complete characterization of a cme-driven shock from uv, white light and radio data
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““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
Complete characterization of a Complete characterization of a CME-driven shock from UV, white CME-driven shock from UV, white
light and radio datalight and radio data
Complete characterization of a Complete characterization of a CME-driven shock from UV, white CME-driven shock from UV, white
light and radio datalight and radio data
Alessandro Bemporad
& Salvatore MancusoINAF – Turin Astronomical Observatory
Alessandro Bemporad
& Salvatore MancusoINAF – Turin Astronomical Observatory
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
Outline
• Introduction
• The March 22, 2002 CME
• Shock front: radio, white light and EUV signatures
• Estimate of up-stream plasma parameters
• Rankine-Hugoniot equations for oblique shock: estimate of down-stream plasma parameters
• Conclusions
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso Coronal Mass Ejections
observed by UVCSCoronal Mass Ejections are sporadic events where 1015-1016g of mass are launched into the Interplanetary Space at velocities ranging between ~ 500-2000 km/s.
ee
epe n
m
neff
2
Fast CMEs drive fastfast shocksshocks that accelerate SEPs and electron beams (~10 keV) able to generate plasma wavesplasma waves at the local plasma frequency fpe that scatter off ions or combine to produce
type II radio emissiontype II radio emission at fpe (fundamental) and 2fpe (harmonic).
Metric type II radio bursts offer clear evidence of coronal shocks but: 1) no spatial resolution: direct imaging of coro-nal shocks remains in fact an outstanding observational challenge; 2) no direct information on physical properties of shocked plasma.
Over the last 14 years observations of coronal shocks by the
UV Coronagraph Spectrometer (UVCS) on SOHO provided
both spatial resolution and unique diagnostics for the physical
processes in coronal shocks.
arc
sec
time
2fpe
freq
uen
cy
fpe
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
The passage of a shock heats the emitting material and is detected as broad wings mainly in the non neutral ions. In the UVCS spectra the presence of a shock front is more likely dete-cted in the brightest spectral lines such as the O VI doublet and the H I Ly-line, providing a direct diagnostic of the kinetic temperatures behind the shock.
Detections of shocks in UV spectra have already been reported for four CMEs (Raymond et al. 2000; Mancuso et al. 2002; Raouafi et al. 2004; Ciaravella et al. 2005; Mancuso & Avetta 2008).
Broad wings in the O VI doublet (right) as results of a shock passage (left; from Mancuso et al. 2000, A&A ).
CME-driven shocks as seen in UV spectra
shockfront
None of these works made a determination of pre- andpost-shock physical parameters of plasma
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso The March 22, 2002 event
• CME start time ~ 10:30 UT• Fast CME (vLASCO cat = 1750 km/s)• Associated to: - X-class flare - Strong radio burst• UVCS observationsFOV: slit centered at 4.1 Rʘ, lat = 70°SWTime coverage: 00:55 – 18:29, 200s exposures
11:06 11:30 11:54
LASCO/C2 images
UVCS slit
coronalstreamer
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso Shock signature in Radio data
Nancay Radioheliograph – 164 MHz
CME source AR
CME
A few minutes after the CME start time a strong arch-shaped radio emission (164 MHz) appears above the limb. The radio emission is located just above the region where the plasma has been evacuated. At the same time interval a type-II signature has been detected from the Potsdam radiospectrometer
EIT 195
22/03/2002, 10:40 UT
→ possible early signature of the CME driven shock.
In the following minutes a type-II radio burst is detected by the WIND spacecraft. As the shock expands, the streamer plasma density decreases with altitude, leading to the observed frequency drift with time.
→ signature of the CME-driven shock
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso Shock signature in white light
LASCO/C2 base difference images
Shock front
Shock front
Shock front
2002/03/22, 11:06 2002/03/22, 11:30 2002/03/22, 11:54
CoronalstreamerUVCS
slit
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
Ly 1215Å intensity O VI 1032Å intensity
Shock signature inUVCS spectra
Ly 1215Å: due to radiative excitation alone. Post-shock plasma accelerated & heated → Ly emission decreases (Doppler dimm.)
O VI 1032Å: due to both radiative and collisional excitations.Post-shock plasma compressed and accelerated → OVI radiative component Doppler dimmed, collisional component increased.
11:30
Shock front
Pre-shock coronalstreamer
Shock front
Pre-shock coronalstreamer
Streamer deflection Streamer deflection
Polar angle (°) Polar angle (°)
Tim
e (h
) →
Tim
e (h
) →
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
Line of sight
post-shock
pre-shock
O VI 1037.6
O VI 1031.9
UVCS O VI line profiles Post-shock plasma:
• Tk ~2 times larger than bgd corona• Tk fades back to
coronal values in ~3h
These are only upper limits to the real Tk:obs. broadening = heating + LOS exp.
• vLOS ~ 120 km/s• vLOS fades in ~3h
Taking into account the shock velocity on the plane of the sky:
• vPOS ~ 1150 km/s• CME ~ 6° toward the observer, mainly on the plane of the skyplane of the sky
backgroundcorona
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
1
32
These equations have in general up to 3 possible solutions for the compression ratio r = d /u. If we stay in the region of the plane [(vu),(Bu)] where rr the has a unique solution:
1
MHD-Rankine-Hugoniot equations for oblique shock
0
0
012
1
0/
02/
0
0
2
0
022
x
xyyx
x
xyyxy
yxyx
yx
B
BvBv
v
BvBvBpv
BBvv
Bpv
v
Mass fluxX-momentum
Y-momentum
Energy
Maxwell’s eq.
Maxwell’s eq.
r
vnT
vuBu
uuu
,,
,,,
vdBdd
ddu
v
BTB
,,
,,,Rankine-Hugoniot eq.
vuBuu
uuu
v
BnT
,,
,,,
vdBdd
ddd
v
BnT
,,
,,,Rankine-Hugoniot eq.
?
Estimate of Upstream parameters1) Derive TTuu, n, nuu, v, vuu from UVCS data;2) Derive r, r, vuvu from LASCO;3) Assume a value for BuBu
Downstreamparameters
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
Ly 1215Å intensity
Polar angle (°)
Tim
e (h
) →
Upstream parametersfrom UVCS data
• Assume ne(r), Te(r), vout(r) profiles along the LOS (Cranmer 1999)• Vary densities and temperatures by introducing two costant multiplier (Kn and KT for density and temperature, respectively);• Compute the expected I(Ly) and I(OVI) by iterating over all the possible values of (Kn, KT) pairs and integrating along the LOS;• Find the (Kn, KT) pair that better reproduces the observed intensities.
Results: (Kn, KT) = (4.3, 0.37) → nnuu(POS)(POS) ~ 9×104 cm-3
TTuu(POS)(POS) ~ 2×105 K
Tim
e (h
) →
vshock = 1150 km/s
Shock frontI(Ly)u = 9.2 x108 phot cm-2s-1sr-1
(interplanetary Ly- subtracted)
I(O VI)u = 7.6 x106 phot cm-2s-1sr-1
upstreamplasma
downstreamplasma
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso Upstream parameters
from LASCO/C2 data
• Measure the pre- and post-shock WL• Assume a thickness L along the LOS for the involved coronal region → L = 0.53 R๏ (sherical shell: thickness d=104km, r=2.5 R๏)• Given L, estimate the fraction k• Estimate the compression ratio rr as
KA
KABr
)1( Result: r r ~ ~ 2.82.8
X (R๏) X (R๏)
Y (
R๏)
Y (
R๏)
vshock
vwind
radial to the Sun
shock front
UVCS slit
R-H equations hold in the frame of reference at rest with the shock front
vshock= 1150 km/s
vwind~300 km/s
vvuu ~~ 1080 km/s 1080 km/s
vuvu~ 15°~ 15°
Bu ║vwind
BuBu~ 70°~ 70°
11:30
L
pre-shockwhite light
LOS
LOS
post-shockwhite light
Compressedplasma
A =
B =
Fraction k
kA =B-A =
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso Downstream parameters
8.2
15
70
/1080
109
10234
5
r
skmv
cmn
KT
vu
Bu
u
u
u
0.38
0.74
/475
063.0
1046.1
051.07
vd
Bd
d
d
d
u
skmv
GB
KT
GB
Rankine-Hugoniot eq.
(pre) = 0.027 → << 1(post) = 3.52 → > 1
vA(pre) ~ 350 km/s > vwind(pre) → sub alfvènic flow (MMAuAu = 0.85 = 0.85)vA(post) ~ 260 km/s << vwind(post) → super-alfvènic flow (MMAdAd = 2.94 = 2.94)
vshockBu
Bu=70°
Bd=74.0°
Bd
vwind(pre)
vu=70°
vwind(post)
vd=22.4°
vshock
These results hold in the reference frame at rest with the shock surface. Hence, in the referenceframe at rest with respect to the Sun:
vwind(pre) ~ 300 km/s vwind(post) ~ 770 km/s
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
Summary
• On March 22, 2002 a fast CME occurred, related to X-class flare and type-II radio burst.
• It is possible to identify the transit of the shock front both in the LASCO/C2 and UVCS data.
• From these data we derived an estimate for the upstream plasma parameters, but the magnetic field.
• Given the upstream parameters and the compression ratio r from LASCO data, the R-H equations give the downstream parameters.
• Results: the shock transit corresponds to 1) plasma compression (~2.8), 2) heating (by a factor ~70) and 3) transition from sub- to super-alfvenic flow and 4) from <<1 to >1.
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
LASCO/C2 wavelet enhanced images
Shock front
Shock front
Shock front
Coronalstreamer
Shock signature in white light
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
Bemporad & Mancuso (2009)
Magnetic field estimate
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso UVCS O VI line profiles
Post-shock profiles are:
• broader than coro-nal profiles (broade-ning fades with time)
• red-shifted (shifting fades with time)
Normalized coronal pre-shock profiles
Normalized post-shock profiles (coronal profile sutracted)
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
Ciaravella et al. (2005)
Raymond et al. (2000)
Mancuso et al. (2002)
SEP ?
East Limb NO SEP
West Limb SEP
Coronal shocks Coronal shocks detected by detected by UVCS/SOHOUVCS/SOHO
Proxy for SEPsWE
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
When the shock arrives at the UVCS slit
- H I Lyman alpha intensity drops down
- O VI lines develop broad wings
- Si XII line intensities increase.
June 11, 1998June 11, 1998 (Raymond et al. 2000)(Raymond et al. 2000)
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
June 28, 2000June 28, 2000 (Ciaravella et al. 2005) (Ciaravella et al. 2005) O VI 1032
18:59 UT
19:05 UT
19:02 UT
O VI 1037
““IAGA2”, Cairo – 05/12/09IAGA2”, Cairo – 05/12/09
““Characterization of a CME-driven shock from UV, Characterization of a CME-driven shock from UV, white light and radio datawhite light and radio data ” – Bemporad & Mancuso” – Bemporad & Mancuso
A compression ratio of 1.8 was the only value consistent with both O VI and H I line widths
March 3, 2000March 3, 2000 (Mancuso et al. 2002)(Mancuso et al. 2002)
O VI 1032, 1037
t = 02:21 UT t = 02:24 UT
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