Ionospheric weather: cloning missed foF2 observations for derivation of variability index

Abstract

Abstract.A techique for filling the gaps of the missing F2-layer critical frequency is proposed and applied for the derivation of the ionospheric weather index, characterizing the degree of disturbance at each particular station. A dailyhourly analysis of ionosonde observations of foF2 for 16 stations at latitude range 37 • to 70 • N, longitudes of 10 • W to 150 • E, is performed during the solar minimum, 2006. Missed ionosonde observations are reconstructed by cloning data of another station. The process of gap filling considers hourly values of the F peak density NmF2 (deduced from foF2), normalized to the respective median, and assumes that this ratio remains the same for the parent and cloned data. It is shown that the correlation coefficient between cloned fcF2 and observed foF2 is greater than 0.75 for the positive and negative ionospheric disturbed days during a year at solar minimum, independent of the distance between the stations in high and middle latitudes. The quiet reference is determined as a running daily-hourly median for 27 days, preceding the day of observation calibrated for a seasonal trend with ITU-R foF2 predictions. The hourly deviation DNmF2 is defined as the logarithm of ratio of NmF2/NmF2med. A segmented logarithmic scale of the ionospheric weather index, W , is introduced, so that W =±1 refers to the quiet state, W =±2 to a moderate disturbance, W =±3 to the ionospheric storm, and W =±4 to the extreme or anomalous conditions. The catalog of the ionospheric disturbances for W exceeding ±2 at least during 3 consecutive hours is produced and presented online at the SRC and IZMIRAN web pages. It is found that the moderate disturbance is a prevailing state of the ionospheric weather for all stations. The stormy conditions comprise 1 to 20% of the times which occur more frequently at high latitudes, by night, during equinox and winter.

Ionospheric Weather During Five Extreme Geomagnetic Superstorms Since IGY Deduced With the Instantaneous Global Maps GIM‐foF2

“…The W index is introduced as a segmented logarithmic scale of the ionospheric weather for the different thresholds of change in peak plasma density NmF2 or TEC for quantifying the ionosphere variability (Gulyaeva et al, ). The thresholds of the logarithmic ratios for NmF2 or TEC to their quiet reference are selected by equal increments in absolute values for the positive and negative logarithm magnitudes varying from W = −4 (extreme negative storm) in step of 1 to W = +4 (extreme positive ionosphere storm).…”

A new pair of indices to describe the relationship between ionospheric disturbances and geomagnetic activity

“…Jakowski et al [] proposed the use of the variance of total electron content (TEC) as a new ionospheric perturbation index to describe ionospheric disturbances. Gulyaeva et al [] used logarithmic deviations of TEC to construct an ionospheric weather index W , and subsequently, Gulyaeva and Stanislawska [] used the W index to construct a planetary ionospheric storm index, W P , which describes global ionospheric disturbances. Subsequently, Mielich and Bremer [] developed an ionospheric activity index, AI , which correlates with geomagnetic activity during equinoxes.…”

Proxy for the ionospheric peak plasma density reduced by the solar zenith angle

“…The advantages of the proposed approach proved to be useful for reconstruction of missed ionosonde observations of the critical frequency f o F 2 with the data of another station using the cloning technique discussed in (Gulyaeva et al, 2008) so that the complete daily/hourly data sets for selected location/season/month are available for derivation of the ionospheric weather indices.…”