GPS‐TEC Observation of Gravity Waves Generated in the Ionosphere During 21 August 2017 Total Solar Eclipse

Nayak, Chinmaya; Yiğit, Erdal

doi:10.1002/2017ja024845

Cited by 50 publications

(63 citation statements)

References 43 publications

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“…Another remarkable variation seen in Figure 3 was a quick recovery from the eclipse and a large Ne increase that commenced soon after the eclipse, peaking at 23-24 UT. A similar posteclipse increase above the background value was reported in several studies of the 21 August 2017 solar eclipse over many locations across North America (Chen et al, 2018;Cherniak & Zakharenkova, 2018;Nayak & Yigit, 2018;Reinisch et al, 2018), though the TEC increase is weaker in general as it reflects the integrated Ne response over all altitudes. Mechanisms that contribute to a quick recovery and Ne increase after 21 UT could include disturbances in the neutral wind and O/N2 ratio (Chen et al, 2018;Muller-Wodarg et al, 1998).…”

Section: A Summary Of the Midlatitude Electron Density (Ne) Vertical supporting

confidence: 82%

Ionospheric Response to the Solar Eclipse of 21 August 2017 in Millstone Hill (42N) Observations

Гончаренко

Erickson

Zhang

et al. 2018

Geophysical Research Letters

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This study examines the ionospheric changes associated with the solar eclipse of 21 August 2017. The effects associated with the passage of the eclipse shadow were observed more than 1,000 km away from the totality at midlatitudes using the Millstone Hill incoherent scatter radar and digisonde. There was a 30–40% decrease in electron density, a 100‐ to 220‐K decrease in electron temperature, and a 50‐ to 140‐K decrease in ion temperature. Surprisingly, the greatest decrease in electron density occurred above 200 km. The most unexpected effect was a large 20‐ to 40‐m/s upward vertical drift observed in the topside ionosphere right after the local maximum obscuration. We suggest that this drift led to a posteclipse increase in the topside electron density.

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Section: A Summary Of the Midlatitude Electron Density (Ne) Vertical supporting

confidence: 82%

Ionospheric Response to the Solar Eclipse of 21 August 2017 in Millstone Hill (42N) Observations

Гончаренко

Erickson

Zhang

et al. 2018

Geophysical Research Letters

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“…The findings presented by Nayak and Yigit () and Sun et al () concern the specific TEC disturbance enumerated (2) in our Figure . These authors attributed this feature to an eclipse‐generated gravity wave and to an acoustic shock wave, respectively.…”

Section: Discussionsupporting

confidence: 73%

“…The relative amplitude of the latter disturbances is of order of 3–7% of the zeroth‐order modification; thus, we refer to them as first‐order perturbations. Most of these effects have already been identified and discussed in one way or another by Coster et al (), Zhang et al (), Nayak and Yigit (), and Sun et al (). However, these researchers erroneously linked them to the edge of the penumbra (Zhang et al, ), in situ‐generated thermospheric waves (Coster et al, ), or eclipse‐generated gravity waves (Nayak & Yigit, ; Sun et al, ).…”

Section: Discussionmentioning

confidence: 87%

Direct EUV/X‐Ray Modulation of the Ionosphere During the August 2017 Total Solar Eclipse

Mrak

Semeter

Drob

et al. 2018

Geophysical Research Letters

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The great American total solar eclipse of 21 August 2017 offered a fortuitous opportunity to study the response of the atmosphere and ionosphere using a myriad of ground instruments. We have used the network of U.S. Global Positioning System receivers to examine perturbations in maps of ionospheric total electron content (TEC). Coherent large-scale variations in TEC have been interpreted by others as gravity wave-induced traveling ionospheric disturbances. However, the solar disk had two active regions at that time, one near the center of the disk and one at the edge, which resulted in an irregular illumination pattern in the extreme ultraviolet (EUV)/X-ray bands. Using detailed EUV occultation maps calculated from the National Aeronautics and Space Administration Solar Dynamics Observatory Atmospheric Imaging Assembly images, we show excellent agreement between TEC perturbations and computed gradients in EUV illumination. The results strongly suggest that prominent large-scale TEC disturbances were consequences of direct EUV modulation, rather than gravity wave-induced traveling ionospheric disturbances.Plain Language Summary A total solar eclipse is a rare astronomical event, which offers an opportunity to study how the Sun interacts with our atmosphere in great detail. The solar irradiance at X-ray and extreme ultra violet wavelengths is so energetic that it ionizes the neutral gases in the upper atmosphere, whereas longer wavelengths penetrate deeper in the atmosphere and heat it up. The great American total solar eclipse on 21 August 2017 offered an extraordinary opportunity to study the atmospheric response to the occulted solar disk at a time of its largest energy deposition (around noon time). The ionosphere is affected by variations in the solar illumination and by temperature changes in the lower atmosphere. We identified four large-scale perturbations in ionospheric plasma using signals acquired from a large network of Global Positioning System receivers. For the first time, we show firm evidences that irregular solar flux deposition inside of the penumbra causes a continental-wide modulation of the ionospheric plasma. Specifically, the observed disturbances were caused by two sunspots which created four stark deviations from a uniform solar disk model. The discovery of a direct solar modulation is a revolutionary turnabout, since the previous reports attributed the disturbances to thermospheric or stratospheric sources.

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“…When it comes to GWs in the ionosphere, along with meteorological origin in the lower atmosphere (convection, weather fronts, thunderstorms, and wind flow over mountains), they can also originate from the auroral region during geomagnetically disturbed periods (Hocke & Schlegel, 1996). The GWs can also be generated during a solar eclipse (Nayak & Yigit, 2018;Sauli et al, 2006) or more generally during solar terminator passage (Galushko et al, 1998;Somsikov & Ganguly, 1995). Although the GWs play an important role in the dynamics Journal of Geophysical Research: Space Physics 10.1029/2018JA026048 of the upper atmosphere, their role in the ionosphere is still studied insufficiently.…”

Section: Introductionmentioning

confidence: 99%

Variation of Small‐Scale Gravity Wave Activity in the Ionosphere During the Major Sudden Stratospheric Warming Event of 2009

Nayak

Yiğit

2019

JGR Space Physics

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The present study investigates the effect of the major sudden stratospheric warming (SSW) event of 2009, on the small‐scale gravity wave (GW) activity in the ionosphere. Small‐scale fluctuations with time periods within the range of 10–90 min observed in Global Positioning System total electron content (TEC) data have been used as a proxy for GW activity in the ionosphere. TEC data from five longitudinally separated Global Positioning System stations located around 60∘N latitude have been utilized for this purpose. In the initial phase of the major warming, when the stratospheric conditions are similar to a minor warming during which the mean zonal flow starts to weaken, the ionopsheric GW activity tends to increase. However, during the peak phase of the SSW, as the zonal mean wind starts to reverse its direction, and after the peak warming, as the winds remain weak, conditions are less favorable for upward propagation of a spectrum of GWs, and thus the ionospheric GW activity is reduced, as seen from the behavior of the small‐scale TEC fluctuations during the latter period of the SSW. Similar reduction in GW activity is also observed in the middle atmosphere (65–100 km) as seen from GWs derived from SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) temperature profiles. The reductions in GW activity is more prominent during local daytime as compared to nighttime period. The reduction in GW activity shows a longitudinal variation with some locations showing relatively more reduction in the GW activity as compared to others.

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GPS‐TEC Observation of Gravity Waves Generated in the Ionosphere During 21 August 2017 Total Solar Eclipse

Cited by 50 publications

References 43 publications

Ionospheric Response to the Solar Eclipse of 21 August 2017 in Millstone Hill (42N) Observations

Ionospheric Response to the Solar Eclipse of 21 August 2017 in Millstone Hill (42N) Observations

Direct EUV/X‐Ray Modulation of the Ionosphere During the August 2017 Total Solar Eclipse

Variation of Small‐Scale Gravity Wave Activity in the Ionosphere During the Major Sudden Stratospheric Warming Event of 2009

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