Radio Emission from the Sun, Heliosphere, & Planets

1. Radio Emission from the Sun, Heliosphere, & Planets T. S. Bastian NRAO

2. Plan of Talk • Instrumentation • Emission mechanisms • Low frequency solar and IP radio emission • Planetary radio emission (Jupiter) • An aside: extrasolar planets • Radio emission from the outer limits

3. Instrumentation • Current groundbased UTR-2 (10 – 30 MHz) Guaribindanur (40 – 150 MHz) GMRT (150, 235, 327 MHz) Nancay Radioheliograph (150 – 450 MHz) VLA (74, 327 MHz) Numerous spectrographs (e.g., GB/SRBS 17-1050 MHz) • Current Spacebased WIND / WAVES (20 kHz – 1040 kHz, 1.075 – 13.825 MHz) Ulysses URAP RAR (1.25 – 48.5 KHz, 52 – 940 kHz)

4. Instrumentation • Planned groundbased FASR (50 MHz – 20 GHz) MWA (80 – 300 MHz) LWA (10 – 80 MHz) • Spacebased (imminent!) STEREO / WAVES two spacecraft! (10 – 40 kHz, 40 – 160 kHz, 0.16 – 16.075 MHz, plus 50 MHz)

5. Emission Mechanisms • Plasma radiation (n = npe, 2npe npe= 9 ne1/2 kHz) coronal and IP radio bursts – e.g., bursts of type II and type III • Cyclotron maser (n = nBe, 2nBe nBe = 2.8 B MHz) planetary radio emission – e.g., terrestrial AKR, Jovian DAM • Synchrotron radiation solar type IV bursts, CMEs, Jovian magnetosphere • Thermal radiation Ubiquitous – e.g., solar corona, CMEs, planetary disks

6. Plasma radiation “coronal” ground ionosphere RAD 2 space 2npe RAD 1 npe

7. Solar Radio Bursts Numerous, short-lived (~1 s), narrow-band (few MHz) bursts occurring over a BW of 10s of MHz in storms lasting hours to days • Type I McCready, Pawsey, Payne-Scott 1947; Allen 1947; Wild & McCready 1950 • Type II Wild & McCready 1950 • Type III Wild & McCready 1950 • Type IV Boischot & Denisse 1957 • Type V Wild 1959 Rare slow-drift bursts (~ -0.25 MHz/s) that occur in association w/ flares, lasting 5-20 min. Narrow-band emission often occurs in harmonic lanes. Broadband (~100s MHz), fast-drift bursts (~ -20 MHz/s) that occur in association w/ impulsive phase of flares. Broadband (~10s-100s MHz) continuum following large solar flares, often following an associated type II burst, lasting >10 min. Continuum emission following groups of type III radio bursts, typically polarized in the opposite sense.

8. GB/SRBS type III type III + type II type II + type IV + fadeout Dulk 1985

9. Interplanetary Radio Bursts type III SA type IIIs type II type IV space WIND/WAVES ionosphere Culgoora ground Dulk et al. 2001

10. Motivating issues Understanding relationship between flares, coronal mass ejections (CMEs), solar energetic particles (SEPs), and radio proxies: • CME initiation & propagation Bastian et al 2001, Kathaviran & Ramesh 2005, Maia et al 2006 • Drivers of coronal type IIs Cliver et al (2004) • Interplanetary shocks (type II proxies) Gopalswamy et al (2001), Knock et al (2001, 2003ab, 2005) • Coronal energy release (type III/IV proxies) Cane et al. 2002, Klein et al. (2005) • Relativistic electron delays (type III, in situ measurements) Krucker et al. (1999), Haggerty & Roelof (2002)

11. Green Bank Solar Radio Burst Spectrometer (White et al. 2006) WIND / WAVES R1 & R2

12. Knock et al. 2001, 2003ab, 2005

13. Delay of near-relativistic electron acceleration Haggerty & Roelof 2002

14. Role of flares in SEP production Cane et al (2002) identify a correlation between long duration type III bursts (~20 min), CMEs, and solar proton events. Suggests type-III-l-producing electrons accelerated in the corona in the aftermath of a CME. Cane et al. 2002

15. CME “cannibalism”? Gopalswamy et al. (2001)

16. Emission from CMEs Thermal Sheridan et al. 1978: exceptionally slow (60 km s-1) coronal transient observed at 80 and 160 MHz by Culgoora RH Gopalswamy & Kundu 1992, 1993: thermal footprint of a CME possibly observed at 74 MHz by the Clark Lake CH Ramesh et al. 2003: observation of CME with Gauribidanur RH at 109 MHz Kathiravan & Ramesh 2005: an example of a halo CME observed by the GRH at 109 MHz

17. 21 Jan 1998 Guaribindanur RH 109 MHz SOHO LASCO C2 Kathiravan & Ramesh 2005

18. Nonthermal emission Smerd & Dulk 1971?: “expanding arch”, “advancing front” classifications of 80 MHz observations of moving type IV radio bursts with the Culgoora Radioheliograph Bastian et al. 2001:multi-band observations of the 20 April 1998 fast CME with the Nançay Radioheliograph Gopalswamy et al. 2005:microwave detection of synchrotron radiation from the 18 April 2001 fast CME with the Nobeyama Radioheliograph Maia et al. 2006:multi-band observations of the 15 April 2001 fast CME with the Nancay Radioheliograph

19. Nançay Radioheliograph: 15 Aprl 2001 421 MHz Maia et al. 2006

20. LoS a Rsunf (deg) ne (cm-3) B(G) nRT (MHz) Bastian et al. 2001

21. Planetary Radio Emission While all planets emit thermal radiation, the presence of a magnetosphere (and in the case of Jupiter, satellites) greatly complicates and enriches the observed radio phenomena. The cyclotron maser mechanisms (Wu & Lee 1979) is believed to account for the auroral radio emissions which are pumped by the variable solar wind. For Jupiter, interaction between the magnetosphere and the Galilean satellites (Io) also modulates the radio emission in a complex way. 13 cm Jupiter 22 cm from R. Sault

22. Auroral footprints Jovian Decameter-wavelength Radiation L bursts 90 s S bursts Earth: 108 Watts Jupiter: 1011 Watts 160 ms

23. Solar wind modulation of Jovian auroral radio emission Gurnett et al. 2002

24. Jovian DAM can be six orders of magnitude more intense than the synchrotron and thermal emissions! What are the consequences for the detection of exoplanets? Carr et al. 1983, Zarka et al. 1992, Bastian et al. 2000

25. Exoplanet searches • Winglee et al (1986) first pointed out possibility of detecting cyclotron maser emission from exoplanets and performed blind search at 327 MHz and 1.4 GHz using the VLA • With discovery of bone fide planets by Mayor & Queloz (1995), Bastian et al (2000) targeted six known exoplanets and two brown dwarfs at 74, 327, and 1.4 GHz with the VLA • On the basis of the“radiometric Bodes Law” (Desch & Kaiser 1984, Zarka 1992, Farrell et al 1999)andZarka et al (2001) suggested interaction of “hot Jupiters” with stellar winds could produce emissions orders of magnitude stronger than Jupiter’s. See also Lazio et al (2004). Several subsequent attempts to detect exoplanets: e.g., Desch et al. (2003) using the VLA; Ryabov et al (2004) using the UTR-2; Lazio et al (2004) using the VLA; Winterhalter et al (2005) and Majid et al (2005) using the GMRT No detections at radio wavelengths to date.

26. Possible reasons for non-detections: • Lack of sensitivity • Frequency mismatch • Low duty cycle • Source directivity • Planet unmagnetized • No source of energetic electrons Jansky Freq (MHz) Studies of requirements for next-generation instrumentation for exoplanet detection and study underway: e.g., Taylor et al 1998 (SKA),Farrell et al. 2004; Zarka et al. 2004, 2006 (LOFAR); Lazio et al 2004 (SKA); LWA science

27. Radiation from the Outer Limits

28. Kurth et al. 1984, Cairns et al. 1992, Gurnett et al. 1993, Gurnett and Kurth 1996, Cairns & Zank 2002,

32. Concluding Remarks • Low frequency observations of the Sun, planets, and interplanetary medium vigorous and ongoing • Observations reveal rich and dynamic environments and complex physical processes • Observations yielding insights into particle acceleration and transport, shocks, and plasma & radiation processes • The future looks bright!