TY - JOUR

T1 - On the Penumbra-to-Umbra Ratio from 1660 to 1676

AU - Zolotova, Nadezhda

AU - Vokhmyanin, Mikhail

PY - 2025/6/1

Y1 - 2025/6/1

N2 - Sunspot engravings made in the Maunder minimum are used to evaluate the fine structure of sunspots. Based on 78 images of the full solar disk and 77 images of individual sunspots, we have evaluated the ratio of penumbra-to-umbra area (P/U) to be 4.2±2.5 and 3.8±2.3, respectively. These results are consistent with previous estimates before, during, and after the Maunder minimum, as well as with the P/U ratio observed in the largest sunspot groups in Solar Cycle 24. This suggests that the near-surface convection mode has most likely remained unchanged since the early seventeenth century. We also found that schematic sunspot drawings tend to underestimate the P/U ratio.

AB - Sunspot engravings made in the Maunder minimum are used to evaluate the fine structure of sunspots. Based on 78 images of the full solar disk and 77 images of individual sunspots, we have evaluated the ratio of penumbra-to-umbra area (P/U) to be 4.2±2.5 and 3.8±2.3, respectively. These results are consistent with previous estimates before, during, and after the Maunder minimum, as well as with the P/U ratio observed in the largest sunspot groups in Solar Cycle 24. This suggests that the near-surface convection mode has most likely remained unchanged since the early seventeenth century. We also found that schematic sunspot drawings tend to underestimate the P/U ratio.

KW - Observations; sunspots

KW - Penumbra; sunspots

KW - Solar cycle

KW - Statistics; sunspots

KW - Umbra

UR - https://link.springer.com/article/10.1007/s11207-025-02489-x

UR - https://doi.org/10.1007/s11207-025-02489-x

UR - https://www.mendeley.com/catalogue/a4138ec3-f59f-3707-b80f-0c64071702b6/

U2 - 10.1007/s11207-025-02489-x

DO - 10.1007/s11207-025-02489-x

M3 - Article

VL - 300

JO - Solar Physics

JF - Solar Physics

SN - 0038-0938

IS - 6

M1 - 76

ER -