RHESSI/SOHO/TRACE Workshop

NEW workgroup 9:

Solar Origins of SEPs (Solar Energetic Particles)

Working group leaders:

Säm Krucker (krucker@ssl.berkeley.edu)

Dick Mewaldt (rmewaldt@srl.caltech.edu)

The Sun frequently accelerates electrons and ions up to relativistic energies. Some of the accelerated particles lose their energy in the denser, lower solar atmosphere producing hard X-ray and Gamma-ray emissions, while others escape into interplanetary space. Whether the X-ray and Gamma-ray producing and the escaping particles are accelerated by the same mechanism is not known. Combining RHESSI observations with insitu observations of energetic particles from the SoHO, WIND, ACE, and SAMPEX spacecraft allows for the first time a detailed temporal and spectral study. Furthermore, imaging observations at various wavelengths from radio waves to X-rays (Nancay RH, Nobeyama, SoHO, TRACE, GOES SXI, and RHESSI) can reveal the solar source structure around the acceleration site. Together with magnetic field extrapolations, this will provide the best present day picture of how energetic particles are accelerated and how they can escape the Sun and reach Earth.

Questions

1. What is the relation between X-ray and gamma-ray producing particles at the Sun and the in-situ observed solar energetic particles near Earth?

2. Are they produced by the same acceleration mechanism or by different mechanisms?

3. What is the geometry of events releasing energetic particles into interplanetary space?

4. How does the energy content of the ions and electrons observed in the flare region compare to that of the ions and electrons observed in interplanetary space?

Organization

IONS:

The only RHESSI gamma ray events with simultaneous SEP observations are the events from October/November 2003. The October 28, 2003 event is the most promising candidate. The following questions will be discussed:

1) What is the relative timing between the SEP onset near Earth and the solar events (flare/CME)?

2) How do the in-situ observed ion spectra compare with the derived ion spectra from the gamma-ray observations?

3) How does the composition of accelerated and ambient ions compare to that of energetic ions observed in situ?

4) How does the energy content of the ions observed in the flare region compare to that of the ions observed at 1 AU?

5) How can ions escape the acceleration region?

ELECTRONS:

Many HXR events are observed with simultaneous in-situ electron observations. First results were already presented (Krucker, Kontar, & Lin 2004, SHINE meeting, COSPAR). Timing studies (Krucker et al. 1999, Haggerty & Roelof 2002, Maia & Pick 2004)) suggest the existence of two groups of events: (1) on-time events, i.e. electrons are release during the impulsive phase of the flare; and (2) delayed events, where the electron release occur up to 30 minutes after the onset of the flare. The following questions will be discussed:

1) compare insitu observed electron spectra with electron spectra derived from the X-ray observations. Are there differences for on-time and delayed events?

2) How is the X-ray emission produced: Thick or thick target model?

3) How does the energy content of the electrons observed in the flare region compare to that of the electrons observed at 1 AU?

4) imaging of solar source structure: What is the geometry of the solar source region?

5) Magnetic model of field lines connecting the Sun and the spacecraft: How can particles escape?

6) Comparing He3 rich events and electron events.