Corotating Interaction Regions

Glenn Mason, JHU/APL

ACE / SOHO / STEREO/ Wind In-situ Science Symposium

Kennebunkport, Maine, June 8-11, 2010

Acknowledgements:

R. BucikM. I. DesaiA. B. GalvinG. Gloeckler

A. KorthR. A. Leske

U. MallR. A. Mewaldt

K. Simunac

Outline:

• Introduction

• Energetic particle properties and acceleration theories

• STEREO observations of short term variability

CIR overview -

see ISSI Space Science Series book - 1999• solar origins

• formation in IP medium

• turbulence and acceleration

• etc

Richardson et al. 1993, after Belcher & Davis 1971

Solar wind and magnetic field signatures of CIRs

Sheeley et al., ApJ Letters, 674, L109, 2008

Sun from SOHO9/17/2007 23:58

STEREO / SECCHI

white light difference images of

CIRs

Magnetic field and plasma signatures of a CIR --

will be covered in CIR session by Lan Jian’s talk

Energetic Particle properties and

acceleration theories

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

Mason et al., Solar Phys, 256, 393, 2009“STEREO science results at solar min”

Energetic Particle Activity DuringCurrent Solar Minimum

CIRs

“quiet”periods

plot file: uleis_2007_001_2010_140

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

2005 /

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

ULEIS #21; Jian et al #23 ULEIS #22

s

Particle intensities during 2 CIRs in 2003

10-9

10-7

10-5

10-3

10-1

101

103

105

107

1 10 100

ACE master CIR 03_303_330 3:48:58 PM 11/4/09

F(W) =f(w)F(W) =f(w)tail power lawtailtail2sum

chi2

parabola

10-9

10-7

10-5

0.001

0.1

10

1000

105

107

Phase Space Density (s

3 /km

6 )

Proton speed (in solar wind frame)/solar wind speed (w)

314.455315.663

2003Start DOYStop DOY<Vsw>

Downstream of Forward Shock

Compression ratio rn= 3.3±1.4

Mach number MA = 3.2±0.9

fit1m1=3.9e4;m2=5;m3=12;m4=.6;m5=2.;m6=1;

c1=m1*(c0^-m2)*exp(-(c0/m3)^m4)*exp(-(m5/c0)^m6);c2=2.7e3*c0^-9;c3=c1+c2

fit 2m1=6e3;m2=4.3;m3=9;m4=.72;

c1=m1*(c0^-m2)*exp(-(c0/m3)^m4)c2=1.65e3*c0^-9.7;c6=c1+c2

Upstream of Forward Shock

Halo Solar Wind

677.793

Suprathermal–5 Power Law Tails

SWICS

m1=15;m2=5;m3=100;m4=1;m5=0;m6=1;m7=20e5;m8=1.1;m9=1;m10=28;m11=1.15;m12=5e2;m13=14.5;

ULEIS

Pickup Protons

Roll over 1

Roll over 2

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]

10-9

10-7

10-5

10-3

10-1

101

103

105

107

1 10 100

ACE master CIR 03_303_330 3:48:58 PM 11/4/09

F(W) =f(w)F(W) =f(w)tail power lawtailtail2sum

chi2

parabola

10-9

10-7

10-5

0.001

0.1

10

1000

105

107

Phase Space Density (s

3 /km

6 )

Proton speed (in solar wind frame)/solar wind speed (w)

319.121320.496

2003Start DOYStop DOY<Vsw>

Downstream of Forward Shock

Compression ratio rn= 3.3±1.4

Mach number MA = 3.2±0.9

fit1m1=3.9e4;m2=5;m3=12;m4=.6;m5=2.;m6=1;

c1=m1*(c0^-m2)*exp(-(c0/m3)^m4)*exp(-(m5/c0)^m6);c2=2.7e3*c0^-9;c3=c1+c2

fit 2m1=6e3;m2=4.3;m3=9;m4=.72;

c1=m1*(c0^-m2)*exp(-(c0/m3)^m4)c2=1.65e3*c0^-9.7;c6=c1+c2

Upstream of Forward Shock

Halo Solar Wind

707.545

Suprathermal–5 Power Law Tails

SWICS

m1=1.3e3;m2=5;m3=18;m4=1.5;m5=0;m6=1;m7=0e3;

ULEIS

Pickup ProtonsRoll over 1 Roll over 2

1.3003.7001.0001.9007.6000.9009.000

100.0000.700

319.121 320.496 319.809 707.545 734.242 59.261 1367.4405.056 0.189 4.830 1771.378 5.284 0.252 3.86913389.887 6.053 0.433 108.425 0.80000

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]

Proton spectra during CIR #22

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

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

Spectral index shows large range of values at low energies, with steepening above ~1 MeV/nucleon

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

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 bya 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 smallsystematic rise from low to higher energies

Ratios of heavy ion abundances show that spectralforms are virtually identical for species with a wide

range of Q/M values

intensities change by a factor of ~10^8 over range shownMason et al., ApJ., 678, 1458, 2008

Evidence for a solar wind source for CIR Fe

the CIR Fe/O ratio is significantly correlated with the solar windFe/O ratio 2-4 days before passage of the CIR

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

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

Ulysses 4.5 AU

Gloeckler et al., JGR, 99, 17637, 1994.

10-9

10-7

10-5

10-3

10-1

101

103

105

107

109

1 10

F(W) Phase Space Density (s

3

/km6)

W Ion Speed (SC frame)/Vsw

HI-SCALE

SWICS

H+He+

He++

He

1991.292.0400-293.04004.485 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

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

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

CIR maximum intensities

&

Comparison of 2007-2008 with 1996-1997 solar minimum

period

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”

Mason et al., Solar Phys, 256, 393, 2009“STEREO science results at solar min”

Mason et al., 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<25Re; for solar activity days 1997/308.0-318.0, and for interplanetaryshock event on 1997/326 (ACE disturbance list)

Mason et al., Solar Phys, 256, 393, 2009“STEREO science results at solar min”

Theories of CIR

energetic particle

acceleration

Richardson et al. 1993, after Belcher & Davis 1971

Solar wind and magnetic field signatures of CIRs

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

Fisk & Lee CIR spectral form--

CIR spectral form:

where: v = particle speed; r = radius of observer; rs = shock radius;

= shock strength; diffusion coefficientV = solar wind speed

note: Jones & Ellison (1991) model produces a similar but not identical spectral form without transport (r) term

f =

r

rs

⎛

⎝

⎜⎞

⎠

⎟

2 / ( 1 − ) + V / ( o

v )

v− 3 / ( 1 − )

exp −

6 o

v

V ( 1 − )2

⎛

⎝

⎜⎞

⎠

Ulysses observations at 5 AU show well formed shocks and associated intensity increases of ions to > 10 MeV

Desai et al. 1999

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

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

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)

is scale of compression region; is mfp

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

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)

€

dj /dE = j0E−1.5 exp[−(m /q)γ • (E /EC )(1+γ ) / 2 ]

Preliminary box score on interplanetary acceleration models:

Model Spectral

form

Power Law at

high energies?

Deriving spectral

form from other

observables

Acceleration region is

observed?

Transport to 1 AU a

problem?

Constant ratios of

x/O?

Suprathermals Also

accelerated (3He, He+)?

Fisk & Lee

OK, except high en

p.l.

Problem

Y, but doesn’t work

Yes, shocks beyond 1 AU

Yes OK

Prob OK, since assumed injection at 5

keV/n

Giacalone et al.

OK, but only one

test ? Y

Yes, compressions

at 1 AU

No ? ?

Fisk & Gloeckler

OK, high en

dep on

Depends On

Gives low energy E-1.5

Higher en involves

other variables

Plasma turbulence in

solar wind

Not implemented

Depends On

OK since injection

above SW peak

STEREO observations of

short-term variabity

Morris et al., API CP598, 2001

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

plot from R. Bucik, MPS

Spectograms from -A and -B in spring 2007...quite similar

plot from R. Bucik, MPS

July 2009 spectograms (~8 days corotation) ... some features shifted as expected, others not seen on both S/C

?

?2009-07-23 1:13 EIT

Ahead

Behind

The energetic particle signatures are only loosely correlated with the solar wind speed and peak duration

Stereo-B SECCHI 19.5nm image

Aug 7, 2007 00:06:32

(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 224-26, 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

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”

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” --• 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

Summary --• many fast solar wind streams and 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, probably 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 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

CIR activity update

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

STEREO-A

PLASTIC &

SIT