than prior solar minimum in 1996-1997, and many more C
49、IRs 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 CIR activity updateAlthough CIR activity declined after 2008 there were still sizable CIRs in late 2008 and in 2009SEPs provided largest increases in 2010 so farSTEREO-APLASTIC &SIT
