Xinlin Li
University of Colorado Boulder, CO·Astronomy & Astrophysics
Earth sits in a stream of fast, charged particles from the Sun and from deep space. Its magnetic field traps some of them in the radiation belts, rings of high-energy electrons and protons around the planet.
- Fields
Astronomy & Astrophysics
Physics
Earth & Environmental Science
- Topics
space weather
radiation belts
Van Allen belts
- Grants
- 3 known grants, through Jun 2028
What they work on
- Analyze more than 12 solar energetic particle events seen by the REPTile-2 CubeSat detector, combined with NOAA/POES, MetOp and ground riometer data, to measure how storms shift the latitudes where particles reach the polar atmosphere.
- Test whether energetic electrons contribute to polar cap absorption events, radio blackouts at high latitudes, by relating particle energy spectra to geomagnetic conditions, local time and riometer-measured absorption.
- Find the energy breakpoint, for a given geomagnetic storm, below which outer-belt electrons can be transported into the inner radiation belt (L<3) and above which they cannot.
- Identify the physical mechanisms behind energy-dependent deep inward penetration of electrons from tens of keV to multi-MeV, to support better predictions of inner-belt electron changes.
- Refurbish a REPTile engineering model into a 129-channel flight telescope measuring protons and electrons in interplanetary space, with students building, testing and calibrating it.
- Track how solar energetic particle spectra evolve across the inner heliosphere and compare their contribution with galactic and anomalous cosmic rays to radiation near Earth and on the lunar surface.
More about the research
These particles damage spacecraft electronics, endanger astronauts, and can black out high-frequency radio used by aircraft and emergency responders. Its projects ask how these particles move, where they can reach, and how they shape space weather. The work builds on a series of small particle detectors called REPTile (Relativistic Electron and Proton Telescope integrated little experiment). The first flew on the student-built CSSWE CubeSat. It showed that electrons from cosmic ray albedo neutron decay (CRAND) form the inner edge of the inner belt. CRAND is a process in which neutrons knocked out of the atmosphere by cosmic rays decay into electrons.
Why it matters
Energetic particles damage satellites, threaten astronauts, and disrupt high-frequency radio used in aviation, emergency response and national security. Better knowledge of how these particles reach the inner radiation belt, the polar atmosphere and interplanetary space could improve space weather prediction. This could also inform spacecraft design and operation, including for missions near the Moon.
Known grants
From NIH and NSF research grants. Labs often have other funding we can't see.
EAGER: On the Impact of Solar Energetic Particles in the High Latitude Regions
NSF · Jul 2026 – Jun 2028
On the Energy-Dependent Deep (L less than 3) Penetrations of Energetic Electrons (10s of keV to multi-MeV)
NSF · May 2024 – Apr 2027
RAPID: A Relativistic Electron and Proton Telescope to Probe the Inner Heliosphere
NSF · Nov 2023 – Apr 2027
Closest labs
James Ryan
University of New Hampshire, NH·Physics
Operate and maintain the Simpson Neutron Monitor Network of ground-based detectors that record cosmic-ray intensity, delivering real-time count rates, archived datasets and high-resolution data.
Veronica Bindi
University of Hawaii at Manoa, HI·Physics
Operate and maintain the Simpson Neutron Monitor Network, ground detectors counting cosmic-ray secondaries, and deliver real-time count rates plus archived and high-resolution datasets to the research community.
Evan Tyler
College of Saint Scholastica, MN·Physics
Determine the properties of whistler-mode chorus and hiss waves in plasmasphere–plasmatrough transition regions, where the plasmapause density drop is gradual and spans up to several L-shells.
The school
University of Colorado Boulder: 36 labs on PI Pages, $718M a year on research, 447 research doctorates a year.
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