Equatorial plasma fountain and its effects over three locations: Evidence for an additional layer, the F₃ layer

Abstract

Abstract. The equatorial plasma fountain and equatorial anomaly in the ionospheres over Jicamarca (77øW), Trivandrum (77øE), and Fortaleza (38øW) are presented using the Sheffield University plasmasphere-ionosphere model under magnetically quiet equinoctial conditions at high solar activity. The daytime plasma fountain and its effects in the regions outside the fountain lead to the formation of an additional layer, the F 3 layer, at latitudes within about plus or minus 10 ø of the magnetic equator in each ionosphere. The maximum plasma concentration of the F 3 layer, which occurs at about 550 km altitude, becomes greater than that of the F2 layer for a short period of time before noon when the vertical E x B drift is large. Within the F 3 layer the plasma temperature decreases by as much as 100 K. The ionograms recorded at Fortaleza on January 15, 1995, provide observational evidence for the development and decay of an F 3 layer before noon. The neutral wind, which causes large north-south asymmetries in the plasma fountain in each ionosphere during both daytime and nighttime, becomes least effective during the prereversal strengthening of the upward drift. During this time the plasma fountain is symmetrical with respect to the magnetic equator and rises to over 1200 km altitude at the equator, with accompanying plasma density depletions in the bottomside of the underlying F region. The north-south asymmetries of the equatorial plasma fountain and equatorial anomaly are more strongly dependent upon the displacement of the geomagnetic and geographic equators (Jicamarca and Trivandrum) than on the magnetic declination angle (Fortaleza). IntroductionThe horizontal orientation of the geomagnetic field at the geomagnetic equator is known to be the basic reason for the active nature of the low-latitude ionosphere, which is characterized by the equatorial electrojet, equatorial plasma fountain, equatorial anomaly, plasma bubbles, and spread F. The equatorial plasma fountain and equatorial anomaly arise from the vertical upward drift of plasma across the geomagnetic field lines at equatorial latitudes due to E

Studies of ionospheric F-region response in the Latin American sector during the geomagnetic storm of 21–22 January 2005

“…A westward electric field drives the F-layer to move downward and causes an increase of the F-peak density and TEC. The downward movement of the F-layer and the resultant increase of NmF2/TEC with westward electric field are the opposite process of the enhanced fountain with eastward electric field, which was termed the reverse fountain by Balan et al (1995Balan et al ( , 1997. Our observations are consistent with the simulations of Balan et al (1995Balan et al ( , 1997.…”

“…The daytime westward electric field after 20:00 UT is most likely to be driven by the disturbance dynamo process and causes a reverse fountain (Balan et al, 1995(Balan et al, , 1997, which can also result in changes of VTEC.…”

Comparison of the measured and modeled electron densities, and electron and ion temperatures in the low-latitude ionosphere during 19-21 March 1988

“…The importance of diffusion, electrodynamic drift, and neutral wind on the generation and modulation of the equatorial anomaly in the electron density, N e , the plasma fountain and several fountain related features (an additional layer, a reverse fountain, an equatorial anomaly in vertical ionospheric electron content, a noon bite-out in NmF2, a nighttime increase in N e , plasma bubbles and spread F) were studied by Balan and Bailey (1995) and Balan et al (1997a). In the present work, we investigate the equatorial anomaly characteristics (the equatorial trough, and crest latitudes and magnitudes) from the comparison between the measured and modeled N e and electron temperatures, T e , during 19-21 March 1988, using the new two-dimensional time dependent model of the low-and middle-latitude plasmasphere and ionosphere (Pavlov, 2003), which employs the updated rate coefficients of chemical reactions of ions and the updated N 2 , O 2 , and O photoionization and photoabsorption cross sections.…”

Theoretical simulation of O<sup>+</sup> and H<sup>+</sup> densities in the Indian low latitude F-region and comparison with observations

“…Simulations carried out by Watanabe et al (1995a) show that maximum in ionization starts developing around the equator at ∼ 10:00 LT and continues until midnight. Balan et al (1997a), from a study of the equatorial plasma fountain and equatorial ionization anomaly in the ionosphere over Jicamarca (77 • E) and Fortaleza (38 • W) using the SUPIM model under magnetically quiet equinoctial conditions of high solar activity, have shown that the EIA is evident up to an altitude of 700 km in the three locations. The EIA is asymmetric about the equator in all the three sectors and has been found to be strongly influenced by the asym- metric neutral winds and displacement of the geographic and geomagnetic equators.…”

“…The upward flow of plasma outside the fountain region can cause convergence of plasma above the F-region peak close to the equator leading to the formation of an additional layer F3. Using the SUPIM, Balan et al (1997a) have found that the north-south asymmetries of the equatorial plasma fountain and equatorial anomaly are more dependent upon the displacement of the geomagnetic equator from the geographic equator. Watanabe et al (1995a) had used a time dependent three-dimensional simulation procedure to study the variation of electron and ion temperature and density within ±30 • and 200 km to 1000 km altitude region.…”