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You might not get the chance to publish the first paper in a field, but you always can try to write the best paper in this field.

Fan Guo

with LPL since 2007

About me

I am a graduate student of Lunar and Planetary Laboratory (LPL), and also Department of Planetary Sciences in University of Arizona. I work with Professor Joe Giacalone and Regent Professor Randy Jokipii. My research interests are Space and Astrophysical Plasma Physics. The projects I was/am working on including Particle acceleration by collisionless shocks (bow shocks, interplanetary shocks, termination shock, and supernova blast waves, etc.), the transport of energetic particles in solar wind and interaction between shocks and MHD turbulence. I use various numerical models (TestParticle/Monte Carlo, Hybrid, MHD, and a little PIC). Check out our new group website Solar and Heliospheric Research Group

My CV is here

Links

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Publications ADS List


[9] Fan Guo, Joe Giacalone (2012) Particle Acceleration at a Flare Termination Shock: Effect of Large-scale Magnetic Turbulence, The Astrophysical Journal, in press PDF
[8] Xiangliang Kong, Yao Chen, Gang Li, Shi-Wei Feng, Hong-Qiang Song, Fan Guo, Fang-Ran Jiao (2012) A broken solar type II radio burst induced by a coronal shock propagating across the streamer boundary, The Astrophysical Journal, in press PDF
[7] Fan Guo, Shengtai Li, Hui Li, Joe Giacalone, J. R. Jokipii, David Li (2012) On The Amplification of Magnetic Field by a Supernova Blast Shock Wave in a Turbulent Medium, The Astrophysical Journal, 747, 98 PDF
[6] Fan Guo, Shengtai Li, Hui Li, Joe Giacalone, J. R. Jokipii, David Li (2011) The magnetic field amplification downstream of supernova blast wave, 32nd International Cosmic Ray Conference Proceeding PDF
[5] F. Guo, J. R. Jokipii and J. Kota (2010) Particle acceleration by collisionless shocks containing large-scale magnetic-field variation, the Astrophysical Journal 725 128-133 PDF
[4] Fan Guo and Joe Giacalone (2010) The Effect of Large Scale Magnetic Turbulence on the Acceleration of Electrons by Perpendicular Collisionless Shocks, the Astrophysical Journal 715 406-411 PDF
[3] Guo Fan, Lu Quan-Ming, Guo Jun and Wang Shui (2008) Nonlinear Evolution of Lower-Hybrid Drift Instability in Harris Current Sheet, Chinese Phys. Lett. 25 2725-2728 PDF
[2] Lu, Q. M., Guo, F., Wang, S. (2006) Magnetic spectral signatures in the terrestrial plasma depletion layer: Hybrid simulations, J. Geophys. Res., Volume 111, A4207 ADS PDF
[1] Guo Fan, Lu Quan-Ming, Wang Shui(2005) Excited low frequency waves by beam plasma in upstream of collisionless shock and their effect on dissipation of shock, Chin. J. Space Sci., 25(4):248-253 PDF 3/7/18

Current Projects

1. Shock Acceleration Theory

Collisionless shocks are commonly believed to be remarkable accelerators of energetic charged particles, for example, Solar energetic particles accelerated by coronal shocks, Cosmic rays accelerated by supernova shock waves, pick-up ions accelerated in termination shock(i.e., Anamolous cosmic rays), etc. With the standard diffusive shock acceleration theory is proposed three decades ago(Bell 1978, Blandford 1978, Axford 1977), there are still many unsolved problems, like how thermal particles are injected to diffusive shock acceleration (injection problem), and the effect of turbulence. My works focus on effect of large-scale turbulence on particle acceleration. The nice thing about DSA is it natually gives a power law distribution that does not vary much for a strong shock, which is strongly supported by cosmic ray observations. One thing to note in diffusive shock acceleration is that, while the simple 1-D planar shock gives nice description on cosmic rays we observed(power law, distribution downstream, etc.), the 2D/3D effect can contribute a lot to the modification. And because the turbulence have to be included in order to give enough scattering needed in DSA, one need to include full 3D variation in, although physicist usually use simplified approximation. Especially, for perpendicular shocks, particles do not get much acceleration since charged particles are tied on their original magnetic field lines in a non-3D magnetic field.
Voyager 1 & Voyager 2 have acrossed termination shock and entered heliosheath, both of them found a continuing unfolding spectrum of anamulous cosmic rays (ACR, pickup ions accelerated by termination shock). These results rise an issue on if DSA can explain these spectra and if it does, what's the effect we must account in in order to do so. We did some calculation by considering the large scale magnetic field fluctuations, the results will be coming soon.

2. Acceleration of electrons by collisionless shocks

Electron are thought to be hard to get accelerated. Since in low energies (below relativistic energy), their gyroradii are too small to interact with large scale magnetic turbulence. Our group has developed a theory which do not require strong pitch-angle scattering. [Jokipii & Giacalone 2007 ApJL]. My work with my advisor Joe Giacalone [Guo & Giacalone 2010 ApJ] has demonstrated that in a collisionless shock containing large-scale magnetic turbulence, the electron acceleration is very efficient. Previous work also shows ion acceleration is efficient. Thus these geometry helps to trap both ions and electrons along shock front, leads to efficient acceleration. Accelerated Electron Profile

3. Propagation of energetic particles in turbulent magnetic field

Transport of energetic particles in magnetic field can be very complicated when consider the turbulence. Particles do not follow field lines because 1) field lines meandering even if the averaged magnetic field lines are unchanged [FLRW, Jokipii 1966,1971] and 2) particles scattering and drifting in these turbulent magnetic fields.

4. Termination Shock, Pickup Ions & Anomalous Cosmic Rays

The remarkable crossing of the Termination shock by Voyager 1 and Voyager 2 have made several surprising discoveries. One of major issues is that Voyager 1 found the intensity of anomalous cosmic rays (ACRs) is not peaked at the termination shock and the energy spectrum is still unfolding after entering the Heliosheath, which strongly indicates the simple planar shock model is inadequate to interpret the acceleration of ACRs. Several possible solutions have been considered. We recently discussed a possible solution. We consider the effect of the large-scale spatial variation of magnetic field on diffusive shock acceleration. We find that the region where connection points approaching each other will trap and preferentilly accelerate particles to high energies and form "hot spots" along the shock surface. This effect could explain the observation of ACRs in Heliosheath. Hot spots of accelerated particles

Courses

Spring 2009 PTYS507 Ptys554 Fall 2008 PTYS510 Ptys558
MondayTuesdayWedsdayThursdayFriday
9:30~10:45PTYS558PTYS558
11:00~12:15PTYS510PTYS517PTYS510PTYS517PTYS510
Spring 2008 PTYS505B PTYS512 ASTR582

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