An official website of the United States government
Abstract On 21–22 June 2015, three consecutive interplanetary shocks slammed into the Earth's magnetosphere. Immediately after the third shock at 18:36 UT on 22 June, marked by an exceptional sudden storm commencement with an amplitude of ΔSYM‐H = ∼106 nT, a major geomagnetic storm commenced. In the present study, a multi‐instrument approach comprising observations, data analysis, and modeling is used to examine the global ionospheric response. Results show that enhanced storm time processes produced major total electron content (TEC) variations at different latitudes, longitudes, and phases of the storm. A closer inspection of the TEC observations reveals strong longitudinal and hemispherical asymmetry. In addition, multiple equatorward and poleward propagating traveling ionospheric disturbances (TIDs) were detected in the TEC data. Equatorward propagating TIDs are consistent with vertical neutral winds simulated from Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model; however, poleward TIDs were not reproduced in the model. We find that a combination of driving processes including enhanced high‐latitude injection, prompt penetration electric fields, disturbance dynamo effect, neutral winds, and composition changes were acting at different stages of the storm.
more »
« less
This content will become publicly available on December 1, 2025
Complex Ionospheric Fluctuations Over East and Southeast Asia During the May 2024 Super Geomagnetic Storm
Abstract The May 2024 super storm is one of the strongest geomagnetic storms during the past 20 years. One of the most remarkable ionospheric responses to this event over East and Southeast Asia is the complex ionospheric fluctuations following the storm commencement. The fluctuations created multiple oscillations of total electron content (TEC) embedded in the diurnal variation, with amplitudes up to 10 TECu. Along the same latitude, the fluctuations were nearly synchronized over a wide longitude span up to 35°. In the meridional direction, the fluctuations over low latitudes were the most significant and complex, which contained two main components, the poleward extending oscillations originated from the magnetic equator, and the equatorward propagating traveling ionospheric disturbances (TIDs) from high latitudes. The TIDs likely occurred around the globe. The storm‐time interplanetary electric fields penetrating into equatorial latitudes of the ionosphere and the auroral energy input were suggested to drive the poleward extending oscillations and the equatorward TIDs, respectively.
more »
« less
- PAR ID:
- 10571661
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 129
- Issue:
- 12
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract This work conducts a focused study of subauroral ion‐neutral coupling processes and midlatitude ionospheric/thermospheric responses in North America during a minor but quite geo‐effective storm on September 27–28, 2019 under deep solar minimum conditions. Several prominent storm‐time disturbances and associated electrodynamics/dynamics were identified and comprehensively analyzed using Millstone Hill and Poker Flat incoherent scatter radar measurements, Fabry‐Perot interferometer data, total electron content data from Global Navigation Satellite System observations, and thermospheric composition O/N2data from the Global‐scale Observations of Limb and Disk mission. Despite solar minimum conditions, this minor storm produced several prominent dynamic features, in particular (a) Intense subauroral polarization stream (SAPS) of 1,000 m/s, overlapping with a deepened main trough structure. (b) An enhanced westward wind of 230 m/s and a significant poleward wind surge of 85 m/s occurred in the post‐SAPS period. (c) Large‐scale traveling ionospheric disturbances (TIDs) were generated and propagated equatorward across mid‐latitudes in the storm main phase. TID characteristics were significantly affected by SAPS, evolving into divergent propagation patterns. (d) SAPS was situated on the poleward edge of a considerable storm‐enhanced density structure. (e) The midlatitude ionosphere and thermosphere exhibited a prolonged positive storm effect in the main phase and beginning of recovery phase, with 5–10 TECU increase and 10%–30% O/N2enhancement for 12 h. This was followed by a considerable negative storm effect with 5–10 TECU and 20%–40% O/N2decrease. Results show that minor storm intervals can produce substantial mid‐latitude ionospheric and thermospheric dynamics in low solar flux conditions.more » « less
-
Abstract Using NASA's Global‐scale Observations of the Limb and Disk (GOLD) imager, we report nightside ionospheric changes during the G5 super geomagnetic storm of 10 and 11 May 2024. Specifically, the nightside southern crest of the Equatorial Ionization Anomaly (EIA) was observed to merge with the aurora near the southern tip of South America. During the storm, the EIA southern crest was seen moving poleward as fast as 450 m/s. Furthermore, the aurora extended to mid‐latitudes reaching the southern tips of Africa and South America. The poleward shift of the equatorial ionospheric structure and equatorward motion of the aurora means there was no mid‐latitude ionosphere in this region. These observations offer unique insights into the ionospheric response to extreme geomagnetic disturbances, highlighting the complex interplay between solar activity and Earth's upper atmosphere.more » « less
-
We use simultaneous auroral imaging, radar flows, and total electron content (TEC) measurements over Alaska to examine whether there is a direct connection of large-scale traveling ionospheric disturbances (LSTIDs) to auroral streamers and associated flow channels having significant ground magnetic decreases. Observations from seven nights with clearly observable flow channels and/or auroral streamers were selected for analysis. Auroral observations allow identification of streamers, and TEC observations detect ionization enhancements associated with streamer electron precipitation. Radar observations allow direct detection of flow channels. The TEC observations show direct connection of streamers to TIDs propagating equatorward from the equatorward boundary of the auroral oval. The TIDs are also distinguished from the streamers to which they connect by their wave-like TEC fluctuations moving more slowly equatorward than the TEC enhancements from streamer electron precipitation. TIDs previously observed propagating equatorward from the auroral oval have been identified as LSTIDs. Thus, the TIDs here are likely LSTIDs, but we lack sufficient TEC coverage necessary to demonstrate that they are indeed large scale. Furthermore, each of our events shows TID’s connection to groups of a few streamers and flow channels over a period in the order of 15 min and a longitude range of ∼15–20°, and not to single streamers. (Groups of streamers are common during substorms. However, it is not currently known if streamers and associated flow channels typically occur in such groups.) We also find evidence that a flow channel must lead to a sufficiently large ionospheric current for it to lead to a detectable LSTID, with a few tens of nT ground magnetic field decreases not being sufficient.more » « less
-
Abstract Plasma blob is generally a low‐latitude phenomenon occurring at the poleward edge of equatorial plasma bubble (EPB) during post‐sunset periods. Here we report a case of midlatitude ionospheric plasma blob‐like structures occurring along with super EPBs over East Asia around sunrise during the May 2024 great geomagnetic storm. Interestingly, the blob‐like structures appeared at both the poleward and westward edges of EPBs, reached up to 40°N magnetic latitudes, and migrated westward several thousand kilometers together with the bubble. The total electron content (TEC) inside the blob‐like structures was enhanced by ∼50 TEC units relative to the ambient ionosphere. The blob‐like structure at the EPB poleward edge could be partly linked with field‐aligned plasma accumulation due to poleward development of bubble. For the blob‐like structure at the EPB west side, one possible mechanism is that it was formed and enhanced accompanying the bubble evolution and westward drift.more » « less
