Absence of High Frequency Echoes From Ionosondes During the 23–25 April 2023 Geomagnetic Storm; What Happened?

Author:

Habarulema John Bosco123ORCID,Zhang Yongliang4ORCID,Matamba Tshimangadzo1ORCID,Buresova Dalia5ORCID,Lu Gang6ORCID,Katamzi‐Joseph Zama12,Fagundes Paulo Roberto7ORCID,Okoh Daniel89ORCID,Seemala Gopi10ORCID

Affiliation:

1. South African National Space Agency (SANSA) Hermanus South Africa

2. Department of Physics and Electronics Rhodes University Makhanda South Africa

3. Centre for Space Research, Physics Department North‐West University Potchefstroom South Africa

4. Johns Hopkins University Applied Physics Laboratory Laurel MD USA

5. Institute of Atmospheric Physics Prague Czech Republic

6. High Altitude Observatory National Center for Atmospheric Research 3080 Center Green Drive Boulder CO USA

7. Laboratório de Física e Astronomia Universidade do Vale do Paraíba (UNIVAP) São José Dos Campos SP Brazil

8. United Nations African Regional Centre for Space Science and Technology Education ‐ English UN‐ARCSSTE‐E Obafemi Awolowo University Campus Ile Ife Nigeria

9. Istituto Nazionale Geofisica e Vulcanologia (INGV) Roma Italy

10. Indian Institute of Geomagnetism Mumbai India

Abstract

AbstractWe report an unusual event on absence of high frequency (HF) echoes in ionosonde observations from the ionospheric F2 region during the geomagnetic storm of 23–25 April 2023. This event was observed in both southern and northern hemispheres over two stations, Grahamstown (33.3°S, 26.5°E), South Africa and Pruhonice (50.0°N, 14.6°E), Czech Republic. Significant O/N2 depletion over the stations was observed by TIMED/GUVI, indicating a strong negative ionospheric storm. This is unique since absence of echoes in ionosonde measurements is usually due to strong radio absorption in the ionosphere associated with solar flares. However, there was no flare activity during the periods of “absent” F2 HF echoes. On the other hand, the ionosonde detected echoes from E‐layer. TIEGCM simulation reproduced TIMED/GUVI O/N2 depletion and showed that NmE was larger than NmF2 on dayside over Pruhonice. TIMED/GUVI O/N2 also showed a clear spatial gradient in the O/N2 depleted regions, suggesting F‐region ionosphere was tilted. By estimating the critical frequency of the F2 layer using GNSS observations, we have shown that it wasn't possible for the ionospheric electron density to reach depletion levels prohibiting reflection of HF echoes from ionosondes. We suggest that this phenomena may have been caused by either (a) maximum electron density of E layer exceeding that of F2 layer and/or (b) ionospheric tilting which made the signals to be reflected far away from the ionosonde locations.

Funder

National Research Foundation

National Aeronautics and Space Administration

Publisher

American Geophysical Union (AGU)

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3