Plasma flux and gravity waves in the midlatitude ionosphere during the solar eclipse of 20 May 2012

Abstract

The solar eclipse effects on the ionosphere are very complex. Except for the ionization decay due to the decrease of the photochemical process, the couplings of matter and energy between the ionosphere and the regions above and below will introduce much more disturbances. Five ionosondes in the Northeast Asia were used to record the midlatitude ionospheric responses to the solar eclipse of 20 May 2012. The latitude dependence of the eclipse lag was studied first. The f o F 2 response to the eclipse became slower with increased latitude. The response of the ionosphere at the different latitudes with the same eclipse obscuration differed from each other greatly. The plasma flux from the protonsphere was possibly produced by the rapid temperature drop in the lunar shadow to make up the ionization loss. The greater downward plasma flux was generated at higher latitude with larger dip angle and delayed the ionospheric response later. The waves in the f o E s and the plasma frequency at the fixed height in the F layer are studied by the time period analytic method. The gravity waves of 43-51 min center period during and after the solar eclipse were found over Jeju and I-Cheon. The northward group velocity component of the gravity waves was estimated as~108.7 m/s. The vertical group velocities between 100 and 150 km height over the two stations were calculated as~5 and~4.3 m/s upward respectively, indicating that the eclipse-induced gravity waves propagated from below the ionosphere.

Physical Processes Driving the Response of the F2 Region Ionosphere to the 21 August 2017 Solar Eclipse at Millstone Hill

“…On the other hand, after about 20:00 UT, changes in ambipolar diffusion (Figure f) and O + production (Figure c) were the major contributors to the changes of electron densities in the lower F 2 region, with some contribution from the winds (Figure d) and transport by electric fields (Figure e), but at the same time, in the topside ionosphere above 350 km, the dominant processes were ambipolar diffusion and wind transport, with little contribution from the chemical production or loss process. Thus, the results shown in this paper for an afternoon partial eclipse at middle latitudes may not be the same as those for the eclipse occurring at other times and latitudes or with a different kind of eclipses (e.g., Chen et al, , ; Madhav Haridas & Manju, ; Shweta Sharma et al, ).…”

“…The cause of the changes in electric fields was eclipse‐induced disturbance winds. The eclipse‐induced effects of electric fields on ionospheric density changes at middle latitudes are smaller compared with those at low and equatorial latitudes, where electric fields can be a dominant process driving the changes in F 2 region electron densities during eclipses (Chen et al, , ; Madhav Haridas & Manju, ; Shweta Sharma et al, ).…”

GITM‐Data Comparisons of the Depletion and Enhancement During the 2017 Solar Eclipse

“…The locally direct ionospheric response includes the decrease of the electron and ion temperatures due to lack of the extreme ultraviolet (EUV) heating, as well as the depletion of the electron densities resulting from the reduction of the photoionization. Studies have shown that the density below the F layer decreases substantially, while the net ionization in the F layer may decrease slightly, remain unchanged, or even increase during the solar eclipse, depending on the competing effects of the loss in photoionization and the diffusion above the F2 peak (e.g., Boitman et al, ; Chen et al, ; Ding et al, ; Le et al, ). Neutral composition and neural winds also play a crucial role in the ionospheric response to the eclipse (Le et al, ; Madhav et al, ; Müller‐Wodarg et al, ; St.‐Maurice et al, , etc.…”

Simultaneous upward and downward propagating inertia‐gravity waves in the MLT observed at Andes Lidar Observatory

“…These observations suggested that IGWs in the TLS have typical horizontal wavelengths of 200-2000 km, vertical wavelengths of 2-10 km, and intrinsic frequencies of 2-5 f (where f is the inertial frequency). In the upper stratosphere and mesosphere/lower thermosphere (MLT), IGWs were reported from lidar [Collins et al, 1994;Hu et al, 2002;Rajeev et al, 2003;Xu et al, 2006;Li et al, 2007Li et al, , 2010Lu et al, 2009Lu et al, , 2015aLu et al, , 2015bLu et al, , 2017Chen et al, 2013Chen et al, , 2016Cai et al, 2014;Baumgarten et al, 2015] and radar [Muraoka et al, 1987;Yamamoto et al, 1987;Gavrilov et al, 2000;Zhou and Morton, 2006;Nicolls et al, 2010;Chen et al, 2011Chen et al, , 2014Chen et al, , 2015Suzuki et al, 2013] measurements. These observations indicate that most IGWs in the MLT evidently exhibited a quasi-monochromatic feature.…”