====== NF04: Neutrinos from natural sources ======
Co-Conveners: Yusuke Koshio (Okayama U.), Gabriel D. Orebi Gann (UC Berkeley/LBNL), Erin O'Sullivan (Uppsala), Irene Tamborra (NBIA)

===== Description=====

This topical group covers neutrino detection from all natural sources, including the Sun, the Earth, and astrophysical sources.  Specific topics include:

** Early Universe **
  * Cosmic neutrino background: prospects for detection
  * Neutrino flavor composition and impact on the nucleosythesis
  * Absolute neutrino mass: prospects for measuring it
**Geoneutrinos **
  * Flux and spectral measurements
  * Separation of U/Th contributions, flux & mantle contributions 
  * Geographical spread
**Solar**
  * CNO: solar metallicity, solar model
  * 8B spectral shape: sensitivity to NSI, matter effects, day/night
  * Precision low-energy measurements (pp, pep): luminosity
**Supernova**
  * Prospects for DSNB measurement
  * Galactic supernova: flavor composition, pointing, supernova mechanism, BSM physics
  * Pre-supernova neutrinos
**Atmospheric**
  * Identifying prompt component
  * Neutrino flavor conversion physics
**Extragalactic**
  * The origin of high energy neutrinos and the birthplace of cosmic rays
  * The physics of cosmic accelerators: neutrino flavour, energy spectrum, and BSM
  * Cosmogenic neutrinos: GZK neutrinos and cosmic ray composition
  * Cross sections at high energies

===== Submitted LOI =====
Here is the list of submitted LOIs to this topical group.   First index before "/"  corresponds to the primary frontier used for the submission.
 {{url>https://www.snowmass21.org/docs/files/list.php?frontier=NF4  noborder 95%,600px}}