Transcript Document

Extreme CME Events from the Sun
Nat Gopalswamy
NASA/GSFC
[email protected]
Extreme Space Weather Events (ESWE) workshop, Boulder, CO May 14-17, 2012
Extreme Event
• Event on the tail of the distribution
• An occurrence singularly unique either in the
occurrence itself or in terms of its consequences
• Occurrence: CME
• Consequences: SEP events, magnetic storms
• Will use CME speed as the key parameter
Significant CMEs & their Consequences
Cycle 23 – 24 CMEs from SOHO/LASCO
Gopalswamy, 2006; 2010
m2 – Metric type II
MC – Magnetic Cloud
EJ – Ejecta
S – Interplanetary shock
GM – Geomagnetic storm
Halo – Halo CMEs
DH – Type II at λ 10-100 meters
SEP – Solar Energetic Particles
GLE – Ground Level Enhancement
Plasma impact Energetic electrons Energetic protons
p~0.3%
p<10-4
Tail of the CME Distribution
Category
Number of CMEs
All identified CMEs
18000
# CMEs with V ≥ 1000 km/s
539
# CMEs with V ≥ 1500 km/s
131
# CMEs with V ≥ 2000 km/s
39
# CMEs with V ≥ 2500 km/s
9
# CMEs with V ≥ 3000 km/s
2
# CMEs with V ≥ 3500 km/s
1
# CMEs with V ≥ 4000 km/s
0
CME speed and in-situ shock association
100%
Had type II bursts extending
below 1 MHz
Originated from close to
disk center
Ended up with shocks
surviving to 1 AU
Type II Burst
CMEs faster than 1000 km/s
0%
AR Potential Field Energy ~ Free Energy
Free Energy ~ Magnetic Potential
energy (Mackay et al., 1997)
Free energy is > Mag PE
by a factor 3-4 (Metcalf et al. 2005)
Max potential energy during
cycle 23 ~ 4 x 1034 erg
Max CME KE observed
~ 1.2 x 1033 erg
(1000, 3675)
V = 675logE33 + 1650
E = ф2/(8πA½)
CME Speed limit  maximum
energy that can be stored
depending on A, B
B < 6100 G; A < 5000 msh
 E ~ 1036 erg
1000
ф = AR flux; A = AR area; E = AR Potential energy
Livingston et al. 2006; Newton, 1955
Gopalswamy et al., 2010
Max speed from mag PE
•
•
•
•
V = 675logE33 + 1650; E = ф2/(8πA½) ф = BA
E~1036or E33 = 103 V = 3675 km/s
Transit time = 11.3 h
But there is the solar wind  longer transit
time ~12.6 h (2005 Jan 20 CME had this
speed; transit time was 34 h because the
source was at W60)
Alfven Speed in the Source Region
½ ρV2 ≤ B2/8π  V ≤ VA
 a ≤ VA/tA= VA2/L
 (Vrsnak et al. 2007)
V – CME speed
VA – Alfven speed
L – size of the eruptive
structure
VA = 1500 km/s; L ~175,000 km  a ≤ 13 kms-2
Initial Acceleration of CMEs
Zhang et al., 2001; Vrsnak et al., 2007; Bein et al. 2011; Gopalswamy et al. 2012
Significant CMEs & their Consequences
Cycle 23 – 24 CMEs from SOHO/LASCO
Gopalswamy, 2006; 2010
m2 – Metric type II
MC – Magnetic Cloud
EJ – Ejecta
S – Interplanetary shock
GM – Geomagnetic storm
Halo – Halo CMEs
DH – Type II at λ 10-100 meters
SEP – Solar Energetic Particles
GLE – Ground Level Enhancement
Plasma impact Energetic electrons Energetic protons
p~0.3%
p<10-4
Large SEP Events: Shock-driving CMEs
2005/01/15
FR
Core
S
06:24
a
06:30
b
S
06:30 - 06:24
Fast CMEs drive shocks
Shocks accelerate particles
Particles travel along interplanetary field line
Particle radiation most hazardous in directly
affecting astronauts, space technology
Kahler, Hildner, & Van Hollebeke (1978)
c
Coronal Alfven Speed
CMEs need to be superAlfvenic
to drive a shock
Height of
shock formation
Height of
Particle release
Shock formation typically happens
close to the surface
as indicated by the type II bursts
Around the time of release of SEPs,
CMEs reach a height of ~3.6 Rs,
where the Alfven speed is ~600
km/s
For Mach 2, the CME speed needs
to be 1200 km/s
Gopalswamy et al. 2012
SEP Producing CMEs
The CMEs are very fast
Almost all CMEs are halos or partial halos
Halo CMEs are generally wide
CMEs are Efficient Accelerators
Typically about 10% of CME
kinetic energy goes into SEPs
Similar to flare energy
Expect GLEs to be associated
with energetic CMEs
Mewaldt, 2006
GOES provides Proton flux
for >1 MeV to >100 MeV
1 MeV proton
100
Thermosphere
80
Mesopause
10 MeV proton
Altitude (km)
Mesosphere
60
40
Middle
Atmosphere
Stratopause
100 MeV proton
Stratosphere
20
Tropopause
Troposphere
1 GeV proton
0
Particle radiation from the Sun can destroy ozone
courtesy: C. Jackman
NOx Production due to Jan 2005 SEP Events
Seppälä et al. 2008
log (Ip) = - 9.08 + 3.7 log (V)
- from cycle 23 SEP events
Ip = >10 MeV proton intensity (pfu)
V = CME speed
For the Carrington event, transit time
is known (17.5 h). Estimate
V = 2356 km/s from ESA model
Ip = 2495 pfu
May not be an extreme SEP event
but:
# SEP Events with intensity ≥F
Cumulative Distribution of SEP Events from NOAA
Proton Events List
233 large SEP events
1976 – 2012 March
Carrington Event
(Est. 2495 pfu)
Cycles 21-24
Manchester et al. 2006: The model CME started out with
~4000 km/s and ended up having 2000 km/s at 1 AU (average speed: 3000 km/s)
Historical Fast Transient Events
Cliver et al., 1990; Gopalswamy et al., 2005
Historical Fast Transit CMEs:
KE Estimate
Gopalswamy et al. 2005
SOHO CMEs
31.8 h
1.2x 1033 erg
27.9 h
1 Aug 4, 1972 14.6 h
V=2854 km/s
2 Sep 1, 1859 17.5 h
V = 2356 km/s
18.9 h
Cycle 24 CMEs: Shock
Transit time ≥35 km/s
19.7 h
V
T = abV + c; a = 151.002, b = 0.998625, and c =11.5981 (ESA model)
CMEs Producing Magnetic Storms
The CMEs are very fast (projected speed ~1041 km/s)
Almost all CMEs are halos or partial halos (92%)
Geomagnetic Storm and CME parameters
Gopalswamy 2008
Dst [nT]
Dst = – 0.01VBz – 32 nT
The high correlation suggests
That V and Bz are the most
Important parameters
( - Bz is absolutely necessary)
V and Bz in the IP medium are
related to the CME speed and
magnetic content
VMCBz [104 nT•km/s]
Origin of V and B
Dst = – 0.01VBz – 32 nT
Solar Wind speed
CIR Speed
CME speed
Active Region
Free energy
Alfven waves
CIR: Amplified Alfven waves
ICME: Sheath & Flux rope
Heliospheric
Mag Field
Active Region
Mag Field
V and Bz in CIRs and ICMEs
Carrington Event:
VBz = 1.6 105 nT•km/s
V = 2000 km/s,
Dst = -1650 nT
 Bz = -81 nT
Cycle 23 Storms:
Major (Dst < -100 nT): 86%
due to CMEs; 14% CIRs
No CIR storm with
Dst < -130 nT
Gopalswamy, 2008
# Events with intensity ≥|Dst|
Occurrence Rate of mag. storms
Cumulative Distribution
Occurrence Frequency
Carrington Event
See also Riley, 2011
Geoeffective & SEP-producing CME
Sources
Carrington Event
N20W12
CMEs need to arrive at Earth
CMEs must contain Bz South
Similar to MC and Halo CME sources
CMEs need to drive shocks
Source region needs to be magnetically
connected to Earth
Many double-whammy events
Super flares from Solar-type Stars
• Super flares: Flares with energy at least 100 times
that of a solar flare of importance 2 [Schafer, King
and Deliyannis, 2000]
• The frequency of super flares is likely to be zero on
the Sun based on 9 super flares in stars of spectral
type F8 – G8 (main sequence stars)
• Using Kepler observations, Maehara et al. (2012)
found 365 super flares from 148 G-type main
sequence stars (including 101 stars with rotation
period >10 days)
Solar and Stellar Super Flares
Different?
• Maehara et al. (2012) concluded that super flares
with energy ~1035 erg may occur once in 5000 years
(may also occur with a similar frequency on the Sun)
• Absence of world-spanning aurorae in historical
records (Wolff et al. 2012)
• Many F and G main-sequence stars have close
Jovian planetary companions  different type of
magnetic reconnection: star field tangled by the
Jovian planet field (Rubenstein and Schaefer, 2000)
• What type of CMEs?
Summary
• The extreme CMEs can be related to the available
free energy in active regions, which in turn depends
on the strength of the AR field and AR size
• Using the highest observed values, one can get up to
a CME speed of ~7000 km/s
• SEP and Dst consequences depend critically on the
CME structure (Shock for SEPs, BzS for Dst), but also
on the CME kinematics
• Super Flares from solar-like stars are worth
studying: different type of magnetic reconnection
possible
Max speed from mag PE
• V = 675logE33 + 1650; E = ф2/(8πA½) ф = BA
• E~1036or E33 = 103 V = 3675 km/s
• If all the energy went into a single CME,
V~14,000 km/s (for M ~1018 g)
• Halloween 2003 period: 5 – 26% of free
energy went into the CME kinetic energy
•  CME speed is expected to be ~3200 to
7000 km/s
CMEs and Flares
• VA = 2.18 × 106n−1/2B
• V = 3675 km/s; n = 109 cm-3
• B=