Radio Observations of Coronal Mass Ejections

N. Gopalswamy

NASA/GSFC, Greenbelt, MD

FASR Workshop, May 22-25, Green Bank WV

Summary: CMEs in Radio

Microwave Observations (FASR HF)

Prominence Core (best observed)

DSF (for Space Weather App.), Cavity on the disk

à Arcade formation – CME aftermath

Frontal structure (new)- rarely observed – DR problem

Meterwave Observations (FASR LF)

à Thermal (CME, Filament, Cavity)

à Nonthermal: type II (shock)

à Nonthermal: type IV (CME core, or other substrucutres)

Longer wavelengths (LOFAR, SIRA)

Nonthermal: Type II, type IV, complex type III

Nonthermal: CME cannibalism

Maybe thermal emission from CMEs

Reviews: (Gopalswamy, 1999, 2002) http://cdaw.gsfc.nasa.gov

CME Structures in the
IP Medium: Magnetic Clouds

• Axial field orientation from Multi-spacecraft Observations (Helios 1&2, Voyager 2, IMP 8

• Flux Rope Structure from Force Free equilibrium calculations

(Burlaga et al., 1981)

Prominence: H-alpha (left, Hiraiso) versus Microwaves (right, Nobeyama)

Prominence Eruption in Microwaves

A Prominence Eruption in Microwaves & EUV (304 A)
click on images to start movie

The Eruption of 2001 Dec 20

Dec 20, 2001 EUV

Arcade formation at the site of eruption in EUV movie

The filament can be seen in the previous day’s movie

2001 Dec 20 LASCO/C2

The ejection occurs into a less dense region. Clear 3-part structure

2000 Oct 22 Event (Fast)

2000 Oct 22 LASCO/C2

Statistical Results
Gopalswamy, Shimojo, Shibasaki et al. (2002)

BBSO Statistics: 50 limb events (from the last bin)

BBSO study concluded that only 36% of prominence eruptions were associated with white light CMEs!

(Yang & Wang 2002)

Radio Vs Ha Prominence Eruptions (PEs)

A Microwave CME: 2001/04/18
Gopalswamy, Shimojo, Shibasaki, & Howard (2002)

Nobeyama movie of the 2001/04/18 Eruption

The remote brightenings indicate the extent of the CME

Spatial Association: Radio & White Light

Microwave, SXT, EIT, LASCO

Height-Time Plot

CME speed: 1925 km/s (microwaves)

à 2465 km/s in White light

- initial accel: 440 ms^-2

- later decel 10 ms^-2

• Core: 1625 km/s à close to the LE speed in microwaves.

Hudson et al (2001) associated HXR source (930 km/s) with the microwave core – may not be correct

• Imaging was possible because the flare source was occulted

Density, Mass, Size, & Energy
(Preliminary Results)

Speed & Source Longitude of SEP-associated CMEs of Cycle 23
Gopalswamy et al. 2002, ApJL June 10 issue

SEP CMEs are very fast

(> 900km/s)

They occur west of E45

The largest bin is 90+: 21% of SEP events à can be imaged in microwaves

Radio Sun in Meterwaves

•Thermal emission: optical depth could be large at low frequencies.

• Direct imaging using free free emission from the corona & CMEs (Sheridan et al., 1978; Gopalswamy and Kundu, 1992; Maia et al., 2000)

Radio CMEs

A Type II Radio Burst

Image of a type II Burst

Imaged by the Clark Lake Radioheliograph in the 1980s

Meterwaves: Nonthermal

Type II radio bursts due to shocks: Relation to CME is controversial (Wagner & MacQeen, 1983; Cane 1984; Gary et al., 1994; Gopalswamy et al., 1998; Cliver et al., 1999; Reiner et al., 2001)

Two Shocks from the same source?

Easy to drive shocks on either side of the “Alfven-speed hump” Gopalswamy et al. JGR (2001)

Easier to shock the corona in the transverse direction?

(Gopalswamy, Kaiser & Pick, 2000)

Meterwaves: Nonthermal

Type IV radio bursts: Nonthermal electrons trapped in CME cores or substructures produce plasma or synchrotron emission (Boischot, 1957; Stewart, 1985; Gopalswamy & Kundu 1990; Bastian et al, 2001)

DH Type II Radio Bursts

New radio window in the decameter-hectometric (DH) wavelength domain due to WAVES experiment on Wind (Bougeret et al. 1995)

All are CME related: Early phase of IP shocks

Shock-accelerated (SA) electrons produce complex type III bursts (Reiner & Kaiser, 1999)

Associated CMEs are faster and wider (Gopalswamy et al. 2000-GRL, 2001-JGR)

Good Indicators of geoeffective CMEs

CME interaction discovered (Gopalswamy et al. 2001, ApJL, 548, L91)

No imaging: Need SIRA and LOFAR for studying these radio burst sources

Example of a DH type II burst due to a CME

Radio Signature due to CME Interaction: 00/06/10
This event is unlike the previous: there is a broadband emission for ~0.5 hr following a regular type II burst

A Slow CME is Deflected

Slow CME (290 km/s) overtaken by a fast CME (660 km/s)

The slow CME core deflected to the left from its trajectory

Before reaching the slow CME, the fast one produces a normal type II. During collision with the slow CME, the enhanced radio emission is produced

A DH Type II & its CME

Properties of radio-rich CMEs

Type II burst starts when the CME reaches ~ 2 Ro !

The RAD2 spectral range (14-1 MHz) Wind/WAVES correspond to 2-10 Ro à Type II bursts can identify shock-driving CMEs in the near-Sun IP medium.

For accelerating CMEs: shocks form at large heliocentric distances

For Halo CMEs: type II occurs first because it takes some time for the CME to be visible above the occulting disk.

(CME time – when the CME first appears in the C2 FOV)

Conclusions for FASR

CME core: optically thick at all FASR frequencies, but can be imaged only at higher frequencies because of the low brightness temperature

CME frontal: can be easily observed in meterwaves if the nonthermal emission is not too strong. In microwaves behind-the-limb high density CMEs can be imaged.

Nonthermal emission from electrons trapped in CME substructures can be a good source of information

Filaments & filament Cavities on the disk à CME source regions


	N. Gopalswamy
	NASA/GSFC, Greenbelt, MD

	FASR Workshop, May 22-25, Green Bank WV


	Microwave Observations (FASR HF)
	Prominence Core (best observed)
	DSF (for Space Weather App.), Cavity on the disk
	à Arcade formation – CME aftermath
	Frontal structure (new)- rarely observed – DR problem
	Meterwave Observations (FASR LF)
	à Thermal (CME, Filament, Cavity)
	à Nonthermal: type II (shock)
	à Nonthermal: type IV (CME core, or other substrucutres)
	Longer wavelengths (LOFAR, SIRA)
	Nonthermal: Type II, type IV, complex type III
	Nonthermal: CME cannibalism
	Maybe thermal emission from CMEs
	Reviews: (Gopalswamy, 1999, 2002) http://cdaw.gsfc.nasa.gov


	• Axial field orientation from Multi-spacecraft Observations (Helios 1&2, Voyager 2, IMP 8

	• Flux Rope Structure from Force Free equilibrium calculations
	(Burlaga et al., 1981)


	Arcade formation at the site of eruption in EUV movie
	The filament can be seen in the previous day’s movie


	The ejection occurs into a less dense region. Clear 3-part structure


	BBSO study concluded that only 36% of prominence eruptions were associated with white light CMEs!
	(Yang & Wang 2002)


	CME speed: 1925 km/s (microwaves)
	à 2465 km/s in White light
	- initial accel: 440 ms^-2
	- later decel 10 ms^-2
	• Core: 1625 km/s à close to the LE speed in microwaves.
	Hudson et al (2001) associated HXR source (930 km/s) with the microwave core – may not be correct
	• Imaging was possible because the flare source was occulted


	SEP CMEs are very fast
	(> 900km/s)
	They occur west of E45
	The largest bin is 90+: 21% of SEP events à can be imaged in microwaves


	•Thermal emission: optical depth could be large at low frequencies.
	• Direct imaging using free free emission from the corona & CMEs (Sheridan et al., 1978; Gopalswamy and Kundu, 1992; Maia et al., 2000)


	Type II radio bursts due to shocks: Relation to CME is controversial (Wagner & MacQeen, 1983; Cane 1984; Gary et al., 1994; Gopalswamy et al., 1998; Cliver et al., 1999; Reiner et al., 2001)


	Easy to drive shocks on either side of the “Alfven-speed hump” Gopalswamy et al. JGR (2001)

	Easier to shock the corona in the transverse direction?
	(Gopalswamy, Kaiser & Pick, 2000)


	Type IV radio bursts: Nonthermal electrons trapped in CME cores or substructures produce plasma or synchrotron emission (Boischot, 1957; Stewart, 1985; Gopalswamy & Kundu 1990; Bastian et al, 2001)


	New radio window in the decameter-hectometric (DH) wavelength domain due to WAVES experiment on Wind (Bougeret et al. 1995)
	All are CME related: Early phase of IP shocks
	Shock-accelerated (SA) electrons produce complex type III bursts (Reiner & Kaiser, 1999)
	Associated CMEs are faster and wider (Gopalswamy et al. 2000-GRL, 2001-JGR)
	Good Indicators of geoeffective CMEs
	CME interaction discovered (Gopalswamy et al. 2001, ApJL, 548, L91)
	No imaging: Need SIRA and LOFAR for studying these radio burst sources


	Slow CME (290 km/s) overtaken by a fast CME (660 km/s)
	The slow CME core deflected to the left from its trajectory
	Before reaching the slow CME, the fast one produces a normal type II. During collision with the slow CME, the enhanced radio emission is produced


	The RAD2 spectral range (14-1 MHz) Wind/WAVES correspond to 2-10 Ro à Type II bursts can identify shock-driving CMEs in the near-Sun IP medium.
	For accelerating CMEs: shocks form at large heliocentric distances
	For Halo CMEs: type II occurs first because it takes some time for the CME to be visible above the occulting disk.
	(CME time – when the CME first appears in the C2 FOV)


	CME core: optically thick at all FASR frequencies, but can be imaged only at higher frequencies because of the low brightness temperature
	CME frontal: can be easily observed in meterwaves if the nonthermal emission is not too strong. In microwaves behind-the-limb high density CMEs can be imaged.
	Nonthermal emission from electrons trapped in CME substructures can be a good source of information
	Filaments & filament Cavities on the disk à CME source regions