Vertical Distribution of Ionizing Radiation and Nano-Aerosols in the Austral Troposphere and Stratosphere with Concurrent Solar Flare

Showers of ionizing radiation are generated in Earth’s atmosphere by inbound galactic cosmic rays (GCRs) and solar energetic particles (SEPs). Characterizing the vertical distribution of ionizing radiation is important not only because of health risks for airborne travellers, but also because it drives chemical reactions that form nano-scale aerosols—which ultimately influence climate. To date, theories regarding radiation–aerosol interactions have been derived through modelling studies, or inferred via indirect observational correlations, rather than via direct concurrent observation of radiation flux and aerosol concentrations. For this work, a high-altitude balloon payload carrying two solid-state PIN diode detectors (one shielded and one unshielded) was launched to 34 km (110,000 ft) over western Victoria, Australia. Simultaneously, a multi-channel nano-aerosol detector was flown on the same payload. The Regener-Pfotzer Radiation Maximum was determined using both diode detector streams, and deposited radiative energy spectrum analysed. Two regions of high-energy particle fluxes were identified: one between 6–12 km altitude, overlapping primary altitudes for commercial airline travel, and another above 30 km near the flight’s apex. Coincident measurements of the vertical distribution of nano-aerosols were obtained, providing a unique dataset for relating radiation flux with aerosol genesis in the stratosphere. This work represents a first step toward correlating radiation and nano-aerosol distributions through direct measurements. • The Regener-Pfotzer maximum was measured in the Southern Hemisphere, with radiation measurements over an altitude range of 0-34 km. • Two distinct radiation energy populations were observed versus altitude. • The vertical distribution of nano-aerosols, CO 2 , and HCHO in the atmosphere were measured concurrently. • Radiation from a Class-C solar flare was also potentially observed for the first time using a simple X100-7 solid-state detector. • For the first time, the PIN diode X100-7 detector sensitivity was characterised vs wavelength.