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Coronal IP Shocks Nat Gopalswamy NASA/GSFC

Coronal IP Shocks Nat Gopalswamy NASA/GSFC. Sun. Elmau CME Workshop, 2003 February 7 Plenary talk. Earth. Plan of the talk. Type II bursts & CMEs Type II bursts, SEPs & CMEs Metric & IP type II bursts  Wind/WAVES & SOHO/LASCO Data  IP: 15 MHz – 20 kHz (3Ro – 1 AU); 15-1MHz DH.

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Coronal IP Shocks Nat Gopalswamy NASA/GSFC

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  1. Coronal IP ShocksNat Gopalswamy NASA/GSFC Sun Elmau CME Workshop, 2003 February 7 Plenary talk Earth

  2. Plan of the talk • Type II bursts & CMEs • Type II bursts, SEPs & CMEs • Metric & IP type II bursts  Wind/WAVES & SOHO/LASCO Data  IP: 15 MHz – 20 kHz (3Ro – 1 AU); 15-1MHz DH

  3. Type II Radio Bursts • Discovered by Payne-Scott et al. (1947) at metric wavelengths (<150 MHz). • Malitson et al. (1973) in the IP medium using spaceborne radio instruments (see reviews by Cane, Reiner, Gopalswamy in AGU monograph 119) • Plasma Emission Process is responsible: - [ Fast CMEs drive] MHD shocks - Shock accelerates electrons (~10 keV) - Nonthermal electrons generate Langmuir waves at local plasma frequency (fp) - Langmuir waves scatter off of ions or combine to produce radio emission at fp (fundamental) and 2fp (harmonic)

  4. coronal Radio Sky Interplanetary (bounded by Red lines) Nelson & Labrum, 1985)

  5. LASCO CME DH Type II Type II H F CME-driven metric & DH type II SA Event (Type III Bursts)

  6. An IP Type II & its CME f = 3MHz  n = 2.8x104 cm-3 (harmonic emission) Type II Type III Type II bursts track the CME through the IP medium

  7. DH Type II burst starts when the CME reaches ~ 2 Ro • The RAD2 spectral range (14-1 MHz) Wind/WAVES correspond to 2-10 Ro  Type II bursts can identify shock-driving CMEs in the near-Sun IP medium. • Too much delay: due to accelerating CMEs • CME delay: Disk events

  8. All, FW &DH CMEs • > 5000 CMEs during 1996-2000 • ~150 Fast & Wide (FW) CMEs • ~150 DH Type II bursts • ~ 50 FW frontside western CMEs • ~ 50 Major SEP events • 1-3% of all CMEs are important for SEPs • Electron accelerators are also ion accelerators

  9. Solar Cycle Variation of Energetic Events • DH type IIs, fast and wide CMEs and major SEP events: similar solar-cycle variation. • Close correlation implies physical relationship: the same CME-driven shock accelerates electrons that produce DH type II bursts, and SEPs. • The number of DH type II bursts is the largest because eastern events are also included. • Minor differences due to other parameters like Alfven speed.

  10. Speeds of CMEs associated with Metric & DH type IIs Lara et al. 2003, GRL, in press Average CME speeds increase in this order: . General population (G) . Metric type II related (M) . DH type II related (D) Similar tendency for width and acceleration of CMEs M D G Since DH type II bursts are 100% associated with CMEs, these properties suggest that metric type IIs are also due to CMEs, but less energetic

  11. Two Shocks from the same source? Metric domain • “Alfven-speed hump” expected based on B, n profiles in the quiet corona (Hollweg, 1978; Krogulec et al, 1994; Mann et al. 1999) • Include active region: 3 regions of interest (Gopalswamy 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 IIs occurring to the right of the hump are likely to be strong and indicative of IP shocks. fp

  12. Example of the metric – DH type II (02/12/22) Hiraiso – metric type II WAVES type II

  13. The CME propagates thru a tenuous medium where Va is expected to be high

  14. Summary • Any short-lived driver with ~ 350 km/s may drive a shock close to the Sun, but not beyond. • Blast wave: 1. Speed declines with time, 2. Weakens further at the Alfven speed hump. (No blast waves observed in situ; “driver-less” shocks are due to limb CMEs!) • CME-driven: 1. CMEs accelerate low in the corona. 2. Depending on CME speed and initial height, CME can drive shocks in the corona & IP medium (cause metric & IP type II) 3. CME can drive a shock in the metric corona, lose it around Va peak and drive again in the IP medium. If it does not drive again (CMEs of moderate speed), situation similar to blast wave. 4. Solar wind works against shock-driving capacity of CMEs in the IP medium 5. SEP release height (Kahler et al., 1994) coincides with Va peak

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