We report the results of our investigations on ionospheric effects potentially caused by the 15 February 2013 Chelyabinsk meteor explosion. We used the observation data from a number of digisonde stations located in Europe and Russia to detect the traveling ionospheric disturbances (TIDs) likely to have been caused by the meteor explosion. We found that certain characteristic signatures of the TIDs can be identified in individual ionogram records, mostly in the form of Y‐forking/splitting of the ionogram traces. Based on the arrival times of the disturbances, we have inferred the overall propagation speed of the TIDs from Chelyabinsk to be 171 ± 14 m/s. In addition to the natural fulfillment of scientific endeavors, this work also highlights the importance of maintaining the mastery of ionosondes as ionospheric diagnostic instruments (in terms of operation, data analysis, representation, and interpretation) for many generations of space researchers to come.

We report our cross-validation of equatorial plasma bubble (EPB) observations based on 2-D ΔTEC data maps over the South American sector, against equatorial spread-F (ESF) observations based on digisonde measurements at several locations. The 2-D ΔTEC data maps were derived using a GPS TEC data detrending procedure [Pradipta et al., 2015] that is inherently capable of distinguishing between wavelike fluctuations associated with traveling ionospheric disturbances (TIDs) and deep depletions associated with EPBs. The data detrending was performed for TEC signals along individual ionospheric piercing point (IPP) trajectories from individual stations, before spatially interpolating the ΔTEC values into a fine 0.2 deg x 0.2 deg geographic latitude/longitude grid. We validated the EPB/depletion observations from these 2-D ΔTEC data maps against digisonde observations of ESF occurrences at Jicamarca (JI91J), Cachoeira Paulista (CAJ2M), and Fortaleza (FZA0M) using data recorded in 2011. A general agreement was found between the EPB and ESF occurrences. Over Jicamarca: 55.1% fall within the EPB=YES & ESF=YES category, 20.6% fall within the EPB=NO & EPB=NO category, 24.4% fall within the EPB=NO & ESF=YES category, and 0% fall within the EPB=YES & ESF=NO category. Over Cachoeira Paulista: 48.5% fall within the EPB=YES & ESF=YES category, 37.4% fall within the EPB=NO & EPB=NO category, 13.2% fall within the EPB=NO & ESF=YES category, and 0.8% fall within the EPB=YES & ESF=NO category. Over Fortaleza: 68.8% fall within the EPB=YES & ESF=YES category, 10.4% fall within the EPB=NO & EPB=NO category, 20.2% fall within the EPB=NO & ESF=YES category, and 0.6% fall within the EPB=YES & ESF=NO category. The classification process of EPB/ESF occurrences (+’s) and no-occurrences (-’s) in this validation work also points at the possibility of performing combinatoric pattern analyses on EPB/ESF occurrence likelihood. This type of analysis may be useful in assessing the fundamental limit of EPB/ESF occurrence predictability that can be theoretically achieved.