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N. Gopalswamy |
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NASA/GSFC, Greenbelt, MD |
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FASR Workshop, May 22-25, Green Bank WV |
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Microwave Observations (FASR HF) |
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Prominence Core (best observed) |
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DSF (for
Space Weather App.), Cavity on the disk |
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à Arcade formation – CME aftermath |
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Frontal structure (new)- rarely observed – DR
problem |
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Meterwave
Observations (FASR LF) |
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à Thermal (CME, Filament, Cavity) |
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à Nonthermal: type II (shock) |
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à Nonthermal: type IV (CME core, or other
substrucutres) |
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Longer wavelengths (LOFAR, SIRA) |
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Nonthermal: Type II, type IV, complex type III |
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Nonthermal: CME cannibalism |
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Maybe
thermal emission from CMEs |
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Reviews:
(Gopalswamy, 1999, 2002)
http://cdaw.gsfc.nasa.gov |
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• Axial field orientation from Multi-spacecraft
Observations (Helios 1&2, Voyager 2, IMP 8 |
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• Flux Rope Structure from Force Free
equilibrium calculations |
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(Burlaga et al., 1981) |
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Arcade formation at the site of eruption in EUV
movie |
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The filament can be seen in the previous day’s
movie |
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The ejection occurs into a less dense region.
Clear 3-part structure |
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BBSO study concluded that only 36% of prominence
eruptions were associated with white light CMEs! |
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(Yang & Wang 2002) |
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The remote brightenings indicate the extent of
the CME |
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CME speed: 1925 km/s (microwaves) |
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à 2465 km/s in White light |
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- initial accel: 440 ms-2 |
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- later decel 10 ms-2 |
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• Core: 1625 km/s à close to the LE speed
in microwaves. |
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Hudson et al (2001) associated HXR source (930
km/s) with the microwave core – may not be
correct |
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• Imaging
was possible because the flare source was occulted |
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SEP CMEs are very fast |
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(>
900km/s) |
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They occur west of E45 |
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The largest bin is 90+: 21% of SEP events à can be
imaged in microwaves |
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•Thermal emission: optical depth could be large
at low frequencies. |
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• Direct imaging using free free emission
from the corona & CMEs (Sheridan
et al., 1978; Gopalswamy and Kundu, 1992;
Maia et al., 2000) |
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Imaged by the Clark Lake Radioheliograph in the
1980s |
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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) |
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Easy to drive shocks on either side of the
“Alfven-speed hump” Gopalswamy et al. JGR
(2001) |
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Easier to shock the corona in the transverse
direction? |
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(Gopalswamy, Kaiser & Pick, 2000) |
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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) |
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New radio window in the decameter-hectometric
(DH) wavelength domain due to WAVES
experiment on Wind (Bougeret et al. 1995) |
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All are CME related: Early phase of IP shocks |
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Shock-accelerated (SA) electrons produce complex type III bursts (Reiner &
Kaiser, 1999) |
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Associated CMEs are faster and wider (Gopalswamy
et al. 2000-GRL, 2001-JGR) |
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Good Indicators of geoeffective CMEs |
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CME interaction discovered (Gopalswamy et al.
2001, ApJL, 548, L91) |
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No imaging: Need SIRA and LOFAR for studying
these radio burst sources |
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Slow CME (290 km/s) overtaken by a fast CME (660
km/s) |
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The slow CME core deflected to the left from its
trajectory |
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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 |
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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. |
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For accelerating CMEs: shocks form at large
heliocentric distances |
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For Halo CMEs: type II occurs first because it
takes some time for the CME to be visible above the occulting disk. |
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(CME time – when the CME first appears in the C2
FOV) |
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CME core: optically thick at all FASR
frequencies, but can be imaged only at higher frequencies because of the
low brightness temperature |
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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. |
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Nonthermal emission from electrons trapped in
CME substructures can be a good source of information |
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Filaments & filament Cavities on the disk à CME
source regions |
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Notes