Observations of Unusual Daytime Range Spread F at Middle Latitude During the Afternoon Hours

• Published in: Space Weather Vol. 19; no. 11
• Main Authors: Wei, Lehui, Jiang, Chunhua, Lan, Ting, Wang, Wenxuan, Shen, Hua, Aa, Ercha, Huang, Wengeng, Liu, Jing, Yang, Guobin, Hu, Yaogai, Zhao, Zhengyu
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 01.11.2021
• Subjects: Atmosphere; Atmospheric gravity waves; Daytime; Echoes; F region; Gravity waves; Ionograms; Ionosondes; Ionosphere; Ionospheric disturbances; Ionospheric irregularities; Irregularities; Latitude; Morning; Plasma bubbles; Spread F; Stratosphere; Sunrise; Thermosphere; Tibetan Plateau
• ISSN: 1542-7390; 1539-4964; 1542-7390
• DOI: 10.1029/2021SW002870

In this study, an unusual daytime range spread F event recorded by the ionosonde installed at Zhangye (ZHY, 39.4°N, 100.13°E, dip latitude 29.65°N) station during the afternoon of December 23, 2016 was presented. Daytime spread F during the afternoon hours have seldom been reported at midlatitude regions. In addition, observations of daytime spread F are mostly the frequency spread F. In this case, daytime range spread F and spread Es in the midlatitude region were simultaneously observed during the afternoon hours (15:15‐16:00 LT). Moreover, some distorted traces of the main traces occurred on ionograms during the morning. The result of these observations seems to indicate that these extra traces and daytime diffused echoes on ionograms might be attributed to the same ionospheric disturbances phenomenon. Analysis of the iso‐frequency of ionospheric virtual height from ZHY ionosonde data during this event revealed the presence of wave‐like disturbances consistent with traveling ionosphere disturbances (TIDs)/atmospheric gravity waves (AGWs). The periods of TIDs on this day are in a range of 20–70 min that can be roughly classified into MSTIDs. We found that the daytime range spread F might be induced by the passage of ionospheric wave‐like structures caused by TIDs/AGWs. In addition, the seeding of TIDs/AGWs might be attributed to the stratosphere gravity waves over the Qinghai‐Tibetan Plateau, which causes the coupled of the atmosphere‐ionosphere‐thermosphere to significantly impact the ionosphere. Plain Language Summary Spread F, as a manifestation of ionospheric irregularities in the F layer, has been widely regarded as a nighttime phenomenon. Recently, daytime spread F events/ionospheric irregularities/plasma bubbles have also been reported by many researchers in the ionospheric community. Most of the daytime spread F events mainly occur in the sunrise and morning hours, and almost rarely occur in the afternoon, especially in midlatitude regions. Moreover, daytime spread F is mostly associated with frequency spread F. Range spread F or mixed spread F is seldom reported at daytime. Can the range spread F or mixed spread F occur during the daytime? In this study, an unexpected daytime range spread F was reported at middle latitudes (Zhangye station, 39.4°N, 100.13°E) during the afternoon hours. We think that the daytime range spread F might be due to the passage of ionospheric wave‐like structures caused by traveling ionosphere disturbances/atmospheric gravity waves at Zhangye station, where the active stratosphere gravity waves over the Qinghai‐Tibetan Plateau could propagate upward to the ionosphere caused the coupled of the atmosphere‐ionosphere‐thermosphere. Key Points Extremely unusual daytime range spread F was reported at middle latitudes Daytime range spread F occurred at the afternoon hours Traveling ionosphere disturbances/atmospheric gravity waves might play an important role in forming daytime range spread F