Contribution of the topside and bottomside ionosphere to the total electron content during two strong geomagnetic storms

Abstract

In this study, the ionospheric observations from ionosondes, GPS receivers, and incoherent scatter radars (ISR) at low and middle latitudes were used to investigate the contribution of the bottomside and topside ionosphere to the total electron content (TEC) during the September 2005 and December 2006 geomagnetic storms. It was found that the contribution of the bottomside TEC below F2 peak (BTEC) to the ionosonde ionospheric TEC (ionosonde ITEC), namely, BTEC/ITEC was almost constant during both quiet and storm times, while the ratio of BTEC to GPS TEC (i.e., BTEC/GPS‐TEC) underwent obvious diurnal variations at all stations. The BTEC/GPS‐TEC during the positive phase was similar to that during quiet time, regardless of the formation mechanisms of the observed positive phases. Moreover, our analysis revealed that the ISR calculated BTEC/ITEC during positive ionospheric phases was comparable to that during quiet time. This suggests that the positive phases in these two events mainly occurred around the F2 peak height. There were large differences between the calculated BTEC/ITEC from the ISR observations and BTEC/GPS‐TEC during the negative phase or at night when the plasmasphere possibly contributed significantly to the TEC in the relative sense. Although the absolute changes of the topside TEC were larger than the bottomside TEC at low and middle latitudes associated with the larger topside effective ionospheric thickness, unlike the October 2003 superstorms, the relative changes of the topside TEC to the quiet time reference in these two strong storms were not greater than the changes of the bottomside TEC and peak density NmF2.

Electron density extrapolation above F2 peak by the linear Vary‐Chap model supporting new Global Navigation Satellite Systems‐LEO occultation missions

“…The EDP modeling under the lack of RO data is typically performed by means of the standard Chapman model, defined by the peak height, h m F 2 , the peak electron density N m F 2 , and the scale height H, which is assumed constant in different works and modeling scenarios, such as (1) the topside of the profile: from in situ low-earth orbiting electron density measurements [see Tulasi Ram et al, 2009], from radio-occultation measurements [see Liu et al, 2008] or for combining GPS and ionosonde data in geomagnetic storm scenarios [Zhu et al, 2016]; (2) the ionospheric and plasmaspheric modeling [see González-Casado et al, 2015;Lee et al, 2016;Kutiev et al, 2016]; (3) the Multilayer Chapman model [Alizadeh et al, 2015]; (4) the Ionospheric correction in tropospheric radio-occultation modeling [see Danzer et al, 2015;Zeng et al, 2016].…”

Long‐duration depletion in the topside ionospheric total electron content during the recovery phase of the March 2015 strong storm

“…One of the biggest challenges in ionospheric physics is to understand the topside ionospheric response to geomagnetic storms and the physical processes that drive this response, because topside ionospheric observations have been relatively sparse [e.g., Förster and Jakowski , ]. There have been some studies that describe the topside ionospheric behavior during the main phase of storms based on ground‐based observations [e.g., Belehaki and Tsagouri , ; Garzón et al ., ; Zhao et al ., ; Zhu et al ., ], spaced‐based topside ionosonde data, or in situ measurements [e.g., King et al ., ; Greenspan et al ., ; Heelis and Coley , ]. Recently, more and more Global Positioning System (GPS) observations from receivers onboard low‐Earth orbit (LEO) satellites have been available.…”

Regional differences of the ionospheric response to the July 2012 geomagnetic storm

“…Altitudinal differences of the ionospheric storms are also reflected in the inconsistency of the topside and bottom ionospheric responses to geomagnetic storms [e.g., Lei et al , , ; Zhu et al , ; Zhong et al , ]. To compare the differences between the topside and bottom ionospheric response to this storm, the GPS TEC values along some GRACE orbits are calculated for the case.…”