2025-07-28 PUNCH Science Nugget
Scale-invariant 1/ƒ noise is a familiar observation across a wide array of natural and artificial systems, including heart rate
fluctuations and loudness patterns in musical compositions. In the solar wind, it is seen mostly in the magnetic field energy
spectrum across timescales from minutes to several days, where it represents fluctuations with equal power per frequency octave.
First identified in the heliosphere in the 1980s, 1/ƒ noise has prompted ongoing discussion concerning its generation mechanism
and place of origin – whether it forms locally in the solar wind or, as suggested by the long timescale of its influence, it stems
from deeper solar processes linked to coronal dynamics and the solar dynamo. NASA’s PUNCH mission will capture high-resolution
images of the inner solar wind and the corona, allowing studies of the spatial structures of the plasma that may be associated
with the 1/ƒ observations1, with the potential to reveal the origin and evolution of these enigmatic heliospheric 1/ƒ signals. In
preparation for these new observations, PhD student Victoria Wang (working with PUNCH Co-Investigator William Matthaeus) and
colleagues have reviewed the current state of our understanding of in the heliosphere as our third featured paper from the Solar
Physics PUNCH Mission Overview Topical Issue (J. Wang et al.,
Solar Physics, 2024, 299:169).