An Eclipse-Ballooning Study of Shadow Bands During the April 2024 Total Eclipse

Abstract

In this study we searched for shadow bands associated with the total solar eclipse of April 8, 2024. Our aim was to improve our understanding of their origin. Shadow bands are debated to arise either from atmospheric turbulence within Earth's planetary boundary layer (PBL) or from a diffraction-interference effect occurring above the atmosphere. To test these theories, high altitude balloons (HABs) equipped with light sensors, similar ground light sensors, radiosondes launched with weather balloons, and an aircraft-mounted light sensor were deployed. Our team was located in Concan, TX, except for the plane which flew to NE Vermont to find clear weather. Unlike Pitt's 2017 HAB study, which detected a 4.5 Hz signal attributed to shadow bands above the PBL and on the ground, no shadow bands were detected above the PBL in Texas or in northeast Vermont, despite the use of improved instrumentation. Cloud cover prevented useful ground based measurements in Texas, limiting our conclusions about the nature of shadow bands. These findings suggest that shadow bands may not always be present or, if they are, may be primarily due to atmospheric turbulence. The results of this study and Pitt's 2017 study emphasize the need for future work.

Figures (10)

• Figure 1: Raw and cleaned light curve from the HAB BL00 photodiode sensor during the April 8, 2024, total solar eclipse. The original signal (blue) includes sharp voltage dips caused by the payload line intermittently blocking the photodiode sensor. The cleaned signal (black) preserves the eclipse structure while removing these interference artifacts. Time is shown in UTC.
• Figure 2: Raw spectrogram of the HAB BL00 light intensity data during the April 8, 2024, total solar eclipse. Spectrogram computed using a Fast Fourier Transform (FFT) with a 5-second boxcar window and 50% overlap. The shown frequency range spans 0–25 Hz. Intensity is shown in decibels (dB). No shadow band signal was detected.
• Figure 3: Cleaned spectrogram of HAB BL00 light intensity data during the April 8, 2024, total solar eclipse. The cleaning process partially removed voltage dips caused by intermittent payload line interference with the photodiode sensor. After cleaning, no shadow bands are detected. The spectrogram is free of distinct periodic signals up to 25 Hz (shown) and even up to 100 Hz (not shown).
• Figure 4: Wind speed components and temperature profiles from radiosonde flights over Concan, TX.Flight 01 (Top) and Flight 29 (Bottom) show that the PBL, characterized by temperature inversions and abrupt wind speed/direction changes, remains consistently below 3 km throughout all flights (all flights not shown). The vertical red dashed line highlights that the PBL is positioned between 1500 m and 2500 m. Flight 25b (Middle), which occurred during the total eclipse, exhibits a significant change in the north-south wind speed component in the same altitude range where a slight temperature inversion is observed, showing that the PBL is below 3 km during the eclipse.
• Figure 5: Wind speed components and temperature profiles from radiosonde flights over New Hampshire.Flight 02 (Top) and Flight 28 (Bottom) show a consistently stable PBL just above 1000 m, as indicated by the vertical red dashed line marking the location of temperature inversions. Flight 25 (Middle), conducted closest to the time of the total eclipse, also shows a clear PBL inversion near this height as well. While no radiosonde was launched during totality, these flights provide a representative view of PBL conditions in the region. The stability of the PBL in these flights contrasts with the more variable PBL observed in Concan.