CMEs, CIRs, and Space Weather

1
CMEs, CIRs, and Space Weather

• Nat Gopalswamy
• NASA Goddard Space Flight Center, USA

Second Asia Pacific Regional IHY School, October
10-22, 2008 Beijing, China
2
Why do we care about Space Weather?

• Analogous to violent terrestrial weather such as
  during a hurricane
• can disrupt satellite communications, destroy
  spacecraft, and expose astronauts and occupants
  of high-flying aircraft to high amounts of
  radiation
• Storms can result in power outage, pipeline and
  railroad disruptions
• Interesting science to understand the mass and
  electromagnetic output and variability of the Sun

3
Solar Wind Structures

• CMEs and CIRs are the two large-scale
  interplanetary structures, both can cause intense
  geomagnetic shocks
• CMEs originate from closed field regions, while
  CIRs are formed due to high speed streams from
  coronal holes pressing against slower ones from
  the quiet Sun
• Both produce out-of-the-ecliptic component of the
  interplanetary magnetic field
• Both CMEs and CIRs can drive shocks and produce
  energetic particles, another important
  contributor to hazardous space weather

4
Dst dependence on V, Bz

• Dst 0.01VBs 25
• Dst in nT
• V in km/s, Bs in nT

5
Discussion on

• Halo CMEs (remote)
• ICMEs/sheaths (in situ)
• Bz South
• Magnetic storm (Dst)

• Coronal Holes (remote)
• CIRs (in situ)
• Bz South
• Magnetic storm (Dst)

6
Geoeffectiveness

• Geoeffectiveness ability to produce geomagnetic
  storms, as measured by the Dst index
• Dst gt -50 nT (weakly geoeffective -50 nT to -30
  nT or non-geoeffective Dst gt -30 nT)
• Dst -50 nT geoeffective (CMEs, CIRs)
• -100 nT lt Dst -50 nT moderately geoeffective
  (CMEs, CIRs)
• Dst -100 nT strongly geoeffective (mostly
  CMEs 10 CIRs)

Gosling et al. 1990 Loewe Prolss 1997 .
7
Some definitions

• Halo CMEs CMEs that appear to surround the
  occulting disk (partial halos 120oWlt360o)
• Geoeffective CMEs CMEs that result in Dst -50
  nT (major storms Dst -100 nT)
• ICMEs Interplanetary CMEs
• Magnetic Clouds ICMEs with flux rope structure
  as observed in the solar wind
• Ejecta, non-cloud MC ICME without flux rope

8
How do we get Bz in the IP medium?

• Normal Parker spiral field does not have a Bz
  component (except for Alfvenic fluctuations in
  the solar wind)
• CMEs with flux rope structure (magnetic clouds)
  naturally have Bz component
• Magnetic field draping can also cause Bz in ICME
  sheaths
• Corotating interaction regions (amplified Alfven
  waves)
• High-speed stream Fast wind from coronal holes
• CIRs corotating interaction regions (interaction
  between HSS and the slow wind ahead)

9
Solar Variability its Impact on the Solar
System
Interior
Sun puts out - electromagnetic radiation (blackbod
y flare) and mass (solar wind, CMEs, SEPs)
Mass Chain CMEs Solar Wind SEPs
Aspects of CMEs related to Space Weather -
ability to cause Geomagnetic storms (geoeffective
ness) - ability to drive shocks that accelerate
SEPs (SEPeffectiveness)
Climate effects mainly from variability in
electromagnetic radiation with a contribution
from the mass chain
10
CMEs Space Weather
Dst (nT)
0
- 100
CMEs
- 200
- 300
- 400
- 500
UT (h)
Magnetic storms
SEPs
On the way and upon arrival
Upon arrival at Earth
CMEs Magnetic Structure Is Crucial (Bz lt0)
Space systems Airplanes atmosphere
Space systems Magnetosphere Ionosphere Atmosphere
Ground
Shock-driving Capability is Crucial VCME -VSW gt
VMS
11
Coronal Hole(example 1996/10/20)
SXT
Unipolar, enhanced B, lower temperature, dark in
X-ray and EUV, bright in microwave, 27-day
recurrence, polar equatorial
12
High-speed Wind from Coronal Hole
Remember Western is earlier because Sun rotates
from east to west
Coronal hole (left) seen in a SOHO/EIT taken on
July 13 2003 and the solar wind speed measured
near Earth over a 15-day period in the coronal
hole.
13
24
28
30
1
03 Oct
22 Sep
14
CIRs
Superposed epoch analysis of 25 CIRs
Gosling 1996
25 Streams
E
SIR
W
the flow is deflected first to the west (in the
direction of Earths motion around the Sun and
then to the east
15
Key element for geoeffectiveness Amplification
of the Alfven waves
CH
East-west
radial
cf. Zong talk
16
High-speed Wind from Coronal Hole
B
Bz
n
V
Dst
Solar wind parameters (total magnetic field Bt,
vertical component Bz, proton density Np, solar
wind speed V) and the Dst index for a 19-day
period in 2003.
17
Gopalswamy, 2008
18
MC
Bt
CME
Flare
Bz
All ICMEs are MCs?
MC has specific B structure
19
Magnetic cloud
Y
High B Smooth Bz rotation Low proton T
sketch of a flux rope
ESA
N
Z
spacecraft
E
SUN
X
S
B and Bz of the MC as recorded by the spacecraft
20
South-North MC
Reconnection during the first half of the MC,
so the storm is due to the first half of the MC
21
MCSuperstorm
E
W
S
ESW (FS)
In this example, Bz is always south pointing so
strong storm
22
Sheath Superstorm
E
W
N
ENW (FN)
When MCs have high inclination the rotation is in
the Y direction. In the Z-direction, the field
will be always to the north or south. In this
example, Bz is always north pointing so no
storm. But there was a big storm due to the
sheath consisting of intense south pointing Bz
23
Four Types of MCs
NS
SN
T 45o
FN
FS
24
Cloud Sheath Storms
NS
SN
- 3.2 h
- 90 nT
FN
10.6 h
- 109 nT
FS
Gopalswamy et al. 2008
25
MCs good for predicting geoeffectiveness

• Well defined magnetic field structure ? we know
  what to expect in terms of geomagnetic storms
• SN clouds produce storms soon after the arrival
• NS clouds produce delayed storms
• FS similar to SN MCs
• FN clouds no storms
• 22 year pattern of bipolar MCs SN (NS) clouds
  dominate in the odd (even) cycle
• Chirality of MCs can be traced to the solar
  sources
• MC sources near disk center (like disk halos) ?
  likely to arrive at Earth

26
MC Latitude with of solar cycle
Phase Lat(N) Lat(S) CMD Rise 25.6
-24.2 5.3 Max 12.6 -20.0 9.7
Decl 8.2 -13.8 1.8 All
14.5 -19.7 6.1
PR
Butterfly pattern ? sunspot regions SN decline,
NS increase N-S asymmetry of unipolar MCs 10 vs.
4 (FN), 7 vs.4 (FS) FS in the north, FN in the
south unipolar at higher latitudes? Connection to
polarity reversal (PR)
27
Global field Yellow to Blue
Hathaway
Global field Blue to yellow
28
Solar Global Field and MC Polarity

N
Agt0
S
N
Alt0
S

29
22-yr pattern of MCs

• Max to min dominant type changes (polarity
  reversal happens)
• Min to next max no change (same polarity of the
  global field)
• Even max have NS dominance (to be so in cycle
  24)
• Odd maxima have SN dominance (as in cycle 23)

30
Solar-cycle variation of MC Types
SN declines NS increases FS increases? FN
declines? -- After Max (polarity reversal)
31
Disk-Center CMEs Produce Big Storms
S15 W02
S16 E08
X17
X10
X08
X28
X28
Heliographic coordinates of the associated flare
is used as the source location.
Gopalswamy et al. 2005 JGR
32
Dst Delay Time
Limb halos are geoeffective because of BzS in
Sheath (Sheath comes first)
33
Halo CMEs
back-side halo
Front-side halo
Disk Halo
F-limb Halo
Partial halo in LASCO C2 FOV becomes asymmetric
halo in LASCO/C3 FOV ? Limb Halo (B-limb)
34
Solar Sources of CMEs Resulting in Large
Geomagnetic Storms
Dst -100nT

• Active regions are the main sources throughout
  the cycle (butterfly diagram)
• Similar to MC sources and Halo CME sources
• - Declining and rising phases have some storms
  (10) due to CIRs
• - Influence of polar and low-latitude coronal
  holes

35
Out of the ecliptic B component due to draping
ICME
Southward B in the sheath Due to draping
Gosling and McComas, 1987 GRL
36
Geoeffectiveness of MC Types
Why?
Similar to Frontside Halo CMEs 71
37
V B are Related
Bz in sheath compression, draping. Bz in MC
flux rope structure
Gonzalez et al., 1998 Echer et al., 2005 Owens
et al., 2005 Gopalswamy et al., 2008
38
Dst Dependence on V and B
Dst has good correlation with VCME x Bz, so
inferring Bz and measuring VCME is very important
CMEs measured days before
MCs measured min before
39
IP Acceleration Predict VICME
V2ICME V2CME 2.a.S
But Can We Predict ICME Bz from Solar Magnetic
field Measurements?
40
Qiu et al. 2007
Longcope et al (2007)
41
Eruption Geometry Tells About Flux Rope axis
PIL
D2
-

HXR, µ
HXR, µ
R2
R1
PEL
D1
FR
Fully North No storm
42
(a) 2005 May Magnetic Cloud
S
Z
Y
(b) ENW MC
Sheath Storm
Days in May 2005
This kind of identification is not always
possible
43
Dimming
PEA
D2
D1
44
Associated CME
45
CIR and ICME comparison
Strongly Geoeff. Structures Speeds and magnetic
field are similar At the Sun, the CME speeds are
much larger
Cycle 23 Storms Major (Dst lt -100 nT) 86 due
to CMEs 14 CIRs No CIR storm with Dst lt -130
nT
46
MC Speeds and Halo Speeds
47
SEPs
48
CME-related Energetic Particles
Radiation hazard is of primary concern for space
missions
SEPs accelerated when the shock is far away from
the detector
Energetic Storm Particle (ESP) events
acceleration when the shock is at the detector
Oulu Neutron Monitor
49
CMEs and SEPs

• At least 5 large SEP
• Events
• - Mostly from 486
• - One from 0484
• 10/28 CME produced the largest gt 10 MeV
• flux (33,600 pfu)

gt104 pfu Events Cycle 23
10/28/03 33,600 11/04/01 31,700 07/14/00
24,000 11/22/01 18,900 11/08/00 14,800 09/24/01
12,900
Bigger (since 1976)
10/19/1989 40,000 03/21/1991 43,000
50
CMEs are Efficient Accelerators
Typically about 10 of CME kinetic energy
goes into SEPs Expect GLEs to be associated
with faster CMEs
Mewaldt, 2006
51
Ozone depletion
100
Thermosphere
80
Mesosphere
60
Altitude (km)
40
Stratosphere
20
1 GeV proton
Troposphere
0
Neutron Monitors
52
CMEs of Cycle 23
Gopalswamy, 2006
11 of CMEs are wide (W 120o) 1000 Fast and
wide CMEs 500 Halo CMEs 500 (some are slower
than 900 km/s MCs 100 intense storms 100
SEPs 100
CME speed lt 4000 km/s ? Limit to the Free
energy available in active regions
53
Geoeffective SEPeffective CMEs
54
Beneficial Effect of CMEs Forbush Decrease
55
Maybe not?
Zazayan, 2005
Some storms alter the rigidity cutoff of the
magnetosphere leading to more Cosmic rays than
usual!!
56
Summary

• Geoeffective CMEs and CIRs need to originate
  close to the disk center of the Sun
• Most of the halo CMEs originating close to the
  disk center become magnetic clouds in the IP
  medium and are highly geoeffective
• Off-centered halos become non-cloud ejecta and
  are geoeffective because of ICME sheath
• CME propagation affected by the ambient
  conditions (solar wind speed, nearby coronal
  holes and CMEs, phase of the solar cycle)
• Geoeffective CMEs are more energetic (average
  speed 1000 km/s, mostly halo CMEs or partial
  halo CMEs)
• We are beginning to understand the magnetic
  connection between the solar source and ICME
  (flux, topology, kinematics). Reconnection seems
  to be the key process in forming/growing a flux
  rope
• Conditions in the ambient medium and solar source
  location are important for SEPs at 1 AU.
• 1-AU properties are similar for CIRs and ICMEs

57
Lab work

• Go to Omniweb.gsfc.nasa.gov
• Plot solar wind speed from 9/24/08 to 10/24/08
• How many HSS do you see?
• Mark the peak days and speeds
• Go to http//sohodata.nascom.nasa.gov/cgi-bin/data
  _query
• Find the corresponding coronal holes
• Same coronal hole returning or different?

58
Answer
10/1 700 km/s
10/11 550 km/s
omni2 data from 20080924 to 20081024
59
CME Problem

• Find the CME corresponding to the 2003 June 18
  CME at 9 UT
• Go to cdaw.gsfc.nasa.gov
• Go to 2003 june18, get Dst
• Narrow down from the set of CMEs that occurred
  1-4 days before the storm