Unusual Multiple Excitation of Large‐Scale Gravity Waves by Successive Stream Interactions: The Role of Alfvénic Fluctuations

Abstract

Instances of multiple excitation of large‐scale gravity waves in the auroral region by solar wind Alfvénic fluctuations are rare. In this paper we report an unusual instance, in which sequential large‐scale gravity waves launched from northern and southern auroral regions are clearly linked to intermittent southward magnetic fields of Alfvénic fluctuations embedded in three successive stream interaction regions. The continuous gravity wave activity persists for ∼7 days, the longest duration currently tracked. The Alfvénic fluctuations are mainly dominated by Alfvén and slow waves, which might play a role in the solar wind‐magnetosphere interaction, leading to impulsive auroral electrojet activity and in turn exciting the sequential gravity waves.

Role of Equatorial Fountain for the Delayed Response of Thermosphere O1D 630.0 nm Dayglow Over the Dip Equator During an X‐Class Flare

“…Alfvénic fluctuations as reported by Guo et al. (2016; 2019) were present in the high‐speed stream and it caused long‐duration impulsive Auroral Electrojet (AE) intensifications (Not shown here). These Alfvénic fluctuations may affect the thermosphere‐ionosphere system over low latitude region.…”

“…In fact, a stream interaction region occurred during the period July 26-30, 2005 as can be seen from the solar wind parameters (https://omniweb.gsfc.nasa.gov/html/ow_data.html). Alfvénic fluctuations as reported by Guo et al (2016;2019) were present in the high-speed stream and it caused long-duration impulsive Auroral Electrojet (AE) intensifications (Not shown here). These Alfvénic fluctuations may affect the thermosphere-ionosphere system over low latitude region.…”

“…Similarly, the solar wind conditions, CMEs, substorms and high latitude energy deposition can also potentially influence the ionosphere‐thermosphere system. In addition, during the passage of the high‐speed stream of interaction region, the intermittent southward magnetic field due to Alfvénic fluctuations can also lead to the transfer of momentum and energy injections into high latitude upper atmosphere via magnetic reconnection (Guo et al., 2016, 2019). However, there could be significant time delays involved to get such energy inputs transferred to low latitude thermosphere‐ionosphere from high latitude region.…”

Quasi-periodic ripples in high latitude electron content, the geomagnetic field, and the solar wind

“…It is suggested that the contribution of Alfvén waves to the fluctuations in F-region electron content is limited because the particle density variations in the solar wind are very small. Furthermore, Guo et al 7 have linked the prolonged multiple excitation of large-scale gravity waves with intermittent southward magnetic fields of Alfvénic fluctuations. Significant auroral electrojet (AE) intensifications were found to have occurred, implying that Alfvénic fluctuations might play a key role in the solar wind-magnetosphere interaction, thus affecting the AE response.…”

East‐West Difference in the Ionospheric Response of the March 1989 Great Magnetic Storm Throughout East Asian Region

“…During the Earth passage of the Alfvénic fluctuations, the intermittent southward magnetic field of Alfvénic fluctuations led to intermittent momentum and energy injections into geospace from the solar wind via magnetic reconnection, and caused the observed long-duration impulsive AE activity. Then the enhanced AE activities could excite a series of sequential gravity waves in the auroral regions of the thermosphere, and their propagation will give rise to disturbances in the ionosphere which is the situation described by Guo et al (2019). Also with the increasing number of GNSS receivers being deployed at low and equatorial areas, transequatorial LSTIDs have been verified during the great magnetic storm (e.g., Pradipta et al, 2016 ;Zakharenkova et al, 2016).…”